Insulation Of Your Greenhouse
Conserving heat is essential, especially if the greenhouse is used in winter. Bubble glazing, formed of three layers of plastic with air-bubbles between them, traps warmth within the greenhouse and is especially valuable for attaching to the coldest and most exposed sides and roof. It is held in place by a range of fittings, including double-sided adhesive pads, drawing pins in wooden greenhouses and special clips in aluminium types.
Both white and green ‘bubble’ insulation is available: the green often makes the greenhouse too dark in winter, although if left in place in summer it creates useful shade. Other forms of isolative material include polythene sheets reinforced with wire mesh.
Large greenhouses can be mad more economic to heat by partitioning them with these materials, but ensure they are firmly secured and cannot fall on top of a heater.
Greenhouses Optimum Temperature
Clearly, the way to save money on heating is to have a ‘cold house’ and not provide any warmth – but this restricts the range of plants.
If the heating is limited to ensuring the temperature never falls below 7°C /45°F, this is called a ‘cool house’ and enables a wider range of plants to be grown
Keeping the temperature at 16°C/61°F or more throughout the year enables tropical plants to be grown, but the cost is high.
An agreeable temperature compromise – and one that saves money – is just to heat the greenhouse in late winter and spring, when sowing seeds and raising young plants; and in summer to grow plants such as tomatoes that benefit from the protection afforded by unheated greenhouse.
Using an electric or paraffin heated propagator in late winter and early spring to encourage seed germination and the rooting of cuttings saves having to heat the entire greenhouse and reduces heating costs dramatically.
Positioning Your Greenhouse
Orientate full-span greenhouses so that the ridge runs from east to west. This enables low, winter light to pass through the glass.
Additionally, if tall plants are positioned on the side away from the sun they do not cast cooling shadows over others.
Avoid places shaded by buildings or trees, as well as overhanging trees that might drip rain on the greenhouse.
Position the door away from prevailing winds. Most doors in metal-framed greenhouses are on runners and slide across the opening, but wooden types are hinged, if possible, so that they open away from the prevailing wind.
A hedge on the windward side helps to reduce wind speed and therefore its cooling effect. Indeed, the benefit of a hedge can be felt up to a distance of thirty times its height. For instance, a hedge 2.4m/8ft high reduces the wind’s speed by 75% at a point 4.5m/15ft from it. And at a distance of 12m/40ft the reduction is still as much as 65%
Lean-to greenhouses require warm walls, especially to encourage the development of early maturing crops
Greenhouse Heat Loss
Heating is a major cost factor in running a greenhouse and any way to reduce this is worth pursuing. Indeed, a wind exposed situation or a frost-pocket could double the expense of heating a greenhouse during winter.
There are several ways to decrease the costs: correctly positioning the greenhouse, installing insulation, and carefully controlling the temperature.
