The USGBCNH group was having a discussion on ventilation systems recently, and we thought it would be a good topic to share here. 

Now that winter is almost here and everyone's windows are staying shut for the next 4-6 months, the question about indoor air quality becomes a lot more relevant.  We all know how important mechanical ventilation is for our health and for the health of our buildings, but in the building industry it is still a relatively foreign concept. 

This is especially true in single family residential design, where the building code is behind where it should be on ventilation requirements.  Homes are now being built pretty air tight thanks to building code improvements, but an air tight home isn't a great solution for the occupant if no fresh air is getting inside. 

A poorly ventilated home leads to high humidity and mold growth, lack of oxygen, and toxins from materials and household products being trapped in the home.

So what do we do about it?! 

I think we are all in agreement that providing balanced ventilation systems is the way to go.  We want to bring fresh air inside the building at the same rate that we exhaust stale air.  But that doesn't go far enough to answer the question.

There are still plenty of options for providing a balanced ventilation system in a home.  I'm in the process of designing a residential art studio with one main room and a small bathroom, and I had the question, 'What's the best way to ventilate this space?'

ERVs and HRVs

We know that using an energy recovery ventilator (ERV) or a heat recovery ventilator (HRV) is a good solution because these units recover heat (and moisture if using an ERV) from the conditioned air to help temper fresh, cold outdoor air before being released in the home.  This helps reduce energy burdens.  

But now we need to decide if we're using an HRV or an ERV!  In our cold climate, an ERV needs to turn off intermittently so that frost doesn't build up on the unit.  Is this the best approach?  An ERV helps keep some humidity inside the home that our cold, dry winter air doesn't bring in.  Is that benefit worth mitigating the frost issues?  

Ducted vs Non-Ducted

And then, as in the case of my small art studio, we need to decide if the fresh air should be ducted through the whole space or if a single distribution system such as the Panasonic WhisperComfort would make more sense.  I asked this question to the group, and it turns out that this type of system doesn't function when it's very cold out.  The Panasonic unit turns off completely when outdoor air dips below 20 degrees F.  

For a home, a ducted system seems to be the best approach so that fresh air is getting into every bedroom, but is there a method that works well for a large open space (such as a studio apartment over a garage) that doesn't require ducting?

After some discussion with the energy experts in the group, it looks like the art studio is going to go with a ducted ERV so we can retain some moisture in the winter and distribute fresh air easily throughout the space.  Is this the best method?

What Would You Do?

What is your approach for residential mechanical ventilation?  Let us know in the comments below.