Dryer-Ell Performance Advantage

UL found that you would have to use six Dryer-Ell LT90s to affect airflow rate as much as one sectioned elbow. Its long radius and smooth interior reduce friction loss and improve duct performance.
One Sectioned Elbow Affects Airflow Much More than One Dryer-Ell
Sectioned Dryer Elbow Duct-length Equivalency
Further, the study found the actual affect of sectioned dryer elbows is equivalent to 15 feet of straight pipe. One Sectioned Elbow Equals Fifteen Feet of Duct

Dryer Vent Duct Run Impact - Current Code

Length of run Penalties under Current Dryer Venting Code
Most code, today, still reflects only a five foot reduction in length-of-run for every ninety degree turn in the duct. This seeming disparity, however, is somewhat offset by the very short overall run length allowed (most dryer OEMs allow longer). There are proposals before the ICC to bring both variables closer together. For now, there is a 5 foot reduction for every typical elbow from an overall 35 feet in allowable length.

International Mechanical Code 504.6.4
35 feet less 5' for each typical 90 degree elbow and 1.5' for each 10" radius elbow.*

International Residential Code M1502.4
25 feet less 5' for each typical 90 degree elbow and 1.5' for each 10" radius elbow.*

* Dryer-Ell Model LT90 Actual Length is 1.5 Feet

International Mechanical Code 504.6.4
35 feet less 2.5' for each typical 45 degree elbow and .75' for each 10" radius elbow.**

International Residential Code M1502.4
25 feet less 2.5' for each typical 90 degree elbow and .75' for each 10" radius elbow.**

** Dryer-Ell Model LT45 Actual Length is .75 Feet

Current Allowable Duct Length Under Dryer Venting Code

Dryer Vent Duct Run Length of Sectioned Elbow versus Long Turn Dryer Vent Elbow

Based on accepted ASHRAE methodology for calculating friction loss in ducts and fittings, this new elbow provides key benefits to the builder and tradesmen by removing the reduction consequence found in most building codes.

Section M1502.6 of the 2006 International Residential Code, Section 504.6.4 of the 2009 International Mechanical Code and Section M1502.4 of the 2009 International Residential Code all permit large radius elbows.

Click HERE for Calculations and Engineering Reports.