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Sustainable Design in Miami: Building Envelopes and Life Cycle Assessment
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Sustainable Design in Miami: Building Envelopes and Life Cycle Assessment

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The presentation summarizes an investigation into regionalism and the design of building envelope systems for low rise affordable housing in Miami and Phoenix. The research involved the application of ...

The presentation summarizes an investigation into regionalism and the design of building envelope systems for low rise affordable housing in Miami and Phoenix. The research involved the application of three platforms: cost, energy modeling, and life cycle assessment in the early stages of design to help the design team make inform decisions about the building envelope system.

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Sustainable Design in Miami

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  • My opinion is that low rise multi-family housing will be the primary building type used to densify our cities-So the investigation is about building affordably and sustainably in urban cities-The challenge in cities is that architects are trained to use site orientation as the first tool to affect the energy performance of a building, but within a city we’re often constrained by the urban grid.
  • Investigate the design of building envelopes as a region problem with very context specific solutionsClimate region and city population were the first sets of criteria to determine where to investigateWe know that construction and the operation of buildings has a significant negative impact on the environmentAs populations in our cities grow the need for sustainable affordable housing will increase in importanceThis investigation seeks to isolate the design and construction of the building envelope as the first line of defense in the attempt to improve the performance buildings from the standpoint of the environmentThe investigation requires additional scope boundaries, so I am focusing on low rise (4 story) multi-family housing in an urban context. The climate region currently investigated is hot-humid and the city is Miami which is considered part of the sub-tropicsTypical floor plate indicating circulation and unoccupied areas
  • Cost, energy use modeling and life cycle assessment are the three models that will be overlayed atop one another to assess what the best options are in a specific city within a particular climate regionThere are four environmental indicators that are relevant to this investigations:Greenhouse gas emissionsNon-renewable resource depletionEnergy useWaste production
  • Energy:GWP:Resources:Waste: 3.2 lbs per capita
  • A: 4 and 2%B: 6 and 5%Boston: 11 and 12% (w/o air infiltration)

Sustainable Design in Miami: Building Envelopes and Life Cycle Assessment Sustainable Design in Miami: Building Envelopes and Life Cycle Assessment Presentation Transcript

  • Jason Tapia, AIA, LEED AP, NCARB, CDT
  • Presentation Goals
    • Problem
    • Previous Studies
    • Method
    • Scope
    • Results
    • Conclusions & Questions
  • PROBLEM
    • Millions of households in sub-standard housing or spending 50% of their income on housing 1
    • Affordable housing shortage in U.S.
    • 2.9 million in urban cities
    • Population will grow by 15% by 2030 2
    • In 2003 83% of the US population lived in metro areas 3—which grew at a faster rate than the general population (3.8% vs. 3.3%)
    • Four states expected to grow the fastest: 1st Nevada, 2nd Arizona and 3rd Florida & 4th Texas
    • Need for housing that is sustainable AND affordable
    1 The Department of Housing and Urban Development 2007
    2 US Census Bureau 2009
    3 Mackun, P.J. Population Change in Metropolitan and Micropolitan Statistical Areas: 1990 - 2003
  • PROBLEM
    • Housing stock in the US:
    • 68% is single family homes and 28% buildings of three stories or taller 1
    • Of the 28%, ¾ were buildings 3-6 stories in height 1
    • Multi-family low rise is an important area of research and well suited to address the housing problem
    • Lower initial costs compared to taller buildings
    • More diverse structural and material options
    • Faster construction times
    • Less skilled labor force
    Goal
    • Building envelope is the most important building system to positively impact the energy performance of a building
    • Investigation: compare the performance of conventional building envelopes in affordable housing to alternative systems with higher R values or that are regarded as best practice, by applying a technical evaluation in the early stages of the design process using three platforms:
    • Cost
    • Energy performance
    • Life cycle environmental impacts
    1 The American Housing Survey 2007
  • PREVIOUS STUDIES
    • Environmental impacts of individual building materials
    • Environmental impacts whole structures as the functional unit of assessment
    • Single family home
    • Office buildings
    • Focused on the envelope in different climate regions but only looked at energy performance
    Gaps:
    Low rise buildings in the US: evaluating cost, energy performance and life cycle impacts
  • METHOD
    Research boundaries:
    • Climate regions investigated: hot-humid and hot dry (the four fastest growing states are in these two regions)
    • Cities: Miami and Phoenix
    • Building type: low-rise affordable housing
    • Owned and operated by developer
    • Rented (eliminates problem of split incentives)
    • 4 stories
    • 2700 sf floor plate
    • Two circulation cores
    • 10,700 sf of façade area
    • 2900 sf of roof area
  • METHOD
    Overlay research from three models:
    • Life Cycle Assessment: Gabi
    • Energy performance modeling: Design Builder
    • Cost: RS Means Costworks
    LCA Boundaries
    • Type of LCA: process analysis
    • Cradle to grave for building envelope assembly
    • Façade: exterior cladding – interior finish
    • Roof: membrane – roof structure
    • Excluded:
    • Foundation, parapets, floor slabs, interior partitions
    • On-site construction
    • Packaging of materials
    • Impact of labor
  • Energy use and embodied energy
    • Residential buildings consume 22% of energy in the US 1
    • Average American family spends about $810 a year on heating and cooling 2
    • Building envelope represents 26% - 30% of initial embodied energy 3
    ENERGY
    Global warming potentials (air emissions)
    • Construction and operation of buildings produces 40% of the country’s CO2 emissions 4
    • GWP Metric: EPA’s TRACI [Tool for the Reduction and Assessment of Chemical and other Environmental Impacts]
    GWP
    Non renewable resource depletion
    • Research has shown that as the population grows, consumption of non renewable resources increases 5
    • Fossil fuels and other minerals
    RESOURCES
    Waste production
    • Construction and demolition waste in 2003 was 170 million tons; 39% was residential construction 6
    • More waste equals more GHGs such as methane
    WASTE
    1 US Energy and Information Administration 2008
    2 US Energy and Information Administration 2005
    3 Cole and Kernan 1996
    4 US EPA 2010
    5 Sznopek 2006. Drivers of US Mineral Demand
    6 US EPA 2009
  • CMU
    R 6
    ICF
    R 22
    FC SIPs
    R 40
  • Wood Frame
    R 22
    ICF
    R 22
    OSB SIPs
    R 39
    • R-Value: CMU 6, ICF 22, SIPS 40
    • Performance difference in this climate appears insignificant
    • ICFs perform better because of thermal mass
    • Florida energy code allows for thermal mass discount (from R13 to 4)
    • Energy code loosely based on IECC 2007
    • Single glazed windows, double laminated for impact resistance (hurricane)
    Excluded from energy model
    • Lighting
    • Occupancy load
    • Hot water service
    • Thermal transfer between
    zones (adiabatic modeling)
  • Assumptions for both cities:
    • 18.2% glazing ratio
    • No mechanical ventilation
    • Only energy required to heat and cool based on heat loss and gain through envelope
    • Air infiltration modeled differently in two studies: .7 AC/H constant and another study that varied based on envelope type
    • R-Value: Wood 22, ICF 22, SIPS 39
    • Arizona code based on IECC 2000
    • Minimum of R13—conventional outperforms code
    • Double insulated glazed windows
    • OSB faced SIPs more competitively priced
    • Windows more than a third of the costs
    • For ICF wall the forms are 10% of the costs
    • SIPs are precision engineered to 1/8” tolerance
    • 8% Difference in cost between
    ICF and CMU
    • Cost difference attributed to additional labor associated with masonry
    • 34% Difference between SIPs and CMU
    1 Data from RS Means 2009 and interviews conducted by investigator
    • Six LCA models built in Gabi
    • Steel recycling modeled
    • Demolition of envelope modeled
    • Recycling of EPS rigid foam in certain applications
    • Transportation of materials factored
    • Maintenance in Use Phases includes:
    • Window replacement (and recycling)
    • Roof membrane replacement
    • Stucco repair
    • Repainting
    • The process of making cement and steel are the most energy intensive—systems with large amounts of these materials are generally the most energy intensive
    • The production of polyurethane (6.5 inches thick) in OSB SIPs is largest contributor of GWP
    • Cement production relies heavily on quarried minerals:
    • Clay, limestone and sand
    • FC SIPs use far less cementitious material
    • Mass of concrete and thickness of the wall impact waste
    • ICFs are nearly 13 inches thick with finishes
    • SIPs outperform because of 9 inch thickness and fewer materials (except wood frame)
  • LCA MODEL DETAIL
    ICF end-of-life map
    Carbonation credit
    Steel recycling credit
    • Landfilling concrete reduces CO2 emissions
    • Recycling steel reduces environmental impacts
  • Conventional wood frame envelope
    Conventional CMU envelope
    • Material sources came from interviews with contractors, suppliers and industry trade groups
    • Truck was assumed to be primary form of transport for site delivery
    • Transport from extraction to factory is embedded into Gabi processes
  • IN PRACTICE
    $7 per SF & 36 MJ per SF
    Wood truss
    Post tension concrete slab
    $31 per SF & 130 MJ per SF
  • Conclusions
    • In general thinner wall systems = lower environmental impact
    • SIPs benefits:
    • Efficient use of material: interior cladding serves as both structure and paint substrate
    • Has the greatest potential for “Design for Disassembly”
    • HOWEVER wood frame construction in Phoenix is less expensive and has a smaller environmental footprint than either alternate system
    • ICFs perform slightly better but the environmental impact is hard to justify
    • Recommend that architects in this practice area incorporate cost, BPM and LCA in the early stages of design in order to:
    • Validate their design decisions
    • Improve energy performance, reduce costs and negative environmental impacts
    • Software platforms incorporating cost, BPM and LCA would likely be too complex or reductive
  • [Sustainable Design in Miami]