Replies

1. GBA Editor
   Martin Holladay | Jan 31, 2011 01:38pm | #1

   Chris,
   This equipment is used for a central-fan-integrated supply ventilation system.

   For more information on central-fan-integrated supply ventilation systems, see Designing a Good Ventilation System.

2. 
   jnarchitects | Jan 31, 2011 02:22pm | #2

   Thanks for the link, Martin.
   That was exactly my question. How effective and cost effective are they relative to a Panasonic or Broan fan on a timer. The furnace is a 95% w/ ECM motor.

   I mean, I understand that it is bringing in fresh air mechanically rather than just allowing the pressure change from exhausting air to provide fresh air, but is it significantly better performing than just using an exhaust only approach.

   It looks like it only runs when the outdoor air is within certain humidity and temp. tolerances. Is there any worry that in a particularly humid climate that it wouldn't run often enough to meet code?

3. 
   Kathy | Jan 31, 2011 02:26pm | #3

   Hi Martin,
   On the same subject... In your article, you say, "For small houses with an open floor plan, they (exhaust only bath fans) make a lot of sense. They are affordable and energy efficient." What is small? I have a 2 story, open concept with loft and cathedral ceiling and 4 ceiling fans along the ceiling peak. The house is a little over 2,000 sq ft. and 32' wide by 40' long. R50 (closed cell foam) in the ceiling and R32 (open cell foam) in the walls. I have a wood stove (that I am thinking about installing a fresh air intake to, through the wall in back of it. I sealed everything from the outside and am now in the process of doing the same inside before I put up sheetrock and do the same sealing with the SR. Can I get away with just exhaust fans in the 2 bathrooms (one up, one down)? I did plan a spot for a dedicated HRV if I need it in a conditioned storage room behind the upstairs loft wet bar. ( It will share the room with my extra beer and wine:)

4. 
   wjrobinson | Jan 31, 2011 02:34pm | #4

   Chris, That Aprilaire device is exactly what my HVAC company uses if we upgrade from manual shut offs. The problem with manual systems is the homeowner will never use the manual system.

   Any simple vent system to me is better than spending $5,000 on the best HRV out there unless the home is large and high end.

   Your other option like has been posted about quite a bit is to put controls on the bath fans to run them enough to meet the code and also to condition the air to appropriate quality.

   My latest thoughts on air quality. Someone mentioned how a radon system also reduces moisture loads coming up thru a slab. My thinking is why not also have this one fan do more duty, triple duty. If a bath fan can meet code ACH venting needs so could a radon system. Less is more. One system doing it all. I like it. I will start a post.

   Back to the Aprilaire. Great product is my take on it (edit) for a cold climate, which is where I have mostly built.

   Edit- Warm moist climates, if using air conditioning and closing up windows, need an ERV. And may need dehumidifiers. The Aprilaire is not designed IMO for humid climates.

5. GBA Editor
   Martin Holladay | Jan 31, 2011 03:10pm | #5

   Kathy,
   A central-fan-integrated supply ventilation system distributes fresh air better than an exhaust-only system, but uses more energy to operate than an exhaust-only system.

   An HRV with dedicated ductwork has the lowest operating costs of any ventilation system, but costs the most to install.

   The decision about which system to use in your house is up to you.

6. 
   wjrobinson | Jan 31, 2011 03:36pm | #6

   Kathy, your house most likely is very tight. I suggest blower door testing now, with sealing up what's left to seal while the door is there. Then definitely with ACH known, head for an HRV in a cold climate and and ERV in a warm moist climate.

   The only other option I would use if you are very tight and are in a cold climate would be the Panasonic bath fans that are actually little HRV units. These by far would be the least expensive and my choice in that situation. I also would shut it down when the home is unoccupied. or when I just wanted a cracked window by my bed instead of a mechanical solution.

   A missing link here, would also say use a standard Panasonic fan with air inlets poked thru the bedroom walls up high. Another good cold climate solution. A link to follow via edit.

   https://www.greenbuildingadvisor.com/community/forum/mechanicals/19471/need-hrv

   Search "Panasonic" in the search box too