Why East and West Façades Are Different
In Muscat, Dubai and Abu Dhabi, the sun is high in the sky at midday, so south-facing glass can be shaded with relatively simple overhangs. In the morning and afternoon, however, the sun is low in the east and west. Its rays strike east and west façades almost perpendicularly and reach deep into rooms.
West façades are usually the most demanding: they receive the strongest sun in the afternoon, when outdoor temperatures peak and the building has already absorbed heat all day. East façades bring intense morning sun and glare into bedrooms and offices.
Glass on these elevations needs to be chosen deliberately, not left as the same clear glass used elsewhere.
The Key Glass Properties
Solar Heat Gain: SHGC and g-value
The solar heat gain coefficient (SHGC) is the fraction of solar energy striking the glass that ends up inside the room as heat — both transmitted directly and absorbed then re-radiated inward. The European equivalent is the g-value; for practical comparison the two are treated as approximately the same quantity, expressed as a number between 0 and 1.
A lower SHGC means less solar heat enters. For hot east and west façades, this is the single most important property.
Visible Light Transmission (VLT)
VLT is the percentage of visible daylight that passes through the glass. Higher VLT gives brighter rooms and better views; very low VLT makes rooms dim and can lead to lights being used during the day.
Light-to-Solar-Gain Ratio
Good solar control glass lets through a relatively large share of light while blocking a large share of heat. The ratio of VLT to SHGC — sometimes called the LSG ratio — is a useful way to compare products: a higher ratio means more daylight for the same heat gain.
Reflectance
External reflectance is how much light the outer surface reflects. Highly reflective glass reduces heat gain but gives a mirror-like appearance and can cause glare for neighbours and roads. Some authorities and developments limit external reflectance, so check local requirements with your consultant.
U-value
The U-value measures heat transfer due to the temperature difference between inside and outside. In the Gulf, where it can be far hotter outside than inside for much of the year, a lower U-value also helps, but on sun-exposed façades the SHGC usually has the bigger effect.
Coatings: Tinted, Reflective, Low-E and Solar Control
- Tinted glass is coloured in the body of the glass. It absorbs part of the solar energy, reducing heat gain moderately, but also reduces light and gets hot itself
- Reflective glass has a metallic coating that reflects solar energy. It achieves low SHGC but often at the cost of low VLT and high external reflectance
- Low-E glass has a microscopically thin coating that reduces radiant heat transfer, improving the U-value
- Solar control Low-E (often called spectrally selective) coatings are designed to transmit much of the visible light while reflecting a large part of the infrared heat. For hot climates, these generally offer the best balance of daylight and heat control
Coatings are normally placed on an inner surface of a double-glazed unit, where they are protected. The coating position affects performance, so it should follow the glass manufacturer's guidance.
Typical Glass Types and When to Use Them
The values below are typical ranges for common glass types in a standard double-glazed unit unless noted. Actual values depend on the specific product, thicknesses and coating, and must be confirmed from the glass manufacturer's data for each project.
| Glass type | Typical SHGC / g-value | Typical VLT | Typical use |
|---|---|---|---|
| Single clear glass | Typical 0.75–0.85 | Typical 85–90% | Not recommended for air-conditioned rooms on sun-exposed façades |
| Double glazing, clear | Typical 0.65–0.75 | Typical 75–80% | North façades and shaded areas |
| Double glazing, tinted outer pane | Typical 0.40–0.55 | Typical 35–60% | Moderate solar control where some tint is acceptable |
| Double glazing, reflective coating | Typical 0.20–0.35 | Typical 10–35% | Very high exposure where low light is acceptable; check reflectance limits |
| Double glazing, solar control Low-E | Typical 0.25–0.40 | Typical 40–70% | East and west façades of villas and buildings — the usual first choice |
| Triple glazing with solar control coating | Typical 0.20–0.35 | Typical 35–60% | High-performance projects, acoustic needs or demanding energy targets |
Double vs Triple Glazing in the Gulf
Triple glazing is common in cold climates mainly to reduce heat loss. In the Gulf, the main problem is solar gain, which depends primarily on the coating rather than the number of panes. A good solar control double-glazed unit is usually the most cost-effective solution.
Triple glazing can still make sense where:
- Very demanding energy or green building targets apply
- Acoustic performance is critical, for example near airports or highways
- Very large glazed areas face east or west and cannot be shaded
Triple glazing is heavier, so the frame and hardware must be designed for it. For example, the T127-90 thermal break lift & slide door accepts 5+20A+5 double glazing or triple glazing and supports panels up to 400 kg.
Shading Comes First
No glass can match the effect of stopping the sun before it reaches the window. On east and west façades consider:
- Vertical fins or screens, which work better than horizontal overhangs against low sun
- Deep reveals that set the window back into the wall
- External louvres or mashrabiya-style screens
- Planting and pergolas for ground-floor openings
- Reducing glass area on the west façade and placing large glazing to the north
Internal blinds help with glare but are much less effective at blocking heat, because the solar energy has already passed through the glass.
Do Not Forget the Frame
Even with excellent glass, a non-insulated aluminium frame conducts heat into the room. On hot façades, combine solar control glass with a thermal break frame such as the S11, X11, F16 or Q35 casement windows, and ensure good sealing so that hot, humid air does not leak in.
Practical Checklist for East and West Façades
- Specify a solar control Low-E double-glazed unit as the starting point
- Compare products by SHGC, VLT and their ratio, not by colour alone
- Check external reflectance against local authority and developer requirements
- Use tempered or laminated glass where safety rules require it
- Add external shading wherever the design allows
- Use thermal break frames sized for the glass weight
- Approve a physical glass sample, viewed outdoors, before ordering
Alminyar Recommendation
For west- and east-facing façades in Muscat, Dubai and Abu Dhabi, we recommend solar control Low-E double glazing in a thermal break frame, combined with external shading wherever possible. Reserve triple glazing for projects with demanding energy, acoustic or large-glass requirements. Share your elevations with us and we will propose glass make-ups for each façade, based on the manufacturer's published data rather than generic assumptions.