Ferrocement Super-Insulated Shell House Design and Construction
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Ferrocement Super-Insulated Shell House Design and Construction JAN LUGOWSKI Master's Degree Project in Energy Technology Stockholm, Sweden 2013 EGI-2013-046MSC Master of Science Thesis EGI-2013-046MSC Ferrocement Super-Insulated Shell House Design and Construction Jan Lugowski Approved Date Examiner Supervisor Jaime Arias Peter Kjareboe Commissioner Contact person Abstract The purpose of this paper is to explore the ferrocement building technique for sustain- able housing. Ferrocement involves the use of conventional cement with fine aggregate and several layers of steel, with the advantage of higher strength than conventional reinforced concrete, limited formwork and thinner sections. It is particularly suitable for thin shell structures, where geometry minimizes bending loads. Architectural flexibility is one of the main priorities considered in sustainable housing, along with energy efficiency, occupant comfort, resistance to seismic and tornado events, affordability and durability. Ferroce- ment's historical and present applications are covered, along with other building techniques, in order to establish best practices and possible improvements. Reducing construction labor is a particular focus, which has limited ferrocement development in recent years. Computer modeling of shell form finding is described, with three case studies created. A structural analysis method is described and applied to each case study to verify general building code safety. Energy modeling is performed in two climates for each case study in the United States and compared to key PassivHaus energy demand limits. Net zero energy use is pos- sible with on-site solar photovoltaic generation. Keywords: shell structures, concrete, ferrocement, green buildings, energy mod- eling i Acknowledgements Thank you to my examiner, Jaime Arias, and advisor Peter Kjareboe for their support during the project and allowing me full flexibility in exploring a topic which I deeply care about. The project allowed me to combine my previous working experience with material learned during the SEE program. I'm grateful for the holistic approach that my mentors embraced. Jan Lugowski Stockholm 2013 ii Contents 1 INTRODUCTION1 1.1 Motivation.......................................1 1.2 Objectives........................................2 1.3 Methodology......................................3 2 FERROCEMENT CONSTRUCTION6 2.1 Overview........................................6 2.2 Competing building systems.............................. 11 2.3 Opportunities for improving ferrocement....................... 21 2.4 Proposed building techniques............................. 26 3 MODELING AND DESIGN OF CASE STUDIES 30 3.1 Overview........................................ 30 3.2 Functionality...................................... 30 3.3 Software implementation................................ 31 3.4 Design guidelines.................................... 32 3.5 Case study 1: Shell Retrofit.............................. 34 3.6 Case study 2: Calabaza................................ 34 3.7 Case study 3: Ballena................................. 35 4 STRUCTURAL ANALYSIS 37 4.1 Overview........................................ 37 4.2 Methodology...................................... 37 4.3 Material properties................................... 38 4.4 Loads.......................................... 38 4.5 Evaluation strategy................................... 40 4.6 Case study 1: Shell Retrofit.............................. 41 4.7 Case study 2: Calabaza................................ 42 4.8 Case study 3: Ballena................................. 44 5 ENERGY SYSTEM DESIGN & ANALYSIS 46 5.1 Overview........................................ 46 5.2 Methodology...................................... 46 5.3 Design considerations................................. 47 5.4 Case study 1: Shell Retrofit.............................. 50 5.5 Case study 2: Calabaza................................ 52 5.6 Case study 3: Ballena................................. 54 6 CONCLUSIONS 56 BIBLIOGRAPHY 60 iii A EXAMPLES OF FERROCEMENT CONSTRUCTION 61 B DESIGN AND CONSTRUCTION DETAILS 64 B.1 Seismic loads...................................... 64 B.2 Wind loads....................................... 65 B.3 Energy model details.................................. 66 C SOFTWARE 68 C.1 Modeling Software................................... 68 C.2 FEA Software...................................... 69 C.3 Energy Analysis Software............................... 69 iv Chapter 1 INTRODUCTION 1.1 Motivation The purpose of this thesis project is to explore and improve the ferrocement building technique as applied to sustainable housing. Ferrocement construction refers to a specific style of steel and concrete construction. It's a method that involves the use of much more steel reinforcement layers in the structure and a concrete mix that includes sand rather than coarse aggregate. The resulting structure can be thinner than traditional reinforced concrete construction, while retaining superior strength. Material costs are typically competitive with conventional building techniques, but there is considerable manual labor involved in setting up the steel reinforcement in the field. This is the reason why today ferrocement is used mostly in countries with cheap labor. A major appeal of ferrocement is that buildings can become very interesting in shape. Famous examples include the works of Antoni Gaud´ı,Felix Candela and even ship hulls. Taking advantage of shell shapes that naturally place the concrete in compression is a key part of designing with ferrocement. Shapes such as domes and catenary beams are especially well- suited. However, more complex shells are very difficult to analyze by hand and therefore a computer tool such as Finite Element Analysis (FEA) can enable complex designs. The term \sustainable housing" has many aspects. For clarity, it is defined in this thesis as incorporating the following features: Aesthetics A beautiful building will be cherished and maintained for a long time, reducing the need for new construction and increasing occupant comfort. Strength The structure's strength to withstand natural disasters such as hurricanes and earth- quakes is key in many regions and avoids costly reconstruction. Construction Minimal ecological footprint during construction, including the use of locally sourced materials, renewable materials, minimizing energy use, minimizing waste, mini- mizing disturbances to neighbors and avoiding the use of ecologically-sensitive land. Fire resistance Use of materials that give occupants time to evacuate. Preferably the struc- ture should not be flammable nor weaken considerably during a fire. Energy efficiency Minimize the energy required to heat, cool and electrify the building. In- cludes strategies such as passive solar heating, insulation, air heat recovery, heat pumps, efficient appliances and smaller living spaces. Energy production To minimize the impact of external power plants, the building should generate as much of its energy needs as possible. Strategies include solar water heating, solar photovoltaics, biomass combustion and small wind turbines. 1 CHAPTER 1. INTRODUCTION Thermal comfort Stability of the interior temperature can be increased with thermal mass to balance changes in the outdoor climate. Rounded building profiles reduce the surface area for a given volume, which reduces thermal losses of the building envelope. Air quality Fresh air should be ventilated constantly and preferably filtered to minimize CO2, dust and other pollutants. Ventilation rates are compromised by maximizing energy ef- ficiency. Air quality also means minimizing materials which give off Volatile Organic Compounds (VOCs) and other harmful gases to the occupants. Natural light Sunlight in the building increases occupant comfort, although maximizing glaz- ing comes in conflict with energy efficiency. Noise External noise should be attenuated in the structure. Internal noise from occupants and equipment should also be minimized. Affordability The building technique should be as economically accessible as possible. Building codes and practices typically cover only the bare minimum of sustainable building ideology. For this reason, voluntary accreditation was created to help fill this gap. Examples include the American LEED [63], British BREEAM [12] and Swedish Milj¨obyggnad [56]. Each takes a different approach, where LEED focuses on lowering energy costs and site selection, BREEAM focuses on minimizing greenhouse gas emissions in construction and operation and Milj¨obyggnad focuses on occupant comfort. The target is to reach net-zero energy use for a typical family in a given year for any climate in the continental United States, while allowing for architectural flexibility and strength that's not available in conventional house building methods. 1.2 Objectives The thesis is comprised of three main objectives: Improved field construction Evaluate ferrocement construction of today and of the past. Evaluate other building methods to find improvements that can be carried over. Attempt to reduce field labor and the number of steel reinforcement layers. Explore novel concrete techniques, such as textile forms, fiber reinforcement, prefabrication and others. Incorpo- rate thick insulation, which historically hasn't been a priority in ferrocement. The goal is to present a viable building technique that incorporates the lessons learned. This work is presented in Chapter2. Structural analysis Create geometry modeling and FEA framework for efficiently