There are many choices in energy efficient wall assemblies. Each article we read has a slightly different approach.
Our current favorite is the Larsen Truss - here's some good overviews:
http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-larsen-trusses
http://www.builditsolar.com/
Here's why we like it:
1. The vapor barrier is in the middle of the wall. This will allow all the electrical/plumbing/heating in the inside wall cavity without penetrating the vapor barrier.
2. The wall can dry from both sides.
3. The Larsen Trusses hanging on the outside of the supporting wall would allow the insulation on the outside of the slab to be covered.
We are not sure how the lake-side porch will be attached to the larsen truss. Nor have we validated our thoughts with architects and builders.
We have also considered:
Our current favorite is the Larsen Truss - here's some good overviews:
http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-larsen-trusses
http://www.builditsolar.com/
Here's why we like it:
1. The vapor barrier is in the middle of the wall. This will allow all the electrical/plumbing/heating in the inside wall cavity without penetrating the vapor barrier.
2. The wall can dry from both sides.
3. The Larsen Trusses hanging on the outside of the supporting wall would allow the insulation on the outside of the slab to be covered.
We are not sure how the lake-side porch will be attached to the larsen truss. Nor have we validated our thoughts with architects and builders.
We have also considered:
- Double wall filled with cellulose: Not sure how to get a continuous vapor barrier with no penetrations. Although it has been used in a number of projects - like this home in Duluth. Wagner Zaun's Skyline House is another good example. Note that offset studs will provide more acoustic insulation.
- 2x6 with spray foam: Foam isn't very green - and we are concerned about the ability to dry and long-term durability/air seals
- SIPs: Can leak and fail if not installed flawlessly and can't find a formaldehyde-free supplier
- Framing in ways to reduce lumber usage - "The future of framing is here" from FineHomebuilding.