Originally Published: March 18, 2016 6 a.m.
Stick framing is a century-old form of construction, and one contractors know very well. Most building inspectors and all licensed architects are also very familiar with stick framing. Materials are readily available, easy to work with and relatively inexpensive. An adaptable form of construction where changes are easily made once the project has started, stick framing also accommodates almost any size or placement of windows or doors and is flexible to specific design changes. There are also no out-of-the-ordinary engineering or code approvals required.
Unfortunately, the process is made up of many steps – measuring, cutting, fitting and nailing each stick is time consuming, encourages mistakes and produces a high material waste. Stick framing is also difficult to seal and effectively insulate, with wall thickness limiting insulation levels. Poor sealing leads to air infiltration, condensation and moisture problems, leaving the wood susceptible to insect infestation and rot. Fiberglass batts and cellulose insulation are only marginal insulators and their performance depends wholly on the quality of installation. Adding spray foam helps to seal and boosts R-value but doesn’t guarantee an airtight envelope.
Integrated Concrete Forms (ICF) and Structurally Integrated Panels (SIPs) are modern solutions that move residential housing forward. They’re popular because you get a lot of results for not a lot of work. You also have low labor costs because installation is easier and quicker. But you need to know what you’re doing.
If you use unskilled labor, there will be mistakes. Also, because SIPs and ICFs are somewhat new to the industry, not many contractors know how to work with them and tend to avoid them. Tradespeople need to learn how to work with these new products no matter what they are. Interview builders that use these systems, ask for references, and talk to those homeowners about whether the builder built a quality product on time - and on budget.
The main selling point of these panels is they provide all the layers in a wall that should be there without having to build them, which saves time and cost related to labor. Both SIPs and ICFs provide integral structural strength without the need for studs; therefore, reducing thermal bridging. Also, every SIP and ICF panel is manufactured according to specific engineered construction plans; you can’t go to the store and just buy them.
Insulated concrete forms offer a high level of energy efficiency compared to masonry foundations and traditional “stick built” wood-framed walls. They have a layer of concrete sandwiched between two layers of foam insulation, usually EPS (expanded polystyrene). This forms a sound structure with excellent thermal properties. However, when pouring the concrete, it’s important there aren’t any air pockets, as gaps in the concrete will compromise the structural strength of the entire wall or structure you’re building.
Conventional foundations are constructed by pouring concrete into temporary wooden forms, which are removed when the concrete has cured. Without adequate curing, the wall weakens and is prone to cracking and even shifting. One of the most common complaints in new homes is leaky basements due to cracked foundation walls. When built with Insulated Concrete Forms (ICFs), foundation forms remain in place, and provide insulation on each side of the concrete. In fact, because of its optimum curing environment, an ICF wall cures to be stronger than a conventional wall.
An ICF foundation is warm and dry, preventing any opportunity for mold growth; since there is no cavity where warm moist air meets a cold wall and condenses.
Typically, a foundation built with ICFs will cost more (20 percent to 30 percent) than a comparable concrete or block foundation. However, in the one step that would have produced a bare concrete wall, an ICF wall produces an insulated wall with a vapor barrier, all the way up to the floor joist. Foundation walls built with ICFs are easier and faster to construct than either a concrete masonry unit or cast-in-place concrete foundations.
What sets an ICF home apart is its sheer mass. Concrete stands up well to high winds (200 mph plus); these heavy walls also deaden street noise, making the home much quieter than a wood frame. And concrete doesn’t get eaten by bugs.
The foams in ICFs are manufactured with flame-retardant additives. In “firewall” tests, they were subjected to continuous gas flames and temperatures of up to 2,000°F for as long as four hours. None of the ICF walls failed structurally; in contrast, wood-frame walls will typically collapse in one hour or less.
Walls made of Insulated Concrete Forms are rated on average, like a wood-frame wall constructed with R-25 insulation. However, the equivalent R-value performance of ICFs consists of three factors. First is the R-value of the expanded polystyrene, second, the thermal stability of the concrete wall, and third the suppression of air leakage (infiltration). As a result, with the combined R value performance and the reduced air infiltration, ICF walls actually perform as high as R-40 to R-50.
One disadvantage of ICF construction is overall wall thickness; total wall assemblies (the structure plus interior finish and exterior cladding) can be upwards of 14 inches thick, which can take valuable space on small lots. Another disadvantage is running plumbing in exterior walls, which is possible but difficult, so it is recommend that you run them in interior walls or in a crawl space and through the floor.
Finally, ICFs are termed a “green product,” as they offer energy savings of 20 percent or more compared to stick framed buildings. However, it is “green” after the house is built, as there is a large amount of energy expended on the production and transportation of these products!
Next time, we will look at SIP features and benefits.
For more information, contact www.greenhomeenergyadvisors.com.