Real world cost of heating a greenhouse
daniel123 Posts: 67
in Fruit & veg
I have used online calculators to calculate the cost of heating a 8 x 8 greenhouse sized not confirmed as greenhouse not bought
How acurate are these calculators
I plan to line the greenhouse with bubble wrap for insulation.
Any other tips for greenhouse heating options
Ps. What is the frost line in the southern uk
What are you planning on growing that will require a fixed heat source?
Heating is such a vague term; for me I heat my greenhouse only when it snows heavily at night by lighting a church candle and leaving it to burn in there to keep the worst of the frost out. For others they may require a +5'C temperature throughout the winter.
I can't help with the frost line but I'm sure someone more with knowledge than me (or good on Google at least) will be along soon.
I don't think an accurate figure would be possible, makes more sense to think about what would happen if you didn't provide some heat.
It depends on where you live and many other factors.I live in the North-West at an elevation of over. 1200 ft. My greenhouse is a lean-to on a west facing stone wall.It gets some sun and also some shade from evergreen trees, for longer in winter as sun is low. I bubble wrap it well and my heater is an electric one that can be set to frost free.
On a sunny day, even in winter, the GH will heat up and the stone wall acts as a storage heater. But the predominant wind is from the west so a windy day brings a lot of wind chill (felt in our draughty old house too!) The last couple of winters have been mild and wet (which usually means low cloud here and clammy dampness), but we can get severe frosts and sometimes long lasting low temps, though wind levels then tend to be lower. We can also get heavy snowfall, but snow gives good insulation. All these things willl affect the internal temperature and so the use of the heater.
The GH electric is not metered separately and I honestly have no idea how much it costs, but it means I can keep my agapanthus and salvias for the garden alive over winter, and have fuschias and pelargoniums and other tender plants to enjoy, and I can go in there on winter days for a little comfortable pottering and relaxation and even turn the heater up if it is really chilly. All that is of great value to me.
Can I just ask what you mean by " real world cost of heating"?
I presume you've factored in such things as , the thickness of glass?, the closeness of fit of the glass to the frame? the exact location of the greenhouse.
The exact amount of sun you'll have over the winter.
Any chilling effect of wind and frost and cloud have clearly been factored in too.
Just how full the greenhouse will be ( compost holds heat better than air)
etc etc etc
An aluminium greenhouse will be a lot colder than a wooden framed one even with insulation, also a lack of light can be as big a problem as lack of heat depending on what you are trying to grow.
I'm also confused by the 'frost line' query too. It's a variable - not an exact fact which you can rely on. Frost can occur anywhere in the country, from this time of year in the north of Scotland until next June in lots of locations, so you simply have to be aware of your own location and local climate, and check forecasts. Even within a garden, some areas will get frost and others won't. Siting your greenhouse is therefore an important consideration.
Heating's only relevant if the plants you have growing in a greenhouse will suffer if they get below a certain temperature for a long enough period of time, and you'll simply have to be ready for that with an additional heating source as Clari has indicated. The points Hostafan has mentioned are all additional considerations which have an effect on the amount of extra heat you'll need.
I live in west central Scotland - not where that photo is...
Thankyou for mentioning things i need to consider
Lots of us websites mention the frost line and that the floor of the grewnhouse should be below it
Googling revealed this
"In the UK the maximum frost depth is generally considered to be 0.45m below the surface. This was based on data gathered from some very cold winters towards the mid-to-late 19th century and the frost line hardly ever reaches that depth in practise. Typically UK building codes specify that foundations be located a minimum of 0.75m below surface level."
However, wouldn't sinking the greenhouse that low in the ground cut back on the light available?
Depending on what you want to grow, you do not need to heat the whole greenhouse. Could you give us some idea of whatr use you are going to make of the g/h over winter?