The use of ICF construction and SIP walls is the subject of a heated debate 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 US Green Building Council. Both products will build such a tight space that heat recovery ventilation systems are needed to produce airflow. These systems must be installed with care to eliminate thermal breaks in the superinsulated space. Traditional stick framing can claim walls up to R-20. However, this only considers the highest rated component in the wall, the insulation. Other wood and utility elements in the wall contribute to thermal bridging, which is a major 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 biggest benefits both systems share is the ability to build quickly and accurately.
Obviously both wall systems provide sustainable construction, but when it comes time to build, which one should you use? Since most construction decisions eventually happen, it all comes down to cost. When looking at the cost of these wall systems, it is important to understand that the price varies by design, availability, and installation. This issue is debated by representatives of companies on the Internet. I am not a SIP or ICF vendor, so please consider this a fair analysis.
Cost per square foot?
It is very difficult to provide a cost estimate based on square footage. Many factors are involved that can only be taken into account in the exact specifications of the architect’s plans. An overall cost per square foot of gross wall area can be compelling as a feasibility estimate in theory, but more factors must be involved according to the design to make a proper estimate. A wide range of cost estimates can be researched and found from vendors and builders. The average of these values should not be considered when estimating cost, as they come from people trying to sell you a product. Instead, I have analyzed the trends of these values to find that the difference in these prices suggests that SIP construction costs 5-10% less than ICF construction per square foot.
The location and shape of windows and doors must be considered when fabricators cut into panels or shapes. Waste is produced in this process, while labor increases the cost. In some cases, cost can be optimized in home design by strategically sizing the home, including window sizes and wall lengths according to dimensions suggested by multiple panel sizes or shapes.
Many manufacturers consider the dead and live load structural analysis of the design when estimating cost. This analysis of the plans will explain more precisely what thickness is needed, where and how much. Materials for ICF are more expensive; that is, the concrete per square foot. Also, a precast product is not delivered to the site, so the labor cost is higher when the ICF walls are installed. The total price of materials and installation of an ICF wall system can be calculated to be approximately 30% higher than that of traditional poured walls.
In comparison, an ICF wall must be thicker than a SIP wall to achieve the same R-value. Thicker walls mean more material which also contributes to a higher cost compared to SIP construction.
Local availability can contribute to the variation of the price and the level of green construction. Not all contractors build with SIP or ICF, but as this construction and production become more popular, the price of both will drop. Contractors and fabricators abound in the Midwest and Southwest of the United States, making these regions cheaper to build using SIP and ICF. Research which contractor and manufacturer (SIP or ICF) is more local; this makes the project more sustainable and will likely offer lower prices. However, beware of inexperienced contractors because it is new construction practice. Okay, more experienced contractors can generally charge less.
Sustainable construction is favored by return investment. An airtight, super-insulated home created by any of these wall systems allows for lower operating costs due to monthly utility bills. Plus, the HVAC equipment needed to heat and cool this super-insulated home doesn’t have to be as powerful, saving you hundreds or even thousands of dollars in initial HVAC costs. While these savings are equal between the two systems, other returns are not. Homeowners insurance savings are 15-25% for ICF construction due to fire protection and disaster resistance ratings. However, there is no significant capital gain when it comes time to sell. At this time, there are no tax benefits for the construction of LEED projects, but hopefully in the future there will be. If you consider a LEED scorecard in your decision, SIPs will score higher because it is a pre-built panel set.
SIP construction is generally considered less expensive when deciding which sustainable building envelope to use. However, each project varies in price for each one according to the design specifications. The design can be optimized to the standard dimensions of each wall system to encourage lower costs. Any product that is manufactured closer to the site is more sustainable and will cost less compared to each average cost. Taking this into account, the cost difference between the two can go up or down. ICFs can cost more, but generally offer a higher return in terms of insurance deductions. In general, it is important to research all of these aspects when deciding which will be the least expensive.