Frame Construction and ICF’s a side by side comparison of two nearly identical homes and energy consumption

What are the real benefits of ICF’s (Insulated Concrete Forms) compared to stick built homes? In a side by side comparison for energy consumption preliminary data shows that the ICF home is consuming almost a third less gas than the lumber-framed home next door.

The Greenbuild 2010 Legacy Project is interested in comparing “apples to apples” to get real data on energy consumption. The homes have identical floor plans, 1,300 square foot, one story with 3-bedrooms, 1-bath, ranch style homes. The  windows, doors, mechanical systems  and interior finishes are the same.

Home A is built of LOGIX ICF’s with fiber-cement siding and a metal roof. Home B was built using conventional lumber-framing and spray-foam insulation with vinyl siding and concrete tile roof. Both homes were built by volunteers with donated materials in November 2010 as a demonstration project that benefited Habitat for Humanity Lake County.

According to U.S. Green Building Council (USGBC) about a quarter of the heating losses and gain in a new home is due to air leakage through the thermal envelope. Tighter homes consume less energy and are more comfortable due to less air-infiltration and fewer drafts. They are also more durable reducing the flow of moisture and lessening the risk of condensation within the exterior envelope.

A blower door test was conducted on both homes, this is a test used to determine the tightness of a building. Overall the ICF home tested 2.4 times air tighter than the lumber-framed home. Remember the wood-framed home was insulated with spray-foam insulation which seals much better by filling in gaps than a fiberglass batt insulation. However, the spray-foam insulation cannot match the performance value of ICF’s. Wood-frame construction will always have gaps where panels meet and at each butt joint, ICF’s by comparison have no gaps or joints in the wall structure. Another factor in traditional wood-frame construction is that you have long joints where dissimilar materials meet. The concrete slab has to tie to the bottom plate of the wood-frame wall and it’s very difficult to get a good seal there. On the other hand ICF’s have 100% continuous insulation on both sides of the wall and you complete the air seal with the concrete pour.

The R-value of the lumber-framed home was 20.13 and the ICF home was 24.63, this isn’t a huge difference and both homes far exceeded the 16.17 R-value required by the local code. This project demonstrates that R-value isn’t the only thing to consider, air-infiltration is also an important factor in the efficiency of a home.

Read more on this project in Concrete Homes Magazine March 2012 and in upcoming articles here.

Apache Creek Builders – Charlie Kattnig owner and ICF Builder in Southern Colorado including Pueblo, Westcliffe, Rye, Colorado City and surrounding areas.

www.apachecreekbuilders.com 719-251-3003