New basement wine cellar construction -- planning stage

Hi all,

I’m getting ready to build a wine cellar in my currently unfinished basement in Falmouth, Maine (Portland area). I’ve read with interest all of the cellar-building threads I could find on WB, and I think I want to do this project DIY. I probably will not begin construction until August, but look for pictures and progress reports then.

I did want to throw out an issue to the group now though that I have not seen addressed in the other threads and am hoping that the collective wisdom will point me in the right direction:

At this point, I’m planning on a passive cellar, at least at first. According to the information AndrewH posted in another thread, the ground temperature in my area should average around 48 degrees, and at 6 feet below grade, should fluctuate around 8-9 degrees above and below that number. Using the spreadsheet also posted by AndrewH, I think that I can use my basement floor (the plan is tile, without insulation) as a heat sink, and with properly insulated walls and ceiling, the temperature of the cellar should never rise above about 62-63 degrees, based on various fairly reasonable assumptions regarding insulation and the temperature of the rest of the basement and space above the cellar throughout the year. The questions I have are, if the floor is significantly cooler than the air in my cellar (particularly in winter), am I going to have a big condensation problem? If so, is that going to create a cascade of other problems (i.e. mold)? Any tips on how I should treat the floor given the assumption that it will almost always be colder than the air?

Thanks in advance.

How dry is your basement in the winter? Usually houses are really dry in winter, in which case condensation is unlikely to be a problem. If your house is newer, and more air tight the potential for a problem exists - I would take some humidity readings now to get a feel for how humid the basement is in the winter.

Almost impossible to have condensation issue in winter without a source of humidity. Even though your basement remains cool I would wire the cellar for a cooling unit. Much easier to do with new construction then to do later if your cellar is warmer than you thought or you want to increase the temperature of the basement around the cellar for other reasons. The cooling unit can also help control humidity in the summer.


Andrew, we are currently dealing with some moisture issues in the basement that will hopefully be resolved over the next few months before we start finishing the basement and building the cellar. But I’m not yet sure where the humidity levels will end up.

George, thanks for the advice. I’ve thought a little about this issue already. Because the cellar will be in the middle of the basement, any future cooling unit will probably be a ducted system from the unfinished portion of the basement. Doing it myself, I figure installing ductwork during initial construction would add $200-400 to the total cost of the project (including boxing in the ductwork, which would mostly be in the closet of the future adjoining bedroom). But I have no idea what it would cost or how difficult it would be to add a ducted system after the cellar has already been built and finished. Do you think adding ducting now (knowing that I may not use it at all) is a good investment weighed against the potential cost and difficulty of introducing a cooling system later?

For condensation, you’ll need to look at a chart like this:

Basic idea is to look at your potential temperature on the curve (say 10C, or 47F) and move horizontally to the right to see what the air temperature is, and then determine what relative humidity curve you’re on. If RH is above that you risk condensation. A quick look shows moving from about 10 to 15C you’d still need about 70% RH, which is very high. As temperature warms up, RH will be lower though.

Thanks. This is very helpful