We went to the Energy Fair in Custer Wisconsin. It was like TED for renewable energy and efficient building. We wanted to leave the fair with a good approach for our wall assembly. We achieved that by learning from the following presenters:
High Performance Wall Systems - The Newenhouse Builders
Layers from the outside in:
Homes for a Changing Climate - Root River House - Christi Weber from Design Coalition Architects in Madison
Like the wall assembly after we understood it:
Gimme Shelter - Wall Assemblies for Contractors
Considerations for the Site
Wind wicks heat from walls.
Insulation Rvalues are measured based on 70 degrees with no infiltration
Consider permeable pavers in front of garage - better at managing water and snow
August and April have the same sun angles - but very different usage of solar gain.
Use a living screen - vines, trellises, corn, sunflowers to block heat load in the summer.
High Performance Wall Systems - The Newenhouse Builders
Layers from the outside in:
- Siding - Exterior finish doesn't matter - cedar, stucco, metal
- Rain screen - 1x3 strapping over WRB. No siding should be compressed against the house.
- Plastic vent strip at the bottom and top for insect protection - CorraVent. Run the siding vent all the way to the attic - can eliminate the vented soffit (we didn't think that was a good idea if snow builds up at the bottom of the wall)
- WRB - use Tyvek, stucco wrap, other materials - key is to have a gap
- Fiberboard/Buffalo Board/Beaver board. Vapor permeable
- Wall - Larsen Truss filled with self settling cellulose. Leave it a foot above wall and fill more later on - takes a couple of months to settle.
- OSB - Tape the seams using a tape from 3M8067. Use all weather flashing. Put the smooth side of the OSB where the tape will be applied for better adhesion.
- Plastic vapor barrier wraps up from the foundation and is taped to the OSB.
- Wall - Spaced the walls inside and outside at 2 feet. Walls fall directly under the truss. This causes issues with the interior trim, so prefer the interior wall on a 16 in spacing to avoid additional blocking.
- Drywall - NO vapor barrier, want wall to dry to both sides.
- Rubber membrane on the bottom of the sill plate. 1/4 inch thick. Even on a 2x6 wall, use the 4 inch product for ease of install. Use acoustic sealant between the OSB - for movement.
- Do not use spray foam - may not adhere to the wall over time. If applied when the wall is cold and the foam is warm, there's a durability issue.
- Blower door tests - standard equipment doesn't work. Need a duct blaster to be small enough to read in a tight house. Want to reach the final number at the time of framing - typically doesn't get better.
- Electric and plumbing are the word to seal - have to get every hole when you make it.
- Doors are set in, windows are set out. Mostly for function and visual appearance.
- R value is 52.62 for a 16 inch wall.
Homes for a Changing Climate - Root River House - Christi Weber from Design Coalition Architects in Madison
Like the wall assembly after we understood it:
- Larsen on the inside: Because it had the least risk of leaves, insects, and other gaps for things to hide.
- Air barrier in center of the wall, continues across ceiling, and under the slab - very easy to install and eliminate penetrations.
- Foundation: No foam on the outside of the foundation due to damage from lawn mowers, people, and critters.
Other tips:
- Put a PVC pipe/sleeve through the wall for the line sets to run - easy to replace.
- High solar heat gain windows - should be at least 50%
- HRV runs - will fit in 2x4 walls. Use Zender but also like RenewAire made in Wisconsin
- Would cost about $1000 to $2000 to certify the house as passive
- Window manufacturers are changing all the time - make sure there are air spacers and multiple gaskets
- Like the TuTuff air barrier under the concrete. Taped all layers of the EPS foam.
- ecoHeater is a model that plugs into a regular outlet - good back up option in cold winters
- Use 2 layers of latex paint on the inside - do not use wall paper or the walls won't dry well.
- Next house: 7 1/2 inches of EPS under the floor, 12 inches of cellulose.
Gimme Shelter - Wall Assemblies for Contractors
- 2x6 with strapping results in 7 inches of cellulose for R30 wall - see handout.
- Also build R45 wall with 12 inches of cellulose - very few customers looking for this level of insulation. Wall built 2 feet on center. Interior wall is non-load bearing.
- Use smart vapor retarder/membrane - intello
- Use OSB rather than plywood on the wall because it can be permeable when wet. Sheathing always on the outside of the wall.
- On a 1500 square foot house, going from R30 to R45 would cost about 10K to 12K with window and wall upgrades.
- Build to a standard of 1 ACH50
- Tyvek on the outside - designed to dry to the outside. Use solid wood sheathing and siding for this reason.
Considerations for the Site
Wind wicks heat from walls.
Insulation Rvalues are measured based on 70 degrees with no infiltration
Consider permeable pavers in front of garage - better at managing water and snow
August and April have the same sun angles - but very different usage of solar gain.
Use a living screen - vines, trellises, corn, sunflowers to block heat load in the summer.