Open or close return registers in basement ?

Old 06-08-08, 08:17 AM
Thread Starter
Join Date: May 2008
Location: Cleveland Ohio
Posts: 41
Received 0 Votes on 0 Posts
Open or close return registers in basement ?

This seems like a basic question but after doing some searches I couldn't find what seemed like a direct answer. I'm trying to figure out what I should do with the registers, both output and return, in my basement when the using the central air.

Is it better to open up the return registers in the basement or leave them closed ?

My guess is that the goal here is to 'tune' the registers so as to minimize negative pressure in the basement. Negative pressure is bad because it causes hot moist air to get sucked into the basement from the outside. If avoiding negative pressure is the goal then does that mean that it's best to leave the door to the basement from the upstairs open ?

My house is kind of weird because access to the basement is through the garage. So that means that I don't have a big low resistence channel for air to get sucked down from the upstairs to the basement when the blower is runnning (assuming the door to the basement from the upstairs is open).

I have a dehumidifier in the basement and if I don't have the A/C going then the temp down there stays in the low to middle 60's with humidity at 50%. But once I turn on the A/C then the temp in the basement goes up to the low 70s and the humidity goes up to 54% and the dehumidifier is working hard to keep it there.

Here are some details about my HVAC set up.

The home is a 1950's ranch and was built with a plaster ceiling in the basement. The return 'ducts' are the literally in the ceiling joists. By that I mean that the channels between the joists, which is enclosed because of the basement ceiling, is channel that is used for the return. Hopefully this will help explain what I mean:

My basement has two intake registers in the basement and has two 'output' registers. One set of these registers (if I'm calling them by the correct term) is built into the furnace.

The other two registes may have been hacked into the existing ducts after the fact:


You can see how what I'm calling a intake/return register is a just covering up a hole in the ceiling. But that hole is located in one of the the return channels.

Thanks in advance for any replies !
Old 06-08-08, 06:34 PM
Jay11J's Avatar
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,427
Received 0 Votes on 0 Posts
If you are not using the basement for anything, then I'd close it all up since you got a dehumidifier going down there in the basement.

Then come to heating, open them back up.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: