Saturday, August 23, 2008
The Green Shop - Trusses and Heating Systems
So you've figured out how you're going to build the shop. If you're like me, you decided to do it yourself and probably went with traditional (in the U.S.) stick framing. Hopefully, you will choose a better alternative than fiberglass batt insulation. If not, remember to go crazy with the caulk and foam, and be extremely anal in doing a "perfect" installation of the batts.
Now for the truss system. This one is easy. It's gonna cost a little extra, but go with what is called a raised heel or energy truss. If you use a traditional truss, you do have a way to do a "better" job of getting the insulation all the way to the edge of the eave, but it will cost more than if you had originally purchased the energy truss. Three years ago, when I started my shop, I didn't know about energy trusses and therefore took the more expensive route. When it came time to spray the foam in my wall cavities, I hung the sheet rock on the ceiling at the eaves and had them also spray eighteen inch in. That is the approximate distance in from the eave I had to go before I could get an R49 (15 inches) of blown in cellulose.
If you opted to build on a slab and plan on a traditional (again, only in the U.S.) heating and cooling system. Think seriously about a conditioned attic. The idea is very similar to what I discussed in "Slab or Crawl Space". You would place the insulation against the roof, not the ceiling and you will not be installing vents. See "Slab or Crawl Space" also for how heat moves.
I installed a traditional HVAC system. I've since learned about ductless heat pumps and plan on installing a multi-split system in my house. I currently heat with propane and, like all fossil fuels, the cost has been rising dramatically and I believe will continue to only go up in price. The system I'm planning on installing will pay for itself in less than five years. That is my house. My shop is another story. Because it is so energy efficient, I'll be holding off until the price of propane goes up another $2.00 or more. In both cases I will be keeping my existing units in place as back up. While these ductless heat pumps are very efficient, they do have a threshold for how cold the air can be and still be able to have heat extracted.
If I was building my shop today, I would install a single or double unit ductless heat pump and have, as back up, a couple electric resistance wall units or a few portable units. We rarely get very much below zero and don't stay there for long.
I hope The Green Shop posts have been helpful to those of you who are building, or have built, a shop. If you are planning on building a house, most of what I've written about also applies. Get your contractors and sub-contractors involved, and on board early on, if you plan on building a highly efficient green house. Again, if you have any questions, feel free to ask. If I don't know, I know people who do. Also, make sure to check with your local utility to see if they offer free, or low cost, household inspections. There are a few very lost cost measures anyone can do to their house and get a good return on the investment.
P.S. For photos of my shop, check out the Flickr widget in the right hand column.