David Maxwell wrote:In terms of ventilation during te summer, I found that passive ventilation was inadequate, no matter how big. I now use a salvaged hot-air furnace blower to suck the excess heat out.
But there is an angle here which I have only recently thought through. The question has an underlying assumption that the greenhouse is to be used year-round. There are people who actually use the greenhouse only fall, winter, and spring, (and design the slope of the glazing to maximise heat capture with the sun low on the horizon), and then actually close the greenhouse tightly in summer to super-heat the soil, killing any and all insect pests etc. (What this does to the fungal soil networks upon which many plants, (but not brasiccas) depend, I do noty know...)
Jeffrey Sullivan wrote:Shane, Google IBC caps and you'll get all kinds of options.
shane connor wrote:I'm planning on doing something similar with ten totes in a row, but above ground and
boxed in on all sides with 5" freezer panels I'd salvaged @ 50 cents sq ft via craigs list.
My question is; I'm trying to find simplest cheapest plumbing for connecting all their 2"
outlets together. Like to find a simple screw on "T" that'd accept push on hose or any
other easy combo requiring fewest parts & adapters that won't stick out significantly.
Any suggestions appreciated, everything I've seen so far looks more convoluted than it
Michael Jay Anthony wrote:thanks for sharing Dan! I'm also in 5b in Maine. Building a cheep cold frame for this winter, but would like to explore something more efficient like your design. Please keep us updated! Thanks again!
David Maxwell wrote:From what I have read, the main heat loss in small-scale greenhouses occurs at the edges of the curtain, which needs to be sealed. So, multiple smaller curtains suffer from the problem of multiple edges. Hence a single wide blanket is preferable..
How best to seal the edges? Neatest way I have seen is to fasten magnetic tape to the sides of the curtain, and build ledges along the outer walls to support the edges, also equipped wth magnetic tape. The two magnetic tapes will automatically align themselves, avoiding the issue of the roll getting off-centre. The long section of curtain is supported by wire cable stretched parallel with the joists, (metal clothesline has been suggested). The designs I have seen urge the incorporation of weights to maintain an equal tension on the wires so they don't sag as the temperature rises, but I am not convinced an 8 ft. length of wire is going to change in length that much. Have any of you any experience here?
Nick Kitchener wrote:I only just found this thread so this is possibly too late...
Did you run some math regarding thermal uptake of the water mass vs thermal loss of the greenhouse? It usually works out that you can't efficiently transfer enough heat from a hot greenhouse to the water during the day to completely offset the thermal loss by the greenhouse at night. Remember that not all days are cloudless...
What happens is that the system "runs down" to equilibrium over about a week or so. Here is a video explaining what goes on:
Mike Phillipps wrote:Sorry for the late comment.
Dan, your math looks right.
My analysis is indicating that the water tank shouldn't be insulated because it's better to have the added thermal mass of the soil and groundwater if any.
I was surprised to discover that thermal diffusion in still-water or wet soil is actually *lower* than dry soil! So in theory having wet soil is better than dry soil because it actually *decreases* the rate at which heat diffuses away, although only if the water isn't flowing through the soil in the particular time-frame of interest.
Dennis Bangham wrote:Dan,
Any updates on your IBC totes and how effective they heat and cool your greenhouse? I live in the southern USA and have been thinking about doing something similar.
I am thinking of a full diffused light (' by 20') greenhouse with sunlight coming through the roof and all the walls. I also have a high water table and expect the temperature to stay around 55F all year round.
The lowest temperatures maybe 9 degrees for a couple of nights in winter and a couple of months of 95F during summer.
Davis Tyler wrote:has anyone considered a shallow pond/trough as the thermal mass in the front of the greenhouse? Would save all the digging and soil stability concerns of the IBC totes.