Benches from Big Box:
{{gwi:289158}}

Heater position:
{{gwi:289159}}

Many thanks.

Heat rises so unless you either push the hot air back down or mix the air up then you will always have this problem.

I use a oscillating fan that is pointed downwards slightly (mounted at the peak of my greenhouse) and found this mixes up the air enough that i don't have the cold layer near the floor of the greenhouse.

I don't think that using your blower on the heater will stop your problem. You need to use a fan to push the heat back down.

-renee

I agree, I just wanted the satisfaction of hearing from someone else.

Thank you,

Dax

We have 2 small ceiling fans - one rotating clockwise & one counter clockwise that keeps the air circulating well. Our heater also has a small fan on it.

Our big problem is air leaks around our door. Still trying to figure out how to stop that.

kim

I have figured out a way to prevent air from leaking around the door frame by buying heavy duty velcro and attached heavy vinyl around the entire door frame, inside the greenhouse. Then i purchased a larger zipper from a hardware store (it has sticky tape on one side) and then during the winter I keep this closed and it really helps prevent air loss. It is a little difficult to explain. I should try to take a picture for everyone here.

-renee

I was trying to figure out some way to do something similar to what you have. Don't know where I'd be able to find the large zipper around here, but I know sealing off the door somehow would make a big difference. You can feel quite a draft when standing inside - mostly coming from the hinged side of the door.

Kim

Think about this. buy some vinyl siding or like substance. Mount it on the door frame so that it presses against the door with a slight pressure when the door is closed. I have done something similar in the drafty trailer I live in and it has helped a lot. Also a simple falling curtain with weights at the bottom will work. Before I used this a candle in the trailer would dance every which way. Since doing it the flame burns straight up.

1eyedJack and the Dawg

You definatly need more air movement in your green house, the fan on your heater will not move that much air. I only have a box fan inside my 10 x 12 and have not seen any large problems with the floor area being very much different in temp.

As far as zipers go for plastic I use the ZIPWALL products for work www.zipwall.com

ZipWall® Heavy Duty
Zippers includes two self
adhesive zippers, two cords
for tying up a plastic flap,
and the innovative ZipWall®
Zipper Knife (patent pending).
Can be used in freezing
temperatures.
Item #HDAZ2

Here is a link that might be useful: ZIPWALL catalog

Thanks for your suggestions. We'd considered doing the weighted curtain - just haven't gotten that far yet. Got my electric bill today - that will motivate me to get moving! It would be great to seal around the door and add the zipper opening. Thanks for the link.

Kim

Hi,
Circulating the warmer air from the top of the gh is a good plan, but one important point to consider is whether the concrete slab has perimeter insulation.

If not, it`ll be almost as cold as the ground outside the gh. Heat escaping sideways from the uninsulated slab will make the floor seriously cold.

If it has, the new warm air should make quite a difference to the temps :)

As a worst case scenario, redistributing the warm air downward without perimeter insulation in place will result in losing heat at a much higher rate due to the increase in slab temperature. Not a good thing :)

I found a "curtain" inside the sliding door of my greenhouse to be very effective in reducing drafts and heat loss. Using leftover clear solar pool cover material, I made three wide strips and hung them to overlap slightly just inside the door. It does make entry/exit a little awkward, but I feel it's worth the trouble. It is effective enough that if I'm working out there on a cold but sunny day, I can leave the door open, especially if I'm in and out a lot, thereby saving wear and tear on the sliding door.

Have you looked at the heavy duty self sticking insulation strips for house doors? Some are as large as 1/2 thick.

You may want to add a small fan for better air/heat circulation as others already suggested. You can add bubble wrap on the inside of the walls, especially around the bottom to help insulate the polycarb.

You need a thermol break on the concrete floor.What is happening is the concrete is transfering the cold directy from the outside.Sealing up the door is only a band-aid fix.You should use some plastic and perhaps some foam insulation.When the temps rise remove them to prevent mold and moisture build-up.I hope this helps

(Dax, I hope you don't mind me borrowing your thread to see if I can gain some advice for a friend.)

tfb4me and hex2006, I have a friend who is planning to erect a 10x12 HFGH on the end of a long existing patio, with the long wall up against the house. It will be a situation kind of similar to Dax's...the patio will extend beyond the GH.

The patio is long but only 8' deep, so she plans to build an additional foundation for the extra 2' and fill that portion with gravel.

Do either of you folks have any advice I could pass on to her about steps she could take during the foundation construction to prevent heat from escaping sideways into the uninsulated concrete pad? (She lives in a cold climate.) When you mention foam insulation, are you talking about applying it to the two sides of the concrete slab (the patio edges, so to speak?) Thanks for any help,
Sheri

I have the same question as Sheri. To save money during construction, all that was done was the truck came in and poured concrete over existing earth and then stress lines were ripped. This is a very basic slab and how could I possibly insulate this entire slab at this point in time? I feel like foam in a can ain't gonna cut it! :-)

I agree about the oscilating fan. Thanks for reminding me, I didn't forget but I need to get it squared away on my things to do.

Thanks for the help so far, it's definitely appreciated,

Dax

Hi Dax
Foam in a can would be a very expensive option.
I guess you have a damp proof membrane below the slab?
its amazing how many attached slabs compromise the house dampproof course :)

Insulating the slab isn`t too difficult.
Use closed cell rigid foam boards 1"-2" thick, no need to go thicker than 2".. the law of diminishing returns becomes a factor.
You can install the rigid insulation board vertically ~2ft deep or horozontally (aka "wing" insulation), at least 2ft wide with a gentle slope away from the slab. Don`t forget about drainage.

Don`t worry too much about insulating underneath the slab (unless using underfloor heating)

Heat always moves to cold, cold doesn`t move.
The deeper the soil below the slab..the warmer it is.
The temperature differential eventually reduces to zero and all downward heat movement stops.

On the other hand, at the edges of an uninsulated concrete slab you find pretty huge temperature differentials driving the heatloss for the full length of the perimeter, which is about 44ft for an HF 12x10.

Hi Sheri,
If the slab length extends well beyond the greenhouse length in one direction, theres not much you can do in that direction unless you can create a gap..not easy to do :)

Insulate the perimeter of the extra 2ft width and around the slab in proximity of the gh where you can, in this case maybe only 3 sides.

It won`t be cost effective to insulate the entire slab perimeter if the gh is located at one end.. the exposed top surface of the concrete will be responsible for most of the heatloss.
Horizontal insulation over the concrete is an option, but again probably not worth the expense.

Doing what is practically possible without going overboard is usually the best plan, insulation investment vs return :)

Thank you hex.

Dax

Yes, thanks hex, I will pass that info on to my friend! I appreciate the help.
Sheri

It just happened that I came home yesterday with three cans of that foam insulative and today while I re-organized my system, I found an opening between the slab and the greenhouse frame of over 1 inch in the middle running a distance of at least 5 feet. This too was the iciest section of the wall containing the frosted and iced panels as well as the iciest spot ont he floor.

Thanks again hex,

Dax

Dax, has the "foam fix" made a big difference? I use a Lasko 10 inch Breeze Machine fan which pivots on a horizontal axis. I sit it on the floor and it pushes cooler air upwards and makes the warm air which accumulates at the top circulate down the outside walls where it is most needed. A new one cost $14. I bought mine at the charity thrift store for $4 about 4 or 5 years ago. It moves lots of air.

If the concrete extends beond the exterior wall of your GH a real simple farmers solution would be to cover it with a tarp or vapour barior then a row of bales of straw along the outside of the wall on top of the concrete so they overlap the slab.real cheap and very effcetive.Again removable in the spring. Hope this helps ya somwhat..

Thanks tfb4me, I'll pass that suggestion on to my friend!
Sheri

I want to thank "mudhouse" Sheri for alerting me to this thread, I will keep a watch here as well, but am thinking from the suggestions above, that perhaps a vapor barrier or tarp with the hay could possibly work best for my situation here unless I pour more concrete, I am not positive which route to take just yet as we have bought the kit but have yet to install because of the weather, so it could be that we may re-think the layout a little bit or even pour concrete for the remainer where the greenhouse will sit, just some thoughts on which way to do it before we actually begin construction. This has me thinking though, so at least I have some ideas on correcting this problem before I get it started :)

Thank you all for the suggestions and tips in this thread.

Again Sheri, thank you for alerting me to this link!!!

Laurrie