GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

If you live in a mild climate with tolerable summer humidity, is it reasonable to have fresh air intake directly into home rather than ERV/HRV?

aunsafe2015 | Posted in General Questions on
I’m located in the pacific northwest, with average winter overnight lows in the high-30s (99% design = ~30F), average summer daytime highs in the mid-70s (99% design = ~85F) with a “humid” summer day having dewpoints around 60F.
I live in a house that has a ducted HVAC system, but adding dedicated ERV ductwork is not a feasible option because my basement is 100% finished and I have no accessible attic, and I don’t want to tear up my walls/ceilings.  The house has a Fantech Fg8 air intake fan that automatically supplies fresh outdoor air into the furnace return plenum when I turn on my 400cfm kitchen range hood.  So the house does have a fresh air source–just an inefficient one with no energy recovery.
Rather than doing a ducted ERV connected to my existing ductwork (concerned about ERV balancing issues because you have the furnace blower sucking on the ERV supply/exhaust and likely overwhelming the smaller ERV fans), or standalone ERV/HRV units like Lunos E2 or Twinfresh (don’t really want to cut four 6″ holes into my house), am I crazy to consider just using the existing Fantech Fg8 air intake fan as my primary fresh air source?  I would add a controller to allow it to run a certain amount of time per hour (instead of only when my range hood runs) and to allow me to adjust airflow so it’s only ever supplying about 100 cfm at a time.  The downsides of this setup are positive house pressure (how bad would the positive pressure be from 100 cfm of intake air on a 3200 sq ft house that is 4.9 ACH50? Not terrible, I would think) and, of course, that I still have no energy recovery of any kind.  Advantages are that it’s simple, it’s cost effective, it requires no new ductwork or house penetrations at all.
Is that reasonable in my situation?  Mild climate, low summer humidity, so lack of energy recovery may not be a deal breaker.  Simple and cheap.  Would the positive pressure be a deal breaker?
Thanks for any input!

Edit:  My setup is pretty similar to the duct diagram figure in this article:

Except that I have an actual fan (Fg8) to go along with the dampers for the air intake, and all of my equipment is in a basement garage.

Edit 2: My furnace blower motor uses about 50 watts when in “fan only” mode.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |