Keeping a small lean-to planthouse frost-free?

amcluesent

As title really, I have a lean-to plant-house which is only the size of a wardrobe. I'd like to keep it frost-free, but a 2kW heaters seems OTT!

Any ideas for devices - I have an outside plug, so electric with a frost-stat would seem best...

angelavdavis

Is paraffin not an option? Something like this would be cheap to run. I think if you are looking for less than 2Kw that paraffin is likely your only option.

londonsurrey

Has anyone tried the Victorian idea of putting a greenhouse on top of a compost heap, to capture the heat from the compost?

angelavdavis

londonsurrey wrote: »

Has anyone tried the Victorian idea of putting a greenhouse on top of a compost heap, to capture the heat from the compost?

Ah the hot bed. I have used it with a small cold frame and it does work to get plants kick started or speed them along a bit (or raise the temperature earlier in the season for melons, etc) but I wouldn't personally rely on the concept to keep plants frost free in winter. It depends on so many factors that are difficult to control - plants, insulation on the cold frame, construction, depth of rotting matter to provide heat, outside winter temperatures etc.

It would be good to hear if others have had better luck sustaining this type of hot bed approach to overwinter plants though.

To be honest, Paraffin is about £7 for 4L from B&Q, in the South East, two or three might do you through the worst weather in winter for a small greenhouse with a very small heater and good insulation. It isn't extortionate really. I suspect it would cost me more in petrol driving to and from the stables to collect the manure in my case!

Davesnave

The 500w version of this used to suit my Dad's shed:

http://www.shopwiki.co.uk/Dimplex-Coldwatcher-MPH500-Convector-Heater/stores/Dimplex

Just make sure you link it to a 30milliamp trip switch, as you are using it outdoors. (EDIT: Whoops! I see you have one, but not everyone does.;))

If MSEers are careful and confident, the thermostats on most heaters may be re-calibrated so that they only kick-in at around zero, instead of the usual 5 degrees at their 'frost' setting. This saves electricity. To do this, one must play with the adjustment screw whilst having the heater outside on a night when it's freezing(!) The aim is to hear it 'click' when the dial is reduced to near the lowest setting. YOU SHOULD NOT HAVE THE HEATER CONNECTED WHEN YOU DO THIS!:eek: The thermostat switch is mechanical and needs no electricity to operate. It can benefit from a squirt of WD40 too.

I would do the above with my 1-3 kW fan heater once a year after internal cleaning, (spiders!) marking a new 'real' frost setting on the dial if necessary. Even though it was quite powerful, it would be on for very little time on an average frosty night, so it probably cost little more than a smaller one to run.

Half a kW should be ample for your situation though, or you might find a tube heater better :

http://www.cnmonline.co.uk/home.php?cat=213&cnid=213&gclid=CMGjj5_J_KoCFUVTfAodcQoy2A

alanobrien

If all you are looking to do is to keep it frost free then depending on where you are, why not just line the inside with bubble wrap. Unless you are in the depths of the highlands that should keep it frost free without the need for heating.

RAS

Well 400 miles south of the Highlands the outdoor temperature was minus 17 some nights and sometimes did not rise about minus 11 all day. The contents of sheds and greenhouse froze solid, as did the first 8 inches of top soil.

And it was not much better in wet and warm Devon over the mid winter.

Davesnave

RAS wrote: »

Well 400 miles south of the Highlands the outdoor temperature was minus 17 some nights and sometimes did not rise about minus 11 all day. The contents of sheds and greenhouse froze solid, as did the first 8 inches of top soil.

And it was not much better in wet and warm Devon over the mid winter.

This is the problem. The extremes may not last long, but protection measures have to be geared to cope with them, otherwise there's not much point.

Near me, "wet & warm Devon" was -19C at one time in early 2010; something pretty unforgettable for those caring for farm animals.

However, remembering my time in the city, the unheated bit of my 25' greenhouse, even though insulated, often dropped to around -5C. In that bit, I had a heated sand bed with a mini greenhouse made from old windows on top. That ran on 40w of heating cable and would have been ideal for overwintering a small number of tender plants.

The difference between that & a blow-away is that it had about 1/4 tonne of sand as a heat store and it was inside another insulated structure.

J_J_Carter

Everything seems so expensive! I'm toying with the DIY idea of a 250W heat bulb used for reptiles and a cheap CH frost-stat, ideally less than £15 all up.

emiff6

If your lean-to is only the size of a wardrobe, can you not just bring the plants into the house over the worst of the winter?