Can I get by with a 4" duct for a 8'x7' bathroom I'm building in the basement? Didn't know if there was a code for the sq. ft. or not. This is a new house and they put 6" duct throughout just thought 6" for a small bathroom might be too much air.
you should get by for the bathroom. It may even be too much. You may however have problems with the reat of the house. If the did the whole space in just 6", the must not know that duct comes in different sizes. I would be willing to bet that you will have problems with airflow. In all likelyhood you will have coil freezeups and tripped limit switches. Then again, they may have done a full heat loss/gain and it just happens that 6" feeds will work perfectly for your space. Unlikely, but it is possible.
Best of luck
12:47AM | 03/12/03
Make sure you put a damper on the run going to that bathroom. It needs to be right at the take-off from the main trunkline. Depending on were this take-off is located within the system, you may get a loud air noise due to the smaller duct size. I would put the 6" in and just dampen it down. If you have any hidden issued with static pressure, it will show it's ugly face real quick. Air of the same CFM will go through 4" duct with much more velocity that 6". It's best to go larger and just dampen down what you don't need.