You Don't Have to Be Stuck in a Box: Sustainable Alternatives to Wood Framing

When you think of building a home, probably some of the first steps you think of are building the foundation and walls. Convention probably even has you thinking of some form of concrete block foundation with a wood frame wall. While these are the most common forms of construction for these components of the home, they are not the only way to build.


There are several nonconventional methods to build a home, and some of the methods can even provide benefits that the standard wood frame home cannot provide. If you have been interested in the sustainable movement for a period of time, I'm sure you've heard of the construction practices that stray far from conventional, such as Strawbale, Cob, Rammed Earth, and EarthShip. However, you may not have heard of some of the other techniques that are closer to conventional methods.

The following three methods can either be used in conjunction with or as standalone methods, but they all turn out a product that looks similar to a conventionally built home. Each has their pros and cons, but ultimately they are solid building practices for sustainable homes.

Structurally Insulated Panels (SIPS):

These are panels made of foam insulation sandwiched between two panels of oriented strand board, plywood or other panel siding. They are used to construct all faces of the building; floors, walls, and roofs. One of the main advantages of SIPS is because of the rapid construction that is possible with them. SIPS are engineered and cut to size off-site, limiting the amount of time on-site prepping the material. SIPS also speeds up the process because the insulation is included, so once the framing is up, several steps are already completed. Finally, the properties of the panels help seal the home better and reduce noise from the outside.

There are a few downsides to the panels. First, there is a large learning curve for everyone on the job and they must be kept dry - so flashing is critical. Also, they may require a crane to install. Planning for electricity in the home is also critical. The panels are predrilled for wiring based on wiring plans that are submitted. Many people may also point out that petroleum is used to make the rigid foam board that is vital to the component. However, this shows a common issue in all green products; if you look at them hard enough, you can bring into question their sustainability. One must look at the overall product in some cases, and the life cycle impact it may have.

Autoclaved Aerated Concrete (AAC):

AAC looks very much like a standard concrete block until you pick it up. AAC is made with a variation of concrete made with aluminum powder to create an increase in volume while trapping air. This trapping of air insulates the blocks and makes them surprisingly light. The blocks will even float! They're produced in 8” and 12” thicknesses, 8” high and 24” long. One of the advantages to AAC is that it can be easily cut on site with specialized handsaws, bandsaws, or just ordinary tools that are no longer sharp enough to cut wood.

One of the advantages of AAC, like SIPS, is that once the walls are constructed, the framing and insulation is finished. Some sources say that the 8-in block can have an insulating value as high as R-21! AAC is also fire-poof, mold-proof, insect resistant, and sound absorptive. The blocks are laid very similar to standard concrete blocks using a type of mortar. It has been found by some installers, though, that individuals that are trained in laying standard blocks have a harder time learning to install AAC than someone who has little construction training.

AAC is not all pros; there are some cons to this material. It has a large learning curve for electrical and plumbing trades. While AAC can float, it does absorb water over time. Once the water is absorbed, the blocks no longer have the insulating properties that it has when dry. For this reason, the blocks are not a good fit for below-grade construction. The blocks can be cut to run chases, but for someone who's used to working with wood and the cavities that comes along with that style of construction, the idea of having to cut through solid block may be a little daunting. Homeowners may also find it a little unusual hanging a picture or other items on a wall made out of concrete.

Insulated Concrete Form (ICF):

ICF is made of polystyrene forms that interlock like Legos. The forms are then filled with concrete to form the structure. They're typically not stacked more than four high at a time to keep a blow out from occurring. After the concrete cures, the forms are left in place to allow for insulation, space to run electrical and plumbing, and to act as a backing for drywall or stucco.

As with all these products, ICF creates a tight envelope, and it includes its own insulation. The construction techniques used to build with ICF are easy to learn, and it is much stronger than wood frame construction.

A few of the downsides to ICF construction:

• Retrofits are typically costly, as concrete saws must be used to make openings or move walls
• Curing the concrete can also cause humidity issues inside the home for a period of time during construction
• Pricing is also typically more than traditional construction.

As mentioned before, each one of these can be used independently of each other or together. I've had the privilege to visit homes that used ICF for the foundation, AAC for the walls, and SIPS for the roof. These homes took advantage of all the alternative construction forms to construct a very sustainable home! Each one of these construction methods has its own pros and cons, and you may find one may fit your style better than the other. Talk to individuals who have worked with and lived in homes incorporated with these technologies to see which one best fits you.