While modern greenhouses tend to be more draft-proof than their antiquated counterparts, owners of older greenhouses can keep the heat in by using insulation.
The Royal Horticultural Society (RHS) recommends that insulating a greenhouse will save as much as 25 per cent on heating bills over winter.
But gardeners should beware not to over-insulate as it can block out the much-needed light for the plants.
With this in mind, only the northern or windward side should be insulated, regardless of the material.
The RHS advises that wooden or polystyrene panels can be used both outside and inside the greenhouse to provide maximum insulation.
Another option is to use horticultural fleece or bubble wrap on the inside of the greenhouse, but take care not to let the plants come into contact with the bubblewrap as it can hold condensation and lead to the plant drowning.
The increased condensation means the greenhouse may have to be kept more ventilated than normal, but this will stop any drips damaging plants.