If you are building a new house, or remodeling an older home, here are six ways to incorporate energy efficient walls into your building design.
They will add to the initial cost of the job, but over time, they will pay for themselves in energy savings. Energy efficient homes have higher resale value than older non-efficient ones.
Talk to your contractor to see if he/she is familiar with these methods. If not, conduct a search in your area to find contractors who are. Don’t be put off by a quick “they don’t work” comment- chances are that contractor doesn’t know what you just asked.
Most of these wall designs are not DIY, however. Perhaps with innovations in designs and materials, they may be.
Double Stud Walls
This method involves building the first outer wall frame with conventional lumber (2-by-4), then a second frame using 2-by-3 lumber inside the first. The wall can be anywhere from six inches or more from the first wall. The second wall studs are offset, except at the windows and doors. The interior wall is not load bearing, so it doesn’t need the same framing for doors and walls as the exterior framing.
Cellulose insulation or other insulation methods are employed for the resulting cavity for R-value of 40.0 or better.
This can be a DIY project for existing homes- no tearing out the original wall framing is needed.
The Larsen truss involves building a wall cavity with conventional 2-by-4 framing and a second frame on the inside of the house. Vapor barriers are placed between the inside wall board and the frame. On the outside, OSB and house wrap are used.
The frame studs are held together with 1-by-4’s or other materials. The top of the frame is sealed with plywood. Blown in cellulose insulation packs the cavity, and creates an R-value of 39.5 to 50. The Larsen truss walls are typically 12 inches deep. In two-story houses, the floor is also 12 inches deep and filled with insulation.
The downside is loss of interior space. New construction can certainly take this into consideration.
The homeowner should be careful when deciding on using Larsen trusses for their framing. It works well in the Northeast United States area, but may not be suitable for other climates.
Be sure to check with a contractor who has experience with this system.
Engineered Lumber Walls
Since old growth trees are becoming scarce, engineered lumber was developed to step in. Stronger than regular wood, it is routinely used to create wooden I-beams, roofing trusses and much more.
These walls have an R-value of 44.0 or better, depending on the extra insulation used. Many are treated to be fire retardant and bug resistant. I’d still treat for termites, though- those little buggers eat just about anything made from wood.
Spray Foam Insulation
There are different types of spray foam insulation on the market. One is soy-based for those who only want to choose eco-friendly products. This insulation is sprayed in by a professional (sorry, no DIY here), and within seconds it reacts to the air and grows, filling every nook and cranny.
It’s waterproof, bugs won’t eat it, it will never settle, mold, mildew, etc. It will give your walls an R-value of 41.5 or more.
Rigid Foam Insulation
When remodeling, if the existing insulation has settled, has insect/rodent/water damage, remove and discard it. Installing layers of rigid-foam insulation can give your walls an R-value of 40.0 or more.
The foam insulation is available in different thicknesses and materials. Talk to your contractor or DIY store associate for the best product for your home. Yes, that’s a hint- this is a DIY project. You can cut this stuff with a utility knife or an electric kitchen knife.
Structural Insulated Panels, or SIPs
These walls can have an R-Value of 40.0 or better. OSB (oriented strand board) is attached to a layer of rigid foam insulation to form a sort of “building block.” This incredible design allows for homes to be built quickly and easily.
They arrive on the site either as full panels or can be pre-cut at the factory to build the entire house as a pre-fabricated kit. Air tight and fire resistant, they are gaining acceptance across the country.
By doing careful research, you’ll be able to choose the right design for your home. I think I’ll put the double wall to use in my home. Initially, I think an 8- inch deep wall – measured from the outside stud to the inside of the second wall- will work for me. Spray foam insulation will do the trick, and as my project is DIY, I can work on one room at a time. Source: Bruce Coldham, “Six Proven Ways to Build Energy-Smart Walls,” Fine Homebuilding Website, 12 November, 2009