Cold Air Return

I would like to hear some opinions on the subject of blocking the cold air return vents.
My house is built on a crawl space with cold air ducts running through the attic. I have three unused rooms with the the heat vents closed. All rooms have cold air returns. would it be beneficial to also block the cold air return vents in these rooms? We use propane and my heating bills are killing me. Any suggestions would be welcome . Thanks Dave
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I doubt it would save much if any. Think pressure. If there is no air going in, then no air can get out. This is an assumption that the room is sealed. The rooms where the heating vents are open has air going into them, therefore the the cold air returns need to be open in order for that room to get heat. Closing the cold air return is the same as closing the heating vent and vice-versa (in reagrds to air flow).
Another thought is how will the cold affect the room and its contents? Will the expansion/contraction affect the furniture, water pipes (in the walls, ceiling and etc), drywall/paneling, fixtures and such? Is it really worth it?
Just my opinion.
Hank
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I'd close off the returns in the unused rooms. That's what I do. A room isn't perfectly sealed, especially from the rest of the inside of the house. For example, it's common to have a gap at the bottom of inside doors. With the supply registers closed, the return will have more tendency to draw air from anywhere else, eg under the door, through outlets, through window leaks, etc.
The caveat in all this is you don't want to close off too much of the return capacity.
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On Sun, 1 Feb 2009 04:16:29 -0800 (PST), snipped-for-privacy@optonline.net wrote:

Damn trader. Just when I thought you had it with that one inch hole in the ductwork then you go and screw up on this one. Even ransley got this one pretty close. If a system is properly sized and installed you do NOT close any supplys or returns. IF properly sized, closing any supplys or returns will cause increased static pressure in the duct system. This increases noise in the ducts. Then you starve the furnace of the required air flow. This increases the temp rise through the furnace. Increased temp causes high limit switches to fail and heat exchangers to fail. It also puts unnecessary stress on all the operating controls and motors as they cycle more often than needed. All the while you are wasting energy as the higher flue temp causes a greater draw on the vent pipe system which sucks the air from your home. If you close off vents you need to get a smaller furnace and smaller ductwork. Bubba (but ransley, you are still stupid)
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Close off the returns *and* the heat ducts as close to the furnace as you can. [and insulate the ductwork in that unheated attic]
Jim
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wrote:

    I will only add to the prior comments that you should be careful about blocking too much off. You heating and cooling units are designed for a certain range of air flow. Bock off too much and you can damage the units and will result in less efficiency from the heating unit.
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Be carefull the exchanger has a max design temp stated. Closing supplys will raise it alot. I would not close any supplys until I knew the temp just above the exchanger and monitored what closing vents does. The exchanger is thin metal overheating it will shorten its life dramaticly. You might need a pro to get it lowered. I lowered mine. Close off to much and you burn it up.
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*I don't think closing the returns will do much good. It may actually be detrimental to your system. However I do recommend that you insulate any ducts in your attic; return and supply.
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David B. wrote: ...

Insulate these (note if also have exposed plumbing that's relying on the escape heat for freeze protection)

Probably not much more to be gained if the vents are already closed--that minimizes the input. Depending on the size of the house otherwise, and w/ the other caveats of excessive flow blockage; try it and see...

Probably the most bang for the buck will still be more insulation throughout the house and the normal energy-loss items of storm windows if don't have them, sealing any leaks around doors, windows, outside wall electric outlets, plumbing and other penetrations, etc., etc., etc., ...
Check if local utility companies have free energy audits and leak tests, etc., ...
What's the efficiency of the furnace? If it's old, it could be as low as 50%, easily. It might even pay to upgrade it.
--
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David B. wrote:

Are the returns actually returning any air? Incense or cigarette smoke in front of the vent will tell you. If the vent IS sucking air from a closed room, the air has to be coming from somewhere: The supply vent not completely closed, under the door, from outside, somewhere.
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David B. wrote:

If you have the heat register blocked off and want to save heat, also block off the cold air return if one is in that room, otherwise it will suck heat in from other parts of the house under and around the door and electrical outlets or anywhere else there is an opening from other rooms.
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