uPVC top hung casement windows have become a preferred choice in Pakistan’s residential and commercial construction due to their durability, airtight performance, weather resistance, and low maintenance requirements. This type of window operates using a top-mounted friction hinge system, allowing controlled outward opening while maintaining structural stability and ventilation efficiency.

This technical guide provides detailed insights into design, functionality, installation standards, adjustment procedures, testing, typical failure points, and Pakistan-specific performance considerations.

Understanding the uPVC Top Hung Casement Window

1.1 Definition

A top hung uPVC casement window is a window in which the sash is hinged at the top and opens outward from the bottom. The system uses friction stays (hinges) engineered to hold the sash at various angles without the need for external support.

1.2 Working Mechanism

• The sash is supported by a pair of friction hinges, mounted at the top of the frame.

• As the handle rotates, the espagnolette or multipoint lock disengages.

• The sash opens outward, controlled by the tension in the friction stays.

• Ventilation is regulated by the hinge design, allowing partial or full opening depending on user preference.

1.3 Key Hardware Components

• Top-mounted stainless steel friction hinges (10–16 inches)

• uPVC sash and frame profiles

• Multipoint locking system

• Double or single glazing bead system

• Weather seals (EPDM gaskets)

• Reinforcement (GI or aluminum) inside uPVC profiles for structural rigidity

Technical Advantages of Top Hung Casement Windows

2.1 Optimal Ventilation Control

Top hung windows offer upward-directed airflow, ideal for:

• Kitchens

• Bathrooms

• Staircases

• High-rise buildings

Because the opening is at the bottom, air flows upward without causing direct drafts.

2.2 Monsoon-Proof Design

A significant advantage for Pakistan’s weather:

• The sash acts like a rain shield when opened.

• Prevents rainwater from entering due to the top hinge angle.

• EPDM gaskets ensure water-tight closures during storms.

2.3 Enhanced Acoustic & Thermal Performance

When paired with double glazing and proper gasket sealing:

• Reduces external noise by 25–35 dB.

• Provides excellent thermal insulation, reducing heat transfer in Lahore, Karachi, and Islamabad climates.

2.4 Structural Stability

Top hung designs distribute load evenly across hinges:

• Lower risk of sash sagging compared to side hung windows.

• Suitable for larger openings where horizontal stability is required.

Types of uPVC Top Hung Casement Windows

3.1 Single Sash Top Hung

Standard design for bathrooms, kitchens, and commercial ventilation zones.

3.2 Combination Top Hung + Fixed Panel

Common in modern homes:

• Large fixed glass panel for lighting.

• Smaller top hung window above for controlled ventilation.

3.3 Double Sash Top Hung Units

Two independent top hung sashes in one frame — used in wider window openings.

3.4 Custom Geometric Designs

Architects may specify:

• Arch top hung units

• Triangular top hung windows

• Trapezoid casement windows

Special hinges are used based on geometry.

When a uPVC Top Hung Window Needs Adjustment

4.1 Stiff Operation

Indicates:

• Insufficient lubrication
  

• Excessive friction hinge tension
  

• Accumulated debris in hinge arms
  

4.2 Sash Misalignment

Visible gaps on one side due to:

• Loose hinge screws
  

• Frame expansion (typical in hot climates)
  

• Incorrect factory calibration
  

4.3 Air or Water Leakage

Usually caused by:

• Gasket compression loss

• Improper sealant application around the frame

• Overuse of non-structural silicone
  

4.4 Rattling or Loose Sash

Due to loose friction hinge rivets or worn-out hardware.

Technical Guide: Adjusting uPVC Top Hung Windows

Required Tools

• Screwdriver set

• Allen key (4mm or 5mm)

• Silicone spray lubricant

• Measuring tape

Step-by-Step Adjustment

Step 1: Check Friction Hinge Tension

• Locate the friction adjustment screw on the hinge arm.

• Rotate clockwise to increase resistance.

• Rotate anti-clockwise to ease opening.

Step 2: Correct Sash Alignment

• Loosen the hinge screws slightly.

• Reposition the sash to achieve uniform gaps.

• Retighten screws with consistent torque.

Step 3: Inspect and Replace Gaskets

• Remove old EPDM gaskets if cracked or flattened.

• Install new ones ensuring no stretching occurs.

Step 4: Check Locking Points

• Ensure multipoint lock engages evenly.

• Adjust striker plates if misalignment occurs.

Installation Standards for Top Hung uPVC Windows

6.1 Pre-Installation Requirements

• Confirm plumb, level, and square opening.

• Allow 5–10mm tolerance for expanding foam or sealant.

6.2 Fixing Technique

• Use stainless steel fasteners.

• Maintain 150–200mm screw distance from each corner.

• Reinforcement must be securely anchored inside profiles.

6.3 Sealing & Waterproofing

• Apply polyurethane foam or backer rod around gaps.

• Finish with external-grade silicone for weatherproofing.

6.4 Post-Installation Testing

• Wind-load test

• Water penetration test

• Sash operational test

• Lock engagement verification
  

Cost of uPVC Top Hung Casement Windows in Pakistan

(Approximate ranges based on 2024–2025 market trends)

Best Glass Options for Top Hung uPVC Windows

8.1 Single Glazed (5mm–8mm)

Suitable for:

• Bathrooms

• Storerooms

• Non-critical openings

8.2 Double Glazed Units (DG)

• Improves thermal and acoustic performance.

• Ideal for bedrooms and lounges.

8.3 Laminated Acoustic Glass

Recommended for:

• Main roads

• Commercial buildings

8.4 Low-E Glass

Enhances energy efficiency during hot Pakistani summers.

Maintenance Guidelines

9.1 Lubrication

Use silicone spray (not WD40) on:

• Friction hinges

• Locking system

• Handle mechanism

9.2 Gasket Inspection

Replace if:

• Flattened

• Cracked

• Allowing water ingress

9.3 Annual Cleaning

• Remove dust from hinges.

• Clean uPVC surfaces with mild detergent.
  

9.4 Hinge Replacement Cycle

Typical lifespan: 5–8 years depending on usage and environment.

Common Problems & Troubleshooting

Issue 1: Water Leakage

• Check gasket compression.

• Inspect sealant joints.

• Ensure drainage slots are not blocked.

Issue 2: Window Not Closing Properly

• Realign sash.

• Adjust lock striker plates.

Issue 3: Hinge Noise

• Apply silicone lubricant.

• Check for worn rivets.

Frequently Asked Questions

Q1: Are top hung windows suitable for bathrooms?

Yes, they are ideal due to ventilation efficiency and rain protection.

Q2: What hinge size is best?

10", 12", and 16" hinges depending on window height and sash weight.

Q3: Can these windows handle strong winds?

Yes, friction hinges are engineered for high-pressure wind loads, suitable for high-rise buildings.

Q4: How long do uPVC top hung windows last?

The uPVC profile lasts 25–40 years, depending on exposure and hardware quality.

Conclusion

uPVC top hung casement windows offer a reliable, weather-resistant, and technically sound solution for modern Pakistani architecture. Their controlled ventilation, energy efficiency, and durability make them suitable for residential, commercial, and institutional building projects. With proper installation, periodic maintenance, and correct hardware selection, these windows deliver long-term performance even under Pakistan’s challenging climate conditions.