Fermentation closet questions

I'm looking into building a fermentation closet within my garage and am looking for some pointers.
I have a stand alone garage that gets very hot and humid in the summer (100 degrees). My idea is to make an insulated room ( say 4'x 6') within the garage that is cooled by a window a/c unit.
I was thinking just framing out the room and lining it with rigid foam panel insulation. I'm a construction novice and don't want moisture problems.
How would Holmes on Holmes make it?

 

Vapor Barrier on the warm side (outside of chamber insulation). Make sure you calculate your R-values/Cooling capacity, especially if you are getting up to 100 deg ambient

For example, assuming a 8 ft high ceiling the required BTU's per hour to stay at 60 degrees (for cleaner ales) given a overall R-Value of 13.5 is:

BTU/hr
= (SURFACE AREA (SF) x delta T) / ( R VALUE )
= 208 SF * (100-60) / (13.5 ) = 616 BTU/hr

Double the R-value by increasing insulation and you can cut that number in half. If you are looking at getting down to lager temps that number will go up.

 

Don't forget to insulate the floor. I'm sure the slab is getting quite hot and you will want to insulate against it.

 

HOH claims that you dont need a vapor barrier with rigid foam... just tape the seams, but you might get a better R-value if you go with vapor barrier and regular fiberglass insulation.

Insulating the slab is a good idea too

 

I have 3 mil plastic sheeting taped together covering everything, followed by fiberglass insulation and topped off with sheets of foam insulation. I figured overkill couldn't hurt. Make sure you use foil tape, duct tape is porous.

 

Thanks for the tips. Any ideas on constructing a door?

 

This was the most challenging part of my build. I used rigid foam on the door as well, and lots of weather stripping, several different types too. I then needed several slide bolts to keep door tight to the weather stripping.

 

Does the "door" really need to be a conventional door? How about a "hatch", with plywood front and back, plus a 2" foam board core? Thick foam rubber weatherstripping on the hatch and the hole it goes into.

The hatch will not be used like a door. It will only be opened at most once a day or so. Should be able to seal it better than a regular door.

 

exterior steel door: $150 at a big box store, and super easy to install...

 

I'm also doing this in my brewshed. Even though I'll have some heatloss, I'm planning to use a mostly glass door from HD so I can show off my conical inside. The whole shed is well insulated, so I think I'll be OK. But I'm a little worried about too much condensation on the glass.

 

Check out Coolbot. Whether you buy their controller or not, there is a lot of good information on that site about building a walk-in cooler.

From what I remember, the basics are:
4" of Foam insulation. Eventually fiberglass will get wet, even with a vapor barrier.
Buy an exterior door because well insulated doors are very hard to make.
No cracks. Not even tiny ones. You can fill in gaps with spray foam.

 

Food for thought.... Cheers!!!

5250 BTU AC with a RANCO Controller. Fan on top to blow warm air out of the room.