# Aluminium System

> Part of: [Greenhouse Construction](/greenhouse-construction.md) · Provider: [DutchGreenhouses](/)

The aluminium super-structure carries the glass and drains the roof at once. Glazing bars hold the panes and channel condensation into the gutter, which is simultaneously a structural member tying trusses together, the rainwater collector and part of the cladding — one element doing three jobs.

## Facts
| Property | Value |
|---|---|
| Calculation program for the aluminium | GlazenStad program |
| What decides whether a system is calculated in it | The supplier's engineering, not the country of manufacture categorical |
| Horizontal aluminium members in the roof | 2 members |
| Duties carried by the gutter | 3 functions |
| Venlo roof pitch | 22–23 degrees |
| Condensation handling | Grooves in the glazing bar detail |
| Material choice driver | Corrosion resistance plus extrudability property |
| Span widths the system serves | 8, 9.6 or 12.8 m |

Structure

# Aluminium system.

    Gutters and glazing bars that work as structure.

## Gutters and glazing bars that work as structure

    In a Dutch greenhouse the aluminium is not just trim around the glass — it is working structure. The centrepiece is the aluminium gutter that runs between the trusses: erected together with the steel, it ties the frame together, carries the edges of the glass roof on either side, and simultaneously collects and discharges the rainwater running off the V-shaped roof. One extruded profile therefore does three jobs at once — structural member, glass support and water system — which is exactly the kind of integration that makes the whole system efficient.

The glazing bars do the same multi-tasking higher up. They hold the panes of glass across the roof, and where the ventilation windows sit they also form the frames of those opening lights, carrying the hardware that lets the vents swing open and shut. Rather than adding separate framing for glazing and separate framing for ventilation, the aluminium profile serves both purposes, keeping the roof light and the parts count low.

Aluminium is the right material for this because of where it sits and what it does. It is naturally corrosion-resistant in the warm, humid, often condensation-laden environment just under the glass, so it lasts the life of the greenhouse without the protection steel needs; it is light, which keeps loads down on the steel skeleton below; and it can be extruded into precise, complex profiles that combine several functions in a single section. Those properties are why aluminium and steel are paired the way they are — steel for the heavy structural skeleton, aluminium for the lightweight, weather-facing super-structure.

The result of this thinking — every profile made to do more than one thing — is a roof system that is light, strong, weathertight and cost-effective, and a large part of why the Dutch Venlo greenhouse became the world standard. DutchGreenhouses® engineers the aluminium system as an integral part of the structure, glazing and water strategy. Get in touch to discuss the construction of your greenhouse.

From the knowledge base

## Reads you might find interesting

          ceacultivationbusiness-case

### Grow Like a Pro: Starting Smart, Growing Strong

          How Grow Like a Pro combines smart farming, CEA technology and local partnerships for eco-friendly, profitable, pesticide-free greenhouse pr

          Read article

          education

### The Case for a College Greenhouse

          Why a college greenhouse belongs in the curriculum: teaching science, craftsmanship, business logic and sustainability, and preparing studen

          Read article

          education

### The Case for a High School Greenhouse

          Why every high school greenhouse matters: how it makes STEM tangible, builds responsibility and teamwork, and helps students discover their

          Read article

          education

### Greenhouses in Education: The Case for Schools

          Greenhouses in education reconnect students to reality — the full case for why every school, high school, college and trade program should h

          Read article

          historyconstruction

### The Origins of Greenhouse Horticulture: My Backyard

          A tour through greenhouse horticulture history: from 19th-century Westland fruit walls to the “City of Glass” and today’s international high

          Read article

          company

### DutchGreenhouses Rebranded: A New Corporate Identity

          Announcing our new corporate identity — a visual style reflecting our dedication to advanced, high-quality greenhouse projects and The Futur

          Read article

## FAQ
**Is the aluminium on a greenhouse calculated, or just extruded to a profile?**
It should be calculated. Greenhouse roof-deck aluminium has its own calculation program, GlazenStad, covering the glazing bars, gutters and ridges — the counterpart to CASTA on the steel side, and output from CASTA reads directly into it. Both are governed by Stichting Hortivation and verify against NEN-EN 13031-1. A profile that looks identical to a calculated one can carry a different alloy, wall thickness or span rating, and the drawing alone does not tell you which.

**How do I check that a supplier's aluminium is properly dimensioned?**
Ask whether the roof deck aluminium is calculated in GlazenStad, to which version of EN 13031-1, and ask to see the calculation. That is a better question than asking where the aluminium was made: the established Dutch system houses participate in GlazenStad and calculate in it including for their own manufacturing abroad, while suppliers outside that framework often calculate to no published greenhouse standard at all. Adherence follows the engineering, not the address.

**Why does it matter if the aluminium is under-dimensioned?**
Because the failure is not graceful. The aluminium carries the glass and ties the trusses; when it deflects too far the panes go, and a roof full of broken glass over a crop is a total loss rather than a repair. It also damages the sector: every greenhouse that fails somewhere in the world makes the next buyer more sceptical of all of them.

**Which aluminium members run horizontally in the roof?**
Only two: the gutter and the ridge. Everything between them is vertical — the glazing bars run up the slope from gutter to ridge, carrying the glass. Nothing horizontal crosses the roof in between, and no steel member does either, because a Venlo roof has no purlins.

**Why is the gutter considered structural?**
Because it ties the trusses together along the length of the greenhouse as well as collecting water. Removing it would not simply stop the drainage; it would remove a load path. That dual role is characteristic of Dutch construction, where the V-shaped roof is the rainwater system and the cladding forms part of the gutter.

**What are the grooves in a glazing bar for?**
Condensation. Warm humid air meets cold glass and water forms on the inside of the roof. The bar carries grooves that collect it and run it down to the gutter, so it drains away instead of dripping on the crop — where it would mark produce and spread disease. The bar's vertical run is what makes that drainage work.

**Why aluminium rather than steel for the super-structure?**
Two properties at once. Aluminium resists the permanently humid interior without needing a protective coating, and it extrudes into the complex asymmetric profiles a glazing bar needs — glass seat, drainage groove and fixing channel in a single section. Steel carries the heavy loads below; aluminium does the precise work above.

**What sets the roof pitch?**
A Venlo roof sits at roughly 22 to 23 degrees, which balances three things: light incidence through the glass, condensation running to the gutter rather than pooling, and snow sliding off rather than accumulating. Together with gutter height it defines the roof geometry.

## Related
[Greenhouse Construction](/greenhouse-construction.md) · [Steel Structure](/greenhouse-construction/steel-structure.md) · [Greenhouse Glass Covering](/greenhouse-construction/greenhouse-glass-covering.md) · [GlazenStad](/glossary/glazen-stad.md) · [CASTA](/glossary/casta.md) · [Aluminium Glazing Bar](/glossary/glazing-bar.md) · [Gutter](/glossary/gutter.md) · [Ridge](/glossary/ridge.md) · [EN 13031](/glossary/en-13031.md) · [Venlo Greenhouse](/glossary/venlo-greenhouse.md)