Made-to-Measure Double Glazed Unit

First Six Months: Monthly Checks

Watching for Condensation

Condensation between panes indicates seal failure requiring complete unit replacement. Temporary external condensation is normal when outdoor temperature drops below dew point (typically below 5°C).

External condensation evaporates within 2-3 hours after sunrise. This is actually a good sign showing your glazing insulates effectively.

Testing Hardware Function

Window hardware should operate through 30 complete open/close cycles without resistance. Friction hinges maintain 90° opening position without sagging.

Increased resistance indicates debris accumulation in track channels. This requires cleaning to prevent hardware damage.

Every Three Months

Inspecting Seals

Perimeter seals should show no gaps, tears, or separation from the frame. Seal degradation appears as grey discolouration or hardening texture.

Replace seals at the first sign of deterioration. This prevents water ingress and maintains thermal performance.

Verifying Drainage

Weep hole covers should lift easily. Channels should drain within 30 seconds when you pour 50ml water into the frame cavity.

Blocked drainage requires clearing with a 5mm diameter nylon brush or compressed air at 30-40 PSI. Never use sharp metal objects that might damage drainage channels.

Lubricating Hardware

Friction stays, hinges, and locking mechanisms need lubrication. Apply 3-4 drops of 3-in-One oil per hinge point, or use PTFE-based dry lubricant.

Avoid WD-40 and petroleum-based lubricants. These attract dust and create gummy residue that degrades hardware function over time.

Twice a Year: Deep Clean

Cleaning Frames Properly

Wash frames with pH-neutral detergent (pH 6-8) diluted at 1:20 ratio with warm water (15-25°C). Use a soft cloth or sponge.

Never use abrasive cleaners containing pumice, silica, or alkaline compounds above pH 10. These etch uPVC surfaces and remove protective UV stabilisers that prevent yellowing.

Cleaning Glass Surfaces

Use microfibre cloths (300-400 GSM density) with 1:10 white vinegar solution. This removes mineral deposits without scratching Low-E coatings.

Overlap squeegee strokes by 20mm to prevent streaking. Avoid paper towels - their wood fibre content scratches soft Low-E coatings.

Conditioning Gaskets

EPDM and neoprene gaskets need silicone spray lubricant (silicone concentration 30-40%) to maintain flexibility. This simple step extends gasket life significantly.

Untreated gaskets harden within 5-7 years. Hardened gaskets lose compression properties and allow air infiltration that increases heating costs.

Annual Professional Check

Testing Thermal Performance

Thermal imaging identifies areas exceeding target U-value by more than 0.2 W/m²K. Double glazing should maintain 1.2-1.4 W/m²K. Triple glazing should maintain 0.8-1.0 W/m²K.

These values apply when glazing is properly installed and maintained according to manufacturer specifications.

Checking Seal Integrity

Inert gas concentration testing measures argon retention in sealed units. Argon concentration below 85% of original fill (starting at 90-95% fill) indicates seal breach.

This requires unit replacement within 12 months to prevent complete seal failure and internal condensation.

Adjusting Hardware

Euro-cylinder locks adjust at three points: height, width, and compression. Use a 4mm Allen key for adjustments.

Properly adjusted locks engage at 5-8mm penetration depth without forcing. Misadjustment causes lock mechanism failure within 3-4 years of installation.

Preparing for Installation

Understanding Frame Capacity

Your existing frames need proper assessment before new glazing installation. Triple glazing units weigh 28-32 kg/m², whilst double glazing weighs 18-20 kg/m². This weight difference matters significantly.

Timber frames older than 25 years require reinforcement. Steel or aluminium angle brackets install at 300mm intervals to support the additional weight. uPVC frames manufactured before 2002 lack internal reinforcement chambers and need complete replacement rather than retrofit.

Getting the Frame Square

Frame squareness directly affects glazing performance. Diagonal measurements must match within ±2mm for openings under 1200mm width. Larger openings allow ±3mm tolerance.

Out-of-square frames cause uneven seal compression. This irregularity reduces the expected 20-year lifespan down to just 8-12 years.

Setting Up Drainage

Proper drainage prevents water damage. Weep holes position at 600mm intervals along the bottom frame rail. Each hole measures 8mm diameter and angles 15° outward.

Blocked drainage allows water accumulation exceeding 200ml capacity. This leads to seal degradation within 18 months of installation.

Installation Process

Installing Glazing Beads Correctly

External glazing beads follow a specific sequence: bottom first, then sides, finally top. Internal beads reverse this order: top first, then sides, then bottom.

This sequence prevents glass unit sagging during installation. It maintains the critical 3mm minimum edge clearance around the entire perimeter.

Positioning Setting Blocks

Distance pieces position at quarter points along the bottom edge. Units under 1200mm width need two blocks. Units between 1200-2400mm require three blocks.

Setting blocks measure 25mm wide × 5mm thick. They use neoprene or EPDM rubber with Shore A hardness between 60-70.

Applying Sealants Properly

Low-modulus neutral-cure silicone applies at 6-8mm bead width with continuous coverage. Two-part polysulphide sealants cure at 3mm depth per 24 hours at 20°C ambient temperature.

Full cure takes 7-10 days. Avoid exposure to cleaning agents during this period.

Maintaining Edge Clearances

Glass edges maintain 3mm minimum clearance from frame on all sides. Inadequate clearance causes thermal stress cracking.

This cracking occurs when temperature differentials exceed 30°C between glass edges and centre pane.

Preventing Heat Loss

Insulating Frame Cavities

Frame cavities fill with polyurethane foam (0.024-0.028 W/mK thermal conductivity) or PIR board cut to exact dimensions. Gaps exceeding 2mm reduce frame U-value performance by 0.15-0.22 W/m²K.

Creating Expansion Gaps

Perimeter expansion gaps maintain 10-12mm width around the frame exterior. These fill with closed-cell polyethylene foam backer rod before external sealant application.

Temperature fluctuations cause uPVC frame expansion and contraction. Frames move 0.6mm per metre for every 10°C temperature change.

Required Documentation

Maintain installation certificates, warranty documents, and maintenance logs in a safe place. Warranty claims require evidence of annual maintenance.

This maintenance must be performed by qualified installers or documented DIY maintenance following manufacturer specifications exactly.

Actions That Void Warranties

Warranty exclusions include several specific actions. Never drill frame members or apply paint and coatings to uPVC surfaces.

Don't install aftermarket restrictors without manufacturer approval. Avoid abrasive cleaners and never attempt to modify sealed units yourself.

Inspection Requirements

Manufacturers require access for inspection within 10 working days of warranty claim submission. Failed units must remain in place until inspection occurs.

Retain failed units until replacement authorisation is provided. This typically takes 14-21 days from the inspection date.