Recent changes in dryer venting code has made your only choice for code-compliant venting very clear. DryerJack®. DryerJack has always provided minimal airflow restriction. The adoption of this code in the latter part of 2017 drastically limited the number of roof vent caps available that meet this efficiency requirement. Take a look at the new code and the chart below.
M1502.3.1 Exhaust termination outlet and passageway size. The passageway of dryer exhaust duct terminals shall be undiminished in size and shall provide an open area of not less than 12.5 square inches (8,065 sq mm).
View the code at International Code Council's website.
|4” Round Pipe||Popular Broan Style||4" Type Gooseneck||DryerJack DJK477||DryerJack DJK486|
12.5 sq inches
|5.25 x 2 inches =|
10.5 sq inches
|4 x 2.25 inches =|
9 sq inches
|6 x 3.5 inches =|
21 sq inches
|6 x 3.12 inches =|
18.72 sq inches
More information here:Code change alert.