Tuesday, November 17, 2009

Of walls, and wide angle lenses

Newt and I went over some of the build details with the rep from Nudura. Nurdura makes the insulated concrete forms we are planning to use. As I have said, the walls will be poured concrete. The concrete will be 8 inches thick. However, if we just poured concrete walls, and backfilled around them, I would end up loosing a lot of heat in the winter. In the summer, they would draw a lot of heat out of the inside air, however they would probably do such a good job at it, that they might sweat like a cold glass of lemonade outside. Neither one of those outcomes is desired. The walls must be insulated so that heat loss is managed and to prevent condensation when the air gets humid.

There are a few different approaches to building and insulating the walls in an earth sheltered house.

One is to pour traditional concrete walls, but then before backfilling with gravel and dirt, insulation and waterproofing is applied to the outside of the wall. This actually provides the best positioning of insulation and mass of the wall for the desired effects, according to what I have read. The best route from a performance standpoint is to have the insulation enveloping the house. This limits the influence of outside temperature, and allows the large mass of the concrete to most effectively absorb and release heat into the inside, to maintain comfortable temperatures.

Another way to construct the walls, is to pour traditional walls, waterproof the outside and backfill, then add insulation to the inside of the wall. This however prevents the mass of the concrete from being able to assist with moderating inside temperature swings.

Block walls can also be constructed, and then insulated the same way the poured walls would be. If I were building the wall myself, this might be a consideration, as building a block wall is something that one person can do. I have read about successful use of block walls, however it is labor intensive, and since I am having someone else build the walls I did not really consider block walls.

Pre-fabricated concrete panels might be used. I have seen a couple different systems of factory built concrete panels. The are built in a factory, then shipped to the build site and set up and fastened together. This could be a very quick system for getting a wall, but with so much of my walls burried, I was concerned with how well the panels would hold up against the forces from the ground. From what I have seen this also has much less mass than a poured wall, and the insulation is on the inside of the mass.

Insulated concrete forms were the route I chose. I had seen some references to them being used in earth sheltered houses and so I researched them. They would offer the potential for a single person to set them up since the systems consist of individual pieces one person can handle. However they also offer a fast system for having a contractor come in and provide an insulated concrete wall. The various insulated concrete form systems all end up producing a similar structure. They consist of rigid foam peices that are tied together through the concrete wall. They offer insulation and a form for the concrete to be poured into in one product. The insulation is on both the inside and the outside of the concrete. From the research I have done, this will produce a wall that won't perform as well as if all the insulation was on the outside of the wall, but it offers a number of other advantages over a traditional poured concrete wall. So ICF is the route I have chosen.

As for photos, it is a bit of a challenge to get a photo that has the whole floor. To get back far enough for my camera to be able to photograph the whole floor, I have a wall of dirt blocking the view. I need a wider angle lens.

See what I mean? You can see the southwest corner here, but that is it.

So here is one where you can see about 3/4 of the floor. It is a pretty big floor.

This was taken from the opposite corner. This is the southwest corner. In this corner will be the master bedroom and bathroom and the hobby room. If you look close, you can see where I set out a tape measure where the garage would end. You can see the yellow tape starting to the left of center and angling across the dirt toward the right to below the center of the photo. The garage is about 20 feet by 20 feet.

There probably won't be much to update on for a few days. Newt has some more information to get before we proceed any further. I just ordered a text book on designing radiant heating systems. We were not satisfied that we got enough details from the contractor who was supposed to design it, so I am off to fill in my knowlege on the finer details of designing a radiant floor heating system. I am going to be very knowlegable about the systems in this house and how they should operate. BD Heat and Power is at it again.

Oh, and yes I am having fun!!

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