Yeah, insulating the floor is a good idea. Just throw down some rigid foam with a sheet of wood over it?

Yep that's the plan.

I just took a quick look and the cold room is already back up to 10 degree's and climbing after only 15 minutes. I know the R14 insulation isn't the best in the walls but it's better then 2 degrees every 15 minutes so it has to be coming from the exposed concrete.


The concrete foundation wall is at 14 outside of the room and 11 inside, the floor is at 16 outside 8 inside. I hadn't planned on insulating away from that wall inside the cold room but I may do it in the end if I have enough left over insulation.

I can't tell from your pictures but how do you have the vent fan setup? I would assume the top vent is the out and the lower vent is the inlet with the tubing ran to the furthest side. I would try running the outlet vent tube to the upper most opposite corner from the inlet, that way it should be pulling the warmest air out.

Also you could try getting some smaller stones 4-5" and place them by the inlet that way they can retain the cold and help regulate the temp. The down side to that is since they will take time to heat and cool if they are warmer than the incoming air they will slightly heat it.

right now on the top right is the outlet vent with the fan attached directly to the wall pushing out. The inlet tube runs down to the opposite bottom corner but the actual vent is below the outlet by about a foot.

I finished insulating the basement wall with the rigid insulation. It took a day and then I noticed that the cold room had stabilized at a temperature over a degree cooler then before even though the outside temps were the same and inside temps were the same. My best guess is the 15 or so sqft of concrete wall right next to the cold room wall that I hadn't finished insulating yet was absorbing enough heat to bring the temp in the cold room up that 1 degree. After figuring that out I put 1.5" rigid across the entire floor in there then used the fan to bring the temperature back down to the 8.7 it had been sitting at. I'm hoping it will get much closer to the outside temperature now, stable at 4 C without needing the fan is the goal.

Is there any specific temperature you're aiming for or need to get to store properly?

most veg/fruit are best preserved at 4-8 degrees depending on what they are. I can also use it for meat curing if I can get it to stay stable near that range.

Right now my goal is to see how close to 4 degrees I can get it and how long it will stay there. My fridge is at 4 degrees so I figure it's as good a goal as any. Right now it's 5.8 but the basement has dropped to 18.2 and outside is -4.5 so it's hard to say if this is a case of the floor insulation working or the other lower temps making the difference. This temp was achieved with out the use of the fan.


The woodstove is working hard on getting the inside temps back up to the 21 we normally keep things but it may not be able to pull it off as the temps drop down tonight. so I may have to wait a few days to see if the temps will stabilize inside when the basement rewarms.

outside hit -11 last night but is currently only -7 inside right now the basement is 17.9 The coldroom is at 4.1 Any colder and it's too cold but last night's temps are a real rarity around here. I don't think I'll need to shut off the venting. Now to see how long it stays near this temp.

this evening I finally taped the poly in around the windows. As I was getting close to sealing it up and only had a few pieces of tape to go it was amazing how much cold air was channeling right to that last spot on the wall to get in while hot air must have been pouring out somewhere. Before I started putting on the poly the windows just felt cool all over. At the end their was a noticable breeze of cold air pouring out strong enough to bend a piece of paper.

If you are sealing up a house I'm sure anything is better then nothing but leaving two areas unfinished where a circulating loop can get going is going to result in a lot of cold air pouring in.

Making a house airtight is one of the most difficult challenges of energy efficient construction.