INSULATION AND AIR SEALING: CURRENT AND EMERGING TRENDS IN EUROPEAN MASONRY BUILDINGS
David Olivier, BSc, MlnstE, MASHRAE *
* Principal, Energy Advisory Associates, 8 Meadow Drive, Credenhill, Herefordshire, England, HR4 7EF. Tel.: Hfd. (0432) 760787. Fax. (0432) 760787-0088.
ABSTRACT ers routinely achieve U-values of less than 0 .2 Wtm2K, in both heavyweight and lightweight building structures. Across the world, the dominant form of buil Under changing conditions, two parameters aff ding construction is heavy, load-bearing mas ect the behaviour of superinsulated heavy onry or poured concrete, not timber- or steel weight buildings. As well as their thermal res frame. It is possible to make these buildings istance, discussed in the last paragraph, one very energy-efficient, but they present very must consider their thermal capacity. different problems from those associated with timber-frame buildings. The dynamic thermal behaviour of lightweight superinsulated buildings is stab1e, and fairly Much of the initial development of highly predictable. In response to a sudden heat input, energy-efficient masonry dwellings occurred in or the onset of a spell of cold weather, they Sweden, Denmark and Switzerland. However, heat up and cool down at a noticeable rate. the same principles are now being applied in However, high mass, superinsulated buildings other countries with a masonry building tradit have an exceptional level of thermal inertia, and ion. they behave in a way which is outside most Valuable lessons have been learned. As a rule, peoples' everyday experience. This has potent it is considerably easier to reach good airtight ial benefits, but also has a few disadvantages. ness in masonry buildings than in site-built Both are discussed. timber-frame ones. Conversely, to avoid therm With the aid of examples from Scandinavia, al bridges needs much greater care in load mainland Europe, north America and the UK, bearing masonry structures than in wooden this paper presents experience to date with the frame ones. improved insulation of masonry buildings and With care, very similar levels of insulation may attempts to reduce the level of air infiltration. be reached in masonry buildings and in timber Some noteworthy case studies are described. frame buildings. The comparison is seen most vividly in Denmark and Sweden, where design-
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INTRODUCTION and the need t o seal precast concrete compon ents, either w ith in situ concrete or w ith sealant, at joints. In addition, where these In the UK, Ireland, Denmark and mainland Eur elements of the building meet others, one must ope, most buildings are constructed of brick, provide a positive sealing detail, and all services stone, in situ concrete, concrete blocks, pre penetrations must be sealed. cast concrete and other heavy materials. The The first evidence that air sealing of masonry timber-frame construction used in North Amer buildings was relatively easy came from ica and most of Scandinavia is less common. Sweden, in the 1970s. At the time, the build This situation may well continue; the UK has ing code was being tightened to conserve just 8% forest cover, and it imports over 80% energy and airtightness testing was about to be of its timber. introduced. Table 1 shows some results of To achieve the expected performance, energy tests carried out then on buildings with a struc efficient buildings need good insulation, with no ture of concrete, brick or timber, or a mixture major cold bridges, well-designed glazing and of constructions; e.g., concrete walls and tim external doors, good air sealing and low vent ber roof. ilation heat loss. As a rule, it is a greater design There is a consistent tendency for the totally challenge to avoid cold bridging in masonry concrete structures to leak less than the timber buildings, but air sealing presents fewer ones. Without special efforts, their leakage was problems. This paper presents recent exper less than 3 ac/h at 50 Pa, which the Swedish ience with both. building code specified for detached houses Historically, with few exceptions, masonry from 1977 onwards, and often approached the buildings have been far less well-insulated than 1 ac/h at 50 Pa, which became a requirement timber ones. Even within a single country, like in 1978 for three-storey flats and taller Sweden, there was a timelag of some decades buildings. At the same time, Swiss experience between the widespread adoption of thermal was publicised 4 . This came to exactly the insulation in timber and in masonry buildings. same conclusion. Reasons are briefly discussed. Very low air infiltration was reported from proj U-values of below 0.2 W/m2 K in the external ects in Denmark, dating back to the 1970s and walls and ground floor, and below 0 . 15 W/m2 K early 1980s 5-7 . It was of the order of 0 .02- in the roof, are required by law in Sweden, 0.03 ac/h under normal w inter temperatures under its 1989 building code. Masonry build and windspeeds. ings; e.g., most blocks of flats, have to meet Air leakage as low as 0.2 ac/h at 50 Pa has the same standards. Although the building been achieved more recently on some state-of codes of Switzerland, Germany and the Nether the-art energy-efficient houses in Switzerland lands are less strict, several thousand equally and Germany 8·9 . This may correspond to infilt energy-efficient masonry buildings have been ration of some 0 .01 ac/h. built there 2 . Such figures seem to be lower than any result The most energy-efficient dwellings, numbering reported from t imber-frame buildings in perhaps 50, have gone even further. They have Sweden, where few houses leaked at a rate of achieved U-values of little more than 0.15 less than 0.6 ac/h at 50 Pa 10. It seems at W/m2 K. Along with stringent reductions in air least as tight as the best-sealed timber-frame leakage and ventilation losses, and improved houses reported from Canada. glazings, this has proved to be sufficient in temperate climates almost to eliminate space Moreover, these European houses had timber heating energy. roofs. The clear message is that buildings with concrete roofs would leak even less. In masonry construction, the airtight layer is AIR SEALING usually wet plaster or in situ concrete. Stand ard workmanship on this layer is usually suffic ient to give an acceptable result, as long as Buildings which employ 'heavy, wet' construct some details are done differently. The need for ion can achieve a good level of air sealing. greatest care arises at window and door open Provided that a few basic rules are followed, it ings, and services penetrations. Ways have is a fairly robust method, in this respect. been developed to give an acceptable level of These basic rules include the need for wet sealing here, almost always in accordance with plaster instead of plasterboard, the importance Danish experience. of fully-filled mortar joints in masonry walls, Most of the recent energy-efficient UK projects 218 have masonry walls and a timber pitched roof ope and the former USSR, where the coldest 11 -12. The external walls have been plastered, month is below -5°C, the thickness reached as to make them acceptably airtight. However, the much as 700 mm. roofs, being of timber construction, need a vap In heat loss terms, this was totally ineffective. our barrier. This polyethylene sheet has been 1 00 mm of mineral fibre has more thermal res trapped below a strip of reinforcing mesh, and istance than a medieval stone wall 3 m thick. It the plaster layer overlaps it. took a long time for this to be translated into To date, in terms of air leakage, vapour barriers actual building practice. have probably given more problems than any By the 1970s, several regions, notably Scand other part ofthe building. The UK building inavia and Switzerland, had learned that mas trade is inexperienced in the use of vapour barr onry buildings definitely needed insulation. iers, but well-practised in their misuse. This is Their regulations of this time generally specified largely because of ignorance and widespread 80-100 mm insulation. misinformation. For example, it is still widely believed that water vapour diffusion is respons Most other countries used no insulation in mas ible for most of the moisture transported onry walls until the late 1 9 70s _or even the through building structures, although it is well early 1980s. By then, such countries; e.g., known in building research circles that most Greece, Turkey, the UK, the Netherlands and occurrences of interstitial condensation are att Ireland, started to require some insulation. ributable to the physical movement of warm, Meanwhile, Denmark, which had used 50 mm moist air. to 100 mm insulation since the early 1960s, began to use 150 mm or even 200 mm in 'nor In addition, UK workmanship is definitely of a mal' buildings. lower standard than continental European countries. As a result, more robust details have In all these countries, the 'low-energy' masonry to be produced. For example, in situ concrete buildings constructed after the 1973 oil crisis floors and poured concrete walls are likely to all had 2-3 times as much thermal insulation as be tighter than precast floors or masonry walls. 'normal', whatever that was. As early as 1977, Otherwise, a higher rate of air leakage has to low-energy buildings in Denmark had walls with be accepted, for a masonry building, than up to 300 mm of insulation 14. The connection would be expected on the European mainland. between severity of climate and heat loss rem ained weak. Buildings of timber-frame construction undoubt· edly present greater problems than masonry buildings. However, they can be radically DYNAMIC THERMAL BEHAVIOUR improved. One UK example of energy-efficient timber-frame construction was the 1985-86 Two Mile Ash houses. These had leakage of Under changing conditions, a superinsulated 1 . 5 ac/h at 50 Pa 13. This level was considered heavyweight building behaves very differently exceptionally low for the UK; it may not have from a lightweight building of the same heat been equalled since in timber-frame. The same loss. Their static behaviour is the same, and care has to be applied to the timber roofs of this is the familiar quantity, but their dynamic otherwise heavyweight buildings. behaviour is very different. A lightweight structure responds faster to a THERMAL INSULATION change in internal temperature, or a change in external conditions, than a heavyweight one. This may be a reason why, in the past, far For years, masonry buildings right across poorer insulation was tolerated in masonry buil Europe, even in the colder climates of the east, dings than in timber buildings. had no thermal insulation. At the same time, Adding either thermal resistance or thermal timber-frame buildings in adjacent countries capacity lengthens the building's time constant, were being built with some insulation. The Dan Insulation was evidently used to alter the ish building codes of the 1 960s required insul behaviour of lightweight buildings. ation in timber frame buildings, but not in mas onry ones. Although they lost heat equally rapidly, med ieval stone buildings behaved in a different way The reasons are unclear. Historically, it was from timber-frame buildings. Once their mass noted that on going across Europe from the was heated to comfort temperatures, which maritime west to the severe winters of the might take a very long time, they stayed warm east, masonry buildings simply had thicker for a long time, despite being uninsulated. If brick walls. On reaching the boundary of Eur- 219 ( I
the heat input was cut off, a timber building energy, heavy buildings may be more comfort cooled very rapidly. able than lightweight ones. Sudden heat gains, from the sun or elsewhere, give rise to smaller The behaviour of superinsulated timber build temperature fluctuations. In a temperate clim ings is similar to that of minimally-insulated ate, if one wishes to eliminate the need for masonry buildings, of the type generally built in space heating energy by 'passive' means, the Europe today. The heat loss is reduced five- or use of high mass construction seems to be 1 0-fold relative to past practice, and a cooling important. This conclusion may be different in time constant of 50-75 hours is typical. Their cold climates. higher thermal resistance offsets their lower thermal capacity. The corollary is that, if prolonged over- or under-heating has occurred as a result of cont However, the behaviour of superinsulated mas rol failure, it is hard to alter the internal temper onry buildings transcends modern experience. ature rapidly. This may need cultural shifts to They are characterised by a cooling time const be accepted, or people may welcome operative ant of hundreds or thousands of hours. 500 temperatures which change extremely slowly, hours is typical of an above-ground masonry or and, unlike normal buildings, are virtually concrete structure; 1,000 hours is possible. always within the ASHRAE comfort zone. See Table 2. An earth-sheltered structure resp onds even more slowly, because so much of its envelope is coupled to the earth, not to the HEAVYWEIGHT BUILDING ELEMENTS outside air. Their thermal response is more sluggish than that of medieval European churches. Changes ROOFS in internal temperature, which may be caused Most roofs can be classed as pitched timber by either an internal free heat input, the onset structures or flat concrete ones. The former of sunny weather, or a sudden change in exter present basically the same problems, and the nal temperature, are dampened and delayed. same opportunities for insulation, as North Short of opening the windows or doors, signif American roofs. icant shifts take weeks or months to be felt. The latter are increasingly being treated as inv In the most extreme case, the temperature may erted roofs. The insulation is outside the water change by less than 1 K between the beginning proofing/vapour barrier. In a concrete roof, of a month and the end. The internal temperat there is usually nowhere within the structure ure profile shows little daily variation; over a where insulation could be sited. series of sunny February days, with over 20% of the floor area in south-facing glazing, the air Turf-covered roofs are a new departure in the within the heavy masonry building only heats UK. From an insulation and waterproofing view up by 2.5 K, falling back slowly later. A low point, the bulk of them have been treated as mass building of the same heat loss and same inverted concrete roofs, and extruded polystyr glazed area overheats to the point of discomf ene has been used. ort, rising from an air temperature of 20 to However, there are still very few earth-shelt 27°C within hours; Figure 1. The dwelling ered buildings. The protective effect of the turf construction details are taken from a compan may be found to lengthen the membrane life ion paper to this conference 15. span, to virtually the same lifespan as the rest For this reason, Swiss architects found that the of the building structure. If so, more 'warm' U.S. work on passive solar houses was actually flat roofs may be used; they can use cheaper, far more readily-applied to the buildings const and perhaps less environmentally-harmful, ins ructed in central Europe. These were so heavy ulation materials. weight that they could absorb the solar gains without overheating 16. WALLS This thermal sluggishness could be a problem, in buildings which need a large energy input for Today, heavyweight building practice varies space heating. It almost rules out intermittent w idely between countries. This reflects differ heating, and the attendant energy savings. ent traditions, and also reflects building However, where the mean solar and internal practice in those regions before the advent of gains, combined, are enough to heat the build thermal insulation. ing, it may be an advantage, as the building is There is as much diversity as with timber-frame always comfortable. walls. However, walls can be broadly divided Once one has reached ultra-low space heating into two classes, according to the position of 220 the insulation. In situ polyurethane foam has extraordinary abilities to seal cracks and gaps, but it has not Cavity masonry walls dominate northern Eur been widely-applied this way yet. This is appar ope; e.g., the UK, Ireland, the Netherlands, ently because of a 'catch-22' situation; it is too Denmark and north Germany. Here, the insulat expensive as a one-off job, and it will not be ion goes in the cavity. Solid masonry walls used in. bulk until it is cheaper. dominate central and southern Europe; e.g., Germany and Switzerland. Here, the insulation Virtually the only advantage of using plastic usually goes on the outside. In Sweden and foams seems to be their lower thermal cond Norway, where masonry walls are used, in flats uctivity, and the thinner wall which results for or offices, they are usually cavity walls. a given thermal resistance. It appears that it is usually cheaper to design a thicker wall and Internal insulation is not considered further. It is insulate it with a cheaper material. ineffective in well-insulated masonry buildings, as it leads to extensive thermal bridging. It also There are limits to the width of insulation in gives the building a dynamic behaviour more masonry walls. The first is the structural be like that of lightweight buildings. haviour of wide cavity walls. Danish plastic wall ties, developed for use in cavity walls, The cavity wall did not develop because it was stop at a length corresponding to a cavity a good place to put the insulation. It developed thickness of 250 mm. Beyond this, there is because, in cold, wet climates, it was a good much doubt over whether a cavity wall func way to keep the water out of the building. tions as a single unit. If it does not, one must Following a spate of cavity failures in the UK in use a self-supporting outer leaf, thickened with the 1970s, this has given rise to claims that piers. full cavity fill raises the risk of water penetration. In solid walls with external insulation, the main limit is the strength of the bond between the For several reasons, a clear cavity no longer insulation and the masonry, and the bending seems so appropriate. The energy-efficient forces exerted. Until about 1 988, the usual buildings now constructed in the Netherlands, limit to insulation thickness was around 180 Germany, and all the new buildings in Den mm. Now, systems for 350 mm insulation, mark, have 1 25 mm or more insulation in the either high-density mineral fibre or expanded cavity, not 50 mm. It is generally agreed that polystyrene, are available from German comp wide cavities are considerably less prone to anies. problems. The most common defect, namely mortar lumps which totally span the cavity, is 'Normal' energy-efficient buildings in Denmark actually quite difficult to replicate when the gap are still using only 200 mm wall insulation, and to be bridged is 150 mm. in the UK and Germany they are using around 150 mm. The ability to 'expand' to 250 mm in Second, it is worth considering experience from cavity walls and 350 mm iri solid walls should Denmark, the country with the most experience suffice for the foreseeable future. of insulating brick cavity walls. Its west coast suffers from horizontal driving rain, but res Table 3 indicates the wall thicknesses implied earch was done 25 years ago to determine by high, and very high, levels of insulation whether cavities fully-filled with mineral fibre (characteristic of so-called 'low energy' and caused water penetration. At the time, 80 to 'zero-energy' houses in Germany and the UK. 100 mm cavities were prevalent. The U-values are respectively 0.2-0.25 and 0. 1-0.12 (respectively, R-4 to -5 and R-8 to - The answer was that with reasonable work 10). manship, insulation did not cause water prob lems, and with poor workmanship, even empty In the extreme case, to get the lower U-value, cavities led to water penetration. The need for one ends up with a 600 mm (2 ft.) thick wall. satisfactory workmanship was paramount. If To readers from 'timber-frame' countries, this condition was satisfied, fully-filled cavities where 300 mm constitutes a very thick wall, were the best strategy to save energy at these are massive structures. However, they moderate cost. confor.m closely to the vernacular architecture of Europe, pre-1850. This was dominated by There are more doubts over the water resist thick masonry walls, 400-800 mm thick. ance of walls filled with the other insulating materials, such as plastic foams. However, We have come full circle, back to the thick some cavity walls are being built in the Neth wall. The main change is that the centre of this erlands and sheltered parts of the UK which are new wall is filled with insulation, not masonry fully-filled with expanded or extruded polystyr rubble, and its thermal resistance is 5 to 10, ene, or with polyurethane foam slabs. not 0.4-1 m 2 K/W. With the same thermal insul- 221 ation levels elsewhere in the building, it can be on the above-ground walls. Ge.rman and Swiss heated mainly by the occupants; the roaring designers have also used cellular glass in this fire so typical in the past, even in moderate situation, albeit at substantially higher cost. climates, is not needed. In the context of modern energy-efficient buildings, it is too early to comment on UK basement insulation. A few insulated base GROUND FLOORS ments have been specified for non-domestic buildings, generally with external insulation of extruded polystyrene or cellular glass. Ground floors can be divided into concrete slabs-on-ground, suspended concrete floors and In a recent building at the University of East basement foundations. Timber suspended Anglia, Norwich, England, the cellar retaining floors are becoming rarer, and are not wall has been insulated externally with 100 discussed. mm extruded polystyrene, but the cavity wall continues down below ground as far as poss Except perhaps in areas of deep, well-drained ible. At the transition point between masonry sandy soil, experience suggests that floors built and reinforced concrete, lightweight concrete on the ground need full insulation. In Denmark, block is used, and the insulation layers overlap. it was found advisable for heated basements, This gives an entirely acceptable path length, at and foundations in general, to be almost as the overlap. well-i'nsulated as the structure above the ground 17. Suspended ground floors Cel!ars With rising timber costs, and worsening ground conditions, suspended concrete ground floors Basements have been rare in the UK since the have become common in the UK. Usually, in 1 9th century, but may return. On the mass housing, rigid insulation is laid above a shrinkable clay soils which prevail in south-east beam-and-block floor and chipboard is laid on England, foundations must now be 1 .5 m deep; top, in a floating floor arrangement. the extra excavation needed to form a cellar is modest. In urban areas, basements make better This arrangement is not very durable, and being use of scarce land, and are routinely used in dry construction, has a risk of air leakage. To non-domestic buildings. In earth-sheltered give a more robust construction, one can use structures built into a south-facing slope, base proprietary, 50-150 mm thick polystyrene ment-style construction is used. formwork as permanent shuttering, on a base of precast concrete beams. This gives an air In Sweden, almost without exception, new tight, fairly well-insulated ground floor, albeit dwellings have concrete slabs on ground, with with an insulation layer of uneven thickness. a layer of high-density mineral fibre below the slab. Concrete basements, where used, may Some builders who want even more insulation utilise external mineral fibre insulation and than this have placed a sand-cement screed drainage only, without active waterproofing. above the insulation, on top of a beam-and block floor. Up to 1 50 mm expanded polystyr In Germany, cellars are a virtual requirement, ene has been used in this way. but insulation is not, even where the cellar is within the thermal envelope. To date, the best Concrete slab-on-ground example of proper insulation is the 1 6 Darm Concrete slab-on-ground foundations are ins stadt ultra low-energy houses. The cellar ceiling ulated either below or above the slab. A subs was insulated and a course of lightweight conc tantial level of insulation is being used in rete concrete blocks, with insulating mortar, energy-efficient buildings, up to 100 mm extr was used in the external walls, to achieve cont uded polystyrene or 200 mm of expanded poly inuity in the insulation layer at this point. See styrene. Figure 2. Whole floor insulation is being used. On one UK In Switzerland, the most effective insulation project with perimeter insulation only, the floor system to date was applied to the ten Wadens heat loss was surprisingly high 18. In the cont wil zero-energy and ultra-low energy houses. ext of low-energy buildings, the consequences Here, a heated cellar was specified. A reinf seem far too high to risk omitting the insulat orced concrete raft was used to spread the ion. load, and the 3.5-storey concrete buildings were supported on a layer of 1 20 mm extruded Most UK projects are using expanded or extr polystyrene. This achieved total continuity with uded polystyrene. Few clients seem able or the 150 mm extruded polystyrene on the cellar willing to pay the extra cost of high-density walls, and the 1 80 mm extruded polystyrene mineral fibre or cellular glass. 222 Unless care is taken, there is a cold bridge at such buildings must have air leakage of < 3 the foundations; the floor insulation fails to m3/h per m 2 external envelope area, at 50 Pa. meet the wall insulation. Research in Denmark For a four-storey block, this translates as < 1 showed that the most effective way to reduce ac/h at 50 Pa 20. edge heat losses was to use lightweight One existing heavyweight, superinsulated UK concrete blocks in the inner leaf of a cavity house has given a far superior standard of sum wall, and to extend this construction 0.6 m mer comfort to conventional buildings, even below ground. high-mass ones with no insulation 21 . This was In Germany, the same detail has been used in the most unexpected result of the project, solid walls; Figure 3 . There are even ways to which was designed principally to reduce win achieve continuity of the insulation, without ter space heating costs. even interrupting it by lightweight concrete At least one heavyweight Swiss office building block. To do this, one uses load-bearing insulat provided operative temperatures which were al ion, such as cellular glass. This approach has ways in the range 18-23 °C, and never changed been restricted by the high cost. by more than 0 .2 K per hour in summer, or 0 .1 K/hour in winter. Although these temperatures could not be changed rapidly, they proved very CASE STUDIES acceptable to the occupants. The temperature next day, and the appropriate level of clothing, could be forecast by reference to the temperat It is too early to be definitive, but some super ure history of the last week 22. insulated heavyweight buildings in the UK are giving excellent results. The air leakage is low, and so is the resulting energy costs for space LOW EMBODIED ENERGY - DOES IT heating. RULE OUT HEAVY BUILDINGS? In Scandinavia, the Netherlands, Germany and Switzerland, the evidence is conclusive. Such buildings perform as well as timber-frame ones In the UK, the embodied energy used to cons of the same insulation level, and they are less truct buildings has attracted much attention difficult to build. and misunderstanding. While important, it is The first UK example is a masonry and conc emphatically a second order effect, and it is rete earth-sheltered structure built at Caer Lian, bizarre to pay as much attention to this as to Monmouth, South Wales, in 1988. It is basic reducing the amount of energy consumed to ally a well-insulated, passive solar, single-storey heat and light the building. The latter is an building, partly buried in a south-west-facing order of magnitude greater. bank. It is insulated with 15-100 mm polyur One's first assumptions can be counterintuitive. ethane foam, and the S.S.W-facing windows In timber-importing countries, the more favour are argon-filled double glazing 19. able forms of heavyweight construction do not It cost some £330 per m2, excluding the own necessarily take any more 'embodied' energy er's management time in acting as general than a timber-frame building of the same insul contractor. This was the same as a convent ation level 23. The materials to avoid are gen ional new building. erally clay bricks, and unnecessary use of reinf orcing steel in concrete, in circumstances Since completion, Caer Lian has used no fossil where a somewhat greater thickness of mass fuel for space heating and cooling. The air concrete would suffice. temperature has remained in the range 18-24 °C. The only energy cost for space cond A poster paper at this conference contains det itioning has been £110/year worth of electricity ails of a project where this issue will be a des to operate the mechanical ventilation system, ign criterion. The embodied energy of the main and even this could be reduced, if the design elements of this building should be 30% lower was replicated, by using larger ducts and more than normal UK buildings, despite a more rob efficient fans. ust external wall construction, and a thermal resistance four times higher than normal 24. The second example is a recent block of stud ent residences at the University of East Anglia. Unless it obtains its energy supply entirely from They are built of dense concrete masonry, with renewable sources, even an ultra-low-energy insulated cavity walls, concrete upper floors building consumes more fossil fuel to operate and flat concrete roof. Preliminary results sugg over its life cycle than it takes to build. If total est that they may be as tight as typical new demolition is needed every 250 years, and Swedish multi-family buildings. In Sweden, more energy must then be reinvested in a new 223 ~- ......
structure, the construction energy is about 11 P J Webster, The Salford Low-Energy 20% as much as the operating energy. This House: A Demonstration at Strawberry Hill, assumes that 360 GJ is taken to build a 1 00 Salford. Dept. of Civil Engineering, Salford m2 house, and 8 GJ/yr of fossil fuel is used to Univ., for BRCESU, Building Research operate it. The answer may be to design and Establishment (November 1987). build structures to last many centuries, not 12 Robert and Brenda Vale, "Low Energy Cott decades. ages", J. CIBSE, pp 19-23 (February 1992). 13 David Olivier, The Energy Scene in Scandin REFERENCES AND NOTES avia: Research, Development and Practice. EAA, Hereford ( 1984, reprinted 1987, 1992). 14 Paul A Ruyssevelt et al, "Experience of a 1 David Olivier and Derek Taylor, "The Energy Year Monitoring Four Superinsulated Houses". Showcase", paper presented to this confer Proc. 1st Cont. on Superinsulation. The Solar ence. Energy Society, London (1987). 2 David Olivier, Energy Efficiency and 15 The descriptions of these dwellings are Renewables: Recent Experience on Mainland given more fully in ref. 1, op. cit. Europe. Energy Advisory Associates, Hereford, 16 Ref. 2, op. cit. England ( 1 992). 17 Ref. 6, op. cit. 3 See the relevant chapter of Air Infiltration Control in Housing: A Guide to International 18 R C Everett, et al, Linford Low Energy Practice. Document D2: 1983. Swedish Council Houses. Report ETSU-S-1025. Energy and for Building Research, Stockholm in association Environment Research Unit, Open University, with Air Infiltration Centre, Warwick University Milton Keynes (1986). Science Park (1983). 19 Peter Carpenter, The Gaer Lian Berm House. 4 Bjorn Karlsson et al, Airtightness and Thermal Caer Lian Conference Centre, Lydart, Mon Insulation: Building Design Solutions. Document mouth, Gwent (1989). D37: 1980. Swedish Council for Building Res 20 Andrew Ford, Fulcrum Engineering earch, Stockholm (1980). Partnership, London, personal communication 5 Bjarne Saxhof et al, 6 Lavernergiehuse i Hjort (1993). ekaer. Thermal Insulation Laboratory, Technical 21 David Olivier, "Beyond the Building Regulat University of Denmark, Lyngby, Denmark ions", J. Chartered Institution of Building Serv (1982). Short English translation available, ices Engineers (May 1989). Insulation and Airtightness of Six Low Energy Houses at Hjortekaer. 22 The Meteorlabor building in Wetzikon, described in ref. 2. 6 Bjarne Saxhof et al, Foundations for Energy Conservation Houses. Thermal Insulation Labor 23 Okologisches Bauen: Umweltvertragliche atory, Technical University of Denmark, Lyng Baustoffe. Vols. 1 and 2. Ministerium fur by, Denmark (1982). Soziales, Gesundheit und Energie des Landes Schlewsig-Holstein, Kiel, Germany (Sept. 1989 7 Poul Kristensen, "Low Energy House G", and Sept. 1990). An abridged English Project Monitor Series 41 . DG XII, European translation is included in ref. 2, op. cit. Commission, Brussels (February 1989). 24 Ref. 1 , op. cit. 8 Ref. 2, op. cit. 9 Wolfgang Feist, lnstitut Wohnen und Umwelt, Darmstadt, Germany, personal communication (1992). 10 Ref. 4, op. cit.
224 I 1
Table 3. Examples of highly-insulated (U = 0.2 to 0.25) and very highly-insulated (U = 0.1 to 0.14) external walls.
HIGHLY-INSULATED
Construction 13 mm dense 13 mm dense 13 mm dense 13 mm light plaster (outwards) plaster plaster plaster 100 mm lightweight 100 mm dense 100 mm dense 200 mm dense concrete block (k = concrete block concrete block concrete block 0.2) 150 mm min- 1 50 mm mineral 150 mm expand- 1 50 mm mineral fibre eral fibre fibre ed polystyrene 100 mm lightweight 150 mm stone 100 mm clay 20 mm external concrete block brick render on mesh 20 mm external render U-value 0.22 W/m2 K 0.23 W/m2K 0.21 W/m2 K 0.20 W/m2 K Thickness 400mm 350 mm 370 mm 370 mm
VERY HIGHLY-INSULATED
Construction 13 mm dense 13 mm dense 13 mm dense 13 mm lightweight (outwards) plaster plaster plaster plaster 200 mm dense 100 mm dense 225 mm dense 100 mm lightweight in situ concrete concrete block concrete block cone. block 250 mm min- 250 mm mineral 300 mm expand- 250 mm mineral fibre eral fibre fibre ed polystyrene 100 mm lightweight 150 mm stone 100 mm clay 20 mm external cone. block bricks render 20 mm external render
U·value 0.13 W/m2 K 0.14 W/m2 K 0.11 W/m 2K 0.13 W/m2 K Thickness 600 mm 450 mm 550 mm 470mm
0 -1-~~~~-*-~~~.....!>...-~~~~~~~~~~~~+-~~~~~-"'.;;:~~~~t-~~---j ,,~
il-i...~~~~1--~~~~~~~~~~~~~~~c---f--7'""""~~~~~~~~~~~~~---j ~ ~ -l-~~~-Jl.~1--~~~~~~~~~~~~~~~---f--l.,..-~~~~~~~~~7""\~~---j heavyweight
0.W. 1910 22 Fol>Nary
Figure 1. Simulated hourly temperature variation, very highly-insulated dwellings, over four days of sunny late February weather. 226 Table 1. Air leakage of Swedish detached houses, pre SBN-80, by construction type 3 .
House type External walls Upper floors Roof Leakage (ac/h at 50 Pa)
2-storey Concrete Concrete Concrete 1.38 1.5-storey Concrete Concrete Timber 2.44 1-storey with basement Concrete Concrete Concrete 1.54 1-storey Concrete Concrete Concrete 1.75 1-storey Concrete Concrete Concrete 1.59 1-storey with basement Concrete Concrete Timber 3 .25 1.5-storey with basement Concrete Timber Timber 2.70 Split level Concrete Concrete Concrete 1.28 1-storey with basement Concrete Concrete Timber 1.72
Table 2. Typical cooling time constants of a new dwelling, by thermal integrity and construction type 15.
CONSTRUCT/ON TYPE TYPICAL COOLING TIME CONSTANT (hours) UK Building Code (heat loss 260 WIK for 100m2J Timber-frame 10 Masonry 100 Heavy masonry 200
Superinsulated (heat loss 55 WIK for 100 m 2J Timber-frame 50 Masonry 500 Heavy masonry 1,000
225 1.~ . ·..... · ... ·~ :.
•:~ ~· :.:·o.'· "'. · .; : ... 1, ...... 1.., ..... ~·, p" ·••. · ··.....""° ~ , .... ·.. • • • • • .. • • 4 . !" ... ~., •. ~. ~ : ..
14
I. !l "b. I· ... 0 .. " .... I' 0 0 r:T .. 1 - 15 mm plaster G ');>' 2 • 240 mm fired clay 4 ·~)'\ C> 0 • • 0 .., blocks 0 'i 4. Cl I' 0 3 • 150 mm expanded " polystyrene 4 • exlemal render 1 • polyethylene vapour 11 - 50 mm sand-cement barrier screed 5 - 80 mm polyureth 2 - space for electrical wiring 12 • acoustic insulation ane foam 3 - plasterboard 13 • 180 mm reinforced 6 - 240 mm light 4 - lightweight concrete concrete ftoor weight concrete block blocks 14 • lwo courses of 240 mm 7 - 365 mm dense 5 • reinforced concrete beam lightweight concrete block concrete blocks 6 • mineral fibre-filled I-beam 15 • 300 mm expanded 7 - 400 mm mineral fibre, 8 - BO mm exlruded polystyrene polystyrene 120+140+140 mm 16 - 240 mm calcium silicate 8 - 70 mm mineral fibre blocks 9 • 175 mm calcium silicate 17 • polyethylene film blocks 18 • concrete footings 10 - 15 mm plaster
Figure 3. Typical construction detail used to Figure 2. Cross-section through the Darmstadt reduce thermal bridging at foundation, in ext ultra-low-energy houses 2. ernally-insulated masonry walls 2.
227 Frost Protected Shallow Foundations NAHB Research Center Dan Cautley
Descrjptjon SECTION Desjgn Example HEATED HEATED SPACE SPACE . .
R-6Max. .. . E111111111111111111..;lt5!Ztl=:--- R~.7 Min. \.._ :: ·... R-8.8 Min. WING INSULATION 20"Wlde (Grea18r width and thickness at oomers) -- Design based on Freezing Index of 3,500 F Day (typlcal of U.S. - Canadian border) N N PLAN VIEW 00 Performance Figure A26.~.~~i FPSF data.
86
68 Benefits
Cost Savings $1,500 {+/-) 15 - 20% of foundation cost 2 - 4% of home cost
Tlme Savings Upto3 days
Energy Savings Meets or exceeds MEC -4 requirements
Reference 15 22 I Nov. '92 Mar. ·93 ..._ WTOOORAIA(WS2) • INOOCJRAIA .,._ CORNEAFNO(AS) Frost-Protected Shallow Foundations In Resldsntla/ Construction -0- MDWALL FNO tC5) •• ·•· .. FROM COAN EA tB21 U.S. Dept of Housing and Urban Development (HUD), 1993 Calculating Basement Heat Losses
Ian Morrison (Buildings Group, CANMET) and Gintas Mitalas (Consultant)
step 1: model the basement's cross-section example result: full-height interior insulation with a 20 FEMfiiJ.
50000 Goals: • improve the Mitalas method ,.-... ~ 40000 • develop a user-friendly ...... interface VI • make the method available .3 30000 .... in DOS ro • enhance HOT2000(i) ~ 20000 (ii :i ~ 10000 step 2: model the corners with a modified 20 FEMfiiJ. N 0 N 1.0 coordinate 0 2 3 4 5 Bactual -·t-ra•n•s•fo.rm-at.io•n__ ... insulation (RSI) _~ Walton (ASHRAE 198 7, V.93, Pt.1) example result: interior insulation to 0.6m below grade step 3: superimpose the steady and periodic components. ~ 2.5 steady ccmpcnent (T dis constant) / ph'5e 1,g (months) 1000 groun \ tota~at fl ow 5 ..--- 800 VI 2 s: cv ...... GOO E s 400 iJ 1.5 .g 200 per_io,?c component (Tground varie~p~riodically over year) b ...... / ... ro 0 - ...... -- - .. l/)
The Renlund House The Kanerva House 385
Why? window U .. 0.8 W/m2K Finland uses 6 Mtoe of energy per capita
annually, 22% of this amount just for facades made 01 wood fibreboard 9 mm heating buildings. Something needs to be masonry or timber glass-wool Insulation wapour borr1er ~~~t~~~r~~~llon -+-H-Jfx::::-"jf- board with wind done to decrease this amount. borrler 70 mm barrler60mm glass-wool insuloflon 190 mm gypsum board 9 mm-+-1-!E-lL wood fibreboard Smm Tasks of this pilot project: To develop and build single-family houses N w for two ordinary Finnish families, the aims 0
being: rendering 15 mm - improved indoor air quality - decreasing heating energy down to
40kWh/m2a polyurethane lnsulolion - no sophisticated new products: All boards 2x70 mm building components must be generally
available in shops 2x100+ 100+ 15+2x70+ 125
60+150+120 Next phase: polystyrene lruulallon boards 100+100mm In the next pilot houses some companies will develope their products into ready-for use industrial products. These products will allow everyone to build a low-energy house without special consultancy. o0 o~o 0 polystyrene Insulation o "oo boards 100+ 100 mm
r.c. tooting 300x600 drainpipe drainpipe bituminous felt
r.c. faoffngs 1000x1CXX> c 3 . 5 m DYNAMIC INSULATION ENVELOPE ENERGY SAVINGS AND THERMAL COMFORT S.Croce, B.Daniotti, E.De Angelis DISET- Politecnico di Milano - P.za Leonardo da Vinci, 32 - Milano (Italy)
TWO SINGLE GLASS PANES (K = 2,9 W/mq°C) NOTES Total energy losses per unit volume versus its depth Gap air flow increa ses surface tempera tures, heat flow from indoor air to window decreases, while flo wing air looses a part of its enthalpic content. 1i~~~~-;r~ Air flow seems to o.oo 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 O.OO'llo better thermal per Room's depth (m) formances of not ex SINGLE+ DOUBLE GLASS PANE (1.8 W/mq°C) hausting configura Total energy losses per unit volume versus its depth tion: it reduces win ter heat charge, and 10.00'llo improves radiative 8.00'llo Indoor comfort con 4.005.00~ -· ~· ditions. 3.00 ;;...... ·~ 6.00'llo 2.00 4.00'llo
1.00 2.00'llo 0.00 ______....._. __-Jiii._.,....._.,...__.,..._ PPD (%)for a standard winter clothed (1cio), relaxed and sitting person O.OO'llo 1.0 2.0 3.0 4.0 5.0 6.0 7 .0 8.0 9.0 10.0 Room's depth (m) • M (m3im'I h) __._ AIR HEATING SYSTEM II 4.0 (m3/m'I h) --0-- 0 3.0 (m3/m3 h)
SINGLE+ DOUBLE PANE EXHAUSTING WINDOW ~2: RADIANT FLOOR SYSTEM IL a: ~;:!""'° 20.0 (I)~ a:w 18.0 §~ .::I!! 16.0
.0 14.0
12.0
TWO SINGLE PANES EXHAUSTING WINDOW • single pane [i] double pane EXHAUSTING 0 dotb/e and sing• panes + ~ two single panes .. 0 AIR FLOW (mCih] 11xh11usl window exhaust llMnci>w