I use this method for my over winter a/ seed starting season. Is very cheap a/ works well.

Buy a good amount (based on size) of the emergency warming blankets they sell in the camping section at WalMart/KMart/Target. They are great at both retention a/ reflection of heat.

I lined my walls w/ these a/ put a medium level heater to the room to control temp. Worked great plus you can use this setup for a post germination grow area.

Johnny

I wanted to keep the clear walls, that would defeat the purpose... plus, for a 16' x 26' greenhouse... that could get expensive. I purchased a large propane heater for this year, guess I'll see how it does, I still have about 8 electric heaters if worst comes to worst.
Pam

6 mil is not overkill, but not for its better insulating ability. The stuff eventually will degrade in the sunlight (UV apparently kills carbon chains), and the thicker it is the longer it will last. If the outer polycarb is anything close to being sealed, the inner layer - of any thickness - will make a huge difference.

Dennis

Also, staples don't pull through 6mil like they do 4mil.

Pam,
I'm gonna do the same thing this year, but I'm gonna buy the cheap HD 100' roll of 4 mil. I doesn't have to last more than a year, with no wind buffeting, and the UV during the winter will be much less than the summer. I wouldn't invest in the expensive stuff until you see how much heat it retains. The dead air space is an excellent insulator, and you can roll this stuff up and save it for next year.
Just my old cheap azz $0.02 worth...

Yeah, if you take it off after winter, the cheap stuff may be good enough. I left mine on all year.

Dennis

Thanks guys. Oh, I'm way too lazy to take it down like a good girl. The bubble wrap I had up stayed up the entire 2+ years, too much trouble to take it down (too much trouble to put it up ;-)). My friend in town used the bubble wrap too, her greenhouse was about the size of mine, and she had a cheap greenhouse that she bought that had a plastic covering. Maybe it was due to living in the city, but with one heater she kept her greenhouse at night around 72. Me, that year, 5 heaters going and barely kept it at 52.

I was going to use the cheap HD stuff. My only hesitation, I bought some last year to put up to divide the greenhouse in 1/2, it's been sitting on a shelf since I used it, folded nicely. Well, I grabbed an edge of it yesterday and it was brittle. That's why I thought the UV protected stuff might be better, I don't want to have to take down and put up every year. Although, someone on HD's site said they used the stuff to cover a greenhouse and it's lasted 3 yrs... I can live with that.

Pam

I'd probably leave mine on too except the sides/ends roll up so we can use it for a deck when it gets warm.

Pam,
If you rip some 2X4's 1/2" thick (on the 1-1/2" dimension) for battens, and use four screws per batten, and a batten about every 4th stud, it'll be a lot less work. The battens help to secure the plastic, and won't rip out like staples. You can use staples to put it up initially, then go back with the battens. I use that system on the exterior of the GH and my plastic is on it's fourth year. Break the sharp edges with a router or 60 grit sandpaper and a block. Cheap plastic will last longer out of the sun even when folded.

Well, if the purpose of adding clear plastic is doubling up from INSIDE, then thinner the better. Because (1) it lets more solar energy in. (2) it creates a barrier to heat loss by conduction and convection just like thicker plastic. (3) It is light weight and costs less. As far as deteriorating, I think it will happen regardless of the thickness. Since it is stationary (not worked with). Bubble wrap is like double glass or it is like adding 2 sheets of plastics with about 3/8" space between them.
But one thing to consider is that any plastic or bubble wrap will absorb and reflect some of the solar heat. But perhaps they will payoff by preventing heat loss.

> "with one heater she kept her greenhouse at night around 72. Me, that year, 5 heaters going and barely kept it at 52."

I'm going to suggest that's more a problem of the wind whistling through. It doesn't take much of a draft for all that nice hot air to escape to the tropics.

Dennis

I was able to keep my quasi-GH temp with one 6mil layer up over 42 all winter with just an indoor electric heater - so long as it remained nice and tight.

Pam,

You should have put some pex in that cement when you poured it and hooked it to a small water heater. thats what i am planning for next years project. my buddy heats his garage that way and iy works great

I'm lazy, I buy the 6 mil for the whole greenhouse and it lasts a good 5 years. Yours on the inside might last longer. The extra UV stuff in the 6 mil type makes it last a long time, and those are extra years that you don't have to buy plastic again. The extra 4 inches between the layers will make a huge difference. Down here, when we have mid teens, with a double layer, you don't even need to heat the greenhouse.

Thanks for all the advice guys!

Dennis, you might be right, my greenhous is now tighter (instead of home made doors, like I used to have, we used 2 old sliding glass doors, I think that will help a lot, plus, I live on a ridge out in the country, she lives in town surrounded by other homes.

btw, would you guys put the plastic on the ceiling too, or just the walls?

I considered that John, but, since I was only laying concrete in 1/2 the space, I didn't know if it'd be worth it.

Pam

Assuming you have rafters topped with corrugation, definitely on the ceiling or rafters. How are you sealing the corrugated panels to the rest of the structure?

Dennis

btw, would you guys put the plastic on the ceiling too, or just the walls?
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You can and it will save a lot of heat during the cold months. . But how about the dog days of summer ? It might become too hot between the plastic and the polycarb roofing. Might !

Personally, I wouldn't because the humidity condensing on the interior of the polycarb will drip onto the plastic and making it "belly," unless you staple it to the rafters. Plus, I have ceiling fans in mine to keep the air circulating during the winter, and it'd be a PITA to get all that crap up there and down every year.
Just my $0.02 worth...

Thanks guys. Good point seysonn, yep, OK summers the plastic on the rafters might melt. ;-) And thanks Tom, I didn't even think about the condensation. I'm going to add at least one fan for air circulation

Pam

I never asked a question on this forum - but read it all the time. Have a question:

scorpion_john - or anyone else:

can you explain about using water heater? or point me to where I can read about it?

TIA. Rina

Pam,
Google up "Tekfoil." They make a clear and a silvered version. Supposed to last four years in a GH. Saw it in my latest Growers Supply catalog. Kinda pricey though. Might be worth it to do the north and west sides...

can you explain about using water heater? or point me to where I can read about it?

TIA. Rina
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Water heater ?
You can use a water heater like an old boiler to circulate hot water in a closed loop through baseboard. But it will be too involved: Need baseboard, piping, circulation pump, thermostats.
But If I were going to make a decent greenhouse I would look into installing few solar panel water heater, with a pump and a storage tank. This way you can store solar heat during the day to heat the greenhouse at night(even during cold days) almost free. This will need some initial investment but it should have a short payoff time in your zone 5a. The only electricity used will be to run two very small circulator.

seysonn

Thank you for taking time to answer. I did read some about using HWT to heat, and now I understand what you saying.
Yes, solar as you are suggesting would be better.
Rina