Greenhouse heater

My parents have just bought themselves a 6 x 4 Greenhouse, they dont have much garden as they live on an over 55's site and their garden is stoned, so as no need for mowing and weeding for the less abled. So they are really excited about the greenhouse, and have the usual summer plants in there already. I have no experience of greenhouses and neither do they, but I was thinking of buying them a greenhouse heater so they could keep their hobby going through the winter. Mum has a small unit she overwinters geraniums etc so she doesnt need a heater for that, but is there anything they could grow that isnt too exotic. Anything i have looked up is quite specialised and they arent really interested in things like that, just normal fruit and veg if there is such a thing. Also if i do get a heater is a small paraffin one, most convenient for that size greenhouse. Any ideas would be welcome.

 

Hi there Sharon - and welcome. I know the excitement your parents feel with their first greenhouse - I felt the same with mine.

There are some quite good parafin heaters that will keep their new greenhouse frost free over winter. Not much call for it at this time of year. If you go to your local garden centre they will have a selection.

Depending on what way the new greenhouse faces you may find it better to discuss with your parents shading - in the summer, a greenhouse can get very hot, and scorch the plants. Some people shade with a sort of white wash, and wash it off in the winter, but there are others that can be fixed either over or inside the greenhouse.

Sounds like your parents are gonna be having a lot of fun, and you will no doubt be eating the result. :D

 

Hi Sharon,
Here`s the way to estimate it:
Add up the surface area of the greenhouse in square feet (all the walls and roof area)

Multiply that number by the inside to outside temperature difference you need to maintain in winter.

Here`s an example:
Total greenhouse surface area: 130 sq ft
Minimum winter outside temp: 32F
Desired minimum greenhouse temp: 50F

Temperature difference (Td) is: 18F (50F-32F)

Assuming single glazing and no insulation (R=1)
(Area x Td / R-value = Btu/hr heatloss)
130 x 18 / 1 = 2340 btu/hr (or 685w/hr)

You will need a heater that can supply at least that amount to maintain 50F in the greenhouse.

Bear in mind, if it`s raining and windy the outside temps could be a lot colder than 32F

 

Thanks to you both, their garden is a real sun trap so the shading will definately be necessary, now getting the pen and paper out to work the maths out, gosh my parents will think i am bright.

 

Hi Sharon,
I`m sure they know already :D

You`ll still have to figure out how many btu/hr (or kw equivilent)that parafin heater puts out

Btw, if you plan to add bubblewrap everywhere in the winter, you can make R=2 for your calculations which should help cut costs.