Just a hint.
In the winter, my air conditioning ducts, with the AC handler in the
uninsulated attic, let in a lot of cold air. Although there are movable
vanes inside the vents that can be shut, usually with a screwdriver,
they are not airtight. So how do I stop the air infiltration? They sell
magnetic covers for the metal vents, but what about plastic vent plates
which I have? I used to cover my plastic vent plates with pieces of
plastic wrap that I taped on. It was time consuming trying to hold the
thin floppy plastic film and tape it on at the same time. In the last
couple of years though, I use the Contact Paper type of self sticking
plastic shelf covering. Just cut it to size, peel the paper off to
reveal the adhesive, and stick the plastic to the vent plate. I use the
white kind so it hides the vent vanes, leaving the whole plate white,
but that's only a matter of aesthetics, the clear kind, or any of the
various colors and patterned types, work as well.
Don't forget the AC return vents too.
on 12/11/2009 3:11 PM (ET) hr(bob) email@example.com wrote the following:
Yes, but then you have to take the covers off to remove the foil/plastic
in the Summer.
The plastic shelf liner just gets peeled off the vent covers in the
Summer, and if you are really frugal, you might save the sheets for next
When radiant floor or ceiling heat was briefly popular, and even today
for people with old-style radiators, they used the little hi-pressure AC
duct systems. Those outlets usually came with little O-ringed plastic
plugs you could pop in the round holes to shut them off.
In OP's case, I'd either change the vent covers to metal so a magnetic
cover would work, or find some clear or color-matched velcro dots, and
fabricate gasketed covers that would stick to the velcro in cold
weather. One dot at each corner should be plenty- the covers can be very
thin, and the thin foam self-stick stuff applied to the back of the
covers would make an adequate air seal. Basically like how they used to
attach the the front grilles to stereo speakers, back when stereos had
speakers in wood boxes. Most sewing/craft/hobby stores have velcro, in a
wide variety of colors. Overpriced, but you won't need much.
on 12/12/2009 9:04 AM (ET) The Daring Dufas wrote the following:
Try it and get back to us. Those magnetic strips won't attract each
other with a gap of only a few millimeters of space between them. I have
Also, the price of that magnetic material to cover 12 vents "on both
sides" will be a hell of a lot more than a roll of shelf paper.
Besides, like putting the barrier behind the vent cover as someone else
said, my way doesn't require removing the covers twice a year.
Why would it dispense cold air? Why would it dispense ANY air if not
running? It would seem that the air handler is a closed system,
bringing air to itself from the living space and then sending it back
with the heat removed. If it's not running, where is the movement?
Th AC is probably separate from the heating system and the whole
thing sitting in the cold attic is like it was sitting in a fridge.
All of it is cooled down and the cold air being denser than the
warm air inside the house would make it spill out of the ductwork.
If you open your refrigerator and hold your hand close to the floor
in front of the open door, you will feel the cold air spilling out
of your fridge. It's the same principle.
on 12/11/2009 7:37 PM (ET) Steve Barker wrote the following:
There is always air in the ducts, whether running or not. It's not a
vacuum environment. Even if the ducts are well insulated, the cold air
in the attic will cool the air in the ducts and then it drops to the
lowest point and escapes out of the vents..
Your home is a closed system. Turn the heat off in your home and see if
the house stays warm.
It's simple physics.
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