I described the 1st floor range hood preparations, which had to get done prior to the spray polyurethane foam (SPF) insulation.
The other ventilation items we had to complete were the Energy Recovery Ventilator (ERV) supply and exhaust, both of which also required holes through the masonry walls for the duct work.
But before I get any further into the installation process, let’s take a step back and look at the rationales and design of the ventilation system.
Ever heard of ‘sick building syndrome’? That’s when a building does not get sufficiently ventilated. The indoor air becomes stale and unpleasant. Pollutants and toxicants begin to accumulate and impact our health.
With a super-insulated and air-tight building envelope, proper ventilation is very important to us to ensure good indoor air quality (IAQ).
One may conclude that along with ventilation comes an energy penalty. The conditioned, stale indoor air is exhausted from the building while unconditioned fresh air is drawn into the building to replace it.
To minimizing this energy penalty the Energy Recovery Ventilators (ERV) or Heat Recovery Ventilators (HRV) become handy. They are basically air-to-air heat exchangers, taking the energy from the conditioned exhaust air and transferring it to the unconditioned supply air. I now get the fresh air I need for ventilation at a minimized energy loss.
I described the research and design that went into the ventilation system for the garden apartment. That blog post is a good overall introduction, and we can reuse almost all of the same principles for the 1st floor unit. The biggest difference between the two units is that on the 1st floor we have many more rooms to ventilate — nine rooms and two hallways to be precise.
To get good airflow we will need a distribution network of ducts.
The Ventilation Guide by the Building Science Press came in very handy again. It provided good guidelines on the layout options for the duct network, based on how we distribute our supplies and returns of the ventilation system.
- Supply: point where fresh air is supplied from the duct work into the building, typically through a ceiling diffuser.
- Return: point where stale air is pulled back into the duct work and exhausted from the building.
We overlaid the ventilation guidelines with our floor plan in search for the most thorough air distribution and exchange. Allotting the fresh air supplies among the entrance hallway and three bedrooms would give us the best results, if we placed the returns in the two wet rooms. Those would be the full bathroom and the future half bath.
To get the supply air moving from room to room, we have three options.
- To undercut the doors between rooms by up to one inch. We plan this for the French doors between the entrance hall and library, as well as for the pocket doors between the library and living room.
- Using ‘In-door Pressure Balancers’ where we would like the airflow close to the floor. This could be in most other regular doors.
- Using ‘between room vents’ where we would like the airflow closer to the ceiling. The In-door Pressure Balancer and between room vents can be used in lieu of each other or in combination.
To keep the duct runs short, we converted the old hutch opening between the living and master bed room into a ventilation closet. Locating the ERV here places it right next to the old chimney flue, into which we would like to place the exhaust duct.
The more central the location of the ERV, the shorter the overall duct runs, the less the airflow friction and the more efficient the system.
The duct work issues
One problem we have is that the interior architecture does not lend itself to duct work. Six inch round ventilation ducts traverse the dining room or living room ceiling would look out of place.
We are fortunate to have ten foot tall ceilings throughout the 1st floor. These give us the opportunity to hide the duct work to the supplies and from the returns in the ceiling if we lowered it by eight to ten inches, depending on the duct sizes.
But we also would love to keep our ceilings 10 feet tall. After some back and forth, we determined that the most public rooms (library, living room, dining room and kitchen) should keep their ten foot ceiling.
The bedrooms, bathrooms, hallways and closets would accommodate the duct work and end up with slightly lower ceilings.
No matter what duct layout I looked at, I always ended up with a short run through the living room. We thought that if we keep that duct as close to the wall as possible, we could hide it in an elegant soffit right above the door.