Published on August 28th, 2014 | by Henri


Insulating AC ducts to prevent heat loss

Q.  We have hot-water heat and separate air conditioning with ductwork in the attic. I have never seen anything published regarding heat loss through the vents for the air conditioning in each room. There are no levers for shutting off  the vents. Should there be?

A.  The air-conditioning ducts in the attic should be insulated. There are several types of ducts. If they are flexible, round fiberglass ducts, they come insulated. But if they are metal, they are insulated with special blankets with an aluminum facing. The air-handler is also insulated.

But since the system is in a cold space and the registers on the ceilings, warm air will enter the registers, and since the R-factor of the insulation on the various parts of the system is nowhere as high as it is in the other components of the house, there will be some heat loss.

The ceiling registers  should have some sort of adjustment to close them partially or fully, in order to balance the system. Since yours do not, you may want to look for replacements.

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