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bobinphx 02-06-2012 02:15 AM

house depressurization... .from the dryer???
I was over at a friendís house and they were doing laundry. They have an indoor dryer that I noticed was running. At the same time, I noticed draft coming from under an exterior door,. I had them shut off the dryer and the draft stopped!!!!.... So a little research and I find that dryers can pull from 100 to 300 CFM when running. By running the dryer, are they depressurizing the house and causing cold air to infiltrate the house??? I think so.

If this is the case, why doesnít someone make a dryer with an outdoor fresh air intake??????

Then again, I donít understand why refrigerators are not built like a mini split system. The compressor and condenser should be outside, not in the house!!! This way the heat producing equipment would be outside. The bigger plus and you would get more room in the Fridge for beer!!!. LOL

plummen 02-06-2012 02:36 AM

Yeah it makes sense to me that if youre forcing air out you need to replace it at some point.:)
How about bringing in some outside air to the laundry room area like you would for combustion air for a basement with a furnace? :)

beenthere 02-06-2012 04:09 AM

If the compressor and condenser of the fridge was outside. then you wouldn't get any of that heat in winter.

Yep, dryers can depressurize a house. Have a small intake placed in the laundry room as plummen said.

Earnie 02-06-2012 06:31 AM

I have wondered about that too.

Interesting no one has used the same concept used with gas fireplace inserts. Mine has a double tube going up the chimney. One carries hot combustion gasses out while the other allows for some pre-heating of the air going to the insert.

Same idea could work for dryers. Hot moist air venting to the outside would pre-heat supply air. Less energy used to heat the dryer air, plus the reduction of air being drawn into the house.

Dryer manufacturers wake up!

HVACDave 02-06-2012 07:51 AM

Don't know about that one Earnie. Depending on outdoor air temps you could end up with a pile of condensate on your hands and essentially make a really mucky mess that would quickly plug your dryer vent.

Earnie 02-06-2012 11:01 AM

You could be right Dave but it could depend upon your climate zone. Similar to how it is used for other building practices.

It is odd though that the building code would not address this issue. We need to seal up every crack and air gap but have no problem venting conditioned air outside for 30-40 minutes at a time.

HVACDave 02-06-2012 12:04 PM

Hence the requirement in most jurisdictions for new construction that include an HRV,ERV, or dedicated fresh air make up with central exhaust.

Earnie 02-06-2012 12:53 PM

Yes, new construction is the key. Any idea of the ratio of old to new construction? Can't be much so an HRV/ERV won't help us with existing homes.

I do not have an HRV/ERV. Wouldn't the air handler have to be in operation for the HRV/ERV to have an affect? If the dryer is operating but the air handler HRV/ERV is not, how is that any help in off-setting the loss of warm air and infiltration of cold air?

Just did a search on HRV/ERV. Interesting quote from Green Building Advisor

The purpose of an HRV or an ERV is to deliver fresh air to a home’s interior. Neither appliance is designed to provide makeup air for combustion appliances or kitchen exhaust fans. HRVs and ERVs are not space-heating devices, heat-delivery devices, or energy-saving devices. The more hours that an HRV or ERV operates, the more energy it uses — electrical energy to operate its fans, as well as heating or cooling energy to make up for the conditioned air that these devices expel from a home.

bobinphx 02-06-2012 02:21 PM

interesting information about the hrv....

I was thinking that it would be nice of the dry MFGR made some sort of kit available for the use of outside "combustion air" for their dryers.

I was at another friends house today and she has 10 year old white carpet. She commented that She could never keep the edges by the walls clean. Then I noticed that the areas she was talking about were only on outside walls!!!!... and you guessed it, she has an indoor clothes dryer.

Thanks everyone for the information and opinions.

HVACDave 02-06-2012 02:35 PM

True enough that while the HRV/ERV is running it is costing you money as it isn't 100% efficient in heat transfer, however it is satisfying a necessary requirement in new buildings of addequate ventilation to ensure decent indoor air quality in today's new tight construction. If not employed then you raise the issues of mold development, damage to building structure due to high indoor humidity levels, poor indoor air oxygen quality, VOC's etc.etc.

I find that people in general are much more aware of indoor air quality and energy efficiency than ever before (much due to the internet). I have found a good market for adding HRV's to existing structures when renovations have taken place to seal up the structure (new windows, doors, high efficient furnaces, etc.) and have found them to be an effective way of keeping the building fresh and comfortable, while still offering decent energy savings over straight ventilation. Most are about 65-75% effective in heat transfer, with some new dual core models approaching 90% effective.

Earnie 02-11-2012 05:39 PM

Here's how one person solved a related problem.

msaeger 02-11-2012 06:18 PM

Just having the dryer use outside air would make the dryer need more energy. It's 8 degrees f outside here now.

beenthere 02-11-2012 07:02 PM


Originally Posted by msaeger (Post 850817)
Just having the dryer use outside air would make the dryer need more energy. It's 8 degrees f outside here now.

Which means the outside air is dry, and wouldn't take long to dry the clothing.

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