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Question DetailsAsked on 1/16/2018

I have one of these downdraft vents and in cold weather like we are having here in MA there is a very cold draft.

How do I insulate the duct ? is there a louver to the vent that can cut down the draft?

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1 Answer


If the duct is exposed in attic or unheated crawlspace or basement, there is specific wrap-around insulation designed to go around ducts - comes with self-sealing tape so you wrap it around and tape it, though you should also get some proper duct tape (and almost all "duct" tapes out there are NOT actually for sealing ducts and duct insulation) and overtape it, because most of the built-in tapes do not stick over the long run. Duct tape does not stick the greatest either - so be sure all tape is, to the extent possible, taped to itself at the ends to reduce self-peeling with age. Longitudinal seam taping you can "belly-band" tape at intervals, doing the longitudinal taping and then taping around the circumference of the insulation/duct to overlay that to help hold it on.

You can also use fiberglass batt insulation wrapped around it and duct taped - cheaper but usually (unless small duct so you can run it longitudinal using uncut roll batting) more seams to tape. Generally about an R-13 insulation will make a significant difference.

As for blocking off the airflow - doin that reduces ventilation/circulation so can cause moisture issues. Also, blocking off a significant amount of the airflow to/from a furnace is a bad idea - can cause imbalance in the airflow, and in extreme cases cause overheating at the heat exchanger.

Normally, unless the vent itself has adjustable louvers (you can buy those for typically $10-20 depending on color and size), like following - come in various sizes for ceiling and floor registers:

Generally you should not totally block the flow, and any dampening should consider the fact the room will be colder because of it, more condensation/icing on windows, etc. Definitely do not close to the point of the furnace fan motor sound changing pitch - that would indicate you are stalling it by backpressuring the supply ducts.

Some people also jsut use easy-peel (to avoid permanent marking) masking tape to tape paper or fabric over it - sometimes fuly with open-weave fabric to reduce the airflow, or only partly coer with paper or cardboard temporarily. Leave on more than a week or so and you will probably need bby oil or WD-40 or such to remove the tape gum after removal.

Answered 2 years ago by LCD

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