Tips And Advice For Saving Heat In The Greenhouse
If you are lucky enough to have
a greenhouse and enjoy gardening you will probably have been faced with the decision whether to heat it in the winter and possibly the early spring. By their very nature greenhouses are not energy efficient and unless action is taken even a small one will cost a fortune to heat.
Which Is The Best Heat Source For Heating The Greenhouse
How the greenhouse is heated depends on what is easily available. Probably the least efficient method is electricity although it is more controllable by using a thermostat to regulate the heating. Mains gas is probably out for most people as impractical due to installation cost considerations. That leaves three main options: bottled gas, paraffin or if the greenhouse is close to the house the house central heating system. The latter has the disadvantage that it needs good insulation of the pipes feeding the greenhouse, the cost of extending the heating system and the fact that heating times for the greenhouse could well be inconsistent with the times heating is required in the house which will push up heating bills by a disproportionate amount. This means the only real options are bottled gas and paraffin. Bottled gas is the least messy but in our experience works out more expensive than paraffin provided you can buy the paraffin in realistic quantities. In addition paraffin heaters tend to be cheap.
Ways To Reduce The Amount Of Heat Needed To Heat The Greenhouse
Decide what temperature the greenhouse needs to be heated too. This will depend on the plants involved, often plants just need to be kept above freezing and there is very little benefit from heating more than this. For most common plants keeping the temperature above 5C is adequate, however if the temperature regulation is manual a safety margin will be needed to allow for sudden overnight drops in temperature.
Fully insulating the greenhouse temporarily with bubble wrap will make a big difference but make sure there is some air circulation otherwise plants can rot. Mount the bubble wrap on wooden frames to make it easy to re use and keep the cost of the bubble wrap down. Filling empty space also helps considerably by reducing the volume of air to heat, store everything that won't be affected by damp in the greenhouse over winter such as flowerpots and large plastic containers with all sorts of things in them. Having a large tank of water in the greenhouse also helps as the water stores heat as well as reducing the volume of air to heat, it is also useful for watering the plants occasionally.
Do you really need to heat all the greenhouse or just an area large enough to contain the vulnerable plants. It is often viable to create a small insulated area inside the greenhouse with a second bubble wrap enclosure and heat just within this area. Our own experience is that creating an insulated area of about one third of the greenhouse volume is sufficient to house the plants and allow a reasonable volume for good air circulation. This has allowed us to keep the area around ten degrees above freezing using a small 300W paraffin heater running continuously.(the greenhouse is also fully insulated with bubble wrap giving an insulated area within an insulated area).
Keep The Draughts Down
Although you need ventilation in a greenhouse excessive draughts will quickly remove any heat there is. For this reason it is worth sealing as many of the odd holes as you can so that ventilation can be controlled. Hanging a temporary curtain of bubble wrap over the door and taped to the rest of the insulation on two sides can make a big difference. The same approach can be taken with opening windows rather than sealing them completely - you may well need them open sometimes if most of the draughts have been fixed.