We met with Rachel Wagner and Jed Lahti at Wager Zaun to review our project and understand their perspective on building highly efficient homes.
Here's the notes from the conversation:
Passive House: Don't bother to meet standard with a small footprint house.
Dryers: Use a heat pump dryer - whirlpool or kenmore are $1400 and can be stackable.
Foundation: Stem wall or floating slab are both compliant with MN building code. Stem wall is preferred if there are grade issues
Insulation:
Radon management: Code requires remediation. Allow space for an active fan if you need to install it later. Test after the house has been up for a while.
Windows:
Here's the notes from the conversation:
Passive House: Don't bother to meet standard with a small footprint house.
Dryers: Use a heat pump dryer - whirlpool or kenmore are $1400 and can be stackable.
Foundation: Stem wall or floating slab are both compliant with MN building code. Stem wall is preferred if there are grade issues
Insulation:
- Rigid mineral wool as an alternative to foam
- Ants are a problem with foam
- Dense pack cellulose preferred
- Sound insulation: No pocket doors - creates echo chamber
- Radiant Heat: In current leaky house, floors will run at 80 to 85 degrees - which feels good. In a passive house, the floor will only run at 70 to 75 -- which will feel cold because it is taking heat away from your feet. Floor won't react quickly and has larger temperature swings - results in not so comfortable house.
- Mini Split recommended solution: Operate to -20. COP of 2. Mitsubishi or Fijustu
- Electric baseboard: COP of 1. Good backup, but not an efficient primary source.
- Electric boiler: COP of 1
- Like the use of a wood stove in a high efficiency house as an alternative heat source
HRV
- Uses 45 to 55 watts when running.
- VenMar - cheaper
- Zender - gold standard
- Ground tempering: Reduces the defrost cycle - but we won't be here at that time of the year. Ground tempering results in concerns about air quality.
Windows:
- Al Duek - Duxton (recently visited Wagner Zaun)
- Accurate Dorwin
- Builder has 2'8 x 5' windows - do not open, 8 or 9 of them.
Air Barrier: Use OSB with tape. Concerns that some OSB allows air penetration. Zip Sheathing is not available in this market.
Interior vapor barrier: Latex paint as the interior barrier.
Attached garage causes issues with indoor air quality - especially if the workshop is in the garage. Separate with a breezeway and ensure there's an airlock between house and garage.
Attached garage causes issues with indoor air quality - especially if the workshop is in the garage. Separate with a breezeway and ensure there's an airlock between house and garage.
Wall Assemblies:
- Larsen Truss is a good approach.
- Double wall is used because of the two story structure and insulation challenges with a tall wall.
- Transition from house to garage or porch - no specific answers with a Larsen on the outside. Pin concrete to keep from moving.