tdump
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Heating a harbor freight greenhouse

If I was to save up the money and get 1 of those green houses from harbor freight that has the hard plastic panels and aluminum frame, what would I need to heat it with for starting tomatoes and pepper plants in the spring? I have 1 heat mat and would probably get a couple more being I found them on ebay for 15 bucks free shipping.
if it is to costly I may have to stay small and grow stuff here in the house but no more than I have growing it already smells "greenhousey" in here ! :lol:

catgrass
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I am much farther south than you-and really don't need to heat my greenhouse often-but I have an old small BBQ pit that I put some bricks in and use those sawdust logs you buy anywhere, that will burn for 2-3 hours, and use that. I keep the lid low with about a 4 inch crack. I also have some tubs of water in my greenhouse, too, that will absorb heat during the day and release it at night. Again, you get a lot more freezing weather than I do, but this works for me.

ButterflyLady29
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My mom heats hers and spends quite a bit on propane for the heaters. And still last spring we had a severe cold snap and she lost a few plants. The others were brought inside before the temp dropped, she just didn't have room for the ones left in the greenhouse.

In order to keep the panels in place you need an extra set of metal clips and you'll have to caulk all the panels on the inside. Mom used several tubes of silicone caulk just trying to stop the drafts. She lives in a windy area and the first week it was set up several panels blew out. The frame has to be set on a solid foundation. If one part droops a little it warps the whole thing and the panels will fall out. The aluminum frame also gets very cold and I have seen frost build up on the inside on her frame. If there was some way to coat the frame with rubber or some other insulating material it would work much better. Barrels of water do help hold the heat but here in cloudy, cold Ohio that thermal sink doesn't work very well because it really doesn't get a chance to recharge. And it takes up a lot of room.

tdump
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Well,I have read a good bit on the net and from this site and others,it seems although it looks like a good deal, in the long run for someone like me it may not be the best investment.
I have considered building a green house from scratch. But I have so many "projects" and ideas I thought if these things could be heated without spending twice what the plant cost and vegetables cost to heat it I might go this route.
What I might do is draw up my idea and post it and get input on my therotical design. I need to keep heating cost down. I have plenty of fans, some vents that can be opened and shut, but cost of heating is the problem.
For example,my buddies diesel pickup, added 40 bucks to the power bill to keep it plugged in and warm for starting. Sheesh!

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Allyn
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The Greenhouse Megastore has a handy BTU calculator that I use as a reference.
https://www.greenhousemegastore.com/gree ... calculator

I don't have a fancy frame and panel greenhouse, I just use a big tunnel greenhouse along the lines of this:
https://www.helpfulgardener.com/forum/vi ... 50&t=63527
I spent $100 on some awesome, heavy-duty UV weed mat for the floor and $75 for the clear, 6 mil UV greenhouse plastic. That's more in line with my budget than the fancy frame and panel greenhouses.

Similar to what catgrass mentioned, I use black trashcans filled with water. They absorb warmth during the day and release it at night. For extra cold nights when it actually gets down to ::gasp!:: Freezing temps, I've been using a double-terra-cotta-pot heater that is working out really well. I pour my own double-wick candles that burn for 24 hours, so if we get a cold snap, I can heat the greenhouse with no electricity.

I'm a bit farther south than you, though. I didn't do a greenhouse when I was up north.

tdump
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thanks for the first link,I keyed in the size of what I am looking to build in size if I go from scratch and what ever polycarb is is the most efficient.

Thanks for the info folks.

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rainbowgardener
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@Allyn. Really glad to hear that the flower pot/ candle heater is doing well for you. For those that haven't seen them, there's a picture of one in this thread: https://www.helpfulgardener.com/forum/vi ... er#p375343

I got the materials for one, but haven't put it together yet and may or may not end up needing it.

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Allyn
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rainbowgardener wrote:@Allyn. Really glad to hear that the flower pot/ candle heater is doing well for you. For those that haven't seen them, there's a picture of one in this thread: https://www.helpfulgardener.com/forum/vi ... er#p375343

I got the materials for one, but haven't put it together yet and may or may not end up needing it.

Oh! Thank you for the link. I couldn't find it when I posted. The very next day, I went to the store and got the pots to make one. My husband said he'd looked at that design a few years ago and forgot about it. It works so well, I went back a few days later and got pots for two more. I've been using recycled tin cans to pour one-, two- and three-wick candles. (That reminds me; I have to get more wax.) About once every week or ten days it gets down to the freezing mark here and I put one in the cold frame and two in the tunnel greenhouse. I like this system so much better than dragging out the electric heater.

Susan W
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I went back through this thread to check on low level heating. The greenhouse I just got is only 5 x 6, It does have metal frame. Has large roll up door and 2 roll up windows. Most of the time the heat used just to keep temps above 30, when outside gets chilly.

I know this sounds dumb, but about the buckets of water. Do you use 5 gal buckets with lids? Spray paint black, fill with water? In looking at the said GH in a box on living room floor, thinking ahead to anchoring and a bit of warmth. If I had the buckets in corners, can tie frame to handles with bungies to use as weights. (a trick we use at the farmers market with the pop-up canopies. We don't use water, but anything else with weight)

I also checked the net briefly for the flower pot and candle trick. The easiest, and what looks relatively safe is a couple of votives in a loaf pan, flanked by a couple of bricks. Cake rack over that, and 2 flower pots, one inside the other, upside down on rack. I have an ample supply of beeswax votives when I pour an oopsie, or pour out the end of a pitcher of wax that is dirty.

Any comments or suggestions?

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Allyn
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Susan W wrote: ... Do you use 5 gal buckets with lids? Spray paint black, fill with water? In looking at the said GH in a box on living room floor, thinking ahead to anchoring and a bit of warmth. ...
I use 33-gallon black plastic trashcans. That would probably be a bit too big for your setup, but something along those lines. I use auger-style anchors at the corners to keep the thing in place.
Susan W wrote: ... I also checked the net briefly for the flower pot and candle trick. The easiest, and what looks relatively safe is a couple of votives in a loaf pan, flanked by a couple of bricks. Cake rack over that, and 2 flower pots, one inside the other, upside down on rack....
I put a bolt through the hole in the bottom to hold the pots together, separated by a few washers and held together with a nut. I don't use a cake rack. The outer pot straddles the bricks and the inner pot is held by the nut and bolt. I guess the cake rack would work, but you'd be heating the rack and I'd think it would act like a heat sink. You want to heat the pots and let the thermal mass heat the space.

catgrass
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I use 2 gallon buckets-just 2 of them. But I also have some concrete pavers in there that retain a little heat also-I have read about the candle/flower pot trick-haven't tried it yet. I'll have to experiment with that!



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