I'm planning the HVAC portion of my home now and part of what they install is duct work for dryer vents and range hood vents. The range hood in my current home vents to the outside, and if I look at the right angle I can see daylight from my kitchen. My question is, is there a better way to do a range vent or dryer vent? I'm building in a warm climate (central TX) so I'm not so much concerned with conserving cooking heat as I am with losing cool through these holes in the majority of time when my stove and dryer aren't sending hot air through them. Is there an established solution that I'm not familiar with?

You can see daylight around the edges of the vent hood duct and the dryer duct where they exit the home? If that's the case, they represent a huge amount of heating and cooling energy loss in the air that is allowed to exit those holes. They need to be sealed.

If you are talking about the ducts themselves and the dryer air and cooking air that are being pushed out them, you just have to think of it as bad air (moisture laden, grease, bad odors, etc) and accept the loss. Have seen lots of schemes to deal with it. They range from expensive, but possibly workable to just plain worse than doing nothing.

If you are talking about exchanging conditioned air in your new home through the ducts when they are NOT in service, you definitely want backdraft dampers on them to slow that down.

My new house will NOT have a dryer vent, I'm going to combo washer dryer(s) that are vent less, condense the moisture and send it out the drain.   These combos use a heat pump to generate the heat for drying and the same heat pump cools the exhaust and removes the moisture, they are much more energy efficient than conventional dryers but not as quick. I'm also considering eliminating the traditional laundry room and instead having two washer/dryer combos, one in each full bathroom's linen closet. I understand that there are motorized dampers for range vents that really seal when closed, as yet I haven;t found a source so I'm still looking for them.  The metal ducts through the thermal envelope are horrible thermal bridges and in the case of a range vent fire saftey concerns pretty well dictate that the vent pipe be metal. maybe I'l use an UN-vented recirculating hood. 

they are much more energy efficient than conventional dryers but not as quick.

Sounds like it will save a lot of energy, The Sears Kenmore dryers I have had go more than 10 years without a service call. I hope that is the same for the heat pump dryers.

Posted By Liebler on 14 Jun 2012 11:19 PM
My new house will NOT have a dryer vent, I'm going to combo washer dryer(s) that are vent less, condense the moisture and send it out the drain.   These combos use a heat pump to generate the heat for drying and the same heat pump cools the exhaust and removes the moisture, they are much more energy efficient than conventional dryers but not as quick. I'm also considering eliminating the traditional laundry room and instead having two washer/dryer combos, one in each full bathroom's linen closet. I understand that there are motorized dampers for range vents that really seal when closed, as yet I haven;t found a source so I'm still looking for them.  The metal ducts through the thermal envelope are horrible thermal bridges and in the case of a range vent fire saftey concerns pretty well dictate that the vent pipe be metal. maybe I'l use an UN-vented recirculating hood. 

Can you send a link to these dryer setups?

Sounds interesting but new technology like that makes me leery but I am always willing to give it a shot as long as it is not too expensive.

Heat pump condensing dryers are common in Europe but very hard to find in the US.  LG does market a smaller and larger one in a combo machine the larger is WM3987HW.  They have another advantage, they operate with only 120 volt power!  They are available from many sources here is one to get started.
 http://www.compactappliance.com/LG-WM3987HW-Full-Size-Washer-Dryer-Combo/WM3987HW,default,pd.html?mtcpromotion=PLA%3EAppliances%3ELaundry%3EWM3987HW&src=SHOPDISCOUNT&gclid=CPeP5vmQ0LACFUvDtgodKkeUXw

Posted By Liebler on 14 Jun 2012 11:19 PM
My new house will NOT have a dryer vent, I'm going to combo washer dryer(s) that are vent less, condense the moisture and send it out the drain.   These combos use a heat pump to generate the heat for drying and the same heat pump cools the exhaust and removes the moisture, they are much more energy efficient than conventional dryers but not as quick. I'm also considering eliminating the traditional laundry room and instead having two washer/dryer combos, one in each full bathroom's linen closet. I understand that there are motorized dampers for range vents that really seal when closed, as yet I haven;t found a source so I'm still looking for them.  The metal ducts through the thermal envelope are horrible thermal bridges and in the case of a range vent fire saftey concerns pretty well dictate that the vent pipe be metal. maybe I'l use an UN-vented recirculating hood. 

Interesting, I hadn't heard of that condensing heat pump. That sounds like a really nice set-up.

Posted By ICFHybrid on 14 Jun 2012 11:13 PM
If you are talking about exchanging conditioned air in your new home through the ducts when they are NOT in service, you definitely want backdraft dampers on them to slow that down.

Yes, that's what I was thinking of. Haven't heard of backdraft dampers but I will look into them. Thanks for the thought!

There are good, better, best versions of dryer backdraft dampers. The better ones tend to look like this:


http://ecx.images-amazon.com/im...PklSWL.jpg


http://www.energyfederation.org/com.../l_110.jpg


The fact that the air makes it first makes a 90, then a 180 degree turn on the way out introduces a higher duct impedance is somewhat mitigated by the fact that the cross sectional area  roughly over that turn. It's not the same duct impedance as three same-diameter duct ells, but it's slightly more than two.  The initial bend is a longer radius and smooth-bore, so it's not as restrictive as the typical sectioned bends (that are rate as the equivalent of 5' of duct but are often MORE restrictive in testing). Backflow preventers of this type impede dryer flow equivalent to ~8-12' of duct length.

If your dryer duct runs are short this type isn't bad, and the backflow prevention characteristics are quite good. The flip-lid on the exterior makes cleaning any lint accumulation much easier than any louvered type backflow preventer too.

If you have significant duct runs you may want something else though.  (Most dryer manufacturers spec 35 feet-equivalent total duct length.)

I have one of those dryer vents Dana linked to. I have a very short dryer duct run, and it works really well.

-Rosalinda