Where should you locate HRV and ERV exhaust vents?

Micara Muir
Micara Muir

We are building a 816sq ft 2 bed 2 bath home, new build, relatively tight (not passive) with 2" Roxul exterior insulation and 5.5" sheeps wool insulation in the walls and 9.5" sheeps wool insulation in the vaulted ceiling. ICF slab foundation, no attic or crawlspace. Temperate climate (30C summer, -25C winter) with wood stove heat and no A/C. We have therefore decided on a ERV (Lifebreath Metro 120) for good air quality and to maintain somewhat stable humidity.

1. We will have an exhaust vent in both bathrooms from the ERV, and fresh air vents into the bedrooms and main living space. Living space and kitchen is open concept and only 320sq ft. If we run an exhaust vent from the kitchen area as well as the two bathrooms, we will not have the minimum CFM to exhaust the bathrooms according to our district, which is 50CFM each. We will have a dedicated hood exhaust and make up air supply for the kitchen. Do you think this will be sufficient, or do we need to look at a larger ERV and add in a kitchen exhaust for the ERV? We arent even finishing the second bathroom and likley never will unless we sell the house, so upsizing the ERV seems completely unneccesary when you look at how we actually intend to live in the house. Also adding a kitchen exhaust to ERV adds another bulk head to our small house so I would rather not.

2. Make up air for the kitchen exhaust....wowza. It seems that this is required but very little is written into our building code here to suggest best practices. I have decided we will do our best to bring fresh air in directly around the stove to vent directly into the exhaust. I would love to hear your best damper solutions, so far I am leaning towards the BROAN 6" make up air damper (min exhaust requirement for our district is 100CFM so I will go with a small range hoood). We cannot pre-heat the make up air because we are on solar, no electric heat so I believe my best bet is to get the air in and out of the house as efficiently as possible without it circulating with the conditioned air in the house.

Would love to hear your opinons on these matters! Just a note that there will also be "make up air" for the wood stove as required by code here.

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