Windows in Hong Kong: More Than Just a View
Windows are one of the most important building components in Hong Kong. They must withstand typhoons with wind speeds exceeding 200 km/h, keep out torrential rain during the wet season, provide thermal insulation against summer heat, and meet stringent safety regulations in a city of high-rise buildings. Choosing the wrong windows—or neglecting their maintenance—can have serious consequences, from water ingress and energy waste to the catastrophic danger of a window falling from a high floor.
This guide will help you understand your options and obligations when it comes to windows in your Hong Kong home.
Aluminium vs UPVC: The Two Main Frame Materials
Aluminium Windows
Aluminium is by far the most common window frame material in Hong Kong, used in over 90% of residential buildings. Here's why:
- Strength-to-weight ratio: Aluminium frames are lightweight yet strong, making them ideal for large openings and high-wind environments.
- Corrosion resistance: With proper anodising or powder coating, aluminium resists Hong Kong's salt-laden coastal air. This is critical for buildings near the harbour or on exposed hillsides.
- Slim profiles: Aluminium allows for narrower frame sections, maximising the glass area—an important consideration in small HK flats where every bit of natural light matters.
- Wide availability: Being the industry standard, there is a vast range of aluminium window systems, hardware, and replacement parts available locally.
Drawbacks: Aluminium conducts heat readily. Without a thermal break (an insulating barrier within the frame), aluminium windows transfer heat into your flat during summer, increasing air conditioning costs. Thermal-break aluminium windows are available but cost 20–40% more than standard profiles.
UPVC Windows
UPVC (unplasticised polyvinyl chloride) windows are gaining some ground in Hong Kong, particularly in renovation projects. Their advantages include:
- Superior thermal insulation: UPVC frames have inherently low thermal conductivity—up to 1,000 times lower than aluminium. This can reduce air conditioning loads noticeably.
- Good sound insulation: The multi-chambered design of UPVC profiles, combined with double glazing, provides excellent noise reduction—a major benefit in Hong Kong's noisy urban environment.
- Low maintenance: UPVC does not corrode, peel, or need repainting. A wipe with soapy water is all the maintenance required.
Drawbacks: UPVC frames are bulkier than aluminium, reducing the glass-to-frame ratio. They can discolour (yellow) with prolonged UV exposure, though modern formulations have largely addressed this. UPVC is also less commonly available in HK, meaning fewer suppliers and potentially higher costs. Finally, some management offices and deeds of mutual covenant (DMCs) restrict window material choices to maintain building aesthetics.
Understanding Typhoon Ratings and Wind Load
Hong Kong's Buildings Department requires windows to be designed to withstand specific wind pressures based on the building's height, location, and exposure. The relevant standard is the Code of Practice on Wind Effects issued by the Buildings Department.
- Design wind pressure: For a typical residential building, the design wind pressure can range from 1.5 kPa to over 3.0 kPa depending on height above ground and terrain category. Upper floors of coastal high-rises face the most demanding requirements.
- Testing standards: Windows should be tested to relevant standards such as BS EN 12211 (wind resistance), BS EN 12208 (water tightness), and BS EN 12210 (classification of wind resistance). Ask your window supplier for test certificates.
- Hardware matters: Window stays (friction hinges), locks, and gaskets are critical to wind resistance. A window is only as strong as its weakest component. During typhoon season, ensure all windows close and lock securely. Replace worn gaskets and tighten loose friction stays before the first signal is hoisted.
The Mandatory Window Inspection Scheme (MWIS)
Introduced in 2012 under the Buildings Ordinance (Cap. 123), the MWIS requires owners of buildings aged 10 years or above to have their windows inspected by a Qualified Person (QP)—either a Registered Inspector, Registered Structural Engineer, or Authorised Person—when notified by the Buildings Department.
Key points about the MWIS:
- The Buildings Department issues notification letters to selected buildings each year. Once notified, owners have six months to complete the inspection and any required repairs.
- The inspection covers all external windows of the flat, including aluminium windows, metal-framed windows, and their components (glass, hinges, rivets, screws, and sealant).
- Common defects found during inspections include loose or missing rivets, corroded friction stays, deteriorated rubber gaskets, cracked glass panes, and defective window locks.
- If defects are found, the QP will prescribe repair works. These repairs must be carried out by a Registered Contractor and completed within the prescribed timeframe.
- Failure to comply with the statutory notice is a criminal offence, punishable by a fine of up to HK$50,000 and imprisonment for up to one year.
Practical Window Maintenance Tips
- Check friction stays annually: Open each window to its maximum and check if the friction stay holds the window in place. If the window sags or swings freely, the friction stay needs tightening or replacement.
- Inspect rubber gaskets: The gaskets (rubber seals) around the glass and between the sash and frame prevent water ingress. If they are cracked, brittle, or missing, replace them before the rainy season.
- Clean drainage holes: Aluminium window frames have small drainage holes (weep holes) at the bottom to allow accumulated rainwater to drain out. Ensure these are not blocked by dirt or paint.
- Check rivets and screws: Over time, vibrations from wind and daily use can loosen the rivets and screws that hold the window sash together. Check them annually and tighten or replace as needed.
- Lubricate moving parts: Apply silicone spray to hinges, friction stays, and locking mechanisms once a year to ensure smooth operation.
Cost Guide for Window Replacement in Hong Kong
Window replacement costs vary widely based on the type, size, and access difficulty. As a general guide:
- Standard aluminium casement window (3ft x 4ft): HK$2,500–4,500 installed
- Aluminium sliding window (3ft x 4ft): HK$2,000–3,500 installed
- Thermal-break aluminium window: Add 20–40% to standard aluminium prices
- UPVC window: HK$4,000–7,000 installed (for the same size)
Note: for high-floor units, scaffolding or gondola access may be required, adding significantly to the cost. Always obtain multiple quotations and check that your contractor is a Registered Minor Works Contractor (if the window replacement qualifies as minor works under the Buildings Ordinance).