Thursday, November 19, 2009

Improving energy efficiency with less wood

Sustainability. Green. LEED. We have heard the buzzwords in the structural engineering community for a while now; but isn't this something for the architect to take care of? There is nothing I can do, is there?

Well... Funny you should ask, there is. A Fine Homebuilding article details how designers and contractors can more efficiently frame timber buildings. These framing techniques can double the walls R-value while reducing wood framing by 40%.

Wood framing creates thermal bridges in a wall thereby decreasing the efficiency of the wall and increasing heating/cooling costs. Thermal bridging can be seen in the infrared image above. If framing reduces the insulating value of the wall, then we can just reduce the framing. This is exactly what the article proposes. Instead of 2x4 framing at 16" centers you use 2x6 framing at 24" centers. The benefits are two-fold. You increase the thickness (thereby the insulation) of the wall and reduce the number of members or thermal bridges in the wall.

The author also proposes a number of other changes that build upon this concept. Use two stud corners instead of three stud corners, reducing the awkward area in the corner that is difficult to insulate. What about the gyp board you say... use Simpson's clips to support the sheet rock at the corners. Use a single top plate. This eliminates a great deal of wood, however you will need a strap to create splices (I think Simpson has a few to choose from). How about eliminate the cripple studs at doors and window and replace them with... you guessed it, Simpson header clips. I am seeing a theme here. Replace wood with something Simpson makes.

All in all, there are some good ideas here. You end up maybe spending a little more time, saving a little on wood, spending a little more on Simpson products and less on heating/cooling. The big one is going to be the heating and cooling costs because those come every month. Everything else you just do once. I guess there is something we can do after all.