Dryer Venting Forum

Please login or register.

Login with username, password and session length
Advanced search  

News:

SMF - Just Installed!

Author Topic: A Roof Vent for venting a dryer...  (Read 19111 times)

rickharp

  • Administrator
  • Full Member
  • *****
  • Gender: Male
  • Posts: 147
    • View Profile
    • http://www.dryerbox.com
A Roof Vent for venting a dryer...
« on: November 09, 2009, 11:03:05 AM »

The roof area of a house is used to vent many of the homes mechanical systems.  The plumbing stacks are used to vent sewer or waste water odors and allow for proper gravity flow.  Bathroom and cooking area fans also vent to the roof generally through a “gooseneck” style vent that exhibits a damper and grill.  The grill precludes small birds and rodents from accessing the termination. 

In the case of venting the exhaust of a clothes dryer to the roof, a damper is required by code and the same code prohibits any type of screen or grill, as the moist lint-laden air can quickly collect and block the roof termination opening if a grill or grate exists.

Let's go over Vent Locations first: In most cases, the shortest, least restrictive run determines the best termination location, but other factors like proximity to windows, doors, porches, AC compressors should be considered. Venting the dryer to a roof vent is very popular in the south and works well for laundry rooms located in the middle of the house. Pushing hot air upwards uses about the same effort as pushing air horizontally or down so do not discount the potential of a roof vent for the dryer. 

Roof vent hood styles and features vary greatly across the country and can make a huge difference in how efficient your dryer runs and how fast the duct pipe fills up with lint.  Most roof vents do not offer the ease of access when needing to clean the duct with a snake like wand and brush due to the weather resistant gooseneck shape.  In many dryer roof vent installation instances a termination is used by a tradesman that exhibits a grate or screen with small openings.  It can take only a few months before this opening is clogged.  Be aware and concerned of roof vents with grills or grates that are installed for the dryer.   

Any dryer vent should be inspected at least once a year for blockage, proper operation and good airflow.

« Last Edit: November 14, 2013, 03:58:36 PM by rickharp »
Rick Harpenau
In-O-Vate Technologies, Inc
Jupiter, FL  33477
561-743-8696

rickharp

  • Administrator
  • Full Member
  • *****
  • Gender: Male
  • Posts: 147
    • View Profile
    • http://www.dryerbox.com
Re: A Roof Vent for venting a dryer...
« Reply #1 on: October 04, 2010, 09:34:37 AM »

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, 03:47:41 PM by rickharp »
Rick Harpenau
In-O-Vate Technologies, Inc
Jupiter, FL  33477
561-743-8696