Leaking ducts in winter

Anthony D.

> Are these AC only ducts not active in winter? <BR>
> You didn't say. If so the gravity flow is real <BR>
> and some good remedies have been forwarded. If <BR>
> the ducts are used for heating also, does it have <BR>
> a steam generating humidifier? These can cause <BR>
> dripping when ducts are run through HEATED spaces <BR>
> and can pull in the blower without a call for <BR>
> heat. If the ducts are dormant, and through an <BR>
> unheated space, insulation alone may not even <BR>
> stop it, running the blower (on a really low <BR>
> speed) is a quick fix. A piece of foam at the <BR>
> filter is even better. <BR>
<BR>
yes, this is a a/c only duct system

Anthony D.

Leaking Ducts in winter

I have a customer who said for the last three years water has come out of his main supply duct in the winter and damaged his ceiling. I havent seen this before, it sounds like air is gravity flowing into the cold ducts and the moisture is condensing. Has anyone seen this or have a solution?

Thank you

Mark Hunt

Seen it

and you are correct, it is the warm air rising into the ducts and the moisture is condensing inside.

Take a look at the R-value of the duct insulation. It should be R-8. If it is not you should bring it to that level. If these are flex ducts, they should be R-8 as well. If they are not they should be replaced.

I have yet to see a ceiling register that closes 100% but the cooling vents should be closed after the cooling season.

It is typical to see one central return in these sytems with a filter grill. After the cooling season, a 1" piece of foam board should be installed in place of the filter.

Worst case scenario, you could also use the plastic shrink wrap found in those window insulation kits on all of the registers. It's more work and you have to take it all down every year, but it is air tight.

Hope this helps!

Mark H

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rob

Please do not

forget to seal the ducts. Mastic or latex may be used. Seal the duct joints, the collars and flex core connection. It is very important to make sure the ducts are as air-tight as can be and then insulate them with the greatest R-factor possible. Mains should be R-11, we use fiberglass FSK normally used in basement insulation projects, foil-faced with scrim backing. Branchs can be R-8 flex. I personally like to use Bubble Foil with a R-11 overwrap.
If possible keep the supply trunks as short as possible per ManD to reduce joints. By the way the ASHRAE code for insulation is R factor= deltaT divided by 15 (R= TD/15). What is happening air migration and condensing inside the ducts that are cold. Most prevelant on cooling only systems and those with marginal install techniques. Hope this helps you understand and provides a corrective solution.

tombig

Are these AC only ducts not active in winter? You didn't say. If so the gravity flow is real and some good remedies have been forwarded. If the ducts are used for heating also, does it have a steam generating humidifier? These can cause dripping when ducts are run through HEATED spaces and can pull in the blower without a call for heat. If the ducts are dormant, and through an unheated space, insulation alone may not even stop it, running the blower (on a really low speed) is a quick fix. A piece of foam at the filter is even better.

Anthony D.

yes, this is a a/c only duct system