buildings

Article Whole Life-Cycle Ecological Footprint of Rural Existing Houses in Northern China

Ming Liu 1,*, Baogang Zhang 2, Jingwei Ren 1, Chaoli Lian 1, Jie Yuan 1 and Qingli Hao 1

1 Laboratory of Building Technology, School of Architecture and Fine Art, Dalian University of Technology, Dalian 116024, China; [email protected] (J.R.); [email protected] (C.L.); [email protected] (J.Y.); [email protected] (Q.H.) 2 School of Civil Engineering, Dalian University of Technology, Dalian 116024, China; [email protected] * Correspondence: [email protected]; Tel.: +86-131-098-10011



Received: 3 May 2018; Accepted: 28 June 2018; Published: 10 July 2018


Abstract: To solve the increasing contradiction between the living environment and residential energy consumption in rural areas, it is urgent to alter the traditional living mode and create a new living pattern with a pleasant environment. Based on the theory of ecological footprint, in this article we compare the whole life-cycle ecological footprint between the northern rural house with various energy-saving measures and the urban multi-layer residence with only external wall thermal-insulation as the energy-saving measure. The results show that the sustainability of the multi-layer residence is obviously superior to the rural house. Therefore, rural house designers should learn the multi-layer residential design strategies, construction methods, and operation modes to reduce the unnecessary waste of the energy and resources. Through centralized planning, construction, and heating systems, the multi-level residence is conducive to sustainable human development. The study provides relevant theoretical support for low-carbon house construction in village areas.

Keywords: ecological footprint; residential and environmental sustainability; whole life-cycle; rural existing houses

1. Introduction In China, the rural house directly reflects the level of living conditions of rural residences, the development of related production, the cleanliness of a village’s appearance, and the situation of civilized village custom that accompanies the rapid development of urbanization. Reasonable rural low-carbon housing is the key to building a resource-saving and harmonious society. While the residential environment, indoor comfort, and living facilities in a rural house are still significantly worse than in an urban house, the resource consumption of the rural house is more than that of the urban house, causing contradictions between indoor comfort and energy-saving in the village areas to be increasingly significant. Rural residents are no longer satisfied with their traditional living mode and they urgently require new house patterns with beautiful environments and full function. Consequently, due to the large rural population, rural housing construction and operation will annually consume significant resources. Therefore, only by accurately analyzing and evaluating the rural house pressure on the natural environment can a scientific basis to enable the development of design and technical standards that take effective measures, such as residential design, construction, and operation stages, into consideration be realized. Based on this management, the energy consumption of the rural house should be greatly reduced to achieve sustainable development within the advancement of rural house comfort and it can accelerate the process of constructing a resource-saving society.

Buildings 2018, 8, 92; doi:10.3390/buildings8070092 www.mdpi.com/journal/buildings Buildings 2018, 8, 92 2 of 19

Buildings are responsible for consuming 35–40% of energy in the developed countries, especially existing houses. A significant fraction of the energy consumption is transformed into comfortable, habitable, indoor environments [1,2]. B.Z. Li et al. investigate indoor thermal environments in China, and put forward an index suitable for the assessment of thermal environment comfort in the Chongqing area, and analyze the differences between indoor thermal environments in five climate zones [1]. In northern China, the principal way to improve indoor thermal comfort in winter is to enhance the building envelope and material properties. This paper will compare the ecological footprint and analyze the sustainable development of the buildings. As is known to us, the whole life-cycle assessment is the main research method on the environmental factors and their potential effects on the entire process of a product’s life-cycle. In a building’s practical application, the whole life-cycle assessment is intended to reduce the environmental impact to its minimum, shortening the design period, and lowering relevant costs. Ecological footprint theory is an important method to measure sustainability and it has been widely applied in many fields [3], but the application is not yet mature in the field of architectural design. Ecological footprint theory is a quantitative study on the influence of the consumption of resources caused by human activity on the environment from the perspective of sustainability through analyzing all kinds of resources and assessing land area impact [4,5]. Most of the application fields of ecological footprint are used to assess concepts such as the economic system, energy utilization, tourism, diet structure, and more. Currently, the measurement of the ecological footprint as it relates to architecture is mostly concerned with a sustainability evaluation of a construction project. Yan Zhao [6] is the first scholar to use an ecological footprint and energy analysis to evaluate a building. Their article calculates the ecological footprint of the construction stage of a house. Zhe Yan [7] calculated the reduction of the ecological footprint through five key aspects—land saving, energy saving, water saving, material saving, and environmental protection)—and calculated a building’s ecological footprint from another perspective. Shuhe Wu [8,9] uses ecological footprint theory to estimate the ecological footprint of a building, analyzes its sustainable development status, and then uses the theory of energy analysis to evaluate the economic benefits. Nevertheless, there is a lack of research regarding the total ecological footprint on the whole life-cycle of a building for the design stage, construction stage, operation stage, and demolition stage in related research. Therefore, this paper uses the theory of energy ecological footprint to solve the total ecological footprint of the whole life-cycle of rural housing in Wafangdian City and in Liaoyang City. The analysis is intended to evaluate the influence of the village and town housing to the natural environment and the sustainable development of the rural houses. Through comparing the ecological footprint of the buildings with their ecological carrying capacity, one can know the sustainability degree of the building: whether the building is in a state of ecological surplus or ecological deficit. A life-cycle framework of the ecological footprint model is shown in Figure1. When the ecological footprint of a region is greater than its ecological carrying capacity, the region has an ecological deficit and is in a state of unsustainable development. When the ecological footprint is less than the ecological carrying capacity, the region appears to have an ecological surplus and is in a sustainable development state. This paper uses an ecological footprint analysis method based on improved energy theory to analyze the impact on the ecological carrying capacity during the building of whole life-cycle residences from the perspective of sustainable development. As shown in Figure2, by calculating the ecological carrying capacity and comparing it to the ecological footprint in the design, construction, operation, demolition, and recycle stages, the pressure of the building’s life-cycle on nature can be obtained. As a result, the design strategies that increase the ecological surplus in each stage and contribute to sustainability can be analyzed over the course of the building’s entire life. Current research on a building’s ecological footprint is confined to incorporating the ecological footprint produced during the construction period into the analysis model for calculation. This paper, however, comprehensively Buildings 2018, 8, 92 3 of 19

analyzes the building’s ecological footprint in various stages from the perspective of building for the BuildingswholeBuildings life-cycle,2018 2018, ,8 8, ,x x FOR FOR to providePEER PEER REVIEW REVIEW a convenient tool for the quantitative evaluation of a green building scenario.33 of of 19 19

Figure 1. The model frame of ecological footprint calculation. Figure 1. The model frame of ecological footprint calculation.

Figure 2. The research thought of the paper. FigureFigure 2. 2. The The research research thought thought of of the the paper. paper. 2. The Theory of Ecological Footprint 2.2. The The Theory Theory of of Ecological Ecological Footpri Footprintnt 2.1. Contents of Ecological Footprint 2.1.2.1. Contents Contents of of Ecological Ecological Footprint Footprint Ecological footprint is defined as the areas of biologically productive land and water required to produceEcologicalEcological the resources footprint footprint to is satisfyis defined defined the as as consumption the the areas areas of of biologically ofbiologically a given population productive productive or land land economy and and water water and torequired required assimilate to to producetheproduce waste the the generated resources resources by to to thesatisfy satisfy population. the the consumption consumption The development of of a a given given andpopulation population improvement or or economy economy of living and and standardsto to assimilate assimilate are thepartlythe waste waste related generated generated to the by growingby the the population. population. consumption The The development ofdevelopment ecological services:and and improvement improvement the high humanof of living living development standards standards are are in partlydevelopedpartly relatedrelated countries toto thethe growinggrowing has been consumptionconsumption achieved at the ofof ecological expenseecological of services:services: a high ecological thethe highhigh humanfootprint,human developmentdevelopment so decoupling inin deanddevelopedveloped reversing countries countries this relationship has has been been achieved isachieved a key global at at the the challenge.expense expense of of The a a high high challenge ecological ecological for countries footprint, footprint, in so theso decoupling decoupling bottom-left andsectorand reversing reversing is to significantly this this relationship relationship increase is is theiraa key key inequality-adjusted global global challenge. challenge. The The Human challenge challenge Development for for countries countries Index in in (IHDI)thethe bottom bottom (Low-- leftHumanleft sectorsector Development isis toto significantlysignificantly Index) increaseincrease without theirtheir significantly inequalityinequality increasing--adjustedadjusted Human theirHuman ecological DevelopmentDevelopment footprint IndexIndex while, (IHDI)(IHDI) for (Lowcountries(Low Human Human in the Development Development upper-right Index) sectorIndex) havingwithout without high significantly significantly IHDI, the increasing goalincreasing is to reduce their their ecological ecological their footprints footprint footprint (Figure while, while,3). forfor countries countries in in the the upper upper--rightright sector sector having having high high IHDI, IHDI, the the goal goal is is to to reduce reduce their their footprints footprints (Figure (Figure 3).3).

urceurce Buildings 2018, 8, 92 4 of 19 Buildings 2018, 8, x FOR PEER REVIEW 4 of 19 Buildings 2018, 8, x FOR PEER REVIEW 4 of 19

Figure 3. Correlating the Ecological Footprint with IHDI [10]. FigureFigure 3. 3. CorrelatingCorrelating the the Ecological Ecological Footprint Footprint with with IHDI IHDI [10]. [10]. 2.2. Basis of Ecological Footprint Evaluation 2.2.2.2. Basis Basis of of Ecological Ecological Footprint Footprint Evaluation Evaluation The Earth’s total ecological footprint already surpassed the ecological carrying capacity in the TheThe Earth’s Earth’s total total ecological ecological footprint footprint already already surpassed surpassed the the ecological ecological carrying carrying capacity capacity in in the the 1980s, and the ecological deficit has been growing continuously since. The report “China Ecological 1980s, and the ecological deficit deficit has been growing contin continuouslyuously since. The The report report “China “China Ecological Ecological Footprint Report 2012” released by the World Wildlife Fund (WWF) pointed out that, although the FootprintFootprint Report Report 2012” 2012” released released by by the the World World Wildlife Wildlife Fund (WWF) pointed out out that, that, although although the the per capita ecological footprint is below the global average, the Chinese ecological footprint is still the perper capita capita ecological ecological footprint footprint is is below below the the global global average, average, the the Chinese Chinese ecological ecological footprint footprint is still is stillthe largest in the world. The per capita ecological footprint is about twice the per capita ecological largestthe largest in the in the world. world. The The per per capita capita ecological ecological footprint footprint is is about about twice twice the the per per capita capita ecological ecological carrying capacity. Figures 4 and 5 show the main reason for that is the rapid growth of the carbon carryingcarrying capacity. capacity. Figures Figures 4 andand5 5 show show thethe mainmain reasonreason forfor that that is is the the rapid rapid growth growth of of the the carbon carbon footprint due to energy consumption and the waste of resources. The total ecological footprint of footprintfootprint due due to to energy energy consumption and and the the waste of resources. The The total total ecological ecological footprint footprint of of buildings has been increasing and the per capita ecological footprint is over 0.91 ghm22/cap of the per buildingsbuildings has been increasing and the per capita ecological footprint isis overover 0.910.91 ghmghm2/cap of of the the per per capita of buildings in the world, with rapid urban construction still occurring in China. Therefore, it capitacapita of of buildings buildings in in the the world, world, with with rapid rapid urban urban construction construction still still occurring occurring in in China. China. Therefore, Therefore, it it is important to reduce energy consumption and build green buildings with more sustainability to isis important important to to red reduceuce energy consumption and and build build green green buildings with with more more sustainability to to reduce the ecological footprint. Applying ecological footprint theory in the assessment of housing reducereduce the the ecological footprint. Applying Applying ecological ecological footprint footprint theory theory in in the the assessment assessment of of housing housing sustainability is necessary. sustainabilitysustainability is is necessary. necessary.

Figure 4. Ecological footprint and ecological carrying capacity of China in 1961–2008 [11]. FigureFigure 4. 4. EcologicalEcological footprint footprint and and ecological ecological car carryingrying capacity capacity of of China China in in 1961 1961–2008–2008 [11]. [11]. Buildings 2018, 8, 92 5 of 19 Buildings 2018, 8, x FOR PEER REVIEW 5 of 19

carbon footprint

FigureFigure 5.5. CompositionComposition ofof thethe ecologicalecological footprintfootprint ofof ChinaChina inin 1961–20081961–2008 [[11].11].

TheThe corecore ideaidea ofof greengreen buildingbuilding isis sustainabilitysustainability andand thethe impactimpact ofof aa buildingbuilding onon thethe naturalnatural environment.environment. The bearing capacity of the earthearth shouldshould bebe consideredconsidered inin thethe wholewhole operationoperation cyclecycle whilewhile buildingbuilding usingusing thethe existingexisting assessmentassessment systems,systems, suchsuch asas thethe LEEDLEED (Leadership(Leadership inin EnergyEnergy andand EnvironmentalEnvironmental Design)Design) system, system, and and must must be be influenced influenced by by the the knowledge knowledge and and personal personal preferences preferences of theof the assessments assessments [12 –[1216],–16], which which may may incorporate incorporate methods methods that that are subjective are subjective in nature. in nature. Moreover, Moreover, such assessmentsuch assessment systems systems are based are on based weight on and weight expert and decisions. expert decisions.These kinds These of assessment kinds of systems assessment are concernedsystems are with concerned ecological with strategies, ecological such strategies, as energy-saving, such as energy water-saving,-saving, water environment-saving, environment and culture, butand in culture, the harmonious but in the coexistence harmonious of architecturecoexistence andof architecture environment and there environment is no clear expression.there is no clear expression.The ecological footprint method is informed by the perspective of sustainable development, and it quantitativelyThe ecological studies footprint the occupationmethod is informed and influence by the ofperspective various resource of sustainable consumption development, caused and by humanit quantitatively activities Ecologicalstudies the footprint occupation theory and can influence make up of for various the uncertainty resource ofconsumption the existing evaluationcaused by methodshuman activities and the lack Ecological of assessment footprint of theory environmental can make health. up for The the implied uncertainty cost to of the the ecological existing environmentevaluation methods in life-cycle and activities the lack isof well assessment reflected of by environmental the ecological healt footprint.h. The It impliedcan easily cost measure to the theecological required environment materials, activities, in life-cycle operating activities costs, is well consumed reflected resources,by the ecological waste, andfootprint. pollution It can of easily each buildingmeasure bythe the required corresponding materials, natural activities, costs. operating A building’s costs, life-cycle consumed has resources, an impact waste, on the and environment. pollution Theof each calculation building of b they the consumption corresponding items natural that correspond costs. A tobuilding’s each resource life-cycle must has be executedan impact in on order the toenvironment. build a comprehensive The calculation analysis of the of theconsumption impacts on items the environment. that correspond The evaluationto each resource and research must be of residentialexecuted in sustainability order to build can be a accomplished comprehensive using analysis these basic of the data. impacts Ecological on the footprint environ analysisment. Thecan convertevaluation all kinds and research of resources of residential into land areas sustainability to solve the can problem be accomplished of inconsistently using these measured basic units, data. whichEcological other footprint assessment analysis methods can cannotconvert solve. all kinds of resources into land areas to solve the problem of inconsistently measured units, which other assessment methods cannot solve. 3. Ecological Footprint Calculation Methods on a Rural House 3. Ecological Footprint Calculation Methods on a Rural House 3.1. Rural House Introduction 3.1. RuralThe rural House two-family Introduction house is located in Wafangdian, Liaoning province, and covers an area of 474The m 2rural. The two house-family is single-floored house is located with in Wafangdian the height of, Liaoning 5.2 m. One province, of the and families covers lives an area in the of three-bedroom474 m2. The house whose is single main- buildingfloored with area the is 103height m2; of the 5.2 other m. One residence of the infamilies the structure lives in is the four-bay three- withbedroom a building whose area main of building 128 m2. Thearea rural is 103 house m2; the uses other a fire residence pit, Kang, in firewall, the structure wall insulation,is four-bay double with a glazingbuilding windows, area of 128 and m2 a. The series rural ofpassive house uses design a fire techniques pit, Kang, combined firewall, wall with insulation, local traditional double customs. glazing Thewindows, house planand (Figurea series6 )of follows passive the design form of techniques the traditional combined rural house. with local When traditional stepping into customs. the house, The therehouse is plan a kitchen (Figure with 6) afollows fire stove the thatform acts of the as a traditional heat resource rural for house. the master When bedroom. stepping Compared into the house, with athere traditional is a kitchen rural with house, a fire this stove house that adds acts a separateas a heatliving resource room, for diningthe master room, bedroom. and indoor Compared toilets, conformingwith a traditional to a morerural modernhouse, this lifestyle. house adds The a house separate types living are room, simple dining and practical.room, and Itsindoor north toilets, side conforming to a more modern lifestyle. The house types are simple and practical. Its north side contains the stairwell into the underground fuel tank. The terrain on the north compared to the south BuildingsBuildings2018 2018, 8, ,8 92, x FOR PEER REVIEW 66 of of 19 19

is highly different, so the north side of the residence is covered with soil to keep the room insulated containsfrom cold the weather. stairwell into the underground fuel tank. The terrain on the north compared to the south is highly different, so the north side of the residence is covered with soil to keep the room insulated from cold weather.

Fire pit underground Fire pit underground

Figure 6. Floor plan of the rural house. Figure 6. Floor plan of the rural house. 3.2. Ecological Footprint Model 3.2. Ecological Footprint Model Ecological footprint analysis is a method to study the consumption of resources and the life- Ecological footprint analysis is a method to study the consumption of resources and the support services of the Earth. The basic idea of this method is to transform those consumption life-support services of the Earth. The basic idea of this method is to transform those consumption activities that are necessary to maintain human life into a corresponding ecologically productive land activities that are necessary to maintain human life into a corresponding ecologically productive land area. Original data can be obtained from the construction budget books or statements. The ecological area. Original data can be obtained from the construction budget books or statements. The ecological footprint can describe a building or buildings in a region based on specific resources or energy flow footprint can describe a building or buildings in a region based on specific resources or energy flow values, calculate the demands and pressures on the environment, and can be compared with the values, calculate the demands and pressures on the environment, and can be compared with the ecological carrying capacity [15–17]. Thus, the impact on the environment from the stages of design, ecological carrying capacity [15–17]. Thus, the impact on the environment from the stages of design, construction, operation, and demolition can be directly reflected. construction, operation, and demolition can be directly reflected. Full life-cycle theory, also known as “from cradle to grave” [18], refers to the process of the initial Full life-cycle theory, also known as “from cradle to grave” [18], refers to the process of the initial material acquisition, manufacture, operation, maintenance, and disposal in the entire ecological cycle. material acquisition, manufacture, operation, maintenance, and disposal in the entire ecological cycle. According to this theory, the life-cycle of the Wafangdian rural house can be divided into five stages: According to this theory, the life-cycle of the Wafangdian rural house can be divided into five stages: design, construction, operation, demolition, and recycling. According to the basic principles of the design, construction, operation, demolition, and recycling. According to the basic principles of the ecological footprint analysis, the resource consumption and the environmental pollution from the ecological footprint analysis, the resource consumption and the environmental pollution from the building’s life-cycle stages can be summed up into a variety of consumption items. Based on that, the building’s life-cycle stages can be summed up into a variety of consumption items. Based on that, the consumption items can be converted respectively into biologically productive land areas. Concrete consumption items can be converted respectively into biologically productive land areas. Concrete steps steps of the calculation model of the whole life-cycle ecological footprint of the rural house are as of the calculation model of the whole life-cycle ecological footprint of the rural house are as follows: follows: (1)(1) EstimatingEstimating thethe consumptionconsumption itemsitems inin eacheach stagestage of of building building for for the the whole whole life-cycle life-cycle (including (including buildingbuilding materials,materials, labor,labor, machinery, machinery, and and other other energy energy consumptions). consumptions). (2)(2) MakingMaking uniform uniform the the dimensions dimensions of the of various the various consumption consumption items in thisitems building in this and building converting and theconverting consumption the consumption items into the items corresponding into the corresponding solar energy solar value energy by using value an energyby using conversion an energy rate.conversion Then summarize rate. Then thesummarize various consumptionthe various consumption items. items. (3)(3) CollectingCollecting solarsolar energyenergy valuevalue toto weight,weight, thenthen thethe totaltotalsolar solar energy energy value value of of the the rural rural house house of of 18 2.042.04× × 1018 sejsej can be drawn, with thethe resultresult thatthat thethe solarsolar density density of of the the rural rural house house is: is:p jp=j = total total − solarsolar energyenergy value/total value/total building landland areasareas == 4.3 × 10101919 sej·hmsej·hm−2. 2. (4)(4) UsingUsing solarsolar densitydensity toto convertconvert thethe whole whole life-cycle life-cycle consumption consumption items items into into the the corresponding corresponding ecologicalecological productiveproductive areas areas and and make make a a summation. summation. The The calculation calculation formula formula is: is: Buildings 2018, 8, x FOR PEER REVIEW 7 of 19

Buildings 2018, 8, 92 nn 7 of 19 EFNefNrNrrjj Ac/piii (1) ii11 n n Among them, EFr representsEFr the= N ecological·e f = N·r footprintj·∑ Ai = ofNr thej·∑ consumptionci/pi in each stage, measured(1) i=1 i=1 in ghm2; ef represents the per capita ecological footprint, represented byghm2/cap; rj represents the land Amongequalization them, factorEFr represents j measured the by ecological ghm2/hm footprint2, Ai represents of the consumption the per capita in ecological each stage, footprint measured of in ghm2; ef represents the per capita ecological footprint, represented byghm2/cap; r represents the the i resource, represented by ghm2/cap; ci represents the per capita energy consumptionj of the i 2 2 land equalization factor j measured by ghm /hm , Ai represents the per capita ecological footprint resource; pj is the energy density of building, measured by sej·hm−2. of the i resource, represented by ghm2/cap; c represents the per capita energy consumption of the i There will be many by-products, such asi harmful gas, dust, sewage, construction waste, and so resource; p is the energy density of building, measured by sej·hm−2. on. These byj -products should be regarded as waste in the ecological footprint. It is estimated that the There will be many by-products, such as harmful gas, dust, sewage, construction waste, and so building area per 1 m2 brings about 60 kg of construction waste in the construction process. Most of on. These by-products should be regarded as waste in the ecological footprint. It is estimated that the the construction waste in China is buried, and each stacked 1000 kg block of construction waste building area per 1 m2 brings about 60 kg of construction waste in the construction process. Most of the occupies about 0.067 m2. The total ecological footprint of the building waste in the construction and construction waste in China is buried, and each stacked 1000 kg block of construction waste occupies demolition stage is (EFw). The ecological footprint calculation formula [19,20] of the building waste about 0.067 m2. The total ecological footprint of the building waste in the construction and demolition is: stage is (EFw). The ecological footprint calculation formula [19,20] of the building waste is: 342 EFrArw  www60 0 Sn .067 10 10 g m ( h ) (2)  −3 −4 2 EFw = rw·Aw = rw·∑ Sn × 60 × 0.067 × 10 × 10 ghm (2) The whole life-cycle ecological footprint of the rural house (EF) is consisted to be the ecological footprintThe wholeof the life-cyclemain consumption ecological footprintitems (EF ofr) theandrural the building house (EF wastes) is consisted produced to bein thethe ecological life-cycle footprint(EFw), shown of the by main EF = consumptionEFr + EFw [21]. items (EFr) and the building wastes produced in the life-cycle (EFw), shown by EF = EFr + EFw [21]. 4. Analysis and Discussion 4. Analysis and Discussion 4.1. Calculation Results 4.1. Calculation Results Based on the theories above, a program was written to calculate the whole life-cycle ecological footprintBased (Figure on the 7). theories Visual above,Studio ais programused for the was data written processing. to calculate The results the whole can life-cyclebe easily calculated ecological footprintonce the original (Figure7 data). Visual is entered. Studio The is used interface for the of data the program processing. is shown The results in Figure can be 7: easily calculated once the original data is entered. The interface of the program is shown in Figure7:

(a)

Figure 7. Cont. Buildings 2018, 8, 92 8 of 19 Buildings 2018, 8, x FOR PEER REVIEW 8 of 19

(b)

Figure 7. Program of ecologicalecological footprint footprint model model visualization visualization design. design. (a) Design(a) Design stage; stage; (b) Operation (b) Operation stage. stage. The impact of the building on nature during the whole life-cycle and the contribution of The impact of the building on nature during the whole life-cycle and the contribution of sustainable development can be drawn by calculating the ecological carrying capacity and comparing sustainable development can be drawn by calculating the ecological carrying capacity and comparing it with the ecological footprint. Then, the design strategies that increase the ecological surplus in each it with the ecological footprint. Then, the design strategies that increase the ecological surplus in each stage and the contribution to sustainable development can be analyzed. The formula for calculating stage and the contribution to sustainable development can be analyzed. The formula for calculating ecological carrying capacity is ecological carrying capacity is 6
Ec = N·ec = N·∑6aj·rj·yj (3) j=1 Ec NceN()ayjjjr (3) j1 2 Among them, EC represents the ecological carrying capacity (ghm ); N represents the total 2 population (cap); ec represents the per capita ecological carrying capacity (ghm2 /cap); r represents Among them, 퐸퐶 represents the ecological carrying capacity (ghm ); N representsj the total 2 2 2 the equilibrium factor of J land (ghm /hm ); a represents the annual average supply2 of J land (hm ); population (cap); ec represents the per capita ecologicalj carrying capacity (ghm /cap); 푟푗 represents yj represents the yield factor of J land; J represents2 2 the land type of biological production. To calculate the equilibrium factor of J land (ghm /hm ); 푎푗 represents the annual average supply of J land the ecological2 carrying capacity, 12% of the biodiversity conservation area should be subtracted in (hm ); 푦푗 represents the yield factor of J land; J represents the land type of biological production. To accordancecalculate the with ecological the proposal. carrying The land capacity, type of 12% the of rural the house biodiversity is arable conservation land, the equilibrium area should factor be is 2.8,subtracted and the in yield accordance factor is 1.66. with Reconsidering the proposal. withThe land 12% of type the of bioprotective the rural house ecological is arable area, land, the total the ecologicalequilibrium carrying factor is capacity 2.8, and is: the yield factor is 1.66. Reconsidering with 12% of the bioprotective ecological area, the total ecological carrying capacity is: 2 Ec1 = (1–12%) aj·rj·yj = 0.88 × 0.0474 × 2.8 × 1.66 = 0.194 ghm (4) Ec1 = (1%–12%) aj·r j·y j = 0.88 × 0.0474 × 2.8 × 1.66 = 0.194 ghm2 (4) The family population is nine. The ecological footprint calculation results of the rural house are The family population is nine. The ecological footprint calculation results of the rural house are shown in Table1. shown in Table 1. Buildings 2018, 8, 92 9 of 19

Table 1. The ecological footprint calculation model of the rural house.

Energy Per Capita Per Capita Solar Energy Corresponding Equilibrium Ecological Project stage Consumption Items Original Data Conversion Energy Ecological Value/sej Land Type Factor Footprint/hm2 Rate/(sej/unit) Value/sej Footprint/hm2 Design stage Labor costs/$ 2568 5.20 × 1012 1.33536 × 1016 1.6692 × 1015 3.8805 × 10−5 Construction land 2.8 9.78 × 10−4 Wood/g 874,606 4.40 × 108 3.84827 × 1014 4.81033 × 1013 1.11829 × 10−6 Woodland 1.1 1.10711 × 10−5 Brick 1.8 × 108 2.60 × 109 4.79213 × 1017 5.99017 × 1016 0.001392573 Construction land 2.8 0.035092838 Sand/g 7.7 × 107 1.00 × 109 7.6636 × 1016 9.5795 × 1015 0.000222701 Fossil energy land 1.1 0.002204739 Stone/g 7.3 × 107 1.00 × 109 7.2594 × 1016 9.07425 × 1015 0.000210955 Fossil energy land 1.1 0.002088455 Cement/g 2.9 × 107 2.30 × 109 6.7829 × 1016 8.47862 × 1015 0.000197108 Fossil energy land 1.1 0.00195137 Cement/g 9,520,000 2.30 × 109 2.1896 × 1016 2.737 × 1015 6.36288 × 10−5 Fossil energy land 1.1 0.000629925 Cement/g 3.9 × 107 2.80 × 1010 1.10264 × 1018 1.3783 × 1017 0.003204224 Fossil energy land 1.1 0.031721817 Cement/g 90 5.20 × 1012 4.68 × 1014 5.85 × 1013 1.35999 × 10−6 Construction land 2.8 3.42717 × 10−5 − Construction stage XPS/$ 886 5.20 × 1012 4.6072 × 1015 5.759 × 1014 1.33883 × 10 5 Construction land 2.8 0.000337386 Asphalt/$ 954 5.2 × 1012 4.9608 × 1015 6.201 × 1014 1.44159 × 10−5 Construction land 2.8 0.00036328 Steel/g 4,243,458 4.20 × 109 1.78225 × 1016 2.22782 × 1015 5.17915 × 10−5 Construction land 2.8 0.001305145 Glass/g 295,000 7.90 × 109 2.3305 × 1015 2.91313 × 1014 6.77233 × 10−6 Construction land 2.8 0.000170663 Water/g 7.7 × 107 6.60 × 105 5.08134 × 1013 6.35168 × 1012 1.47662 × 10−7 Waters 0.2 2.65791 × 10−7 Electricity/J 1.6 × 109 1.60 × 105 2.59557 × 1014 3.24446 × 1013 7.54262 × 10−7 Construction land 2.8 1.90074 × 10−5 Labor costs/$ 5198 5.20 × 1012 2.70296 × 1016 3.3787 × 1015 7.85468 × 10−5 Construction land 2.8 0.00197938 Finished doors/$ 110 5.2 × 1012 5.72 × 1014 7.15 × 1013 1.66221 × 10−6 Construction land 2.8 4.18876 × 10−5 Other coasts/$ 1000 5.20 × 1012 5.2 × 1015 6.5 × 1014 1.5111 × 10−5 Construction land 2.8 0.000380797 Building wastes ------0.000260014 Water/g 1.9 × 109 6.60 × 105 1.26852 × 1015 1.58565 × 1014 3.68626 × 10−6 Waters 0.2 6.63528 × 10−6 Electricity/J 7.8 × 1011 1.60 × 105 1.25019 × 1017 1.56274 × 1016 0.0003633 Construction land 2.8 0.009155157 − − Operation stage Coal/g 8.8 × 107 3.93 × 104 3.4584 × 1012 4.323 × 1011 1.005 × 10 8 Fossil energy land 1.1 9.94946 × 10 8 Straw/g 1.4 × 108 1.70 × 105 2.448 × 1013 3.06 × 1012 7.11378 × 10−8 Arable land 2.8 1.79267 × 10−6 Other maintenance/$ 2837 5.20 × 1012 1.47524 × 1016 1.84405 × 1015 4.28698 × 10−5 Construction land 2.8 0.00108032 Demolition stage Building wastes ------0.000772799 Total ecological footprint ------0.090518681 Buildings 2018, 8, x FOR PEER REVIEW 10 of 19 Buildings 2018, 8, 92 10 of 19 Buildings 2018, 8, x FOR PEER REVIEW 10 of 19

4.2. Assessment of Sustainable Development 4.2. Assessment of Sustainable Development The index of the ecological ecological footprint footprint and and ecological ecological carrying carrying capacity capacity can can reflect reflect the the degree degree of of a The index of the ecological footprint and ecological carrying capacity can reflect the degree of a asustainable sustainable development development on on the the environment. environment. When When the the ecological ecological footprint footprint is is higher higher than the sustainable development on the environment. When the ecological footprint is higher than the ecological carrying capacity, it presents the ecological deficit deficit and and the the environmental environmental unsustainability. unsustainability. ecological carrying capacity, it presents the ecological deficit and the environmental unsustainability. Quite the reverse, when the ecological footprint is lower than the ecological carrying capacity, the ecologicalQuite the surplus reverse, is when presented, the ecological and the environmentfootprint is lower is in thana sustainable the ecological developmen carryingt capacity,state. The the total ecologicalecological surplus surplus is is presented, presented, and and thethe environmentenvironment is is in in a a sustainable sustainable developmen developmentt state. state. The The total total ecological footprint of the rural house in this research is 0.091 ghm22, which is significantly lower than ecologicalecological footprint footprint of of the the rural rural house house inin thisthis research is is 0.091 0.091 ghm ghm2, which, which is issignificantly significantly lower lower than than its ecological capacity, making the ecological surplus within the ecological footprint index 53%, thus itsits ecological ecological capacity, capacity, making making the the ecological ecological surplussurplus within within the the ecological ecological footprint footprint index index 53%, 53%, thus thus it has higher sustainable level (Figure 8). According to these data, it can be determined that there is it hasit has higher higher sustainable sustainable level level (Figure(Figure8 8).). AccordingAccording to these data, data, it it can can be be determined determined that that there there is is less impact on the local ecological environment during the whole life-cycle stages of the rural house. lessless impact impact on on the the local local ecological ecological environmentenvironment during during the the whole whole life life-cycle-cycle stages stages of ofthe the rural rural house. house. Therefore,Therefore, the the design design strategy strategy andand relatedrelated energy-savingenergy--savingsaving technologies technologies used used in in the the rural rural house house are are

worthworth being being promoted promoted from from the the viewpoint viewpoint of sustainable sustainable development development of of of the the the ecological ecological ecological environment. environment. environment.

2

2

Global hectare/ghm

Global hectare/ghm

Figure 8. Sustainable analysis of rural house. Figure 8. Sustainable analysis of rural house. 4.3. Analysis on Rural House in Whole Life-Cycle 4.3. Analysis on Rural House in Whole Life-CycleLife-Cycle The whole life-cycle of the house is composed of five stages and each stage has a very important The whole life-cyclelife-cycle of the house is composed of fivefive stages and each stage has a very important role. Figure 9 shows the proportion of the ecological footprint of the Wafangdian rural house in each role. Figure9 shows the proportion of the ecological footprint of the Wafangdian rural house in each role.stage. Figure The 9 house shows is the currently proportion in use of and the ecologicaldoes not include footprint the of ecological the Wafangdian footprint rural of the house recycling in each stage.stage. The The Since house house the recyclingis is currently stage in depends use and on does the reusing not include method the of ecological the house footprintafter its demolition, of the recycling the stage.calculation Since the results recycling are uncertain. stage depends Therefore, on the Figure reusing 9 does method not include of the the house recycling after its stage. demolition, It can be the calculationseen from resultsresults the picture are are uncertain. uncertain.that the proportion Therefore, Therefore, of Figure Figurethe ecological9 does 9 does not footprintnot include include theof the recyclingthe construction recycling stage. stage. Itstage can It is be can the seen be fromseenlargest, fro them picture at the approximately picture that the that proportion the87%. proportion The ofproportion the of ecological the of ecological the footprint ecological footprint of footprint the constructionof the in construction the operation stage is stage thestage largest, is is the atlargest,roughly approximately at 11%,approximately the 87%. design The stage87%. proportion Theabout proportion 1%, of the and ecological the of demolition the footprintecological stage in footprint theis in operation the regionin the stage ofoperation 1%. is roughly Thus, stage the 11%, is theroughlyreduction design 11%, stage of the about ecologicaldesign 1%, stage and footprint about the demolition during 1%, and the the stageconstruction demolition is in the stage region stage and ofis operation in 1%. the Thus, region stage the ofcan reduction 1%. effectively Thus, of the ecologicalreductionreduce the of footprint thetotal ecological ecological during footprint thefootprint construction duringof the whole the stage construction life and-cycle operation (Figure stage stage 9).and canoperation effectively stage reduce can effectively the total ecologicalreduce the footprinttotal ecological of the wholefootprint life-cycle of the (Figurewhole life9). -cycle (Figure 9).

Figure 9. The proportion of the Wafangdian farm house in whole life-cycle.

Figure 9. The proportion of the Wafang Wafangdiandian farm house in whole life-cycle.life-cycle.

Buildings 2018, 8, 92 11 of 19 Buildings 2018, 8, x FOR PEER REVIEW 11 of 19

ReducingReducing energy energy consumption consumption and and improving improving energy energy use use efficiency efficiency are are effective effective measures measures to to reducereduce the the ecological ecological footprint footprint of of the the operation operation stage. stage. Figure Figure 1010 showsshows the the ecological ecological footprint footprint of of the the mainmain consumption consumption items items in in the the operation operation stage stage of of the the Wafangdian Wafangdian rural house. Electricity Electricity and and other other maintenancemaintenance takes takes up up a a large large proportion proportion in in the the total total ecological ecological footprint footprint during during the the operation operation stage. stage. TheThe ecological footprint footprint of of electricity consumption is is about about 0.009 ghm 22,, account accountinging for for 89% 89% of of the the totaltotal ecological ecological footprint footprint in in the the operation operation stage, stage, while while the the ecological ecological footprint footprint of of straw straw accounts accounts for for lessless than than 1 1 percent percent of of the total ecological footprint in in the operation phase. phase. Straw Straw is is mainly mainly used used as as fuelfuel for for the the fire fire pit pit and and stove stoves,s, so so the the ecological ecological footprint footprint of of the the heating heating system system is is very very low. low. The The main main componentscomponents of of electricity electricity consumption consumption include include lighting, lighting, air air conditioning conditioning and and other other daily daily household household electricalelectrical appliances. appliances. Therefore, Therefore, the the ventilating ventilating and and cooling cooling measures measures should should be be c consideredonsidered for for the the designdesign in in northern northern China China villages. villages.

Figure 10. The ecological footprint of the consumption items in operation stage. Figure 10. The ecological footprint of the consumption items in operation stage.

The rural house in Wafangdian uses passive technologies such as a fire pit, firewall, and a new stoveThe Kang rural bed, house which in Wafangdianuses crop straws uses passive as fuel technologiesand effectively such reduces as a fire the pit, energy firewall, consumption and a new duringstove Kang residential bed, which heating. uses Currently, crop straws most as fuel of the and time effectively the straw reduces is directly the energy burned consumption in fields that during are notresidential effectively heating. utilized. Currently, However, most the farms of the of time the Wafangdian the straw is make directly full burned use of this in fieldsenergy. that Therefore, are not aeffectively fire pit and utilized. a new furnace However, are the worth farms promoting of the Wafangdian in the northern make rural full use areas. of this energy. Therefore, a fire pitThe and ecological a new furnace footprint are of worth demolition promoting is mainly in the caused northern by rural the direct areas. burial of the construction waste,The which ecological occupies footprint a large of amount demolition of farmland. is mainly Reducti causedon by and the directrecycling burial of construction of the construction waste canwaste, effectively which occupies reduce the a large ecological amount footprint of farmland. during Reduction the demolition and recycling stage. Through of construction reducing waste the occupancycan effectively of arable reduce land the by ecological waste emissions, footprint the during environmental the demolition pollution stage. can Throughbe reduced reducing indirectly. the Theoccupancy directly of buried arable building land by waste waste is emissions, mainly brick the and environmental concrete—by pollution choosing can building be reduced materials indirectly. that canThe be directly degraded buried by buildingway of self waste-classification, is mainly brickor recyclable and concrete—by or reusable, choosing the ecological building footprint materials in thatthe demolitioncan be degraded stage could by way be ofsignificantly self-classification, reduced or or recyclable even brought or reusable, to zero. theThus, ecological the ecological footprint footprint in the isdemolition reduced during stage could the recycling be significantly phase. reduced or even brought to zero. Thus, the ecological footprint is reduced during the recycling phase. 4.4. Selection of Building Materials on a Rural House 4.4. Selection of Building Materials on a Rural House The consumption of building material is the main part of the ecological footprint, so the choice The consumption of building material is the main part of the ecological footprint, so the choice of of building material is critical for building operation during the whole life-cycle. The greater the building material is critical for building operation during the whole life-cycle. The greater the amount amount of building materials, the greater the energy conversion rate, which leads to a greater of building materials, the greater the energy conversion rate, which leads to a greater ecological ecological footprint. The energy conversion rate of the building materials mainly corresponds to the footprint. The energy conversion rate of the building materials mainly corresponds to the productivity productivity required to produce these materials. The more complex the production processes of the required to produce these materials. The more complex the production processes of the building building materials are, the greater the investment in human and material resources, which leads to a materials are, the greater the investment in human and material resources, which leads to a greater greater energy conversion rate. Bricks and concrete eco-footprints are a big part of the ecological energy conversion rate. Bricks and concrete eco-footprints are a big part of the ecological footprint, with footprint, with the second being the power ecological footprint of the construction phase. Among the the second being the power ecological footprint of the construction phase. Among the various building various building materials, the energy conversion rate of concrete is the highest, followed by glass, materials, the energy conversion rate of concrete is the highest, followed by glass, steel, and brick, which steel, and brick, which are the main building materials in traditional house construction (Figure 11). Therefore, when choosing building materials, one should consider using building materials with a Buildings 2018, 8, 92 12 of 19

Buildings 2018, 8, x FOR PEER REVIEW 12 of 19 Buildingsare the main2018, 8 building, x FOR PEER materials REVIEW in traditional house construction (Figure 11). Therefore, when choosing12 of 19 buildinglow-energy materials, conversion one should rate, rather consider than using a high building-energy materials conversion with rate, a low-energy to reduce conversion the ecological rate, low-energy conversion rate, rather than a high-energy conversion rate, to reduce the ecological ratherfootprint than of athe high-energy rural house. conversion rate, to reduce the ecological footprint of the rural house. footprint of the rural house.

Figure 11. The ecological footprint of consumption items of a rural house in the whole life-cycle. Figure 11. TheThe ecological footprint of consumption items of a rural house in the whole life-cycle.life-cycle. 5. Comparison with Multi-Level Residence 5. Comparison with Multi Multi-Level-Level Residence The advantages and the disadvantages of the rural house and the multi-layer residence are The advantages and the disadvantages of the rural house and the multi-layermulti-layer residence are studied in depth, as well as favorable design strategies in the urban house, are compared and studied in in depth, depth, as as well well as favorable as favorable design design strategies strategies in the in urban the house, urban are house, compared are compared and analyzed. and analyzed. Furthermore, how to introduce the modern life style to rural areas while reducing energy analyzed.Furthermore, Furthermore, how to introduce how to theintroduce modern the life modern style to life rural style areas to rural while areas reducing while energy reducing to provide energy to provide guidance for designing low-carbon rural houses is also studied. toguidance provide for guida designingnce for low-carbondesigning low rural-carbon houses rural is also houses studied. is also studied. 5.1. Calculation of Ecological Footprint of Multi-Level Residence 5.1. Calculation of Ecological Footprint of Multi Multi-Level-Level Residence The multi-layer residence chosen in this article is located in the Liaohua chemical industrial park The multi multi-layer-layer residence chosen in this article is located in the Liaohua chemical industrial park of Liaoyang. It is a 6-level concrete structure building with a total land area of 5250 m22, construction of Liaoyang. It is a 6 6-level-level co concretencrete structure building with a total land area of 5250 mm2, construction area of 5613.54 m2, 20.44 m in height, 11.84 m in depth, and 74.4 m in length (Figure12). Its energy area of 5613.54 m2,, 20.44 m in height,height, 11.8411.84 mm inin depth,depth, andand 74.474.4 mm inin lengthlength (Figure(Figure12). 12). Its Its energy saving rate was 65% with routine energy-saving measures such as an exterior insulation system and saving rate was 65% with routine energy energy-saving-saving measures such as an exterior insulation system and double glazing. double glazing.

Figure 12. Standard layer of the multi-layer residence. Figure 12. Standard layer of the multi multi-layer-layer residence. Calculating the whole life-cycle (design, construction, operation, and demolition in four stages) Calculating the whole life-cycle (design, construction, operation, and demolition in four stages) the ecologicalCalculating footprint the whole of life-cycle the multi (design,-layer residence construction, was operation, based on and a run demolition time of in50 four years. stages) The the ecological footprint of the multi-layer residence was based on a run time of 50 years. The thecalculation ecological process footprint of of the the whole multi-layer life-cycle residence ecological was based footprint on a run of time the of multi 50 years.-layer The residence calculation is calculation process of the whole life-cycle ecological footprint of the multi-layer residence is processconsistent of with the whole the rural life-cycle house. ecological The population footprint of the of themulti multi-layer-layer building residence is 210. is The consistent measured with data the consistent with the rural house. The population of the multi-layer building is 210. The measured data ruraland the house. results The of population the whole of life the-cycle multi-layer ecological building footprint is 210. of Thethe measuredmulti-layer data residence and the are results shown of the in and the results of the whole life-cycle ecological footprint of the multi-layer residence are shown in wholeTable 2, life-cycle and its ecological footprintcarrying capacity of the multi-layer is 2.147 ghm residence2 (Ec2 = are (1% shown–12%) in aj·rj·yj Table =2 ,0.88 and × its 0.525 ecological × 2.8 × Table 2, and its ecological carrying2 capacity is 2.147 ghm2 (Ec2 = (1%–12%) aj·rj·yj = 0.88 × 0.5252 × 2.8 × carrying1.66 = 2.147 capacity ghm2) is. 2.147 ghm (Ec2 = (1–12%) aj·rj·yj = 0.88 × 0.525 × 2.8 × 1.66 = 2.147 ghm ). 1.66 = 2.147 ghm2). Buildings 2018, 8, 92 13 of 19

Table 2. The ecological footprint calculation model of multi-layer residence.

Energy Per Capita Per Capita Solar Energy Corresponding Equilibrium Ecological Project Stage Consumption Items Original Data Conversion Energy Ecological Value/sej Land Type Factor Footprint/hm2 Rate/(sej/unit) Value/sej Footprint/hm2 Design stage Labor costs/$ 8622.4 5.20 × 1012 4.48365 × 1016 2.13507 × 1014 6.14827 × 10−7 Construction land 2.8 0.00036 Wood/g 41,524,525 4.40 × 108 1.82708 × 1016 8.70038 × 1013 2.50541 × 10−7 Woodland 1.1 5.7875 × 10−5 Red brick/g 97,364,027 2.60 × 109 2.53146 × 1017 1.20546 × 1015 3.47131 × 10−6 Arable land 2.8 0.00204 Hollow block/g 898,493,730 2.80 × 1010 2.51578 × 1019 1.19799 × 1017 0.000344981 Construction land 2.8 0.20284 Gravel/g 903,291,280 1.00 × 109 9.03291 × 1017 4.30139 × 1015 1.23865 × 10−5 Fossil energy land 1.1 0.00286 Cement/g 162,189,614 2.30 × 109 3.73036 × 1017 1.77636 × 1015 5.11532 × 10−6 Fossil energy land 1.1 0.00118 Cement tile/g 6,043,805 2.30 × 109 1.39008 × 1016 6.61941 × 1013 1.90616 × 10−7 Fossil energy land 1.1 0.00004403 Concrete/g 5,156,518,149 2.80 × 1010 1.44383 × 1020 6.87536 × 1017 0.001979868 Fossil energy land 1.1 0.45734 Lime/$ 1863 5.20 × 1012 9.6876 × 1015 4.61314 × 1013 1.32843 × 10−7 Construction land 2.8 0.0000781 Asphalt/$ 7718 5.20 × 1012 4.01336 × 1016 1.91112 × 1014 5.50338 × 10−7 Construction land 2.8 0.00032 Steel/g 11,903,783 4.20 × 109 4.99959 × 1016 2.38076 × 1014 6.85576 × 10−7 Construction land 2.8 0.00040 Insulation mortar/$ 4216 5.20 × 1012 2.19232 × 1016 1.04396 × 1014 3.00625 × 10−7 Fossil energy land 1.1 6.94444 × 10−5 Construction stage Coating/$ 14,162 5.20 × 1012 7.36424 × 1016 3.50678 × 1014 1.00983 × 10−6 Construction land 2.8 0.00059 Plastic pipe/$ 13,482 5.20 × 1012 7.01064 × 1016 3.3384 × 1014 9.61345 × 10−7 Construction land 2.8 0.00056 Glass cloth/$ 3223 5.20 × 1012 1.67596 × 1016 7.98076 × 1013 2.29819 × 10−7 Construction land 2.8 0.00013 Glass/g 137,415,600 7.90 × 109 1.08558 × 1018 5.16944 × 1015 1.48862 × 10−5 Construction land 2.8 0.00875 Water/g 769,900,000 6.60 × 105 5.08134 × 1014 2.41969 × 1012 6.96787 × 10−9 Waters 0.2 2.9265 × 10−7 Electricity/J 1,622,232,000 1.60 × 105 2.59557 × 1015 1.23599 × 1013 3.55922 × 10−8 Construction land 2.8 0.000020 Cylindrical cast-iron radiators /$ 14,363 5.20 × 1012 7.46876 × 1016 3.55655 × 1014 1.02417 × 10−6 Construction land 2.8 0.00060 Labor costs/$ 138,929 5.20 × 1012 7.22431 × 1017 3.44015 × 1015 9.90645 × 10−6 Construction land 2.8 0.00582 Machinery costs/$ 49,035 5.20 × 1012 2.54982 × 1017 1.2142 × 1015 3.49648 × 10−6 Construction land 2.8 0.00205 Finished doors/$ 16,973 5.20 × 1012 8.82596 × 1016 4.20284 × 1014 1.21027 × 10−6 Construction land 2.8 0.00071 Other costs/$ 11,766 5.20 × 1012 6.11832 × 1016 2.91349 × 1014 8.38984 × 10−7 Construction land 2.8 0.00049 Building wastes - - - - 3.00857 × 10−5 Construction land 2.8 0.00631 Water/g 6,078,240,000 6.60 × 105 4.01164 × 1016 1.9103 × 1014 5.50102 × 10−7 Water 0.2 0.0000231 Electricity/J 5.95728 × 1012 1.60 × 105 9.53165 × 1017 4.53888 × 1015 1.30704 × 10−5 Construction land 2.8 0.00768 − Operation stage Heating costs/$ 900,886.5 5.20 × 1012 4.68461 × 1018 2.23077 × 1016 6.42384 × 10 5 Construction land 2.8 0.03777 Gas/$ 80,892 3.93 × 104 3,179,055,600 15,138,360 4.35933 × 10−14 Fossil energy land 1.1 1.00701 × 10−11 Other costs/$ 560,795.52 5.20 × 1012 2.91614 × 1018 1.38864 × 1016 3.9988 × 10−5 Construction land 2.8 0.02351 Demolition stage Building wastes - - - - 0.000460649 Construction land 2.8 0.09673 Total ecological 0.85942 footprint Buildings 2018,, 88,, 92x FOR PEER REVIEW 14 of 19

5.2. Comparison of Sustainability Assessment on Two ResidencesResidences The life-cyclelife-cycle ecological footprint of the multi-layermulti-layer residence waswas 0.8590.859 ghmghm22 and the ecological carrying capacity was 2.147 ghmghm2,, which is higherhigher thanthan thethe ecologicalecological footprint.footprint. Additionally, the multi-layermulti-layer residence was in a state of ecological surplus with the impactimpact on the environment within the carrying capacity scope of the area. Moreover, it can be seen that the plan design, profileprofile design of ventilation and and heating heating insulation, insulation, heating, heating, and and insulation insulation measures measures of ofthe the building, building, such such as the as theexternal external wall wallinsulation insulation,, double double glazing glazing and central and central heating, heating, and the and operation the operation mode of mode the multi of the- multi-layerlayer residence residence played played a good a goodenergy energy-saving-saving effect effect [22,23], [22 ,23which], which reduced reduced the theload load of the of the house house to tothe the environment. environment. Figure 13 is a comparisoncomparison between the ecological footprint of the Wafangdian farm house and the multi-layermulti-layer residence, both of which werewere inin aa statestate ofof sustainablesustainable development.development. TheThe ecologicalecological footprint indexindex ofof the the multi-layer multi-layer residence residence was was 60% 60% and and the the rural rural house house was was 53%, 53%, which which indicates indicates that thethat sustainability the sustainability of the of multi-layerthe multi-layer residence residence is higher is higher than than that that of the of ruralthe rural house. house. However, However, in the in processthe process of the of ecologicalthe ecological footprint footprint calculation, calculation, the usethe use of residential of residential decoration decoration and and furniture furniture are notare considered.not considered. Multi-layer Multi-layer residences residences generally generally consume consume more more in this in this area area than tha low-leveln low-level residences, residences, so itsso actual its actual ecological ecological footprint footprint index index should should be less be than less 60%. than The 60%. difference The difference of the ecological of the ecological footprint indexfootprint between index thebetween two types the two of residencetypes of residence should be should less than be less 7%. than It can 7%. be It seen can be from seen Figure from 14Figure, the per14, the capita per ecologicalcapita ecological carrying carrying capacity capacity of the multi-layerof the multi residence-layer residence was far was less far than less the than rural the house. rural Thehouse. reason The forreason this for is that this the is that per capitathe per construction capita construction land area land in the area village in the is village much largeris much than larger that inthan the that urban in the areas. urban The areas. per capita The per ecological capita ecological footprint of footprint the multi-layer of the multi residence-layer wasresidence 0.004 ghm was2 0.004/cap andghm the2/cap rural and house the was rural 0.010 house ghm was2/cap, 0.010 which ghm demonstrates2/cap, which that demonstrates the load on the that environment the load oncaused the byenvironment the multi-layer caused residence by the multi was-layer far less residence than that was by far the less rural than house. that by Thus, the rural thedesign house. strategiesThus, the ofdesign the multi-layer strategies of residence the multi used-layer during residence the design, used during construction, the design, and operationconstruction, stages and are operation worthy

ofstages reference. are worthy of reference.

2

/ghm

carrying capacity

and

cologicalfootprint E

Figure 13. The comparison of sustainability assessment of two kinds of houses.

Buildings 2018, 8, 92 15 of 19 Buildings 2018, 8, x FOR PEER REVIEW 15 of 19

Buildings 2018, 8, x FOR PEER REVIEW 15 of 19

2

2

/ghm

/ghm

carrying capacity carrying

carrying capacity carrying

and

and

er capita ecological footprint footprint capita er ecological

P

er capita ecological footprint footprint capita er ecological

P

Figure 14. The comparison of per capita ecological footprint of the two houses. Figure 14. The comparison of per capita ecological footprint of the two houses. 5.3. Whole Life-Cycle Comparison on Two Residences 5.3. Whole Life Life-Cycle-Cycle Comparison on Two ResidencesResidences The proportion of the multi-layer residential ecological footprint in the design stage (Figure 15) The proportion of the multi-layermulti-layer residential ecological footprint in the design stage (Figure 15)15) was small, approximately 81% in the construction stage, about 8% in the operation stage, and around was small, approximately 81% in the construction stage, about 8% in the operation stage, and around 11% in the demolition stage. The proportion of the ecological footprint of the two kinds of residences 11% in the demolition stage. The proportion of the ecological footprint of the two kinds of residences were both large during the construction stage. During the construction stage, the ecological footprint were both largelarge during the construction stage. During the construction stage, the ecological footprint was mainly composed of four parts: labor, machinery, materials, and construction waste. The ways was mainly composed of four parts: labor, machinery, materials,materials, andand constructionconstruction waste.waste. The ways to reduce the ecological footprint in the construction stage were to increase the amount of factory to reduce thethe ecologicalecological footprint in the construction stage were toto increase the amount of factory prefabricated materials and use mechanized operations. The most important measure was to choose prefabricated materials and use mechanized operations. The most important measure was to choose building materials with less ecological footprint. The per capita ecological footprint of the multi-layer building materials with less ecological footprint. The per capita ecological footprint of the multi multi-layer-layer residence was significantly less than that of the rural house during the construction and operation residence was significantlysignificantly less than that of the ruralrural househouse duringduring thethe constructionconstruction and operationoperation stages, which indicates that within an amalgamated dwelling, the organized operation of centralized stages, which indicates that within an amalgamated dwelling, the organized operation of centralized heating and air supply can effectively reduce the ecological footprint and resource consumption heating and air supply can effectively reduce the the ecological ecological footprint and resourceresource consumption consumption (Figure 16). Therefore, when designing the rural house, the centralized heating and daily energy (Figure(Figure 16 16).). Therefore, Therefore, when when designing designing the the rural house, the centralized heating and daily energy consumption system should be considered to make rational use of the abundant renewable resources consumption system should be considered to make rational use of the abundant renewable resources in village areas. in village areas.

Figure 15. The proportion of multi-layer residential ecological footprint in each stage. Figure 15. The proporti proportionon of multi multi-layer-layer residential ecological footprint in each stage. BuildingsBuildings2018, 20188, 92, 8, x FOR PEER REVIEW 16 of16 19 of 19 Buildings 2018, 8, x FOR PEER REVIEW 16 of 19

FigureFigure 16. 16. The The comparison comparison of per of capitaper capita ecological ecological footprint footprint of two of residences two residences in whole in wholelife-cycle. life -cycle. Figure 16. The comparison of per capita ecological footprint of two residences in whole life-cycle. 5.4.5.4. Comparison Comparison of Mainof Main Consumption Consumption Items Items on the on Two the TwoResidences Residences 5.4. Comparison of Main Consumption Items on the Two Residences TheThe main main building building materi materials inals the in ruralthe rural house house and theand multi the multi-layer- layerresidence residence are concrete, are concrete, bricks bricks oror Theblocks, blocks, main sand sand building and and more. materialsmore. Figure Figure in17 theis 17 a ruralissummary a summary house comparison and comparison the multi-layer icon oficon the of residencehigher the higher per are capita per concrete, capitaecological bricksecological orfootprint blocks,footprint sand of oftwo and two kinds more. kinds of Figure residencesof residences 17 is for a summary mainfor main consumption comparisonconsumption items, icon items, to of demonstrate the to higherdemonstrate perthat capita the that ecological ecologicalthe ecological footprintfootprintfootprint of of two ofblocks blocks kinds or ofbricks,or residencesbricks, concrete, concrete, for labor, main labor, and consumption andelectricity electricity consumed items, consumed to demonstrateduring during the operation the that operation the stage ecological are stage are footprintmuchmuch higher of higher blocks than than or during bricks, during others. concrete, others. labor, and electricity consumed during the operation stage are much higherConcreteConcrete than and duringand blocks blocks others. or bricksor bricks were were used used as the as mainthe main building building materials materials of the oftwo the residences two residences envelopenvelopConcretee structure.e structure. and blocks The The sum or sum bricks of the of were theper percapita used capita ecological as theecological main footprint building footprint of these materials of thesebuilding ofbuilding thematerials two materials residences for the for the enveloperuralrural house structure. house was was significantly The significantly sum of thehigher higher per than capita than the ecological multithe multi-layer footprint-layer residence, residence, of these which building which indicates indicates materials that the that for per the per ruralcapitacapita house resource resource was significantly consumption consumption higher of the of thantheenclosure enclosure the multi-layer structure structure of residence, the of multi the multi- whichlayer- layerresidential indicates residential building that the building perwas capita far was far resourcelessless than consumption than that that of of the of the rural the rural enclosure house. house. Regarding structure Regarding of the the gravelthe multi-layer gravel and electricityand residential electricity consumption building consumption was during far less during the than the thatoperationoperation of the rural stage, stage, house. the the per Regarding per capita capita ecological the ecological gravel footprint and footprint electricity of the of rural the consumption rural house house was far duringwas higher far the higher than operation the than multi the stage,- multi- layer residence. Vis-a-vis the multi-layer residential structure, the construction methods and mode the perlayer capita residence. ecological Vis-a footprint-vis the multi of the-layer rural residential house was structure, far higher the than construction the multi-layer methods residence. and mode of operation were more conducive to save energy and operating supplies. Architects should to take Vis-a-visof operation the multi-layer were more residential conducive structure, to save the energy construction and operating methods supplies. and mode Architects of operation should were to take full account of how to use the advantages of the multi-layer residence in the construction of a rural morefull conducive account toof savehow energyto use the and advantages operating supplies. of the multi Architects-layer residence should to in take the full construction account of of how a rural house as well as how to transform the disadvantages of the rural house into advantages. to usehouse the advantagesas well as how of the to multi-layertransform the residence disadvantages in the construction of the rural ofhouse a rural into house advantages. as well as how to transform the disadvantages of the rural house into advantages.

Figure 17. The comparison of main items of two residences. FigureFigure 17. 17.The The comparison comparison of main of items main of items two residences. of two residences. Buildings 2018, 8, 92 17 of 19

5.5. Analysis of Comparative Results Although the overall life quality and public infrastructure in the village areas are far less than those in urban areas, the per capita ecological footprint of the rural house was higher than the multi-layer residence, which indicates that sustainability in rural areas is weaker. Through the comparative analysis of the two houses, in this paper, the reasons are as follows: The multi-layer residence mentioned above was mainly six layers, and a large part of enclosure structures of residential buildings such as walls, floor layers, and other components were for two families in the rural house. The per capita enclosure structure area was relatively small, as well, the amount of per capita building materials was relatively less. Based on these differences, the ecological footprint of the multi-layer residence will drop a lot. However, the rural house was a 1-layer house that was built mostly by users at different times, with a rare case of a common building enclosure resulting in a larger consumption of building materials. The multi-layer residence construction was implemented centrally by developers. Although there were still many shortcomings in the construction stage, compared to the rural house, the multi-layer residences remained centralized, mechanized, and organized, which correspondingly saved labor and material resources, and reduced a lot of the waste; The per capita construction area of the multi-layer residence was small, while the rural per capita housing floor space was relatively large. When the building area was the same, the external wall area of the urban multi-layer residence was smaller than that of the rural independent house, thus the heat flowing outdoors and the heat loss in winter were less in the urban multi-layer residence. Additionally, the heating energy consumption in winter was correspondingly less. Moreover, in summer, due to the small area of the urban building envelope, the received direct solar radiation was smaller, so there was an obvious corresponding decrease in cooling energy consumption; The height of the urban house was generally lower than that of the rural house with the pitched roof. When there was the same area, the per capita interior volume of the urban house was generally less than the rural house, thus the heating volume of the urban house in winter was less than that in the rural house, which results in savings in heating energy consumption to some degree; During the operation stage, the consumption of water, electricity, gas, and heating that are required in the urban house was delivered centrally, which reduced the unnecessary waste, while in the village area, the energy required to heat, cook and manufacture was provided by the tenants themselves. Moreover, many farmers burned coal or wood with low-energy efficiency for residence heating, which caused a large waste of the resource.

6. Conclusions By combining whole life-cycle assessment and ecological footprint theory, we are able to analyze and quantify the effect of the Wafangdian rural house and the multi-layer residence on environment. The higher the ecological footprint value, the larger the share of non-renewable fossil energy use; consequently, the share of the direct consumption of natural capital is larger and the Earth’s biological carrying capacity shrinks.

(1) The Wafangdian ecological footprint is 0.091 ghm2, which is significantly lower than its ecological capacity, making the ecological surplus within the ecological footprint index 53%. Compared to the rural house, the multi-layer residence has a higher sustainable level, with an ecological footprint index 60%. (2) The rural house ecological footprint of the construction stage is the largest at approximately 87%, the proportion in the operation stage is roughly 11%, and in the design and demolition stage nearly 1%. Thus, the reduction of the ecological footprint during the construction stage and operation stage can reduce the total ecological footprint of the whole life-cycle effectively. In addition, although the multi-layer residence only added external wall thermal-insulation and a few necessary energy-saving measures, the sustainability of the multi-layer residence was Buildings 2018, 8, 92 18 of 19

obviously superior to the rural house and the load on the environment caused by the multi-layer residence was far less than the rural house (The per capita ecological footprint of the multi-layer residence was 0.004 ghm2/cap, the rural house was 0.010 ghm2/cap). Thus, the rural house designer should draw on the strategies of the multi-layer residential design and construction methods, while operation modes should be centralized, planned, and constructed. The heating demand of residents should be settled centrally, which could reduce the unnecessary waste of energy and resources. (3) The ecological footprint of the demolition is mainly caused by the direct burial of construction waste, which occupies a large amount of farmland. Thus, the reduction and recycling of construction waste can effectively reduce the ecological footprint during the demolition stage. (4) Electricity and other maintenance take up a large proportion in the total ecological footprint during the operation stage. Therefore, the ventilating and passive cooling measures should be considered for the design in northern Chinese villages. (5) The consumption of building material is the principal aspect of the ecological footprint. Thicker building envelopes can improve the thermal performance of the building. However, a thicker building construction consumes greater building materials and increases the ecological footprint. Thus, when choosing building materials, architects should consider using building materials with a low-energy conversion rate and higher thermal performance indexes to reduce the energy conversion and the ecological footprint. The most important thing is to use local materials. (6) It can be drawn from the value of energy density (the radio of total energy value to residential land area), improving the intensification of construction land can effectively reduce the ecological footprint. The important measures to save the land area are to have reasonable overall planning, reduce the residential courtyard area appropriately, increase the house depth, and use the multi-layer residential forms as much as possible. There are many resources available in village areas, so one should give full consideration to the recycling of resources, which is also an effective way to increase the Earth’s ecological carrying capacity, making it conducive to human sustainable development.

Author Contributions: Conceptualization, M.L. and B.Z.; Methodology, M.L.; Software, B.Z.; Validation, J.Y.; Formal Analysis, M.L.; Investigation, M.L. and B.Z.; Resources, M.L.; Data Curation, M.L., B.Z. and J.R.; Writing-Original Draft Preparation, M.L., B.Z., J.R. and C.L., J.Y.; Writing-Review & Editing, M.L., B.Z., J.R., Q.H.; Visualization, M.L. and J.R., C.L., J.Y., Q.H.; Supervision, M.L.; Project Administration, M.L.; Funding Acquisition, M.L. Funding: The State Key Program of National Natural Science Foundation of China (Project No. 51638003) and the Fundamental Research Funds for the Central Universities (DUT17RW118). Acknowledgments: The authors gratefully acknowledge The State Key Program of National Natural Science Foundation of China (Project No. 51638003) and the Fundamental Research Funds for the Central Universities (DUT17RW118). Conflicts of Interest: Declare conflicts of interest or state “The authors declare no conflict of interest.” Authors must identify and declare any personal circumstances or interest that may be perceived as inappropriately influencing the representation or interpretation of reported research results. Any role of the funders in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript, or in the decision to publish the results must be declared in this section. If there is no role, please state “The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results”.

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