The covering is 4 mm tempered safety glass, which is where the light comes from: it transmits around 92 percent, and unlike a film or a panel it does not degrade, so the crop keeps the same light quality in year ten that it had in year one. Tempered glass also breaks into blunt pieces rather than shards, which matters above a bench of young plants. The frame is hot dip galvanized steel, dipped after fabrication so the zinc reaches the tube ends and the drilled holes. For hydroponic work the house is supplied with pre slotted gutters, channels and return pipes. Spans run from 8 m to 12 m and length is set from 10 m to 100 m.
A nursery sells plants that have to look right on the day they leave. That makes light quality the first specification, because stretch, leaf colour and how even a batch finishes all follow the light the young plants receive. It is also why a propagation house is normally the one place on a nursery where a glass cover can be justified over a film one, even though the structure costs more per square metre.
Film and rigid panels both change with age. Film loses transmission as it weathers and is replaced on a cycle, and some panel grades yellow under UV. Glass does not do either: a tempered glass house holds its transmission, so a batch grown in year ten sees the same light as a batch grown in year one. On a nursery where the crop is judged on uniformity, that consistency is worth more than the lower first cost of a film cover.
Tempered glass is also safer above people and above stock. It breaks into blunt fragments rather than shards, which matters on a house where staff are working under the roof through the season. The wider glass range is listed on the glass greenhouse range page on this site.
The glazing is 4 mm tempered safety glass at around 92 percent light transmission. Panels are held in aluminium glazing bars on a gasket rather than set directly against steel, which lets the sheet move as it warms and cools without cracking at the fixing point and keeps the joint weathertight. Because the covering is rigid, nothing flaps, there is no tensioning cycle, and a damaged pane is released and replaced without stripping the roof.
The frame is hot dip galvanized steel, dipped after fabrication so the zinc reaches the inside of the tube and the cut ends, which are the first places a painted or welded frame starts to corrode. Members are bolted rather than welded on site, so the coating survives assembly and a damaged section can be unbolted and replaced. A tempered glass house aimed at commercial vegetable growing is described in the tempered glass greenhouse for commercial vegetable farms.
For a soilless nursery the house ships with pre slotted gutters, channels and return pipes, so the growing system and the structure are designed together rather than the benches being fitted around whatever the frame allows. Water is delivered to the channel and what is not taken up runs back to the tank, which is the reason a recirculating system uses far less water than irrigating a soil bed of the same area.
Climate control is the other half of the specification. Roll up side curtains exchange the air around the canopy, shade netting holds the light down on a bright day and drip irrigation hooks let a pot crop be watered without wetting the foliage. Vent placement, house width and the level of automation are all set per project. A glass house built around roof vents and pad cooling is described in the Venlo glass house with roof vents and pad cooling.
The table below is the standard build. Span, length, height, glazing and growing system are set to the site and to the crop.
| Greenhouse span | 8 m / 9 m / 10 m / 11 m / 12 m |
| Greenhouse length | 10 m to 100 m, or built to client demand |
| Greenhouse height | 3 m to 8 m |
| Structure material | Hot dip galvanized steel, bolted assembly |
| Glazing | 4 mm tempered safety glass in aluminium glazing bars |
| Light transmission | Around 92 percent |
| Hydroponic fit out | Pre slotted gutters, growing channels, return pipes |
| Ventilation | Roll up side curtains, roof vents to specification |
| Nursery equipment | Shade netting, drip irrigation hooks, bench and trellis options |
| Customisation | Width, vent placement and automation level to client specification |
| Crops | Young plants, cut flowers, leafy crops, tomato and cucumber |
Assembly starts with the base, because a glass house shows any error in the setting out along the full length of the glazing line. Base plates or ground posts are set to the drawing first, the frame is erected and squared bay by bay, and the glazing goes on last, each pane held in the bar on its gasket. On a house with slotted gutters, the gutter run is set out with the frame so the channels and the return pipe fall in the right direction.
Maintenance is lighter than on a film house because the cover is not on a replacement cycle. The routine is checking pane fixings and gaskets after the first season, cleaning the glass once a year because dust cuts transmission more than growers expect, and keeping gutters, downpipes and the return pipe clear. Where the house runs a recirculating system, the tank, the pump and the filters join the routine, and a blocked return is the fault that shows up first as a wet gutter rather than as a crop problem.
Houses of this type are used for propagation and young plant production, for cut flowers and pot plants, for leafy crops, and for tomato and cucumber grown on substrate. They suit nurseries where uniformity across a batch matters more than the first cost of the cover, and growers who want a permanent covering with a growing system designed into the structure rather than fitted to it afterwards.
Standards for the safety glass, the glazing systems and the steel used in structures of this kind are published by DIN, the German Institute for Standardization. Reporting on controlled environment production, including how indoor and glasshouse growing operations are built and financed, is published by VerticalFarmDaily. The question that decides the specification is normally the crop the house will be running in ten years, not only at handover.
Tempered glass breaks into blunt fragments instead of shards, which matters on a house where staff work under the roof through the season and where a break can happen above a bench of stock. It is specified for safety first and for light transmission second, at around 92 percent.
Each pane is held in an aluminium glazing bar on a gasket, so the bar is released, the broken sheet lifted out and a new one slid into the same channel. There is no need to strip the roof, and the rest of the house stays closed while the work is done.
The galvanized steel frame is rated for 15 to 20 years under normal growing conditions, and a tempered glass cover keeps its light transmission for 20 years or more when it is cleaned and left undamaged.
We provide a 10 year structural warranty and a 5 year anti-corrosion warranty on the galvanized frame. Details are set out in the contract for each project.
Send your site dimensions, the growing system you plan to use and your local wind and snow loads. We reply with a layout drawing and a full quotation.
