What is the most efficient roof vent or wall vent?

[rickharp]

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?

[rickharp]

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 wall vents.

Numerous terminations were tested and this table http://www.dryerbox.com/ratings/efficient.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/efficient.htm

[rickharp]

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.

See Link here:
http://shop.dryerbox.com/s.nl/it.A/id.227/.f