Originally Posted by
Jayh5
Hey Guys, First time posting in here. We Install lots of systems at the coast in new construction and existing homes and a ongoing promblem (mainly in new construction) is condensation on ducts. Alot of the Air handlers and portions if not all the main duct is hanging under the house (piling beach houses) and the duct pours water due to being exsposed to outdoor environment. The contractors box in around the duct and use house insulation in that areas, but still sweating issues. These houses have height restrictions, so the builders make everything as tight as they can to go as high as they can and the lower level(under the house can not be conditioned due to being in a flood zone.
with all that being said , has anyone ran into this before? We use 3" duct wrap, I am looking into using a spray foam for more R value and a better enclosure. Does anyone use Foam on ducts if so any thoughts?
Ducts and the underside of the living space are going to have condensation and damage anytime the surface temperature is below the dew point of the air at the exposed surface. Add the problem of moisture being able to move through the insulation like fiberglass and other fiberous materials.
The surface of insulation must have a real moisture barrier like metal/plastic/. Closed cell foam with seams must be sealed. Also the cold air supply temperature must be controlled to avoid extreme cold temperatures yet cold enough to provide moisture removal from the home. Many have adapted a sealed crawlspace with plastic on the exposed earth or skim coat of concrete on the earth and closing vents to damp outside air. Then a dehumidifier is added to the space to maintain a low dew point space for the ducts and living space floors which will avoid moisture damage. You can still have break away ways and the space can be used for storage.
The next stage is to add a small whole house dehumidifier to the space connected to the a/c which will maintain the desire humidity to the crawls and home. With advent of the well insulated home, many are suggesting fresh air ventilation and humidity control to provide a healthy and comfortable space. With a few modifications to the crawlspace is incorporated to the main space. This fixes most of the common moisture problems in a modern home.
Ultra-Aire or Santa Fe dehumidifiers designed for this application.
Ultra-Aire.com
Where are you located?
Regards Teddy Bear
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"