Radiant heat/ Attic A/C and duct

[ruud-man]

I have had several contractors mention the problem of water forming in the airhandler/duct over the winter while the A/C system is idle over the winter. One case was so severe the complete duct system and airhandler/coil had to be replaced because of mold.

I believe the reason for this is the migration of the warm, humid air (cooking, showers, humidifier, etc) from the radiant heated space to the cooler surfaces of the duct and airhandler/coil. There, the moisture condenses on the cooler surfaces and eventually drips from the cieling registers.

My question is what is the best way to prevent this? I know some HOs try to seal the supplies and returns and some try leaving the blower on "continuous".

Any thought?

[simpleman]

You could install the ductwork inside the envelope and get rid of that problem along with a few other issue as well.
Oppps..I better say that is if the envelope is seal as well.

Personally I dont see it happening with radiant floor heat.
one its not depended on convection alone,convection is more
of a mute issue for me being most of your heat from infloor
comes from radiant..hence the name radiant infloor.

Also I know it happen more so with emitter having surface temp of 180 and above which give the air more opportunity
to create more of a stack effect if you will.

Highest emitter temps you will see radiant will, or should
only be 90 degree so that in itself should help, I would think.

Maybe the guys up north in colder climate could answer the
question better,for me personally in my parts I have never experience that problem in the winter.

[Edited by simpleman on 04-01-2005 at 03:31 PM]