I've found room to squeeze in another small lean to greehouse and having had trouble keeping another one without sudden temperature differences or going too cold with a fan heater, would a tubular heater be better.

This lean to is 2ft (D) x 4ft (W) x 6ft (H).

This is a link to Tubular heaters for which I would need a thermostat and a fan heater:-

http://www.harrodhorticultural.com/HarrodSite/pages/product/product.asp?prod=GHE-045&ctgry=Greenhouse%20Equipment_Heaters&cookie%5Ftest=1

I had thought of heat matts but I'm going to have 2 small shelves in there for a small Kumquat, Limequat and possibly Calamondin. Will probably have my Tahiti Lime in there as well as this lean-to will get more light and hopefully sun than the other one. The heat matts I can get here have to be on a flat surface and aren't waterproof.

What would be the best option please

Hi

How cold does it get there, sorry I cant answer your original question...

I am looking at the options I have to grow in a cold frame/green house in New Englan

Night temperatures in the south of the UK where I am vary quite a bit, it's either 5 - 10 degrees F above freezing or 5 - 10 below so it's not guaranteed to be below freezing for say 2 months.

So it's usually either 37 - 42F (3 - 5C) or 23 - 28F (-2 - -5C). The lowest we'd get is about 16F (-9C) and this might happen 10 nights max during the winter. We get some day temperatures, probably a maximum of 10 again where the it stays at 28F (- 2C)

I know to get growth and fruit all year round you need to keep the temperature a lot higher, 68F I think but due to cost and space for a big enough greenhouse, I aim to keep my lean-to greenhouses at 45F (7C) or above.

I contacted the supplier (link in my original post) and this is the reply:-

'They have calculated that to heat the structure you have to a temperature of 7 degrees C would require 960 watts. This means you would need 3 x 1200mm heaters (product code GHE-055). Total cost including delivery - £124.95.

To heat the structure to 15 degrees C would require 1400 watts of heat, which can be provided by 6 x 900mm heaters (GHE-050), set in 2 banks of 3. Total cost - £214.95.

As we suspected, a thermostat would be required to maintain efficieny as without one, the heaters will be on permanently'

£124.95 is about $220
£214.95 is about $380

A thermostat would be about $71

Based on the above and adding on the electricity costs for 900 Watts I decided that for me this is going to be too expensive at the moment.

The problem with small greenhouses is they can get large temperature fluctuations and cool down too quickly. I've used fan heaters so far and this is a problem I get, but last year with a lot of trial and error I managed to get more or less the temperatures I wanted and not too much fluctuations.

The idea of tubular heaters was to get constant temperatures and not stress the trees as much as using fan heaters but due to the cost I'm going to try my luck in my new lean-to greenhouse with a different make of fan heater.

Nick

Nick:

We have a similar climate here on the west coast of Canada. You can calculate the BTUs required to heat your lean-to at this site:

http://www.littlegreenhouse.com/heat-calc.shtml

If it's the shape I assume it is based on the dimensions you've provided, the area inside your green house would be somewhere between 50 and 60 cubic ft.

With your minimum temperature of 16F, assuming that your greenhouse is covered in 4 mil polyethylene, and that you want a temperature in the greenhouse to remain at 32F when it's 16F outside, you would need a heating device that puts out about 1,000 BTUs according to the web site above.

I just strung up a 15 foot string of some old style (not LED) Christmas lights in my mini greenhouse (a string of 20 lights). At 2 ft by 2 ft by 28 inches high the capacity of my mini greenhouse is only 21 cubic feet, or about 1/3 the capacity of yours. The outside temperature right now is 33F, and I turned the lights on to see what the temperature would be inside the greenhouse. After waiting a couple of hours it now reads 60F, so I can calculate the heat produced by the Christmas lights, using the formula on the web site above, at about 680 BTUs.

Making the conversions for your sized lean-to, my set-up would give you a temperature inside of just over 27F when the outside temperature goes down to 16F, and would keep your plants above freezing if the outside temperature stays above 22F. You could increase the heating capabilities by either adding more Christmas lights or using a cover that gives a lower heat loss value.

The lights cost about $10 Cdn (₤5)

Here are some pictures of my set up:

Thanks for the information and pictures, I've heard of a few people doing this. Is it the first year you've done this - do you get any problems with leaf drop etc

The winter here has so far been very mild, only 1 week of freezing night temperatures so far. But I suspect we will pay for it!! Good old global warming!

So my fan heaters seem to be doing the job so far but all I do is make sure temperatures don't go below 45 F. I know they need to be higher to stop the trees going dormant. I'll give the lights a go when the temperatures stay around freezing all the time and I think I'll definately do it next winter when I have more trees. I've run out of room for more lean to's. Probably have to look at a better power supply as well instead of drilling holes through the garage wall to get to a socket.

Let me know how you get on

Nick

Hi Nick,
Have you thought about insulating covers for your lean to greenhouse.

I built a lean to greenhouse several years ago for my hibiscus to winter in. It was made with 4 sliding galss doors taht were just leaning against a slanted frame. I covered the back with the aluminum covered foam that is use for sheathing on houses. It's about 3/4 inch thick with reflective aluminum coating. You could just put them in place temporaily when needed--tape them if necessary.

If you can find that kind of material it should really help keep in the heat from the day and reduce the need for added heat. It is easy to cut and relatively cheap. I never had the need to provide additional heat here, but that would have been my first option.

Skeet
Skeet

Hi Nick,
Have you thought about insulating covers for your lean to greenhouse.

I built a lean to greenhouse several years ago for my hibiscus to winter in. It was made with 4 sliding galss doors that were just leaning against a slanted frame. I covered the back with the aluminum covered foam that is use for sheathing on houses. It's about 3/4 inch thick with reflective aluminum coating. You could just put them in place temporaily when needed--tape them if necessary.

If you can find that kind of material it should really help keep in the heat from the day and reduce the need for added heat. It is easy to cut and relatively cheap. I never had the need to provide additional heat here, but that would have been my first option.

Skeet
Skeet

Thanks for the idea Skeeter

Good to know of a probably cheaper way and that it will work

Nick