Air in, air out... yet airtight!

The week before the blower door test (post soon to come on that), the final component of the HVAC system was added to the nest.  The Zehnder ComfoAir 350 air exchanger, continuously provides fresh air and removes stale air all while recovering 90% of the heat. 

The system takes fresh air from the outside, filters it, and heats or cools it using the temperature of the indoor stale air being ventilated out.  Flexible and smooth HDPE plastic ventilation pipes are fitted within walls and floor joists and connect the air exchanger to air diffusers in the ceilings.  The conduits can be easily cleaned if needed since there are no junctions, angles or cross-sectional changes.

From the air distribution box, a ventilation conduit leads to every room in the house.  Some rooms get 2 or 3 conduits depending on the volume of the room and ventilation needs.  The whole system is balanced for equal air flow in and out.  The fresh air flows into the bedrooms and living areas, while the stale air is removed from the kitchen and bathrooms.   The kitchen has 3 conduits, which should prevent cooking smells from lingering or migrating upstairs.  The system virtually makes no noise, with silencers fitted to the air diffusers.  This will certainly be a change for us, being used to our very loud bath fan and air moving through our old metal grates as the H/AC system kicks on and off.

 As it replaces the stale humid air at maximum capacity of 215 cubic feet per minute, it provides another key service to the tight house which is preventing mold.  The design of the house follows hygrothermal modeling which pertains to the movement of heat and moisture through the home.  The computer based modeling offers highly accurate predictions of hygrothermal performance for preventing early degradation.


To service the system we simply will need to replace the filters when needed.  The heat exchanger itself can be taken out and washed with water every 4 years.  With our 3 kids each about 4 years apart, we can someday use milestones such as high school and college graduations to remind us.