Trying to find the right balance between good looks and good insulation…

Picking out a door for your wine cellar is far more complicated (and important) than you might realize. Installing a beautiful door with poor insulation will basically ruin all the hard work you put into super insulating the walls and ceiling. Putting in a well insulated plain steel door will hold on to your cold air, but could end up looking cold and sterile. A tight budget makes this balancing act even more difficult… Doors specifically marketed as “wine cellar doors” can easily start at $1000!

For my cellar, $1000 wasn’t an option. Heck, $5000 wasn’t an option. My goal was to get the best insulated, most attractive door I could for under $300. If possible, I wanted a door with some glass so we could easily see into the cellar. (Since the cellar will be passively cooled, I really don’t want to be opening the door all the time and letting the cold air out. I figure a small window could greatly increase my enjoyment of the cellar with only a small insulating efficiency penalty. And the cellar is in a dark corner of the basement, so I’m not worried about any light getting in a window and effecting the wine.)

Here are the most important things I learned during my wine cellar door search:

• A door’s insulating value is measured by its “U Factor”. A U Factor is basically the inverse of the R Factor.  IE: U Factor = 1 / R Factor OR  R Factor = 1 / U Factor.  So, if you find a door with a U Factor of 0.22, its R Factor would be somewhere around 4.5 (1 divided by 0.22). Just remember… the smaller the U Factor, the better.
• You can ignore the SHGC number. This is the Solar Heat Gain Coefficient. This measures how much heat comes through the glass when sunlight shines directly on it. If your cellar is in a dark basement, you don’t need to worry about sunlight going through the window. If you’re cellar door is going to be getting any direct sun, DON’T PICK A DOOR WITH A WINDOW!
• Look only at EXTERIOR doors.  Interior doors are usually hollow and have basically no insulting value. You NEED any exterior door for this project.
• Do NOT buy a solid wood door. I know solid sounds good, but it’s actually just about the worst thing you can do from an insulating standpoint. Good insulation results from trapped air. (Think of all the air trapped in a nice fluffy winter coat.) A solid wood door is basically just a highway for heat transfer.  A near as I can tell, a solid wood door 1 3/4″ thick only gives you an R Factor of around 2.  To put that in perspective, it’s less than 1/4 the insulating value of an insulated steel door.
• Steel and Fiberglass are both good options. There are plenty of pros and cons to each, but for use in a wine cellar, I think they’re pretty much a draw. I wouldn’t let this be a deciding factor.
  
• Look for the EnergyStar certification. This certification is a good indication of a fairly well insulated door. If the door doesn’t have this certification, I’d just go ahead and assume it’s not good enough for your wine. (https://www.energystar.gov/products/building_products/residential_windows_doors_and_skylights)
• More glass  = less insulated. Figuring out the relative impacts of various window designs was definitely the hardest part of picking out a door. I really wanted a window, but only if the insulating impact was minimal. After finally figuring out what the hell a U Factor was, I came up with this table to compare the relative insulating values of my options:

In the end, I decided that an insulated steel door with a half moon window would do the trick. My insulating value goes down a bit versus a door with no window, but it’s still way better than a solid wood door. And, realistically, the door is only about 11% of my “warm walls” surface area (17 square feet out of 146) so the impact should be minimal to my overall insulation effectiveness.

I found this one on sale at Menards for $198. It’s EnergyStar Certified and has a U Factor of 0.19. The half moon will allow us to see into the cellar and should fit with the ultimate “Classic Europe” look of the cellar. It’s not perfect, but it will do. My hope is to paint or apply panel over the steel surface of the door to give it more of the classic wood look, like the pic on the right. But that’s a post for another day!

As always, if you have any questions, just drop me a comment and I’ll be happy to clarify or explain anything in more detail.

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