We did some major remodeling to an Eichler style house which included redoing the entire HVAC and moving all the duct work to the flat roof. About 2 months after moving in, around February we noted water dripping from 2 of the HVAC registers with mold formations around the registers. Furthermore, there was clearly condensation happening on the cathedral ceiling. We tried the advice given on the forum and by the contractor ie running the bathroom fans after showers, opening windows to increase air movement, running the HVAC auotfan, applying a reflective coating on the HVAC duct…. to no resolution. We ruled out any roof/duct leakage issues. The problem only went away with the weather warming up but we are worried it will return. The contractor has suggested adding an insulating layer to the HVAC ducts and creating a damper to have better air circulation. But before we agree to additional work without knowing if it will in fact work we like to consult with an expert and get professional advice. Does anyone know any company that can investigate and give professional advice. Please send a PM.
It sounds like you already know the source of the moisture, you're now looking for a solution.
For the record, I have a similar problem in my flat roof Eichler (E11). My vents are encased in foam and coated, yet I still get condensation in the winter. My theory is that the hot moist air rises, encounters a cold vent, and condenses. The vent is the lowest point so the water collects there.
I don't use the ducts for heat in the winter and I suspect if I did, it would eliminate the problem. In the meantime, I don't have a solution either.
I was reluctant to respond to this inquiry, since I was not sure the property was local.
Sarah has since emailed photos of lots of moisture under her sloped roof section, so I looked at a picture of her property (thanks Google Maps) and saw that the sloped section was shingle.
You have a shingle roof on the section of your house that shows photos of moisture under the ceiling. You won't have moisture like this with an insulated roof, since the surface won't be cold. Moist air cools when it contacts the cold surface of your uninsulated roof, leaving the water.
You may also have a 'damp' soil situation, enabling a lot of humidity to be part of your heated air. As the dry air of winter lowers the humidity of your inside air, expect the problem of visible moisture to lessen.....though you situation is the dampest I have seen on the inside of your sloped section.
Here is how it works; With a well insulated ceiling, moisture can only condense on cold surfaces that lack insulation. An insulated ceiling will be close to room temperature. With an UNINSULATED ceiling, you can get a thin amount of moisture over the total ceiling. When we first started installing insulated roofs in 1981, we found that the old, original single dome skylights would actually 'rain' from all the moisture that condensed on the plastic and the metal. Customers unanimously reported that the skylights had not been a problem previously. When we insulated the roof, the condensation problem increased remarkably on the few areas that were not insulated.
Randy from Dura-Foam Roofing and Solar Center