Greenhouse Materials
Greenhouses may be built using a frame of wood, aluminium or steel, glazed with glass or plastic panes. The eventual choice of material will depend on:
- How you want it to look.
- How much money you want to spend.
- How much time you want to spend keeping it in good condition.
Framework
The frame of a greenhouse may be wooden, aluminium alloy or galvanised steel; the advantages and disadvantages of each are detailed in the table below.
| Material | Pros | Cons |
|---|---|---|
| Aluminium Alloy | - Maintenance-free - Narrower frames than wooden greenhouses, allowing for larger panes of glass and better light penetration |
- May be considered less attractive than wooden structures - Slightly reduced retention of heat compared with wooden frames |
| Galvanised Steel | - Light and easy to build - Very strong - Cheaper than timber or aluminium frames - Narrower frames than wooden greenhouses, allowing for larger panes of glass and better light penetration |
- May be considered less attractive than wooden structures - Slightly reduced retention of heat compared with wooden frames - Must be treated regularly to prevent rust |
| Timber | - Traditional - Attractive appearance - Hardwoods such as cedar retain their colour well, will not warp easily and are rot-resistant |
- Expensive - Heavy when constructing - Timber other than hardwoods must be pressure-treated with preservative and painted regularly to prevent rot |
Glazing
Greenhouses may be glazed using glass or plastics such as acrylic or polycarbonate. The best choice in general is horticultural glass; this is thinner and less expensive than ordinary glass, but allows excellent light penetration. The advantages it has over plastic materials include improved heat retention, ease of cleaning and the fact that it will not discolour. However, it is more fragile than plastic glazing, and any cracked or broken panes must be replaced immediately to ensure that heat is not lost. Most local glass merchants will cut replacement panes to size at a reasonable cost; make sure that you measure the glass accurately and that there is enough clearance for the glass to connect with the mounting system.
Plastics panes are less long-lasting and more expensive than glass, and will become scratched and discoloured over time. Not only is this unsightly, but it will also reduce the amount of light that they are able to transmit.
Acrylic may be shaped easily, and so it is very good for creating panes for curved structures. However, condensation tends to form on its surface far more readily than glass. Rigid polycarbonate sheets are also often used as a glazing material, providing a robust, lightweight material with good insulating properties. Unfortunately, it tends to scratch very easily and will discolour over time. Twin-walled polycarbonate has excellent insulating qualities, but it is far more opaque than even the other plastics. However, this may be used to your advantage in some parts of the greenhouse, for example if you want to provide one particular area with slightly more shade.
Plastic glazing material can be supplied in sheets and may be cut quite easily to size at home using a straight edge sharp and a craft knife.