Glass Roof Singapore Guide: Design, Glazing and Heat Control

A glass roof over a courtyard, a back yard extension or a car porch is one of the most requested features in Singapore landed homes. It brings daylight deep into the plan and keeps rain out, and done well it is beautiful. Done badly, a glass roof Singapore homeowners install becomes a greenhouse: a space too hot and bright to use for most of the day, with stained glass and a leak at every joint.

This article explains why heat is the central design problem, how to choose glazing, what the structure and frame have to do, the safety issues with overhead glass, and the practical details of drainage and cleaning. It is written from a structural engineer’s perspective, with an emphasis on decisions that are hard to reverse once the roof is installed.

Why heat gain is the main design problem

Singapore sits almost on the equator, so the sun is high in the sky for much of the year and a horizontal roof receives intense solar radiation for most of the day. A vertical window is partly protected by its orientation and by overhangs; a glass roof faces the sun directly. Sunlight passing through ordinary clear glass heats the floor and furniture below, which re-radiate that heat, and the glass itself warms up and radiates downward. The result can be a space considerably hotter than the open air outside.

The design aim is to admit daylight while rejecting as much solar heat as possible. The relevant glazing properties are visible light transmittance, which describes how much daylight passes, and the solar heat gain coefficient or shading coefficient, which describes how much solar heat passes. A good glass roof for the tropics has a high ratio of light to heat. Our guide to skylight design explores the same balance for smaller openings.

Glazing choices for a glass roof

There are several ways to control heat, and they are usually combined.

Solar control coatings. Spectrally selective and low-emissivity coatings reflect a large part of the infrared portion of sunlight while transmitting visible light. They are the most effective single measure.
Tinted or body-tinted glass. Tints absorb heat and reduce glare, but absorbed heat warms the glass, which then radiates some of it inwards. On their own they are less effective than a good coating.
Insulated glazing units. Double glazing with a coated inner surface reduces heat conducted and radiated from the hot outer pane. It adds weight and cost and needs careful edge sealing.
Frits and interlayers. Ceramic frit patterns or tinted interlayers in laminated glass reduce solar gain and glare and can give a soft, diffuse light.

Glazing specifications vary widely between manufacturers, so compare products using their published performance data for the same configuration rather than generic descriptions such as heat-reflective. A glass roof over an air-conditioned room also increases cooling load, which is worth estimating before the design is fixed.

Shading the glass roof

The most effective way to keep heat out is to stop the sun reaching the glass at all. External shading, such as fixed louvres, perforated metal, timber battens or a retractable fabric system above the glass, intercepts solar radiation before it enters. Internal blinds are much less effective, because the heat has already passed through the glass by the time it reaches them, though they still help with glare.

Planting can shade a glass roof well, as can placing the roof under the canopy of trees or the overhang of a higher building element. Where an open structure is acceptable, a shaded pergola with a partial glass cover can be a better solution than a fully glazed roof; our article on aluminium pergolas discusses louvred alternatives. If the space only needs rain protection, a solid insulated roof with a strip of glazing for daylight is usually cooler and cheaper.

Safety of overhead glass

Glass over people’s heads must be designed for what happens when it breaks. Fully tempered glass is strong but breaks into small fragments that fall; it can also break spontaneously because of nickel sulphide inclusions. Laminated glass, made of two or more panes bonded by an interlayer, holds together when broken and stays in the frame, which is why it is the usual engineering choice for overhead glazing. Laminated units built from heat-strengthened or heat-soaked tempered glass reduce both the breakage risk and the consequence.

Singapore’s Building Control Regulations include performance requirements aimed at reducing the risk of injury from glass in roofs, canopies and overhead glazing, including the risk of spontaneous breakage. The design must also account for maintenance loads, since someone will eventually stand or kneel on the roof to clean it, and for wind suction. Our guide to structural glass explains how glass is engineered as a structural material rather than an infill.

Frame, structure and drainage

A glass roof needs a frame stiff enough to keep deflections within the glass supplier’s limits, typically steel or aluminium beams with glazing bars. The supporting structure has to carry the weight of the glass, which is considerable for laminated or double-glazed units, plus maintenance and wind loads, and its connections to the house must be detailed so the roof does not load walls never meant to carry it. In tropical conditions, corrosion protection of steel and the compatibility of metals at fixings matter.

Water management decides whether the roof is a success. A glass roof should have a clear fall, because flat glass collects water, dirt and leaves and stains quickly. Glazing bars and gutters must be sized for heavy rain, and silicone joints need correct design and periodic renewal. Where a glass roof joins an existing wall, the flashing detail at that junction is the most common leak point. If cost or weight is a concern, our article on polycarbonate roofs compares a lighter option, though it ages differently from glass.

Glass roof Singapore approvals: what to check

A glass roof is building work. Covering an open courtyard, airwell or back yard in a landed house can change gross floor area or the external appearance, so it may need planning permission from URA through a qualified person, and the structure normally needs plans endorsed by a Professional Engineer and submitted to BCA. Condominium owners will need MCST approval and must comply with URA’s controls on balconies and roof terraces. Our guide to landed house renovation in Singapore explains how these submissions fit together.

Frequently asked questions

Will a glass roof make my space too hot in Singapore?

It can, if clear glass is used without shading. A glass roof faces the high tropical sun directly. Solar control coatings, laminated or insulated units, and above all external shading are needed to keep the space comfortable.

What type of glass should be used for a glass roof?

Laminated glass is the usual engineering choice for overhead glazing because it stays in place when broken. It is often built from heat-strengthened or heat-soaked tempered panes and combined with a solar control coating to limit heat gain.

Are internal blinds enough to control heat under a glass roof?

Not on their own. Internal blinds reduce glare, but the solar heat has already passed through the glass by the time it reaches them. External shading or coated glass is far more effective at keeping heat out.

Does a glass roof need approval?

Usually, yes. It is building work that typically needs structural plans endorsed by a Professional Engineer, and covering an open space in a landed house may change gross floor area or appearance and need URA planning permission. Condominium owners also need MCST approval.

Why does my glass roof stain and leak?

Most often because the roof is too flat, the joints or flashings were poorly detailed, or the sealant has aged. A clear fall, adequately sized gutters and periodic resealing are the main remedies.

Designing a glass roof and want the glazing, structure and heat gain assessed together? Talk to our consultancy or get in touch.