INSULATED CONCRETE FORMS
picConcrete is wonderful stuff in many ways, but warmth and insulation properties aren't among the list of advantages. At least, not until recently. But now, something called “insulated concrete forms” (ICFs) are eliminating the traditional thermal drawbacks of concrete by boosting energy efficiency and making poured concrete more of a DIY possibility.
Manufactured by a handful of companies across Canada, ICF systems use rigid pieces of foam as one-time forms for containing concrete used in both foundation walls and above-ground applications. Inner and outer form walls are typically assembled like Lego blocks, and held together with horizontal plastic connectors called “webs.” These webs also support lengths of steel-reinforcing rod that strengthen the completed wall.
Unlike traditional wooden forms, ICFs remain in place permanently, offering effective insulating characteristics. If you're thinking of pouring any kind of wall as part of a home-improvement project, ICFs eliminate the problem of what to do with a bunch of concrete-covered plywood after the work is done. Wood or plastic strips are typically embedded in the foam while it's manufactured, offering areas into which screws can be driven to secure drywall or siding. ICFs are still marketed mostly to professionals, although one brand, Formtech (1-877-848-6155), is now available through selected Home Depot stores.
Most ICFs sold in Canada use two layers of 2 1/2" expanded polystyrene foam-one inside and one outside. This yields a total insulating value of R-20, not including the concrete, drywall and whatever is applied as an exterior wall surface. And while this doesn't sound any better than a traditional 2x6 stud wall insulated with fibreglass, it actually is. Since the foam insulation forms a continuous thermal barrier, it beats frame walls that only have a value of R-5 wherever studs and plates extend from the inside surface of a wall to the outside. Also, ICF walls don't need a vapour barrier, while still eliminating all possibility that internal wall condensation can set in. Although it's hard to quantify accurately, six or eight inches of concrete also boosts the wall's thermal performance by increasing its mass as well as its sound-blocking ability.
-Steven Maxwell
Read more in Home Reno & Design and Indoor
1 Comment
From the article - ..."You also need to install a 6-mil polyethylene vapour barrier on the warm side of the insulation." Apparently it is not always correct to install a vapour barrier. Below is an excerpt from http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers/?full_view=1 Incorrect use of vapor barriers is leading to an increase in moisture related problems. Vapor barriers were originally intended to prevent assemblies from getting wet. However, they often prevent assemblies from drying. Vapor barriers installed on the interior of assemblies prevent assemblies from drying inward.