Author Topic: What is the most efficient roof vent or wall vent?  (Read 7778 times)

rickharp

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What is the most efficient roof vent or wall vent?
« on: September 14, 2009, 10:23:52 AM »
Roof vent or wall vent?  Seems like a roof vent would be most practical and shortest run.  Is there anything I need to know?  Is there an efficient roof vent?
« Last Edit: August 15, 2013, 11:45:11 AM by rickharp »
Rick Harpenau
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rickharp

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Re: What is the most efficient roof vent or wall vent?
« Reply #1 on: September 14, 2009, 10:25:45 AM »
Besides efficiency, aesthetics should also be a consideration.  The outward appearance of a vent may in some cases diminish its efficiency. I've seen roof and wall vents in all sorts of styles with varying degrees of efficiency.  How we test efficiency is with a real dryer and a very sensitive pressure sensing gauge (Magnehelic Gauge) which is connected to a tap fitting in between the dryer and the vent cap we are testing. 

Right off the bat, let's go over the worst vent styles for both the roof and the wall. 

In the south, roof vents, especially in new home construction is very popular, and the vent we continually hear is being installed by the HVAC tradesmen is a 4 inch wide gooseneck vent.  We also see other small profile plastic and metal vents, all of which have tested to be surprisingly restrictive in air flow design.  Bigger is better in this case.  Besides in most cases having to make a 180 degree redirect of airflow, many of these vents exhibit a final opening that is smaller than the area of a 4" round pipe. 

Wall vents historically were the hooded style with a "flapper".  Older versions of this style, the hood only allowed the flapper open about 22 degrees.  This was or is a huge reduction in air space and likewise created a bunch of back pressure.  This design also was easy for birds and rodents to gain access and build a nest. 

Let's return to the original question:  What is the most efficient roof vent or wall vent?

I've been in the dryer venting industry for 17 years, and in my mind there are three important aspects of a roof or wall termination for the dryer: zero back pressure, bird and rodent proof and easy access for future duct cleaning.  Some of the vents I am going to suggest are products we produce and some are not, but this image will give you an idea of the look or design details of vents to avoid or look for. 

In addition, numerous terminations we tested are shown in this table http://www.dryerbox.com/ratings/dryerfittingschart.htm and lists their respective airflow resistance Delta.  The test used a sensitive magnehelic gauge to measure the backflow pressure of in a typical dryers’ exhaust conduit with and without the fitting.  The difference or Delta was indicated on the table. 

Conclusion: Roof vents are very popular in many regions of the country.  Venting upwards should not be discouraged in my opinion as hot air rises so there exists an equal environment for pushing the dryer’s exhaust up or down. 

Beware though, in some cases the roofer can inadvertently install a roof vent that exhibits a grill or screen like grate: this is a major problem as lint builds up very quickly and can become a fire hazard.  Grills, screens or grates of any sort on any dryer termination are prohibited in the building code. 

Once I learned how inefficient my roof jack was, I replaced it with the DryerJack DJK466.

Hope this helps.  Here is link to Efficiency Rating Table.  http://www.dryerbox.com/ratings/dryerfittingschart.htm
« Last Edit: November 14, 2013, 01:55:27 PM by rickharp »
Rick Harpenau
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Re: What is the most efficient roof vent or wall vent?
« Reply #2 on: December 10, 2009, 05:25:48 PM »
Some or most of the older wall vents were simple hooded wall flappers.  The hood only allowed the flapper to open about 22 degrees, thus creating a ton of back flow pressure.  Since then, numerous enhancements to the wall vent have been introduced.  Multiple louvers have made a big impact on efficiency.  Other innovative dampers have been introduced to minimize or completely shut down any backflow of outside air but some are not as effective as others in being efficient in exhausting the dryer air.  Also, rodents and birds pose a serious problem in some regions of the country as they have found the warmth and protection of the duct very attractive and can easily penetrate the dampers.  One wall vent that has greatly impressed me was the No Nest Vent, or also known as the No Pest Vent.  Extremely efficient, yet extremely effective at prohibiting bird and rodent entry. 

Also, just introduced in 2012 is our all metal Premium Dryer Wall Vent that is fully powder coated.  Read the reviews at this link.  Picture is below.

See Link here: 
http://store.dryerbox.com/Premium-Flush-mount-Metal-Dryer-Wall-Vent_p_93.html
« Last Edit: November 14, 2013, 02:04:49 PM by rickharp »
Rick Harpenau
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The most efficient roof vent - Found
« Reply #3 on: November 12, 2010, 01:09:15 PM »
Dryer manufacturers have gone through great strides in R & D in providing a safe and energy efficient dryer.  Building codes on the other hand have made no effort in prohibiting the use of exhaust terminations that are flat out inefficient. 

Even some of the new dryer vent hood designs do not take into consideration the resistance values of the airflow path.  The objective of a vent hood for the dryer is basically two fold; prevent back drafts and reduce or eliminate any surfaces that can promote lint build-up.  In addition to that, preventing bird or rodent entry as well as nest building capability is very important.  Personally, for me, these bullet points sum up what I find critical in designing a vent hood specific to venting the dryer:

-   be aluminum or galvanized metal to minimize UV degradation
-   feature a small or low profile design to minimize unsightliness
-   incorporate a clever light weight damper impervious to rodent penetration
-   allow access and entry by a rotating brush and bendable rod for cleaning
-   not provide a “bird house” like environment on top of or within the damper
-   the least obstructive airflow path
-   absolutely not incorporate a screen or mesh that would catch lint
-   provide a minimum area of 12 inches squared through the entire termination and 15 inches square through any alteration in airflow direction greater than 30 degrees
-   incorporate a integral 4” collar into the base of the vent for positively securing the rigid dryer conduit pipe to
-   offer clever design to minimize any water infiltration
-   provide zero back pressure
-   Complies with IMC 504.4 & IRC 1502.3 building codes
-   (location) not terminate less than 10 feet from any exterior mounted air conditioning equipment
-   (location) not provide direct flow onto a patio, porch, window or door


In new construction, a roof vent hood (generally referred to as a roof jack) designed for the dryer looks almost identical to the one used to vent a bath fan.  With that, the roofer commonly installs the dryer vent at the wrong penetration.  Vents provided for the bath fan are smaller and feature a screen, a major no-no for dryer venting. 

Vent hoods in new construction are generally provided by the HVAC contractor which they attain from the HVAC supply house.  Since most of the duct materials are manufactured from galvanized sheet metal, the vent hood has ended up in most cases to also be constructed in galvanized sheet metal.  Many of the manufacturers continue to provide legacy designs and contractors continue to install them because no one has questioned their efficiency. 

To give you some idea, there are popular wall AND roof vent hoods that provide over .41 inches of water column pressure, approximately 3 times higher than a duct cleaning industry self-imposed rule of thumb. 

The makers of the Dryerbox and the Dryer-Ell have recently introduced a super efficient series of roof vents and a wall vent specifically for venting the dryer.   The DryerJack is a major improvement to what is available for venting the dryer to the roof. 

http://www.dryerjack.com
http://www.dryerwallvent.com


Store links:
http://store.dryerbox.com/DryerJack--Low-Profile--Scoop-Design_p_109.html
http://store.dryerbox.com/Premium-Flush-mount-Metal-Dryer-Wall-Vent_p_93.html
« Last Edit: November 14, 2013, 02:14:51 PM by rickharp »
Rick Harpenau
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Video to watch dealing with all the dryer vents that exist
« Reply #4 on: November 12, 2010, 01:24:35 PM »
Dryer Vent Hoods (wall or roof) come in a variety of styles and efficiencies. Many are very inefficient.  Here is a good video that discusses the idea of promoting the development of a standard or protocol to test the many styles of vents for pressure levels they create and then a modification to the ICC codes that only allow vent hoods that meet the standard.

http://www.vimeo.com/12396871
« Last Edit: August 15, 2013, 11:45:56 AM by rickharp »
Rick Harpenau
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Re: What is the most efficient wall vent?
« Reply #5 on: November 17, 2010, 05:15:16 PM »
We are actually working on a super efficient wall vent made out of metal, that is pretty neat.  Bird and rodent proof too.  Will keep you posted.
« Last Edit: August 15, 2013, 11:46:03 AM by rickharp »
Rick Harpenau
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Re: What is the most efficient roof vent or wall vent?
« Reply #6 on: July 28, 2011, 08:49:26 AM »
I"ve posted some new and interesting videos on the airflow testing results of numerous fittings and hood vent terminations.  This first one includes elbows, wall vents and roof vents. 

All Vents: http://www.youtube.com/watch?v=LuIkAfxqAT0

This video is again a very informative video showing actual testing of several roof vents for dryers.  The more air pressure differential the test provides the longer your clothes take to dry. 

Roof Vents for Dryers: http://www.youtube.com/watch?v=47QHn-DFRcA

This video is about the flex transition hose behind the dryer and shows clearly the pros and cons of the two very popular options.  It also introduces and tests a new flex hose on the market that is pretty impressive. 

DryerFlex: http://www.youtube.com/watch?v=7Nof7KRoxDk
« Last Edit: August 15, 2013, 11:46:14 AM by rickharp »
Rick Harpenau
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ShermanCrawford

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Re: What is the most efficient roof vent or wall vent?
« Reply #7 on: August 10, 2013, 11:06:32 AM »
Besides efficiency, aesthetics should also be a consideration.  The outward appearance of a vent may in some cases diminish its efficiency.  Efficiency is most effected in a roof vent (or roof jack as some call it) due to its required design factor of “hooking” or the 180 degree gooseneck design. 

A wall outlet in most cases is a straight through vent with a flapper.  A roof vent has to redirect the air flow tremendously, provide some sort of grid to minimize rodent nesting, resist driving rain and incorporate a damper to prevent backdraft.  These requirements take there toll and to my knowledge all the roof vent products out there fair very poorly when compared to some of the modern louver and full open flap designed led lighting

Numerous terminations were tested and this table http://www.dryerbox.com/ratings/dryerfittingschart.htm lists their respective airflow resistance Delta.  The test used a sensitive magnehelic gauge to measure the backflow pressure of in a typical dryers’ exhaust conduit with and without the fitting.  The difference or Delta was indicated on the table. 

Conclusion: Roof vents are very popular in many regions of the country.  Venting upwards is not discouraged as hot air rises so there exists an equal environment for pushing the dryer’s exhaust up or down.  Roof vents come in a variety of styles and materials, including a durable UL safe plastic/resin, aluminum, copper and galvanized.

Beware though, in some cases the roofer can inadvertently install a roof vent that exhibits a grill or screen like grate: this is a major problem as lint builds up very quickly and can become a fire hazard. 

Once I learned how inefficient my roof jack was, I installed a “T” in the attic and branched off to a second roof vent.  A “Y” would have been better but it would of required numerous fittings in order to keep the same penetration location.   

Hope this helps.  Here is link to Efficiency Rating Table.  http://www.dryerbox.com/ratings/dryerfittingschart.htm


Thanks for the information.. I am searching for these efficient wall vents and the information served me lot.. Thanks again
« Last Edit: August 11, 2013, 08:51:39 AM by ShermanCrawford »

rickharp

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Re: What is the most efficient roof vent or wall vent?
« Reply #8 on: August 13, 2013, 02:34:33 PM »
You bet... Good Luck.
Rick
Rick Harpenau
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dhayo

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Re: What is the most efficient roof vent or wall vent?
« Reply #9 on: November 12, 2013, 12:50:14 AM »
Hi Rick, what type of wall vent can you recommend for a 14 units of dryers in a common laundry room of an apartment building ?

rickharp

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Re: What is the most efficient roof vent or wall vent?
« Reply #10 on: November 12, 2013, 09:18:19 AM »
Hi Rick, what type of wall vent can you recommend for a 14 units of dryers in a common laundry room of an apartment building ?

Building codes require that each dryer be vented to the exterior in their own duct and with their own termination hood.  Shared plenums with constant negative pressures are the exception. 

What we hear most from customers and installers of our DryerWallVent product is that it is a substantial heavy duty product that will out last anything on the market.  Besides that fact, we love that the vent has a very non obtrusive appearance, that it produces no back pressure at all, that it is super easy for the duct cleaners to access, and that it is pretty dang hard for a bird or rodent to obtain entry. 

I believe this vent, when installed, perhaps in a 2 or 3 level "stacked" (all in one location) configuration, would look and work fine.  Hope this helps, and thanks for asking. 

www.dryerwallvent.com
store link: http://store.dryerbox.com/Premium-Flush-mount-Metal-Dryer-Wall-Vent_p_93.html
Rick Harpenau
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561-743-8696

dhayo

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Re: What is the most efficient roof vent or wall vent?
« Reply #11 on: November 13, 2013, 09:37:26 PM »
Thank you Rick, I appreciate it.