An insulated concrete wall system consists of poured concrete or concrete block insulated with expanded polystyrene (EPS) or extruded polystyrene (XPS) foam insulation. EPS is by far the more common insulator, mostly because it costs a lot less than XPS. The wall itself can consist of stacked concrete blocks, called concrete masonry units or CMUs, or cast-in-place steel-reinforced concrete. Although CMUs account for half the total market share for concrete walls and are especially popular in the South (Florida estimates run to over 80% of new residential construction), cast-in-place systems have been growing steadily nationwide (see below).
The most familiar cast-in-place systems are the various insulated concrete form products, or ICFs,. These foam forms are assembled on site and filled with rebar and concrete, then remain in place after the concrete pour to serve as the wall insulation. According to Donn Thompson, director of market strategy and positioning at the Portland Cement Association, the economic downturn has eliminated many small ICF manufacturers, but he estimates that about 30 of them are still serving the U.S. market.
Most ICF products fall into one of two broad categories: hollow foam blocks that workers stack like Legos, and flat foam panels that are erected and braced like conventional forms. Foam block systems enjoy the largest market share and require less skill to assemble than panels.
Over the years, manufacturers have offered forms that produce a variety of concrete geometries, from conventional flat walls to post and beam systems, to grids that resemble breakfast waffles. While the latter two use less concrete, Thompson says that the industry has standardized around the conventional flat wall, whose familiarity makes it accepted by contractors and homeowners, alike.
A lesser-known alternative to ICFs is the concrete sandwich, in which rigid foam is placed between reusable forms and concrete poured on either side, leaving the foam at the center of the wall. These systems are very minor players in the residential market, but manufacturers say that 10% to 30% of their business is residential--mostly architect-designed custom homes. “Architects like this system because it’s engineered,” says Brad Nesset, VP of sales at Thermomass. “It has well defined structural properties.”
Why Concrete?
Two things to keep in mind about an insulated concrete wall are that it will be more costly and more massive than a stick frame. Cost premiums range from 1% to 10%, depending on a number of factors.
MARKET SHARE OF STRUCTURAL WALL SYSTEMS
> Autoclaved Aerated Concrete: .01%
> Steel Stud Framing: .06%
> Structural Insulated Panels: 0.8%
> Other: 2.2%
> Insulated Concrete Forms: 3.4%
> Concrete Block: 6.0%
> Conventional Wood Framing: 87.5%
Source: Portland Cement Association
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68