Saturday, August 16, 2008

The Green Shop - Choosing a Building Method for Walls

I've been hearing a lot of people talk about how hot and uncomfortable their shops are now that it is summer. My goal when building my shop, was not only to have a comfortable space to do woodwork, but also, to not have my shop greatly increase our energy costs.
If comfort, or energy costs for comfort, are a high a priority for you in your shop, then what I'm talking about in this thread is really going to be a benefit to you. My goal with this thread is to help you make the best decisions on how to achieve the most comfort with the least overall costs.

Sometimes a little more cost upfront will have a huge impact in the future cost of the building. My favorite building method is a case in point. SIPS: Structural Insulated Panel Systems are by far my favorite system because they, can be made completely from recycled material,create an airtight envelope, and completely eliminate thermal bridging. SIPS are made by sandwiching polystyrene (similar to the kind used for ice chests) in between two sheets of OSB (Oriented Strand Board). However, they require a contractor that has knowledge in SIPS construction and, where I live, there aren't any contractors using them.

My second choice for a building system uses ICFs (Insulated Concrete Forms). These are foam blocks that go together like Legos and have a concrete infill. These also provide an airtight envelope and eliminate thermal bridging but, due to the high energy process of making concrete, are not nearly as "green" an option. Plus, if the footing and foundation is not done in such a way that it breaks the thermal coupling with the ground, that large mass of concrete can cost you heating dollars instead of saving them. However, you'll find it much easier to find a contractor who uses this building method.

Since I was building my shop myself, I went with traditional "stick framing". The unfortunate byproduct of this building method is thermal bridging. Thermal bridging lets heat in and out of the building via conduction. In this instance, you'll have a wall stud in direct contact with both the interior and exterior sheathing. You can lessen the amount of thermal bridging by using what is known as "advanced framing", which is basically using less studs. Instead of building with the now typical 16 inches on center, you would go 24 inches on center. This not only decreases thermal bridging, but also increases how much insulation you can install. If you're going to build yourself, either take a class on "advanced framing" or make sure your plans are engineered and drawn up with "advanced framing" details.

Going the framing route means you'll also have to decide what type of insulation you're going to use. I used a closed cell polyurethane spray foam. This created an air tight seal and high insulating value. It is one of the things I had to contract out, due to the specialized equipment needed. A do-it-yourself option is batt insulation. This will work, but requires extreme attention to detailed installation. A small compression, not having the insulation touch all surfaces, or any gap will make this type of insulation perform very poorly. I would also advise caulking everywhere two different members contact each other and all holes in electrical boxes (including unused knock-outs). Anywhere there is any type of penetration needs to either be caulked or foamed, if the hole is too large to caulk.

Again, even though I'm writing about the building process in a linear form, many of the subjects need to be discussed at the beginning. If you're using a contractor, architect, or engineer make sure they are viewing the building process as a whole, not individual parts. All the details need to be worked out prior to breaking ground for best results.


Pops said...

I'm soo jealous of your shop! We loved looking at the pictures of how the shop was coming together. The plywood wood floor is AWESOME, what a great idea! The spray foam was genius. Did it cost a bundle? and can you really tell a big difference with it? and how is it compared to traditional fiberglass?

Vic Hubbard said...

Hi Kendall,

The cost for the spray foam was $3032.40 w/tax. I haven't figured out payback on the cost difference between that and fiberglass batt insulation. I also spent $925.97 for an R49 level of cellulose in the attic. It does make a huge difference. Even when the temps here reach 100, my shop doesn't go above 80 degrees without the air-conditioning. The amount of window surface has a lot to do with that, too.

Vic Hubbard said...

Also Kendall, remember my shop has taken over three years to build and I have been saving for its construction for quite a few years. But, I plan on living here until I die. As energy costs and incentives rise, I'll probably add solar, also. For me, things have to make financial sense before I'll invest in them.