Choosing a Greenhouse Material
Two decisions sit behind every greenhouse: what the glazing is made of, and what the frame is made of. Between them they determine how much light reaches your plants, how well the structure holds warmth, how long it lasts and what it costs to maintain.
There is no single right answer. The sensible approach is to work out how you will use the house, then choose the material that suits that use rather than the one with the strongest specification on paper.
Glazing
Horticultural glass transmits more light than anything else, which matters most in a British winter when daylight is short and weak. It is the traditional choice and the cheapest glazing per pane. It also breaks into sharp pieces, which is worth weighing if children use the garden.
Toughened safety glass transmits almost as much light and breaks into blunt fragments rather than shards. It costs more and weighs more, though the extra weight stiffens the structure.
Twin wall polycarbonate takes a different approach. The air gap inside the sheet insulates, so the house holds warmth longer overnight, and the cell structure diffuses light so plants close to the panel are less likely to scorch. It transmits less light overall, and that shows in midwinter. It does not shatter at all.
Reinforced PVC and PE covers are used on polytunnels and light frames. They are the cheapest option, and the cover is a consumable that will need replacing every few seasons.
Frames
Aluminium is the default for good reason: it will not rot or rust, needs no annual treatment, and is light enough for one person to handle during assembly. Powder coating adds a finish in green or black without changing how it performs.
- Galvanised steel is stiffer for a given section and suits exposed sites where wind load dominates.
- Cedar and treated timber insulate better than metal and suit a traditional or walled garden, at the cost of periodic maintenance.
- Resin and plastic frames appear on the lightest models and suit seasonal rather than permanent use.
Matching Material to Use
If you want the most light for winter growing, glass on an aluminium frame is still the strongest option. If you want to hold heat with the least effort, twin wall polycarbonate does more. If the site is exposed or used by children, polycarbonate removes the breakage question entirely.
For seasonal use only, a covered frame costs a fraction of a glazed house and stores away. The budget range covers those, and the size guide covers what each footprint allows once you have settled on a material.
Living With Your Choice
Every material needs cleaning. Algae builds on glass and polycarbonate alike, and it cuts the light reaching plants long before it looks dirty. A pass with the cleaning range between seasons keeps transmission where it should be.
Glazing also gets broken. Knowing your pane size before you need it turns a broken panel into a routine replacement rather than a problem.
