I think you'll find that at temps that low plants will not actively grow, but merely hang out. All the material I've read for Veggie production in the winter indicate the planst must be grown in the fall, so that when it gets cold they just are there, not actively growing.

Not a flower person though!

May not be true.

Temperature can easily reach above 80 degrees for a good part of the day.

Very nice construction.

I think you may want to have a black floor to collect more solar heat.

On a very cold night, a 1,500 watt heater may not be able to keep things from freezing inside. Depending on your electric rate, if you insulate more the money you saved may be more than enough to buy insulation.

dcarch

Very nice job on your construction. Have you considered a double layer of poly inflated..? That will conserve the heat much better. The 1500 watt heater may be too small to heat the structure due to the massive heat loss.

We just had our first snowfall here and the snow slid off the roof as planned!

Here is a link that might be useful: First Snowfall 2009

I agree with the nice job and the double-wall, but not of 6 mil poly, as the light blockage will be problematic IMHO. You may want to look into greenhouse film for a Christmas present; having a double layer of that will send you over the edge into GH nuttery ;o) .

I'd put a bunch of dark water-filled containers under the south bench to help a little bit, but until you get the heat loss under control I'd refrain from going all in on the tropicals idea and instead do some winter greens until you understand how the GH reacts.

My 2¢

Dan

It would probably not be very expensive to cover it with a double wall poly carb. That would vertainly help.

Here is a link that might be useful: {{gwi:311625}}

Nice GH Tom.

I just bought some Verolite @~2.40 sf for 8mm. Greenhouse film is ~1/2 that (albeit less durable), which gives you some budget flexibility to make sure that's what you want. My 2¢.

You might be able to find an old pool cover to go over the top half and north wall which will help some, as long as you can continue to vent. Regardless, the north side and north roof don't need to be transparent as long as the light can bounce around inside (as off a white wall).

Dan

Tominnh- Thanks for reply. Double wall poly inflated probably wouldn't work in this GH due to the construction; mainly re: vent windows.
Would a covering of clear pool cover or something similar be worth the expense in your opinion?
Can you recommend a good insulation material that I could put on the outside and stake to the ground?

Pete

Dan - Thanks for input.
I am looking to increasing the thermal mass in the GH by adding 1 gallon milk containers. I can't picture myself painting them all black!!! Can you recommend something?

I have purchased a USB temperature data logger which I can leave in the greenhouse to try to understand what is happening. The info could also help me guide me as to how much thermal mass to add.

Any suggestions greatly appreciated!!
Pete

Pete, Dan mentioned the pool covers which many people do use. I have not however but maybe Dan can give a bit more info on them. Tom

"I am looking to increasing the thermal mass in the GH by adding 1 gallon milk containers. I can't picture myself painting them all black!!! Can you recommend something?"

I put ice cream pails in black garbage bags.

I use food coloring in the water for thermal mass. Black garbage bags work too (tie tightly for good contact). In that GH you should be able to make two layers without them touching if you use furring strips as a spacer (HD has decent cheap ones & you don't need them straight).

The pool cover idea is that the light transmission is enough that the plants get light an don't die but the R-value is good enough to retain heat (but the transmission often means supplemental heat). You want to find a used one on CraigsList or somewhere and away from red-green and go towards clear (green means the good light doesn't get through). I don't use one so I don't know the cost. Bubble wrap is Plan B if you can afford it, search this forum and decent greenhouse websites for attachment.

Dan

My advice is only worth 1 penny, but I will add it to the pile:

The bigger concern for plant GROWTH is sunlight, duration and intensity, not temp. (Although typically, more sunlight = higher temps.) Unless you are adding supplemental lighting, do not expect any/much winter growth. (As I'm sure you are aware, photosynthesis is the process by which the plant gets their energy that will enable growth, with less light, photosynthesis will slow down, regardless of the temp.

In general, a lot of growth will not take place a few weeks before or after the winter solstice (~ Dec. 21). The further south you are, the shorter that period of time will be.

Are you looking to simply overwinter plants, or are you trying to grow and force blooming? Different goals will result in different actions.

And remember, the MOST important thing is making sure the temps don't get TOO high! Cooking your plants can happen even on very cold days, if the sun is shining brightly, and it is amazing how quick that can happen! VENTING needs to be your top priority!

As Dan suggested, you should start with the hardiest of plants (winter greens are a great option), and learn about your greenhouse in relation to your latitude and specific microclimate. Then, slowly add in more delicate plants after you understand how your GH reacts to certain outside stimuli. Different plants will require different conditions of course, so the learning will never truly end!

A bit late to the show here, but the question to be addressed is whether the plants you want in there are appropriate. Eucomis are naturally dormant in the winter in their native South Africa (there is one winter growing species, but not likely you have it unless you are really in to Eucomis), Hosta can be kept outside clearly as can the Eucomis in your mild cliamte.....Hellebores....why not plant in the ground? Alocasia and Colocasia will hate temps less than 45F and go dormant. The others I do not grow, but all of the above can be either kept in the ground dormant for the winter and the elephant ears (Alocasia/Colocasia) should be much warmer. Best of luck :o) Dan