Hello,

Would really appreciate some input on my rental unit in Central Vermont. Originally built in the 1840’s, it is currently three 1 bedroom units.  Exterior walls of the living space are dense packed cellulose and the apartments stay nice and warm in the winter.

The problem is the 12x15ft uninsulated shed on the right (red arrows in picture) where my tenants place trash/recycle and keep their winter tires.  The temperature in the un-insulated shed is whatever the outside temperature is while the basement stays a constant 55-60 degrees year round.

In the winter I have serious condensation issues on the bottom of the floor boards underneath the shed where the warm air hits the cold floor boards (Picture included). There is only condensation under this section not under the living space. This led to some serious rot issues and I replaced about 8 floor joists when I bought the place a year ago. Any recommendations on how to stop the condensation? My initial thought was using rigid foam boards as under-joist insulation. Would there still be condensation / mold growing between the floor boards and the rigid foam boards? Are there other options?

Here is a little more background information on the building if it is helpful. The basement is currently vented but I seal the 8 windows in October. Dirt floor basement but I will be installing a vapor barrier on the field stone walls and on floor once I replace one last column. I will run a dehumidifier in the basement in the winter once the vapor barrier is installed. Luckily there is no standing water or serious water infiltration at any time of the year.

Thanks in advance for any advice/insight!

Ryan