Home > Greenhouse Care > Heating Your Greenhouse Naturally

Heating Your Greenhouse Naturally

By: Lucy Debenham BA (hons) - Updated: 4 Jul 2013 | comments*Discuss
Heat Sink Natural Greenhouse Temperature

Greenhouse growing is possibly the most popular way to grow sun-loving plants, fruit and vegetables in our mild British climate.

But with British weather being notoriously unpredictable, sometimes growing plants in an unheated greenhouse can be a gamble.

Although a greenhouse will act as a type of solar unit, trapping the sun’s heat during the day, at night temperatures can plummet so low that tender plants can be damaged.

Therefore it’s during the night that many people turn to greenhouse heaters to maintain the ambient temperature.

Passive and Active Methods

There are principally two greenhouse heating methods – active and passive. The active method basically involves using an electrical power source that provides the energy that pumps heat into the greenhouse. This is usually in the form of an electric heater, which can sometimes prove quite complicated and inefficient in terms of energy usage and cost, even when just used overnight.

The passive method usually employs what we could consider as more natural heat sources that absorb heat throughout the day, and then disperse the heat during the cooler nights.

Heat Sinks

For the passive method to work, it needs a heat sink. This is a material or vessel that absorbs the heat, allowing it to ‘sink in’ during the day. As the air temperature around the object or material cools, the heat trapped within is slowly released during the night, stabilising the ambient temperature and preventing it from dropping too low.

It’s worth noting that passive methods are most efficient and successful during the summer ‘growing season’ months, when the heat of the sun is at its most powerful. British winter days, even with clear skies, may not generate enough sunlight or warmth to enable passive heating methods to be successfully used during the colder season.

Here are some ideas of how you can implement a more ‘natural’ passive heating method:

  • Create a heat sink using rocks, paving slabs or concrete blocks (in a metal cage)
  • Create a heat sink using large plastic water/ disused food barrels
  • Create a ‘hot bed’ using compost or well-rotted manure (so as not to attract flies etc.)

Improving Heat Sink Efficiency

Coating the materials or objects with non-reflective black paint will increase their ability to soak up and store the heat during the day. Also make sure that you site your heat sinks somewhere where they will catch the maximum amount of sunlight during the day. For people in Britain, a south-facing aspect is ideal. You should also make sure that your heat sinks are situated inside the greenhouse, slightly away from the sides. This is because if the heat sink is in contact with panes of glass, once the outside air temperature has fallen, the windows will absorb the trapped heat fairly quickly.

One of the disadvantages of using a heat sink is that they can take up a considerable amount of space in the average sized greenhouse. Heat sinks that use compost or manure will also need to be regularly topped up and turned in order to maintain the production of heat, and can prove messy if not adequately contained.

However you could try to scale your heat sinks to suit the size of your greenhouse – but remember that the more packed your greenhouse is, the less energy you’ll need to heat it. To help with natural passive heating, you could also try to insulate your greenhouse with bubblewrap. This can be done throughout the greenhouse, or if preferred, restrict your bubblewraping to just on the north facing side. Also by making sure that the greenhouse is as air tight as possible during the night (with plenty of ventilation during the day), you’ll help to retain warmth.

It may be that passive heating is only really suited to the summer growing season in Britain. However, it’s a method that has been in use for many years, and proved successful in many a large stately Victorian hothouse. Why not give it a go and see whether natural heating methods work for you?

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

(never shown)
(never shown)
(never shown)
(never shown)
Enter word:
Latest Comments
  • Andy
    Re: Designing a Greenhouse for Disabled Access
    Hi I am working with a community company that has obtained a 18' x 56' polytunnel. It is looking to ensure it…
    27 January 2019
  • BabyGirl
    Re: Designing a Greenhouse for Disabled Access
    When I was eleven I started experiencing severe pain in my lower back. Doc said it had something to do with my…
    23 November 2018
  • GreenhouseGrowing
    Re: Growing Climbers in Your Greenhouse
    scramble - Your Question:I am seeking the same information as Squirrel: flowering climber for greenhouse that gets v hot…
    4 April 2018
  • scramble
    Re: Growing Climbers in Your Greenhouse
    I am seeking the same information as Squirrel: flowering climber for greenhouse that gets v hot in summer and cold in…
    2 April 2018
  • Squirrel
    Re: Growing Climbers in Your Greenhouse
    Dear ???? I have a sunny greenhouse on the 4 floor and wish to grow flowering creepers and plants.It gets very hot in…
    20 March 2018
  • zizi
    Re: Growing Flowers in Your Greenhouse
    l cant imagine world without flowers and plants.My major is agriculture engineering .I need some informstion about develop…
    11 March 2018
  • GreenhouseGrowing
    Re: Greenhouse Vegetables
    Jim - Your Question:I have tried to grow potatoes in my greenhouse for Christmas which appeared to be doing very well. However al I cropped…
    6 March 2018
  • Jim
    Re: Greenhouse Vegetables
    I have tried to grow potatoes in my greenhouse for Christmas which appeared to be doing very well . However al I cropped was lots of very…
    4 March 2018
  • GreenhouseGrowing
    Re: Starting With Orchids
    Pop - Your Question:It is now October is it too late to grow chrisanthimum's in my greenhouse. If not where can I get some cuttings
    10 October 2017
  • Pop
    Re: Starting With Orchids
    It is now October is it too late to grow chrisanthimum's in my greenhouse. If not where can I get some cuttings
    7 October 2017