Rapid Fire

▪ Objective: Understand the role of concrete portion of ICF in reducing building energy use

▪ Approach: Whole-building energy model for typical commercial and residential buildings

▪ Key findings: Small overall, but reduced peak heat transfer; mass via ICF not optimized

▪ Impact: Focus on optimized use of concrete for thermal benefit

Amanda L. Webb, SMArchS Graduate Student

The thermal mass benefits of concrete in Insulated Concrete Forms (ICF)

With L. Norford and J. Ochsendorf

Afternoon Presentation

Residential BuildingsSingle Family & Multifamily

Amanda WebbFeb 17, 2011

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Major Model Changes

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Category Single Family Multifamily

Reference Standard Building America House Simulation Protocol*(IECC 2009 equiv.)

DOE Benchmark Midrise Apartment

Envelope ICF – R-26 -> R-20Attic Floor –R-60 -> R-40 (Chi)

ICF with concrete interior -> ICF with wood/gyp interior

Internal Gains Detailed Input No Change

Infiltration & Ventilation - No infiltration difference**- Nat vent- No HVAC Outdoor Air

No Change

Domestic Hot Water Detailed DHW System No Change

= Most significant changes

*From DOE’s National Renewable Energy Laboratory

**Focus in this analysis on mass benefits of ICF

Infil rates same – focus on mass, insul. benefitsR-values different

Mass portion of ICF does make a difference

Peaks reducedWhat if we add more concrete?

What if we expose the concrete inside?

e.g., ThermomassBetter in PHXCould be better with optimized use of interior mass

Infiltration sensitivity dependent on climate

Operational energy dominates for benchmark building

Embodied energy matters more in very low energy building

Energy Model/LCA Conclusions

• Very solid model specifications• Better contextualize our work – NREL, etc. • Infiltration, R-value, and mass benefits of ICF

should be considered separately• Infiltration highly climate dependent; mass

somewhat climate dependent• Look at optimized use of mass – balance

changes for low energy buildings

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Work Through Aug 2011

• Energy benefits of concrete. Focus: low energy houses.– Analysis to find optimum curve for use of concrete

in envelope, interior [Hacker 2008, Zhu 2009]– Mass vs. insulation tradeoff– Range of climates, thermal performance

• Comfort benefits of concrete [beyond Aug]– Control algorithm testing to understand role of

concrete in comfort-based HVAC controls

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