The use of ICF construction and SIP walls is strongly debated in the sustainable construction industry. Both wall systems are very energy efficient and create super insulated walls that meet LEED accredited standards developed by the U.S. Green Building Council. Both products will construct such an airtight space that heat recovery ventilation systems are needed to produce airflow. These systems must be carefully installed to eliminate thermal breaks in the super insulated space. Traditional stick framing can claim up to R-20 walls. This, however, only considers the highest rated component in the wall, the insulation. Other lumber and utility members in the wall contribute to thermal bridging which is a main factor in heat gain and loss. Both ICF and SIP wall sections contain solid insulation material that will effectively eliminate conduction and convection in the building. In addition to energy efficiency, one of the greatest benefits that both systems share is the ability to construct quickly and accurately.
It is evident that both of these wall systems provide sustainable construction, but when it comes time to build, which one should you use? As most building decisions eventually do, it all comes down to cost. When analyzing the cost of these wall systems, it is important to understand the price varies according to each design, availability, and installation. This topic is debated by company representatives all over the internet. I am not a salesman for SIPs or ICFs, so consider this a fair analysis.
Cost per Square Foot?
It is very difficult to provide an estimation of cost based on square footage. Many factors are involved that can only be accounted for in the exact specifications of the architect’s plans. A general cost for square foot of gross wall area may be compelling as a feasibility estimate in theory, but more factors must be involved according to design to make an appropriate estimate. One can research and find a wide range of cost estimates by vendors and builders. The average of these values should not be considered to estimate cost since they are from people trying to sell you a product. Instead, I have analyzed the trends of these values to find that the difference of these prices suggest that SIP construction costs 5-10% less than ICF construction per square foot.
Window and door placement and shape must be accounted for when the fabricators make cuts in panels or forms. Waste is produced in this process while labor is involved driving the cost up. In some cases, the cost can be optimized in the design of the home by strategically dimensioning the home including window sizes and wall lengths according to dimensions suggested by multiples of panel or form sizes.
Many manufacturers consider structural live and dead load analysis of the design when estimating cost. This analysis of the plans will more accurately explain what thickness is needed where, and how much. The materials for ICF are more expensive; namely the concrete per square foot. Also, a prefabricated product is not being delivered to the site so the labor cost is more by the time the ICF walls are installed. The overall price for materials and installation of an ICF wall system can be gauged at about 30% higher than traditional poured walls.
In comparison, an ICF wall needs to be thicker than a SIP wall in order to achieve equal R-value. Thicker walls mean more material that also contributes to a higher cost compared to SIP construction.
Local availability can contribute in variance of price, and level of green construction. Not all contractors build with SIPs or ICFs, but as this construction, and production becomes more popular the price for both will come down. Contractors and manufacturers are most abundant in the Midwest and Southwest of the United States, making these regions cheapest to build using SIPs and ICFs. Investigate which contractor and manufacturer (SIP or ICF) is more local; this makes the project more sustainable and will most likely offer lower prices. However, beware of inexperienced contractors because it is a new building practice. In accordance, more experienced contractors typically can charge less.
Sustainable building is encouraged by the return investment. An airtight, superinsulated home created by either of these wall systems allows for lower operational costs due to monthly utility bills. In addition, the HVAC equipment required to heat and cool this superinsulated house does not have to be as powerful, saving you hundreds or even thousands of dollars on initial HVAC costs. While these savings are equal between the two systems, other returns are not. Homeowner insurance savings are between 15-25% for ICF construction due to fire protection ratings and disaster resistance. However, no serious gains in equity are made for when it comes time to sell. At this time, tax benefits do not exist for building LEED projects, but it is hopeful that in the future they will. If considering a LEED scorecard in your decision, SIPs will score higher because it is a pre-built panel assembly.
SIP construction is generally considered less expensive when deciding which sustainable building envelope to use. However, each project varies in price of each according to design specifications. Design can be optimized to standard dimensions of each wall system to encourage lower costs. Whichever product is manufactured closer to the site is more sustainable and will cost less in comparison to each average cost. Considering this the cost difference between the two may increase or decrease. ICFs may cost more but they generally offer more return in terms of insurance deductions. Overall, it is important to investigate all of these aspects when deciding which will be less expensive.