- Heat transfer values of roofing materials
- Foil greenhouse and price
- Important when buying film for greenhouses
The price of a poly greenhouse is significantly cheaper than using glass or double-walled plastic sheets for your roof cover. Nevertheless, there are also some quality differences in the greenhouse films that need to be taken into account depending on the planting.
The film for the greenhouse should be UV stabilized
In terms of price, a foil greenhouse is particularly interesting for gardeners who want to start growing their young plants in the last winter months. Greenhouses of this kind are not for year-round use designed because they are often set up without additional heating. Another advantage, in addition to the low costs, is a comparatively high heat transfer of the foils used. This is usually polyvinyl chloride (PVC) or polyethylene (PE), the latter can be disposed of in a slightly more environmentally friendly way after use.
Heat transfer values of roofing materials
A comparison of the different roof coverings with regard to the thermal insulation to be expected (U-value in W/m2K) is important for the decision regarding the pros and cons of a foil house, taking into account the intended planting. The lower the value the smaller the thermal insulation passage will be later stand out. Here are some examples:
| material | material thickness | maximum U-value |
|---|---|---|
| bubble wrap | 8mm | 3,0 |
| Commercial glass | 3mm | 6,0 |
| Coated ESG glass | 4mm | 3,7 |
| insulating glass | 14mm | 2,0 |
| thermal insulation glass | 24mm | 1,1 |
| Double-skin sheets (polycarbonate) | 6mm | 3,5 |
| Triple skin sheets (polycarbonate) | 16mm | 2,3 |
| Acrylic glass (double-wall sheets) | 16mm | 2,4 |
| Acrylic glass (quadruple panels) | 32mm | 1,6 |
Foil greenhouse and price
In practice, the so-called grid foils have proven themselves. They are very stable and tear-resistant, the starting material is transparent and reinforced with different colored mesh fabrics. They are sold by the meter in specialist garden shops. The price is in the lower mid-range at around €3.00/m2, so that a 40 m roll (1.5 m wide) costs around €150. The prices fluctuate quite strongly seasonally, the price of the foil for the greenhouse is particularly cheap in the summer months.
Important when buying film for greenhouses
If possible, choose a UV-stabilized garden film that only becomes slightly cloudy in sunlight and does not become brittle so quickly (light corrosion). From a mechanical point of view, mesh-reinforced films last a long time, but they have the disadvantage that they negatively affect the incidence of light for the plants in the greenhouse. Commercial horticulture works mainly with a double foil covering, where the values for light and UV permeability are particularly favourable. The material has three layers per layer and has proven itself particularly in the cold winter months with regard to the very good insulation values.
tips
Even if the price of greenhouse film (€15.90) is slightly higher, do not use the films from the building materials department for your covering. They are only suitable for packaging or covering and do not come close to achieving the desired values in terms of light transmission, aging and plant compatibility.