Efficiency Values for Dryer Exhaust Terminations and Fittings

Dryer vent hoods come in a multitude of styles and end up in one of three locations on your home: the roof, the soffit or the wall. The objective of a vent hood for the dryer is basically two fold; prevent back drafts and prevent bird or rodent entry as well as nest building. In facilitating these capabilities a prevalent result is a vent hood that promotes lint build-up and creates excessive back pressure.

A vent hood or fitting that creates excessive back pressure not only lengthens the drying cycle but accelerates dangerous lint build-up. Higher energy bills and increased risk of fire become the obvious outcome. Until now, there was no assessment of the back pressure that these popular vent hood designs and fittings provide. The below chart provides the actual difference or delta (∆) of air pressure measured with a Magnehelic Gauge* before and after the fitting was attached (Differential Pressure). The higher the value, the less efficient the fitting is. These days, being energy efficient is important step in the direction of drying smart. Consider these values when shopping for a dryer vent fitting or hood.

 

Airflow Efficient Ratings Matrix by Product

Fitting Type	Description	Model ID	Thumbnail	Buy	Airflow Reduction (wci)*
Roof	DryerJack 466	DJK466		N/A	.00
	DryerJack 486	DJK486			.02
	Roof Jack Plastic	Not Carried		N/A	.35
	Popular Broan Style	Not Carried		N/A	.30
	Typical 4" Wide Goose-neck	Not Carried		N/A	.45
	New Mushroom Style	Not Carried		N/A	.25
Wall	Dryer Wall Vent	DWV4			.00
	4" Louvered Vent	GH4W			.08
	No Nest Vent	NO NEST		N/A	.01
	3 Louver Opening Vent	HS4W			.03
	Dryer Vent Closure	Not Carried		N/A	.60
	Standard 30° Wall Flapper	Not Carried		N/A	.20
Eave	Under Eave Vent	EVEVENT			.10
Fittings	Sectioned 90 Degree Elbow	ELL-4		N/A	.15
	Dryer-Ell 10 Inch Radius 90° Elbow	LT90			.05
	Dryer-Ell 10 Inch Radius 45° Elbow	LT45			.05
	Close Ell	CLOSE-ELL			.25
	Lint Trap	ECCO Lint Trap		N/A	.15
	Periscope Style Connector	Not Carried		N/A	.50
Flex	Foil Wire Bound	Not Carried		N/A	.35
	Semi Rigid Alum Flex	ALUM-439		N/A	.10
	Semi Rigid Alum Flex	ALUM-448		N/A	.10

*Difference with and without fitting, measured with a magnehelic gauge.

Footnote:
*Magnehelic Gauge: A sensitive differential pressure or vacuum gauge manufactured by Dwyer Instrument Co. that uses a precision diaphragm to measure pressure differences. This gauge is manufactured in specific pressure or vacuum ranges such as 0 to 2 inches of water column. Airflow was provided by a typical residential clothes dryer.