What causes moisture on a ceiling in winter?
I bought a duplex that was built in 1978 in Indiana. It gets moisture on ceiling so bad during winter when temps drop below 20 degrees that it will run down the walls & look like its raining. Contractor says there’s enough insulation in the attic. There’s wood siding on 3 sides & brick on the front of the house. I want to put metal siding over the wood & add insulation in between. Will this solve my moisture problem on ceiling or do you think the units need new heat pumps which are at least 15 or more years old?
Condensation forms when humid air meets a cold surface, so if there is condensation on a ceiling then there be either thermal bridging - a lack of insulation. Or, if there is a reasonable amount of insulation then it may be that the air in your home may have high relative humidity. This page about condensation will probably help -
Condensation on walls and windows - what causes it and how to fix it
This page as well about winter preparations covers the topic of condensation forming on walls in winter, and other humidity-related home issues –
Tips for preparing your house for winter: how to make your house more efficient and save money
For your case specifically, we are more than happy to troubleshoot it with you, there are just a few questions that will help identify the problem –
Does the condensation only form on the exterior edges of your ceiling? That may indicate thermal bridging at the junction where your walls and roof meet. If it is over the entire surface then that could be a lack of insulation.
How high is the relative humidity in your home?
Does your home have an HRV or ERV? (heat recovery ventilator or energy recovery ventilator)
Do you use exhaust fans? (bathroom fan and stove hood)
Does your stove hood vent directly outside or does it filter air and blow it straight back at you?
I don’t see how your heat pumps would be the problem, I am more thinking you need improved ventilation, and likely a dehumidifier. Let us know whatever you can of the above questions and we can take it from there. Another page worth a quick read could be this one about learning how to fix Ice dams on your roof before they cause damage; while you may have sufficient insulation in the eyes of one contractor, unless they did a thorough investigation of your attic it is possible you have ice damming.