Roof glazing provides plenty of daylight in a home, conservatory, veranda, skylight or canopy. But glass in a roof requires a different choice than glass in a window: it is located above people, is exposed to rain, wind and snow, and must remain safe if broken. The short rule is simple: always use safety glass for roof glazing. For glass above people, you usually choose laminated glass or insulating glass with a laminated inner pane, so that shards of glass do not fall down if broken.
In this article we explain which glass is suitable for roof glazing, when you need insulating glass and what you should pay attention to in terms of thickness, weight, safety, sun protection and installation.
What is roof glazing?
Roof glazing is glass that is used in a roof construction. The glass is usually horizontal or oblique and brings in daylight. You see roof glazing at:
- skylights and skylights
- conservatories and verandas
- patio covers and carports
- glass roofs, extensions and atriums
- awnings, patios and covered entrances
Because the glass is above people, safety is one of the most important selection points.
Why is roof glazing different from window glass?
Glass in a facade is vertical. When it breaks, shards usually fall down the frame. With roof glazing, the glass is above your head: if it breaks, shards can fall straight down.
Roof glass also has different loads than window glass:
- own weight
- rain, snow and hail
- wind (pressure and suction)
- temperature differences and sun exposure
- falling branches, dirt and leaves
- cleaning tax
That is why you cannot simply choose the same glass for roof glazing as for a normal window.
Which glass do you use for roof glazing?
For roof glazing you use safety glass. This usually concerns:
- laminated glass
- tempered-laminated glass
- insulating glass with laminated inner pane
- sun-resistant insulating glass
- HR++ roof glass
- triple roof glass with high insulation requirements
Which structure you choose depends on the application. For an open canopy, single laminated glass is often sufficient. For a heated living space or skylight, you usually choose insulating glass with a safe interior.
Why laminated glass is important
Laminated glass consists of two or more panes of glass with foil in between. If the glass breaks, the shards remain stuck to the foil. That is exactly what you want with roof glazing: you want to prevent shards of glass from falling down.
Advantages of laminated glass:
- shards stick to the foil
- safer with glass above people
- suitable for roof applications
- can be combined with tempered glass
- can be part of insulating glass
- reduces the risk of injury in the event of breakage
The foil ensures that the glass remains intact as much as possible in the event of breakage.
Rule of thumb: glass above your head = laminated glass. Tempered glass is strong, but falls down in grains when broken. Laminated glass sticks to the film — and that is exactly what you need with roof glazing.
Is tempered glass suitable for roof glazing?
Tempered glass is stronger than normal glass and breaks into small grains. However, tempered glass alone is usually not enough for roof glazing above people. When tempered glass breaks, it shatters into small pieces. Those pieces are less sharp than normal shards, but they can still fall down. With roof glass you want the glass to hang as much as possible in the event of breakage.
That is why laminated glass, toughened laminated glass or insulating glass with laminated inner pane are often chosen for roof glazing. You can read more background in tempered or laminated glass and laminated glass: what is it.
What is tempered-laminated glass?
Toughened laminated glass consists of toughened glass plates with foil in between. It combines strength with safer fracture behavior:
- stronger than ordinary laminated glass
- stays together better in case of breakage
- suitable for heavier applications
- good for roof glass, awnings and canopies
- suitable for larger glass plates
Tempered laminated glass is often used when roof glass needs to be extra strong, for example in large spans or outdoor constructions.
Single roof glass or insulating roof glass?
Not every roof glazing needs to be insulated. The choice mainly depends on the space underneath.
| Situation | Glass selection |
|---|---|
| Open veranda | Laminated safety glass |
| Unheated canopy | Laminated glass |
| Carport | Laminated glass |
| Conservatory without heating | Laminated glass or insulating glass |
| Heated conservatory | Insulating safety glass |
| Skylight in home | HR++ roof glass with laminated inner pane |
| Extension or living space | Insulating glass with safety structure |
| Glass roof above interior space | Insulating roof glass |
In heated rooms, insulating glass is usually necessary — otherwise you lose a lot of heat through the roof. Insulating roof glass with a laminated inner pane assemble it yourself as insulating glass. With the U-value calculator you can see how different structures perform.
Roof glazing per application
Skylight
A skylight brings a lot of daylight into your home. Because the glass is located above an interior space, it must insulate well and be safe. For a skylight you usually choose insulating glass with:
- HR++ construction
- laminated inner window
- possibly hardened outer window
- sun protection coating
- good spacer
- secure edge seal
The layered inner pane ensures that shards do not simply fall down if broken. The insulating structure ensures comfort and less heat loss.
Conservatory
A conservatory can be unheated or heated — and that makes a big difference in the choice of glass. For an unheated conservatory, laminated glass may be sufficient, especially if it mainly concerns shelter. Insulating glass is important for a heated conservatory, otherwise the conservatory will become cold in winter and warm up quickly in summer.
For conservatories, pay attention to: insulation value, sun protection, condensation, ventilation, safety, slope angle, glass weight and construction. A conservatory often has a lot of glass surface, making the right choice of glass extra important for comfort.
Verandah or canopy
With a veranda or patio cover, the space is usually open and unheated. Then thermal insulation is less important, but safety is. Verandas are often chosen for:
- laminated safety glass
- tempered-laminated glass
- possibly frosted or opal glass
- possibly sun-resistant glass
Important are: span, glass thickness, slope angle, snow load, water drainage, rubbers and profiles, and safe installation. Never use standard glass for a canopy over seats. More about this in glass for veranda and canopy.
Canopy
A glass awning often hangs above a front door, entrance or terrace — here too, glass is placed above people. Tempered-laminated glass is often used for an awning. Please note: attachment with point holders or profiles, cantilever, wind load, snow load, glass thickness, edge finish, water drainage and structural substrate. An awning is subject to a lot of load on a relatively small number of mounting points, so the correct structure is important.
What thickness of roof glazing do you need?
There is no standard thickness that is always suitable. The correct thickness depends on several factors:
- size of the glass plate
- distance between beams
- angle of inclination
- snow and wind loads
- single glazing or insulating glass
- layered or hardened-layered
- indoor or outdoor space, heated or not
- mounting system and maintenance access
For smaller roofs you often see layered structures such as 44.2 or 55.2. For larger glass plates or heavier loads, a heavier structure may be required. Do not choose the thickness based on feeling: the construction and load must be correct. See also what thickness of glass do I need.
What do codes like 44.2 or 66.2 mean?
With laminated glass, codes indicate the glass structure. For example, 44.2 usually means 4 mm glass + 4 mm glass + 2 foils in between.
| Code | Construction | Glass thickness without foil |
|---|---|---|
| 44.2 | 2 × 4 mm glass + 2 foils | 8 mm |
| 55.2 | 2 × 5 mm glass + 2 foils | 10 mm |
| 66.2 | 2 × 6 mm glass + 2 foils | 12 mm |
| 88.2 | 2 × 8 mm glass + 2 foils | 16 mm |
With roof glass, the right foil and glass structure are important — it's not just the thickness that counts.
How heavy is roof glazing?
Glass is heavy, and that is important for both construction and installation. Glass weighs on average approximately 2.5 kg per m² per millimeter of glass thickness.
| Glass construction | Weight per m² |
|---|---|
| 44.2 | ± 20 kg |
| 55.2 | ± 25 kg |
| 66.2 | ± 30 kg |
| 88.2 | ± 40 kg |
| HR++ roof glass 44.2-15-6 | ± 35 kg |
| Triple roof glass | often 40 kg/m² or more |
For example, a roof window of 1000 × 2500 mm in 55.2 glass weighs:
1.0 × 2.5 = 2.5 m² 10 mm glass thickness × 2.5 kg = 25 kg per m² 2.5 × 25 = 62.5 kg
In addition, snow and wind loads are added. Calculate your own window with the glass weight calculator.
Snow load on roof glass
Roof glass must be able to carry snow. Wet snow in particular can become heavy and when it accumulates, the load increases considerably. Snow load depends on roof slope, location, sheltered position, surrounding roofs, raised edges, glass surface, distance between beams and structure. Snow remains more easily deposited on gentle roof slopes - the glass structure must be suitable for this.
Wind load on roof glass
Wind can cause pressure or suction on roof glass. This is especially important for open canopies, roof terraces and higher buildings. Wind load depends on the height of the building, its location, an open environment, coastal area, roof shape, mounting and glass dimensions. The mounting must prevent glass from shifting, blowing up or becoming stressed.
Slope angle and water drainage
Roof glazing must have sufficient slope. If glass is too flat, water, dirt, leaves and snow are more likely to remain. A good slope angle ensures:
- better water drainage
- less dirt accumulation and stagnant water
- less chance of leakage
- longer lifespan of rubbers and sealant
- easier maintenance
With flat skylights, water drainage is often solved via the complete profile system. Slope is extra important for verandas.
Is roof glass walkable?
Regular roof glass is not automatically walkable. Even if it seems strong, that doesn't mean you can insist on it. Walkable glass requires a special structural glass structure and calculation. So do not simply use roof glazing to avoid walking on it during cleaning, maintenance, inspection, roof access or installation. Should glass be walkable? Then it must be designed in advance as walkable glass.
Sun protection and light
Sun protection glass for roof glazing
Roof glass lets in a lot of sunlight. That is nice for daylight, but can also cause heat. Sun-resistant glass helps to reduce heat radiation and is interesting for skylights, conservatories, extensions, south-facing glass roofs, large roof surfaces and rooms that heat up quickly. Sun protection glass can be combined with HR++ glass and safety glass. External sun protection, such as screens, can also have a great effect.
Heat-resistant or sun-resistant: what's the difference?
In practice, these terms are often used interchangeably. Usually this means glass that limits solar heat. When choosing, please note:
- how much light the glass lets through
- how much solar heat it blocks
- how dark the glass looks
- whether color reproduction is important
- whether additional sun protection is required
Roof glass is all about balance: you want a lot of daylight, but not too much heat.
Matte or opal roof glass
Matte, milky or opal glass provides diffuse light: the light enters softer and the view is limited.
| Matt / opal roof glass | |
|---|---|
| Benefits | less view from above, softer light, less bright sunlight, dirt is less noticeable, calm appearance |
| Disadvantages | less clear view outside, less direct view of the sky, less transparent appearance |
Opal glass can be useful for roofs and skylights when privacy is important.
Condensation and ventilation
Condensation on roof glazing
Condensation occurs when warm moist air comes into contact with cold glass. With roof glazing, this mainly occurs if there is insufficient insulation or ventilation. Condensation occurs more quickly in unheated conservatories, open canopies, poor ventilation, high humidity, single glazing, cold nights and large temperature differences. In heated rooms, insulating glass helps to limit condensation, but ventilation remains important. See also condensation on windows: inside, outside or between the glass.
Ventilation at roof glass
A lot of roof glass provides a lot of light, but also heat build-up. Ventilation helps to remove moisture and heat and is important in conservatories, skylights, extensions, verandas with side walls, and bathrooms or kitchens with roof glass. Possibilities include ventilation grilles, openable skylights, mechanical ventilation and exhaust ventilation — preferably combined with sun blinds. Without ventilation, a glass room can quickly become warm or humid.
Assembly and maintenance
Installation of roof glazing
Roof glazing must be installed carefully. The glass must be well supported and not under tension. Important for installation:
- suitable profiles and correct rubbers
- sufficient support, no hard contact with metal
- good water drainage and sufficient slope
- correct distance between glass plates
- protection of glass edges
- correct clamping strips
- safe hoisting and lifting method
Glass edges are vulnerable: damage to the edge can lead to breakage later.
Rubbers, profiles and bearings
Roof glass is usually in profiles with rubbers. These parts ensure a watertight connection, protection of glass edges, protection of the operation, tension-free installation, correct support and less chance of leakage. Always use profiles and rubbers that are suitable for roof glazing and outdoor use.
Maintenance of roof glazing
Roof glass becomes dirty due to rain, dust, leaves, bird droppings and deposits. Regular maintenance keeps the glass nicer and prevents blockages:
- remove leaves from gutters
- rinse off dirt first
- use a soft sponge or brush with mild detergent
- avoid abrasives
- don't walk on the glass
- check rubbers, profiles and water drainage
- Have hard-to-reach glass professionally cleaned
Safety always comes first when cleaning — never use roof glass as a walking surface.
Common mistakes with roof glazing
- Use normal glass — unsuitable above people.
- Choose tempered glass only — strong, but will not stick if broken.
- Do not choose a laminated interior window — with insulating glass above an interior space, a safe interior is important.
- Guess glass thickness — the correct thickness depends on dimensions, span and load.
- Forgot about snow loads — snow can add a lot of weight.
- Too little slope — water and dirt are more likely to remain on glass that is too flat.
- Think roof glass is walkable — only if it is designed to be.
- Forget sun protection — roof glass can quickly heat up a room.
Selection aid: which roof glass do you need?
| Situation | Best choice |
|---|---|
| Open veranda | Laminated safety glass |
| Terrace cover | Laminated or tempered-laminated glass |
| Skylight in home | HR++ roof glass with laminated inner pane |
| Heated conservatory | Insulating safety glass |
| Glass canopy | Tempered-laminated glass |
| Extension | HR++ or triple roof glass with safety structure |
| Lots of sun | Sun-resistant safety glass |
| Privacy desired | Matte or opal glass |
| Large span | Have a heavier build-up determined |
| Walkable glass | Special structural structure |
Checklist before ordering roof glazing
- Does the glass come above people? Has laminated safety glass been chosen?
- Is the room heated? Is insulating glass necessary? Should the inner window be laminated?
- What are the dimensions and distance between the beams?
- What is the angle of inclination?
- Have snow and wind loads been taken into account?
- Is solar control glass desirable? Frosted or clear glass?
- Can the structure support the weight?
- Are rubbers and profiles suitable? Is there sufficient water drainage?
- Is the glass walkable or not?
- Is it professionally installed?
Measure your measurements accurately using the tips from measuring glass.
Conclusion
Roof glazing requires a different glass choice than normal window glass. Because the glass is above people, safety is the most important principle: therefore always use laminated safety glass or insulating glass with a laminated inner pane. Laminated glass is often sufficient for open verandas and canopies; For skylights, conservatories and heated areas, you usually choose insulating roof glass with a safety structure. In addition, pay attention to glass thickness, weight, snow and wind loads, slope angle, sun protection and installation.
Continue reading: tempered or laminated glass · laminated glass: what is it · glass for veranda and canopy · compare insulating glass: HR, triple and vacuum · what glass thickness
Do you know which structure you need? View safety glass and insulating glass, or order custom glass directly. Are you unsure about the structure for your roof? Request non-binding advice via our contact form.