Clothes-Dryer Exhaust Vent
Conventional ducting results in an effective 31-ft. exhaust run. Swapping out regular elbows with Dryer-Ell elbows reduces the run to 18 ft 6 in.
It’s important to consider the effective length of the dryer-exhaust duct run. Excessively long runs or runs with multiple turns will reduce the dryer efficiency and in some cases may not be code compliant.
The 2015 IRC allows a maximum effective length of 35 ft. That sounds like a long distance until you factor in fittings. A standard 90-degree fitting has an equivalent length of 5 ft. A 45-degree fitting equates to 2 ft. 6 in.
The dryer location in the second-floor laundry room is on an exterior wall, so a straight duct of about 6 ft. will be all that’s needed. The basement dryer location falls in a spot that requires three elbows and 17 ft. of duct for an effective length of 31 ft. (three elbows = 15 ft. equivalent). While it’s below the maximum 35-ft. code length limit, it’s a long tortured path that will undoubtedly translate into slower dry times and reduced efficiency.
Since I can’t route the dryer duct in a shorter configuration, I may be able change out the 90-degree elbows for 45-degree elbows (if they fit), or I can use long sweep elbows. One brand I’ve used on a few new and remodel projects is Dryer-Ell. The Dryer-Ell is a long 10-in.-radius sweep with a smooth inside surface that translates into a 1-ft. 6-in. effective length while giving you about a foot of length on the X axis and a foot on the Y axis to reach your exhaust point. So by swapping out the 90-degree regular elbows with Dryer-Ells, I reduced the straight pipe sections to a total of 14 ft. and only lost 4 ft. 6 in. in equivalent length with the three Dryer-Ells, for a total of 18 ft. 6 in. Using Dryer-Ells lops 12 ft. 6 in. off the effective length of the dryer-exhaust run.
Dryer-Ells are made of two pieces that you clip and screw together. The joints can be sealed with aluminum duct tape or mastic just as you’d seal other joints.
While Dryer-Ells cost more than regular elbows ($19 vs. $5), I figure the energy savings over the life of the house will be far greater than the additional cost, but I haven’t done a calculation to verify that.