Ok to block return register?

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Old 12-11-11, 01:47 PM
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Ok to block return register?

I have an electric forced air system in my home that originally had two return vents--one on the top floor and one on the first floor. I added an equivalently-sized return in the basement a few years ago because one was not installed when the basement was finished. The upstairs return is in the hallway and services the entire floor, the first floor return is in the family room and services the entire floor, and the basement return services the entire basement. My question is, is it ok to block the return upstairs during the winter so the two returns on the lower floors suck more air? Vice versa, is it ok to block off the basement return during the summer and let the upper two returns do the work? FYI, the basement has an interior door somewhat separating it from the first floor and the first floor has a vaulted ceiling which opens up to the second floor hallway where the upstairs return is located. I currently have the upstairs return blocked off and it already feels warmer downstairs, but I want to be sure I am not going to damage anything. I figure it is fine since the system had two returns to being with and it has lasted 30 years, so blocking the third would still leave two working returns.
 
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Old 12-11-11, 06:00 PM
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It's tuff to say. Most duct work in residential is under sized so the only true way to know is to do a heat load
 
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Old 12-12-11, 11:44 AM
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I close most of the upstairs vents in the winter and most of them downstairs in the summer but I've never considered closing a return.
 
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Old 12-12-11, 01:18 PM
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I also close the registers upstairs and/or downstairs, but never have gone to closing the vents, although I have more than enough capacity.

I do it for seasonal comfort in a home with a major open stairway. I run my fans 24/7 while in the heating season and put the fan on auto for the cooling season. I usually can maintain a max of 2 dregrees difference between levels. - The real benefit for AC in the summer (MN) and I rarely use the programmable thermostat because of the thermal inertia in the lower level and the humidity control.

Dick
 
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Old 12-23-11, 11:55 AM
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Think I'll try blocking off the upstairs return by 50% and see if there are any benefits. I'm sure my basement could be better insulated as well. The basement was finished a few years ago by the previous owner but they did not add additional insulation, so it currently only has the builder grade insulating blanket installed (not sure what it's called). Would having a warmer basement help keep the upper floors warmer or would it not make a difference since cool air drops?
 
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Old 04-18-12, 10:37 AM
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I've heard that by closing off the registers and not the return that I can create a negative pressure in the basement. What problems can this cause? FYI, there are no gas utilities in the basement. They are all electric.
 
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Old 04-18-12, 11:31 AM
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It will mean your basement is lower pressure than upstairs and air will flow into it from upstairs. If anything in the basement has a chimney, this can lead to backflow problems.
 
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Old 04-18-12, 04:43 PM
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Ok. So it sounds like i need to close the return too to avoid a negative pressure but how do i keep the air filtered and circulating down there? It is a finished space and we ise it quite often. Also is negative pressure in the basement undesirable only in the summer or in the winter as well? I should also add that there is a door to the basement but it is only a hollow core interior door.
 
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Old 04-19-12, 04:20 AM
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Do you close off the basement? If so, leave the return and supplies open in the basement. It will provide equal pressure. I figure the two upstairs sections are open to each other. THERE you can fiddle with the supply registers to accomplish equalization. You need good circulation in the basement. If it is below grade, or even a walkout it has better insulation (earth) than the rest of the house. Return should always closely resemble supply in size. There is a formula for it, but maybe airman or someone can expound on it better.
 
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Old 04-19-12, 07:01 AM
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I never block returns but I do close some registers upstairs and down between the summer and winter.

I don't have a lot of returns in the basement so it's pretty easy to make sure I have more vent area open than return area (I do have gas appliances).
 
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Old 04-19-12, 09:07 AM
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I wouldn't say we "close off" the basement, but there is a hollow-core interior door to the basement that remains closed for the most part. The basement is finished with drywall, carpet, half bath, etc., is mostly below grade, and is not a walkout. No gas appliances or chimney. If negative pressue is a big concern, then I can open all the vents back up, but it gets pretty chilly down there if I leave them open so I figured if I closed them off more cool air would blow to the upper levels. If this is not the case due to negative pressure, then I can open them up I suppose. Another major reason for closing off the basement return was to allow the returns on the upper floors to pull harder thus getting rid of the warm air faster especially on the top floor.
 
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Old 04-19-12, 09:15 AM
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Given that the basement return did not initially exist, you're probably ok blocking that in the summer.

However, in the winter, I would block a vent or two upstairs and probably leave all the returns open.
 
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Old 04-19-12, 09:37 AM
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Everything is just fine in the winter time, nice and warm on all floors.


Given that the basement return did not initially exist, you're probably ok blocking that in the summer.
..but what about circulation and filtration?
 
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Old 04-19-12, 09:55 AM
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You're not closing all of the vents down there, right?
 
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Old 04-19-12, 09:59 AM
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Up until last night, I had all registers closed in order to push more cool air upstairs and had the return damper half way open. Now everything is closed off because of the negative pressure issue.
 
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Old 04-19-12, 10:11 AM
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I'd open a vent or two downstairs - I have five in my basement and leave two of them open in the summer.
 
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Old 04-19-12, 10:14 AM
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There are only three vents in the basement though, and two of them are in closed rooms.
 
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Old 04-19-12, 10:15 AM
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Well, then I'd open the one which isn't in a closed room.
 
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Old 04-19-12, 10:39 AM
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..but then it gets too cold. I'm confused. Considering the basement has a door on it, is negative pressure really a concern? Is cool air from the top floors really going to sink down to the basement through a 1/2" gap beneath the door?
 
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Old 04-19-12, 10:58 AM
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Yes............................
 
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Old 04-19-12, 01:00 PM
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Ok. I'll open everything back up in the basement and try blocking off the return on the 1st floor to see what effect that has. If it gets too cool in the basement again, then I may just shut everything as it currently is because the negative pressure is having less of an effect than having all the vents open.
 
 

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