I’ve been spending time reading about passive wine cellars and I’ve even ordered the Gold book from Amazon to help gain understanding on how this project needs to come together. My wife and I are in the process of building a house. The foundation has just been poured and we have 9’ concrete walls in our basement. One thing that we did, was excavate under the rear covered porch to build a cold cellar, that I would like to turn into a passive wine cellar.
Here’s a picture of our cellar and dimensions:
We are located in central PA, where the average ground temperature is 52 degrees. The walls are poured concrete, 10" on the two exterior walls and 8" on the interior walls. The floor is also poured concrete and about 8’ below grade. The ceiling is corrugated steel with about 2-4" of concrete on top. As I’ve been reading a lot of sites, most of the sites talk about insulating interior walls, but most of those walls are interior wood framing, and not poured concrete. So I am really looking for assistance in understanding how to even start this.
I understand I have to insulate the ceiling with sprayfoam as the corrugated steel will condensate, insulate to about R-30 between the sprayfoam and rigid insulation, and then drywall with greenboard. I’m not sure if I have to insulate the other walls or the floor? For the record, the interior (outside of the wine room) will eventually be finished and heated and I assume this would heat the floor, which is why I was thinking I may need to insulate both the floor and walls (interior only?).
Does that sound right or am I approaching from the wrong direction? Thanks!
Spray foam is great when you put it in. Then a few years later it’s not as good. Maybe some of the newer ones are but I’d check before using it.
If you’re in central PA, you probably have a lot of clay and rock around your house? Why not take some temps through the summer and see what kind of conditions you have. My guess, and it’s only a wild ass guess, is that you may be in an area that will allow you to use a passive cellar without thinking through too many problems that people in warmer climes have to deal with. Maybe you can get some info from people in the area?
Again, I have no clue but if you are really going to get temps in the 50s in your basement, you may be able to simply frame out a wall, install a regular room AC, and only use that in mid-July and August.
Heating the outside of the cellar will heat the cellar too, so yeah, you should insulate against that. But you can do that in a number of ways. For example, you can build a closet or closets around your cellar and be sure not to heat those. That could save you a few degrees, and if you use some rudimentary insulation on those, you may not have to worry as much about super insulating your cellar, although I’d still do some insulation. It could help you with the floor heat transfer too.
In the end, it depends on the conditions you’re going to experience in reality and what kind of heat you put in the surrounding rooms. Closest I’ve come to your conditions is Michigan, Saratoga NY, and NYC. The first two allow for decent passive cellars except for mid-summer. NYC is a little warmer but I was able to keep my basement in the low 60s for most of the year except for a few months. In every case though, the surrounding area wasn’t finished or heated.
Thanks for the reply Greg and you are spot on. Clay is rampant in my area and from talking with my builder, he anticipates (based on his experience) that the room will be stable at around 60-62 degrees. That’s my primary goal in going passive as I want to minimize the additional accessories for cooling and just keep the cellar very simplistic.
Thanks for the tips on insulating the interior and floor and I will double check on the sprayfoam side. Do I need a wall AC unit? I was hoping to avoid that. In addition, not sure how humidity is controlled and I was assuming I can get an in-room humidifier or something to help maintain the appropriate balance.
A lot depends upon how big of temp swings you are willing to accept winter to summer. If you are willing to allow drifting up towards the higher sixties in the heat of summer then insulation requirements are not all that much. However if you want to keep it 60-62 like the builder has lead you to believe is possible then you will need more insulation and maybe active cooling for summer. I have a passive cellar in Maryland south of DC that drifts from around 57 in the dead of winter to around 67 in the heart of summer. My cellar exterior walls are facing north and east. I framed out all walls so it looked good and I could secure racking. I did insulate my interior walls as the rest of the basement is finished and has HVAC. I did not insulate the outter walls and I did not cover the concrete floor, only painted it. I did insulate the ceiling which seems to make the most difference. If I were to do it over, I would insulate the exterior walls as the foot or so above grade and the first few feet below grade do heat up more than I like but at the depth of the floor it still acts as a big heat sink. But as I said facing north and east
the impact is less than if a wall faced south or west and it probably only cost me a couple of degrees build up in summer.
I have not had any problems with the heat in the finished basement impacting cellar temperature in winter but as I noted I did insulate the interior walls. I did put a floor over the concrete in the finished part but did not insulate under it. I have not taken measurements so maybe there is heat transfer through the floor but I can’t believe that it is significant based on touching and observation. The floor remains a significant heat sink even in the middle of august and cool to the touch year round.
I doubt that you need to worry about humidity control. Your humidity will fluctuate through the year and I dont believe that the few months where it is at its lowest will cause irreperable harm as your summer humidity should be ample. If it were low all year round I may be concerned.
So if it were me, I would frame out an insulate all walls as well as the ceiling and be done with it. I would not worry about active cooling or humidity control. You may drift up a little higher than you like in summer but you wont come near the point where you need to worry about damaging any wine but you may age faster than if you added active cooling to keep everything below 60 year round.
Brian, thank you so much for the detailed reply. That really helps put things in perspective. How much insulation did you use? and did you use vapor barrier on the interior walls? Do I have to worry about that with interior walls that are concrete?
Not much really. I used faced R-13 in the walls and R-30 in the ceiling. All fiberglass and covered with drywall. I did not use any additional vapor barrier. I dion’t really konw what you need wrt your interior concrete wall.
Mark - you can do it even easier with polystyrene, which is what I did. In your situation, I’d probably do like Brian suggested and see how that worked. And yes, definitely insulate the ceiling.
You just want to be sure about your high temps in the summer. It may seem cool, but it may be up in the 70s. My NYC house is, that’s why I put in an AC. Most of the year it was off, but Jun - Sept I used it. In cooler areas, or if you’re 100 pct below-grade, you may be OK.
Your cellar may not be “perfect” in that you’ll keep a constant 53 degrees, but you’re already aware of that.
