I need suggestions for a high-performance dryer vent
user-969121
| Posted in GBA Pro Help on
Building a LEED Platinum house and need info on drier vents and rangehoods with make-up air
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
David,
If you are looking for a product, here is a nice stainless-steel dryer vent from Seiho:
http://www.seiho.com/product/rcarcc/rcarcc.html
If you are looking for information on makeup air for range hoods, I suggest that you read this article: Makeup Air for Range Hoods.
check out the Heartland Dryer Vent Closure
Broan makes a range hood makeup air damper which operates on a pressure switch tied to the range hood.
For dryers the design of the vent will probably be the biggest factor in efficiency. The dryer should be placed on an exterior wall so that vent is short. Long dryer vents reduce the air flow and clog with lint, Poor air flow either because of poor design or lint buildup can add many minutes to a half hour or more to drying time.
The placement of the vent behind the dryer can lead to big problems. There is not a standard placement of the vent exiting the back of the dryer, Many times I see 8 feet of transition hose behind a dryer because it is hard to align the dryer and vent.
I recommend having the vent off to the side of the dryer or above the dryer. This allows access to the vent with the dryer in its normal position.
Using 3- 4 90 degree elbows cuts down the efficiency and leads to lint build up. The hood also plays a role. The 3-4 flap design has no resistance. The larger 4 inch hood has very little resistance. A 2 in hood (distance it sticks out from wall) adds a lot of resistance. Dryer manufacturers have charts show length of dryer vent with 0-4 elbows. Each elbow changes the length of dryer vent. The 2 in hood has the shortest allowable length.
How you use the dryer also plays in to its efficiency. I take jeans and other heavy clothes out before they are fully dry and let them finish drying on hangers.
Robert, I always rough in the vent centered behind the dryer, as low as possible, and use a "Dryer Box" in the wall. Yes, it displaces some insulation, but you can dress the flex hose impeccably and if you're on an exterior wall, there is one elbow and about 6 inches of straight pipe, max. http://dryerbox.com/
David
I am not a fan of the dryerbox because you use a flex hose with that. You have the dryer pulled out, hook up the hose and then slide the dryer back in. You have a curve in the flex hose and it is no longer stretched out. Most of the flex hose will have a diameter of 3.5in when not stretched out, The smaller diameter and all the ridges are a lint trap. As this collects lint the dyer becomes less efficient.
As the vent gets clogged the air force is less, the dryer no longer has the force to push the lint out with the air flow. Now the whole length of the vent gets a build up.
As the air flow decreases you can find that the moisture starts condensing in the vent.
It is important for homeowners to pull the dryer out and clean the transition hose and the vent every 6 month to a year based on the set up. When the vent is directly behind the dryer it becomes harder to do. Homeowners dont want to pull the washer out to get behind the dryer. What happens is a homeowner will attach an 8 foot section of flexible transition hose with the dryer out. Now the dryer is slide back in place will a tangled mess of flex hose which is even worse.
We fix and clean a lot of dryer vents so I see this on a regular basis. The best vents are all hard pipe with as short of run as possible and as few elbows as possible. Also on long runs it doesnt hurt to insulate the vent. In a cold climate if the duct runs through an unheated space I would recommend insulating the vent,
If you have never seen a dryer vent cleaned you would be amazed at the amount of lint that comes out. We have filled a kitchen trash can with lint, on a 5 year old house with 2 elbows and less than 20 feet of vent. What looked like a decent setup.
A lot gets by the dryer screen. We routinely get plastic collar stays and hair from the vent. We get lint so wet that when you take a handful you can squeeze water out. We have blown large amounts of water out of vents.
To me this is an energy issue. When we have people tell us it takes 2 to 3 cycles to dry a load, well that is a lot of wasted energy. Even 10 to 15 minutes extra per load adds up when you do 5 to 10 loads a week. That is 50 to over 100 minutes of extra run time.
http://www.dryerbox.com/welcome_dryerbox.htm
The makers of dryerbox (In-o-vate) make a flexible dryer duct that's not nearly as susceptible to warpage: http://www.dryerflex.com/.
If you're concerned about the gradual build up of lint in dryer duct, considering using another In-o-vate product, Lintalert. It's basically a magnehelic gauge that gets zeroed to the clean dryer hose pressure, then issues a warning when the pressure rises beyond a certain threshold. Pretty much everything in In-o-vate's product line is focused on reducing problems related to dryer ducts: http://www.inovatetech.com/
The makers or dryer flex make the dryer box. If you look at the video in the link I post you will see that in 1 installation they show a big loop of flex duct. A big no no.
As far as the dryerflex it is still a flex hose. Flex hose will accumulate lint.
There are better setups that don't use flex.
The pictures look nice but thedryer don't get setup as the pictures suggest. For one the flex hose doesnt slip over the metal vent very easy, it usually takes 2 hands. That means the dryer has to be 3-4 feet from wall when the flex tube is hooked up. That much flex does not fit neatly behind the dryer.
The biggest thing is that the dryer should be easy to pull out and the duct must be easy to work with.
We work on a lot of dryers and vents. Flex duct accumulates lint. If the owner cleans it once a year there will be less problems. The problem is washer and dryers are side by side. If the washer is pulled out you can get to the back of the dryer. But that means the water supply hoses must be removed. Homeowners dont like to do that.
So the dryer is pulled out with the washer in place. If the vent is low and directly behind the dryer the homeowner will use an 8 foot section of flex tube . Would you let your HVAC guy snake an 8 foot section of flex duct to make a short connection of maybe a foot, You know what would happen with air flow.
I think the actual practice is different that what the pictures will show
Dryers are one of the leading causes of house fires. Clogged dryer vents are the cause of most of the fires. Dryer venting is left to chance and not good science or practice. Dryer vents should be solid pipe and be as short as possible. This is an energy issue too.
Robert, I have installed a fair number of dryer boxes on houses that I've built and remodeled, and followed up on how they are doing later (i.e removing the vent cap outside, and inspecting/cleaning the pipe) and I think they're great. Yes, it takes two people to install the dryer and it has to be done with the washer out of the way, but we make it happen. There is no big loop of flex. I use a 3' piece, not 8'. If the dryer box is installed at floor level the flex forms a single 90 bend with nothing laying on the floor. They are very easy to clean, as you can practically stick your hand inside the dryer from outside. The dryer is against the wall.
I'm not sure what your installs look like. It sounds like you're still using flex.
David
Your the exception. Most dont do it on an outside wall so we see a lot of bad setups. Being that short the flex is not going to be a problem. We are seeing a lot of the front load pairs that are on the pedestal. That creates problems as they are so heavy and hard to move plus they sit higher. When a dryer box is mounted low it doesnt work out well.