Jere
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| 10/28/2009 9:22 AM |
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I was reading on another thread about ThermoDrain & PowerPipe to recover the heat from the water drains to pre-heat the incoming water into the water heater... I was wondering if there is a heat exchanger to recover the heat from bathroom fans and clothes dryer to also pre-heat the water heater, and maybe the air would also run through an ERV/HRV after? Would lint from the dryer cause any issues with a heat exchanger? There would also be a lot of moisture coming from the dryer and bath fans (moisture from shower). If this topic has been brought up before, please point me in the right direction.
Thanks,
Jere
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Dana1
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| 10/28/2009 9:51 AM |
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There are tiny bathroom HRVs (ERVs not recommended, since you're trying to dump humidity, not preserve or balance it in bathroom ventilation.)
Dryers are particularly problematic from a condensation and lint/fire-hazard point of view. There are some cheap 4" diverter valves for redirecting dryer exhausts directly into the room, but that's a carbon-monoxide hazard for gas-fired dryers, and a humidity/mold hazard in general. It might be OK for electric dryers in very leaky houses or very dry climates, but room humidity would still have to be monitored, and a secondary lint trap (like a nylon stocking) on the output. In most places that's a code violation, but the products are still available over the internet.
The heat saved is quite modest- ~800kwh (~25therms)/year is typical for dryer use. Saving 1/4-1/2 half of that with a heat exchanger or diverter during the heating season is still not a big fraction for most families. In dry enough areas/homes that you could use a diverter you could save as-much or more by air-drying. |
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Duane Amundson
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| 11/02/2009 1:45 PM |
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No air exchanger (I am aware of) recommends sending dryer or range hood exhaust through it (excessive temperature, moisture or grease). Some brands recommend venting bath exhaust. An HRV or ERV will lower winter humidity levels (when outside net humidity is lower than indoor net humidity).
I have an EV200 (ERV) ventilating 2 bathrooms and the general kitchen area (not over range hood). While the ERV recaptures a portion of the humidity to the exhaust air stream (in winter in WI) the net humidity of the house is lowered when the ERV is operating.
If the ERV was adding humidity to my house, I would not need a humidifier to maintain a base level of humidity in winter (WI). (The humidifier was in the house when I moved in, the ERV was added later.) I am recapturing @ half of my (total) exhaust moisture, instead of sending it all outside or down the drain with an HRV. One bath shower may be temporarily exhausting 100% RH, but the other two vents are @ room humidity; in winter @35%, thus ave. exhaust humidity is 57%. With indoor RH @ 50%, ave. exhaust would be 67% RH.
My ERV as a central bath exhaust appliance accomplishes several things. I have a whole house air exchanger and central exhaust in one unit. The exhaust air now has 85% sensible energy recapture, which was all wasted previosly with exhaust only. I now have "balancing air" for my bath exhaust. I no longer have to listen to a noisy bath fan; a vent is ducted to the ERV. My bathrooms and kitchen are ventilated better and are fresher than before.
Always read and follow each manufacturer's directions and recommendations for their HRV or ERVs. They are different. |
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Dana1
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| 11/04/2009 3:48 PM |
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If your house is tight enough you shouldn't be needing to add winter humidity in WI (climate zone 6)- adjusting the ventilation rate should suffice. Often ventilation rates get set unnecessarily high just to avoid buildup of humidity, only to create winter dryness that would otherwise not happen.
Setting it up on dehumidistat control and allowing the indoor RH to rise to 30-35% is about right for health & comfort, and won't create undue hazard of condensation in the wall structures, assuming reasonable construction practices for vapor control are taken. See:
http://www.passivhaustagung.de/Passive_House_E/ventilation_and_humidity.htm
Humidifiers are notorious mold and bacteria growth & dispersion devices only to be used as a last resort. If you live in a tight house you're better off without 'em.
http://www.mayoclinic.com/health/humidifiers/HQ00076
Adding humidity to the house by venting the dryer exhaust inside of conditioned space is still a bad idea, even if you can remove the moisture with an ERV.
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jonr
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| 11/07/2009 9:10 PM |
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1) Ventilation rates are typically too low for optimum health.
2) Read it - they discuss 41% as good and 30% as too low
3) Tank type humidifiers can be a problem - some other types are fine.
4) No - good idea. |
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hoozdis
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| 11/16/2009 6:12 PM |
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| Could you tell me who makes the HRV for bathrooms? I can't imagine how this device could pay for itself....but curious |
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shaferjon
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| 11/16/2009 11:50 PM |
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| As everybody else commented, tying a dryer vent into HRV/ERV voids the warrenty and does not meet code in many states. I am not currently aware of any device that can recover heat from a dryer vent. Panasonic makes a room ERV called "whipser comfort spot ERV" that can be used for a bathroom. It is the only room/spot HRV/ERV that I am aware of. The other option is to tie into a whole home HRV which is another different ballgame.
But I have another question on the same topic. Will an HRV balance the excess load of the dryer blowing air straight outdoors? I am working on a 900 SF home with a HERS rating of 17, and I am wondering what happens when the dryer causes the small, tight house to be under negative pressure.
And, does anyone have opinions on the newer ventless electric dryers?
Thanks!
Jon |
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Brock
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| 11/17/2009 1:42 PM |
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| I know our HRV doesn't compensate for a dryer or kitchen exhaust mechanically in any way. But I can say a whole bunch more air comes in through it when the kitchen exhaust hood is running. I think it is the easiest way for the air to "leak" back in the house and I would rather have it come in that way than any other. I haven't tested it yet, but in thinking about it I wonder if the exhaust from the HRV slows down when the kitchen exhaust is on. It would only make sense that the HRV it would be working harder to push air out of the house and have a much easier time pulling outside air back in. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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Dana1
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| 11/18/2009 3:01 PM |
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Posted By hoozdis on 11/16/2009 6:12 PM
Could you tell me who makes the HRV for bathrooms? I can't imagine how this device could pay for itself....but curious
Panasonic
http://www.kitchensource.com/bathroom-fans/fv-04ve1.htm
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cmkavala
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| 11/18/2009 3:13 PM |
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Posted By Brock on 11/17/2009 1:42 PM
But I can say a whole bunch more air comes in through it when the kitchen exhaust hood is running. I think it is the easiest way for the air to "leak" back in the house and I would rather have it come in that way than any other
very true.......... its best to know or control where the leakage occurs, most homes leak at the sill plate, if insecticides and herbicides are used around the perimeter of a home that whats getting sucked in to the living area
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Chris Kavala
chris@southernsips dot com
1-877-321-SIPS |
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jonr
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| 11/18/2009 5:24 PM |
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| An electric condensing dryer makes sense to me. I'd like to see more discussion about them. |
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