We have a list of considerations for indoor air quality - due to allergies and properly managing air movement in a very tight house.
- No formaldehyde due to allergy: Ensure insulation, particleboard, MDF and hardwood plywood are certified to low formaldehyde emissions standards. Use exterior-grade pressed wood products because they contain phenol resins, not urea resins.
- No carpet due to dust, allergies, and high chemical content.
- Choosing different drywall -- use paperless drywall to eliminate the possibility of mold eating the paper. There are gaskets to put behind the drywall seams to prevent moisture.
- Careful consideration of venting and construction techniques to reduce possibility of mold growth
- Clothes dryers cause an issue with high air exchange (150 to 200 cfm) and are a conflict in a passive house. We looked at condensing dryer options - but they are all expensive, and there are not many choices in the US market. We could just use an electric dryer and open a window when it is running -- but there would still need to be a dryer vent which puts another hole in the building envelope.
- HVAC is a key component for air quality:
- It needs to pull air from baths and kitchen with fresh air to bedrooms/living.
- HVAC will eliminate need for vented range hood.
- Concerned about efficient HVAC operation in cold weather - although we likely won't be there for that season. Hunt's put the HVAC incoming line under the ground to temper the air -- this seems like a potential radon or mold issue. Can we run the inbound duct through a longer run in the house so the air warms prior to entry into the unit?
- UV light and HEPA Air Filtration System - Is this in the HRV or incorporated into ductwork?
- Cover ducts during construction to prevent dust and debris
- No/Low-VOC interior paint, sealants and adhesive
- Radon remediation
- Natural gas appliances are cause for concern - carbon monoxide and backdraft issues are possible. While we always have had natural gas dryers, water heaters, fireplaces, and furnaces -- we are thinking we will just move all of it to electric. Which also eliminates the fossil fuel dependency, eliminates a monthly bill, and would help the house be totally operated by the PV array. Here's the choices we'd make to replace natural gas with electric alternatives:
- Electric stove - considering and induction cooktop range - if we can find one that is not too expensive.
- A simple, small, electric tank water heater with a good insulating blanket.
- Ductless mini-split heat pump to provide supplemental heat and cooling. Because these don't work well in extreme cold, we'll also put in radiant heat with a very small electric boiler.
- Electric fireplace - it still seems like a cabin at the lake should have a fireplace. Maybe just a small one on the porch. We'll take a look at this one and see what we think: Dimplex OptiV LED fireplace - the solo version pictured below is about $900. A small unit like this would allow the porch to remain mostly windows:
