Zac:

You should be able to ventilate that well enough just by opening one side better. This will cool things off down at floor level pretty well.

Now for the bad news. A shelter of that kind won't warm things up at night very much no matter what you do with the flooring. Some water mass would add a couple degrees at most. The only thing that will really warm it up at night is a heater.

I don't have any outside power outlets, would it be safe to use one of those no exhaust propane heaters in something as small as this?

Another thing I had read about was painting plastic or metal drums black and filling with water. Do you think that would work for my greenhouse?

Thanks for your advice about the ventilation.

mozzles:

I'm very wary of any combustion heater that isn't vented outside. In something that small it might be OK if you ventilate well before entering.

Black drums full of water will help some but without insulation at night still not that much.

Things will grow faster this summer inside than out just because days will be warmer.

Then would you have any recommendations? Keeping all of my plants inside all summer is not an option, I don't have the space. I've read that sheets of styrofoam put in at night can help a lot, do you have any experience with this?

I've just realized that you were probably suggesting that things will grow faster inside my greenhouse than outside, and not inside my house like I originally thought you meant. In that case, I hope so! What would you recommend for any cold nights? There are supposed to be 2 or 3 nights under freezing in the next couple weeks where I live, according to the current forecast.

Hi Mozzles,

I bet you can get your plants through the cold nights by putting blankets over them. When I do this I stick a bamboo stake in each pot and then drape a blanket over the whole thing. That way the blanket does not crush the plant. If you have a decently thick blanket the plants will be OK if it's a few degrees below freezing.

I'd also go ahead with some water buckets. It will help a little and it's so easy. But overall I bet you'll have fine results because it will be warm during the day. I made a plastic covered hoophouse last year and our pepper plants loved it in there!

Thanks Karin.. I've been getting so worried since seeing the forecast where I live. I'll look into the blanket thing, would you recommend like quilts, thin blankets.. which kind? I'll go to the thrift store today and see what I can find. Also bamboo stakes.

Any kind of blanket will do - especially on the cheap! Something not terribly heavy but still cozy and insulated. I use fabric from JoAnn's that is made from recycled bottles. But anything will do!

Hey that sounds nice, I'll go to JoAnn's and take a look. Is it very expensive?

I talked to a local gardener earlier today and he said here in a few weeks we should be frost-free so I don't have much longer to worry. Though where I live there's a chance of frost in every month I believe.

I think it was something like $6 per yard? It's in the part of the store that has fleece. It's white. I like it because I am usually covering rows and the shape works well for that because you can buy nice long pieces. But the thrift store is likely to be more economical.

Nowadays I keep the blankets folded up on the greenhouse shelf as they are not needed much. The kitties are in heaven curled up on the cozy pile of blankets in the sunshine. So there you have it - dual purpose frost blankets. :)