I just though I would post some pictures of a double stud house I worked on over the summer. The house is a smaller 1 bath, 1 bed, great room style house. The house has 600ft^2 heated living space, but with 9' ceilings and light colored walls it actually seems spacious. The total cost of the project was roughly 50k, which included cabinets, appliances, hardwood and ceramic tile floors, attached garage ect. This is a good example of what can be done on a tight budget without cutting any corners on quality.

The insulating properties of this house are double 2*3 walls 24" on center with 2.5" foam in between, as is shown in the pictures. The crawlspace is insulated with double layers of foam against the blocks and fiberglass/foam combo in between the joists. The ceiling is blown fiberglass, about 18" deep, along with raised heel trusses to get 16" depth on corners leaving a vent space. The hvac system is a heat pump, and there is an electric hot water heater.

Did it all work? Well, the combined water bill and electric bills haven't broken $70 a month yet, which seems good considering the homeowner likes to keep the house air conditioned to about 68-70F in August here in Tennessee. I expect the bills to go up a little in the winter, as the heat pump will have to work harder, but probably not much.

Were the inner and outer 2x3 walls tied together?  If so, how?  Were the walls built on the floor and then tilted up as a unit?

Noice!

Didja hafta cut some caves in the foam behind the electrical boxes, or are there some that make it?

The inner and outer 2*3 walls were tied together, because the top and bottom plates were prefabricated in my garage about a week before the framing started. As you can see in the first picture the top plates had double 2*6 connectors every 2' that created pockets so that the trusses would drop right in and we could nail them off. These connections were glued and spiral nailed off, and they were very well attached.  For attaching the bottom plates together, they were both nailed to the same sill board, then we hammerdrilled 1" holes in the poured solid blockwork under the wall, then used anchoring cement to set 3/4" all thread rods, and then spanned across both sill boards with 1/4" plate steel pieces with holes in the center and torqued the bolts down on the all thread once the cement set up. You can see in the second picture where the steel is. We actually tilted up just the outer wall with the plates for both walls attached, that way we could add the fiberglass and foam without the other studs getting in the way, and then we just came and put the inner studs in.

We were worried about the electrical boxes, but the cheapo ones from lowes just barely fit.

How are you adequately supporting the truss' over the middle of the window and door?
Did you add the Advantech over a plywood subfloor?

You can't really tell from those pictures, but the "stud cavities" over the door and window are actually the insides of a one sided box beam that was glued and nailed off. Then the outer plywood overlayed the box beam's plywood, and we used a nailgun and glue to tie it all together.

You are actually seeing a temporary floor. We removed the plywood before we put the advantech down. That made it much easier to insulate and work in the crawlspace, because we could just pull up a sheet of the temporary subfloor and stand and work, instead of crawling around. We used extra thick plates that we stuck to the inside so we had a ledge to attach the advantech to when we were finished.

I'm confused about the walls. You must have used additional insulation besides the 2.5" foam? The foam would only be about R-13.

Why the 2x6 blocks for securing the trusses instead of hurricane clips?

We used R-13 fiberglass batts in the inner and outer stud walls with 2-3/8" EPS foam between them. The hurricane clips would have worked just as well at holding the trusses down, but the 2*6's held the inner and outer top plates together. When the walls first went up, the top plates and 2*6's were already there. Also, the 2*6's held the trusses in place temporarily without any other supports. We didn't even have to nail them at first, we just set them in and went on. Also, once we had the jig set up, my dad and I put those together very quickly, and with low material costs for 8"pieces of 2*6 these were very affordable.


Oh yeah, the combined water/electric bill for October was $37, and $12 of that was a "customer charge".

I guess it goes to show that no matter how energy efficient the building is you will never escape the "customer Charge" :)

The building looks very well thought out. It would be nice to see more projects built with such foresight.

I'm taking a closer look at your pic showing the truss, did you have those trusses designed? It looks like you cantilevered a standard truss, or did you build a front porch beam to pick up the truss load at the end bearing?

The company who built them designed them to bear the load at that point. They are basically standard trusses cantilevered out 3' on each side, but with a 2*6 bottom flange to be able to support the trusses at that spot. It's only a few inches in to the first 2*4 of the web anyway.