The use of ICF construction and SIP walls is a hot topic in the sustainable construction industry. Both wall systems are highly energy efficient, creating super-insulated walls that meet LEED-accredited standards developed by the US Green Building Council. Both products create such an airtight space that heat recovery ventilation systems are required to create airflow. These systems must be carefully installed to avoid thermal breaks in the super-insulated space. Traditional bar frames can take up to R-20 walls. However, this only accounts for the most highly rated component in the wall, the insulation. Other wood and utility elements in the wall contribute to thermal bridges, which are a major factor in heat gain and loss. Both ICF and SIP wall sections contain solid insulating material that effectively eliminates heat conduction and convection in the building. Besides energy efficiency, one of the biggest advantages that both systems share is the ability to build quickly and accurately.
It’s obvious that both of these wall systems offer sustainable building, but when it comes time to build, which one should you use? As with most construction decisions, ultimately it comes down to cost. When analyzing the cost of these wall systems, it’s important to understand that the price will vary based on design, availability, and installation. This topic is being discussed by business representatives all over the Internet. I’m not a seller of SIPs or ICFs so consider this a fair analysis.
Cost per square foot?
It is very difficult to provide an estimate of the cost based on square feet. Many factors play a role that can only be taken into account in the precise specifications of the architect’s plans. Overall cost per square foot of gross wall area can theoretically be compelling as a feasibility estimate, but depending on the design, more factors need to be included to make a reasonable estimate. One can research and find a wide range of cost estimates from vendors and builders. The average of these values should not be used to estimate costs as they come from people trying to sell you a product. Instead, I analyzed the trends in these values to find that the difference in these prices indicates this SIP construction costs 5-10% less per square foot than ICF construction.
The placement and shape of windows and doors must be considered when manufacturers make cuts in panels or forms. This process creates waste, while the labor involved drives up costs. In some cases, costs can be optimized when designing the home by strategically sizing the home, including window sizes and wall lengths according to dimensions suggested by multiples of panel or mold sizes.
Many manufacturers consider a structural payload and dead load analysis of the design when estimating costs. This analysis of the plans will explain in more detail what thickness is needed where and how much. The materials for ICF are more expensive; namely the concrete per square foot. Also, no prefabricated product is shipped to the site, so the labor cost is higher when the ICF walls are installed. The total cost of materials and installation of an ICF wall system can be estimated at around 30% more than traditional cast 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 higher costs compared to SIP construction.
Local availability can contribute to the variance in the price and level of green building. Not all contractors build using SIPs or ICFs, but as this type of construction and production becomes more popular, the price of both will come down. Contractors and manufacturers are most numerous in the Midwest and Southwest United States, making these regions the cheapest to build with SIPs and ICFs. Investigate which contractor and manufacturer (SIP or ICF) is more local; This makes the project more sustainable and most likely offers lower prices. Beware of inexperienced contractors, however, as this is a new construction practice. Accordingly, more experienced contractors can usually charge less.
Sustainable building is promoted by the yield. An airtight, super-insulated home created by one of these wall systems allows for lower running costs due to monthly utility bills. Additionally, the HVAC equipment required to heat and cool this super-insulated home does not 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 equal. Homeowners insurance savings range from 15-25% for ICF construction due to fire ratings and disaster preparedness. However, no serious equity gains are achieved on sale. There are currently no tax benefits for building LEED projects, but it is hoped there will be in the future. When you consider a LEED scorecard when making your decision, SIPs score higher because it’s a pre-engineered panel assembly.
SIP construction is generally considered to be more cost effective when it comes to which sustainable building envelope to use. However, the price of each project varies depending on the design specification. The design can be optimized to the standard dimensions of any wall system to promote lower costs. Which product is manufactured closer to the site is more sustainable and costs less compared to the respective average costs. With that in mind, the cost difference between the two may increase or decrease. While ICFs cost more, they generally offer more returns in terms of insurance deductions. Overall, it’s important to examine all of these aspects when deciding which is more affordable.