I would like to hear some opinions on the subject of blocking the cold air
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 .
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.
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
On Sun, 1 Feb 2009 04:16:29 -0800 (PST), firstname.lastname@example.org 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
(but ransley, you are still stupid)
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
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.
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
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.,
Check if local utility companies have free energy audits and leak tests,
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.
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.
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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