Heating a greenhouse

  • 29 Replies
  • 9333 Views
*

ghost61

  • Senior Member
  • ****
  • Location: Peterborough, Cambs
  • 914
Heating a greenhouse
« on: October 09, 2014, 11:39 »
I am thinking about heating my greenhouse on the allotment, as I have some citrus trees in pots inside as well as kiwis.  No electricity obviously, and I'm worried about paraffin heaters in case of idiots coming on site and doing some damage....will bubble wrap and fleece be sufficient as an alternative (also means I don't have to go down to check fuel etc).

What do others do or recommend?

*

surbie100

  • Winner Prettiest Pumpkin - 2014
  • Hero Member
  • *****
  • Location: London
  • 4675
Re: Heating a greenhouse
« Reply #1 on: October 09, 2014, 12:01 »
Would one or two of the clay pot warmer thingies work with 8-hour tealights to keep the frost away? Not sure how that would work in really cold weather.

*

Kristen

  • Hero Member
  • *****
  • Location: Suffolk
  • 4065
    • K's Garden blog
Re: Heating a greenhouse
« Reply #2 on: October 09, 2014, 14:55 »
In the absence of electricity you won't [AKAIK] be able to use a decent thermostat - so you will have to light on the nights you think it may be cold, and extinguish the following morning.

Bottle Gas will have a crude bi-metalic strip type thermostat, so will only use gas for a pilot light when temperature is satisfied (but the inefficiencies of the thermostat will mean that the greenhouse over- (or, perish the thought!) under-heats by maybe as much as 10C before the thermostat cuts out.

Paraffin has no thermostat, plus also the risk of the wick burning unevenly, and sooting-up the whole greenhouse, or going out.

Both generate considerable condensation [compared to electric], and both also rely on convection to get heat into the far flung corners of the greenhouse - an electric fan is obviously better at that.  One counteracting approach is to put the heater under metal staging, which then heats the staging and thus the soil in the pots stood on it, which the plants appreciate (and often means they will tolerate lower temperatures at their leaves).

Either way, insulation is the cheapest form of "heating", so well worthwhile attending to that first - e.g. lining the structure with bubblewrap. Make sure that all air gaps are sealed with tape - you need to reduce all draughts as well as "double glazing" the structure. You could also look at keeping wind off the structure - a panel-fence, or hedge, around the greenhouse (but not close enough to shade it) will keep chilling wind off it.

Another trick is to erect a small polytunnel (like a very large cloche) inside the greenhouse, and only heat inside the tunnel. The greenhouse will provide the first line defence of keeping cold wind etc. off, and inside the tunnel will be a much smaller volume of air to heat.

But in a cold snap temperatures will fall, no matter how good the insulation is, and once the temperature falls you will be relying on the heating to stop the temperature falling further.  To achieve that you need X-killowatts, so T-lights and so on won't be enough ... if we have a mild winter then very low numbers of Watts will be sufficient, in a perishinlg cold snap you'll need all the Killowatts you can throw at the problem.

My solution to the problem is to have substantial growing lights, in the house, and overwinter my plants there. I have sufficient light "power" that they continue to grow, rather than just ticking over, so I don't have to worry about moulds and rot and so on, let alone cold that could kill the plants.

*

cadalot

  • Guest
Re: Heating a greenhouse
« Reply #3 on: October 09, 2014, 15:20 »
I thought about buying a small electric heater for my greenhouse at home but actually it's going to cost me far more to hear it than any overwinter crop is actually worth. So bubble wrap & Growhouse in the greenhouse is the answer for me both on the allotment and at home. Terracotta pot and tea light at home only 

*

Kristen

  • Hero Member
  • *****
  • Location: Suffolk
  • 4065
    • K's Garden blog
Re: Heating a greenhouse
« Reply #4 on: October 09, 2014, 15:57 »
Might be worth having some sort of temperature recorder (a Max/Min at least) so that you can judge how well the heating is performing (or, more correctly!, how low the temperature will fall on a cold night and thus what crops / plants you can keep alive / growing)

I have a couple of USB temperature loggers which I picked up cheap. They plug into my PC and I can "configure" them - basically how often I want them to log the temperature; they have a limit on the number of recordings they can store, so longer intervals between readings means a longer period of elapsed recording time (and the temperature doesn't gain, or lose, 1C in a short period of time, so once every 10 minutes is probably quite sufficient). Then carry to the greenhouse, press button for "START" and then retrieve them a week, or whatever, later and plug into PC and download the data then view it as a pretty graph :)

I also have some real-time wireless sensors, but they are only good for 50M max, and barely reach my greenhouse with direct line of sight from my home office window because there is a hedge in the way ... but they are handy to see the temperature in the greenhouse late at night without having to venture out into the cold night air :)

*

cadalot

  • Guest
Re: Heating a greenhouse
« Reply #5 on: October 09, 2014, 16:17 »
Lidl sell inside/ outside temperature gauges that record max and mins for the home and car for less than a 5 each and I have those in the greenhouses also have one that monitors the relative humidity bought for less than a 10 at a DIY store.

*

bravemurphy

  • Senior Member
  • ****
  • Location: Wales
  • 774
Re: Heating a greenhouse
« Reply #6 on: October 09, 2014, 16:38 »
It was mentioned to me on this forum that you could make a hot bed in the greenhouse, or a pile of rotting manure piled in one corner with a sheet on it?

*

cadalot

  • Guest
Re: Heating a greenhouse
« Reply #7 on: October 09, 2014, 19:39 »
It was mentioned to me on this forum that you could make a hot bed in the greenhouse, or a pile of rotting manure piled in one corner with a sheet on it?

So you really want to be in there with rich manure  :wacko:

*

Growster...

  • Hero Member
  • *****
  • Location: Hawkhurst, Kent
  • 11356
Re: Heating a greenhouse
« Reply #8 on: October 09, 2014, 20:47 »
It was mentioned to me on this forum that you could make a hot bed in the greenhouse, or a pile of rotting manure piled in one corner with a sheet on it?

So you really want to be in there with rich manure  :wacko:

Don't knock it too much, I think it may just work!

It's an age-old process after all, we have a house down the road, with old greenhouses with six huge brick manure arches underneath! Apparently they heated the whole glazed area which was vast in present day standards!

*

Kristen

  • Hero Member
  • *****
  • Location: Suffolk
  • 4065
    • K's Garden blog
Re: Heating a greenhouse
« Reply #9 on: October 10, 2014, 16:00 »
It's an age-old process after all, we have a house down the road, with old greenhouses with six huge brick manure arches underneath! Apparently they heated the whole glazed area which was vast in present day standards!

I saw it, a while back!, on a BBC documentary called something like "The Victorian Kitchen Garden".  Its probably on YouTube ... my recollection is that it was a phenomenal amount of manual labour digging the "spent" manure out, which had to be done [again, from memory] 3 or 4 times over the course of the winter as the fresh manure started to cool.  I imagine they were only barrowing the spent manure a short distance to the rest of the, walled, kitchen garden, but it did seem to be a serious amount of hard work.

*

Dilly Dom

  • Experienced Member
  • ***
  • Location: Lincolnshire
  • 247
  • Living the Dream
Re: Heating a greenhouse
« Reply #10 on: October 10, 2014, 16:35 »
It can get very cold in Cambridge area in the winter, if it were me I'd bring the small trees home.  Have you got a heated conservatory you could over winter them in? 
Dilly
It is better to have nothing to do than to be doing nothing.

*

snowdrops

  • Hero Member
  • *****
  • Location: Burbage,Leics
  • 17324
Re: Heating a greenhouse
« Reply #11 on: October 10, 2014, 18:26 »
They had the same system in lots of old gardens, they have one at Heligan. They used to grow pineapples using the same method. They still grow pineapples in the same glass house but I can't remember if it's heated with manure.
A woman's place is in her garden.

See my diary pages here
and add a comment here

*

cadalot

  • Guest
Re: Heating a greenhouse
« Reply #12 on: October 10, 2014, 21:04 »
In the Victorian Kitchen Garden they used brick hot frames and put in three to four feet deep manure, then cover with another foot of regular soil, and cover with glass. The manure then heated up that frame as it breaks down, allowing for a self-heated cold frame to become a hot bed for start seeds and grow cold-hardy vegetables in even very cold weather.

Handy when you have a stable and a constant fresh supply of steaming hot horse poo - I was going to put a link to the second episode which showed them, but it looks like the BBC have had all copies removed from YouTube so glad a bought a copy from ebay

*

andysmum

  • New Member
  • *
  • Location: South Cumbria
  • 18
Re: Heating a greenhouse
« Reply #13 on: November 10, 2014, 14:18 »
hi im a new member i have a greenhouse and have create a tent of bubblewrap inside it, i dont want to heat it i will use it just for protection from frost for some half hardy perenialls i have lifted from the garden what do you think is the max temprature i should aim for please

*

Kristen

  • Hero Member
  • *****
  • Location: Suffolk
  • 4065
    • K's Garden blog
Re: Heating a greenhouse
« Reply #14 on: November 11, 2014, 07:36 »
i will use it just for protection from frost for some half hardy perenialls i have lifted from the garden what do you think is the max temprature i should aim for please

16C ?  I would ventilate on days when the sun is out once the temperature is over, say,10C. I would close  the greenhouse early - at least 2 hours before sunset (bit of a guess, might be more) - to capture some heat to slow heat loss into the night (even if that raises the temperature to, say, 20C for a few hours)

If temperature doesn't look like rising above 16C then no need to ventilate for heat, but you still may need to ventilate to prevent moulds (or install a fan to circulate the air - that could be on a timer something like 15 minutes on and 45 minutes off (but I suspect you may not have electricity available in the greenhouse).

What I think you need to avoid is the plants making fresh soft growth until the Spring e.g. by the temperature in the greenhouse being toasty-warm. They will probably start early, February-ish, even if you try to keep the heat gain to a minimum, but you don't want them growing much / at all before that.

I would keep them fairly dry too - that will help with moulds, and without any/many leaves they won't be drinking much water anyway, and if their roots get soppy wet that may encourage rot.



xx
heating a greenhouse

Started by hanssg on Growing in Greenhouses & Polytunnels

9 Replies
4781 Views
Last post May 07, 2016, 15:22
by grendel
xx
Heating a Greenhouse

Started by AlistairMcLennan on Growing in Greenhouses & Polytunnels

16 Replies
6080 Views
Last post May 15, 2012, 23:18
by mumofstig
xx
heating greenhouse

Started by davidmw on Growing in Greenhouses & Polytunnels

6 Replies
2656 Views
Last post June 29, 2011, 15:04
by pink aubergine
xx
Greenhouse heating opps

Started by Caretaker on Growing in Greenhouses & Polytunnels

0 Replies
1612 Views
Last post April 13, 2012, 09:20
by Caretaker
 

Page created in 0.135 seconds with 35 queries.

Powered by SMFPacks Social Login Mod
Powered by SMFPacks SEO Pro Mod |