Quiet HRVs?
I think we need an HRV for air exchange in our house, but I have concerns about the noise levels and can find no data on this topic.
We have a 1600 sq.ft., very open plan, super-insulated, extremely tight house. We live in a cold, dry, windy climate – Colorado at 8000′ (winter winds avg ~20mph with gusts to 60, winter temps can get as cold as -28F, but are usually closer to +24- highs). The house is heated with passive solar and we have a small woodstove for backup heat (it has an outside air intake). We have a kitchen exhaust fan and bath fans, but rarely use them as they are too noisy. The extra moisture isn’t a problem in this climate. Even with quieter fans, make-up air would be a problem.
Most of the time, when at home, and when sunny, we open a window for fresh air- even in winter (we usually need to to cool the house down). If it is cloudy, particularly cold, or we will be gone for some time, we keep the windows closed. I have noticed that when the house has been closed up for a couple of days there is a definite musty smell, and my eyes get irritated, so I know we need more air exchange.
The problem is that without a basement, attic, or crawl space, the HRV has to be installed in our living space, so it has to be quiet. Any ideas on quiet HRVs of the appropriate size? The other problem seems to be that the smaller HRVs have fewer control options. It would seem we need ~40cfm to 100cfm (new 62.2 standards vs. .35 air exchanges/hr) and the units I’ve seen in that size seem to pretty basic. I could go up in size, but assume noise levels, as well as power consumption would also rise. I might like to program the HRV to come on intermittantly, or at low level sometimes and high at others. Any suggestions?
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Replies
What kind of bathroom exhaust fans do you have in your house now? If they are standard "builders grade" fans you might want to swap in a panasonic fan and put it on a timer. While I don't have any experience with them (I usually spec an HRV or ERV), they draw between 10-15 watts per hour and are relatively quiet (<.5 sones). If you frequently have a problem with your home overheating it probably wont be worth it for you to go through the trouble of installing an HRV.
VR: I installed one of the Panasonic WhisperGreen fans, and it is hard to hear it at lower rates (20 cfm?) even when you are right under it. We sleep w/in 8' of it, often on high, and it does not bother us a bit. If you are overheating, then obviously some shading would be helpful. If evergreens are out of the question, (limbed as far up as necessary) then perhaps installing vertical 2x12s, spaced about 10" apart (depends on the highest angle of your sun) and about 4' wide, outside your S facing windows would help. Google the UAF, Fairbanks, AK, President's house if my description is not clear.
VR Long,
I hope someone comes along who can comment on the noise levels. I looked up the data on HRVs in the HVI Directory from the Home Ventilating Institute -- but unfortunately they don't have sone levels in their directory.
For other information on HRVs, including airflow, sensible heat recovery data, and power consumption, the directory is extremely useful:
http://www.hvi.org/assets/pdfs/CPD/HVICPD_Sec3_01Feb2011.pdf
The quietest HRV I've seen yet by a fairly wide margin is the Zehnder equipment from Switzerland: http://www.zehnderamerica.com/products/comfounit_home.asp
It's more expensive than typical North Am HRVs, but has higher efficiency and is much quieter. When it's on high boost mode the air moving through the registers is louder than the box itself if it's in a basement or attic.
The Venmar or Lifebreath units we've worked with have been far louder when they go into defrost or high speed mode.
Thanks for the responses.
I certainly could replace the bath fans, Nick, but that doesn't solve the problem of getting fresh air into the house (it is very tight ). John, is your Whispergreen fan an HRV? Shading isn't an answer for us. We use the sun for heating and it works well. We do have a little overheating in the winter -only, but it is easily cured by opening a window. When we are away an HRV would balance out any overheating. The main problem is the stale air when the house is closed up.
I did check the HVI directory and found useful information, but discovered, as you did, that there were no sone ratings. I was hoping some people with direct experience might have some recommendations. I will look at the Zehnder website and their HRVs. Jesse, do you have any idea of the decibel level (or sones) of the Zehnder, if you are in the same room with it ~ 6-8' away? I don't have an attic, or basement. Thanks again.
VR Long,
If you bath exhaust fans are working -- that is, if they successfully blow air out of the exterior outlets -- then they are helping to provide fresh air to your house, even if the house is "tight."
If 50 cfm of exhaust air is leaving your building, then the laws of physics state that 50 cfm of outdoor air is leaking through cracks into your building. Assuming you don't have an attached garage -- we already know you don't have a crawlspace or basement -- there's no reason to believe that the outdoor air entering your house isn't good, fresh, high-altitude Colorado air.
Just a thought: would it be possible to place the unit you choose and build a HRV soffit for it insulated for acoustics?