Cost of ICF Construction vs. Wood Frame Construction
by Pieter VanderWerf & Christina Neamtu
If you've ever tried to nail down a hard answer on this subject, you're probably already familiar with the wide range of estimates out there. Chances are you might have an easier time finding the Holy Grail. In an effort to make your search a little easier, we've taken a look at the major reports on ICF costs and boiled them down to the basics.
One thing that makes cost comparisons difficult is the fact that ICF costs are usually measured in square foot of wall area, while wood frame costs are measured in square foot of floor area. Depending on the study, you might see ICFs converted to relate to floor area, so it's a good idea to keep track of what's being measured to avoid any confusion. Another thing to keep in mind is that different studies use different costs. Some give what the general contractor paid (referred to as builder's costs or total house cost) while others give what the general contractor charges (referred to as sales price).
Let's take a look at some numbers. A Portland Cement Association technology brief drawing from work done by VanderWerf, Feige, Chammas, and Lemay (Insulating Concrete Forms for Residential Design and Construction, 1997) concluded ICFs cost builders about .5-4% per square foot of floor area more than wood frame houses of the same design. At the time of the study, typical US homes cost the builder about $60-100 per square foot of floor area, so using ICFs added about a $1.00-4.00 premium to this figure. This held true only for homes built by experienced contractors (who've built 4 to 5 houses).
Along similar lines, the NAHB Research Center's Demonstration Homes Project also evaluated the use of ICFs in residential construction in 1997. They experienced up to an 8% increase in total house cost, adding about 1-5% to the final price for the buyers. The NAHB's ToolBase report found that ICFs increased builder's cost by $0.75-4.00 per square foot of floor area compared to wood frame construction.
And in 1998, a study by HUD, PCA, and NAHB compared the cost and performance of ICF walls to conventional wood-frame exterior walls again. They found that labor costs for ICFs were slightly to moderately higher, and that total installed costs averaged about $2.73 per square foot of floor area more than the wood frame home. This translated to an increase in builder's cost of 6% to 7%, or roughly a 3% increase in the builder's sales price.
So where do all those studies leave us? The bottom line is this: ICFs usually cost slightly more than wood frame. But by how much depends. There are so many potential influences on cost that it's tough to nail down a solid estimate.
Here's why: concrete, lumber and foam prices, ICF form prices, lumber prices, exterior finishes, design features, crew experience, labor markets, and engineering all influence the cost of the intended project. An added cost of $2.50 per square foot of floor area seems to be in the middle of most of these ranges. But take that figure lightly; construction with ICFs can increase builder's costs much less or more. It's easy to see why there's been so much debate on this issue.
All this being said, ICFs do have major cost savings opportunities. Because ICF construction is more energy efficient, HVAC systems can be downsized and those savings offset part of the cost difference. Using EIFS as your exterior finish will also reduce some of the cost since the foam required for EIFS installation is already set up. And some builders report fewer customer service calls on their ICF homes. (NAHB Research Center Demonstration Home Project.)
ICF homeowners enjoy lower utility bills, better sound proofing, and durability. Some have estimated that the monthly savings provide a good payback on the initial investment. And then you have the benefits of a stronger, quieter, more comfortable home to boot.
For More Information:
VanderWerf, Feige, Chammas, and Lemay. Insulating Concrete Forms for Residential Design and Construction. NY: McGraw-Hill Inc, 1997.
NAHB's Insulating Concrete Forms for Residential Construction: Demonstration Homes Project
NAHB's Insulating Concrete Forms: Installed Cost and Acoustic Performance
Portland Cement Association Residential Technology Brief No. 5.