Sealed Units for Double Glazing
Sealed units for double glazing are essential window parts that sit at the heart of your uPVC double-glazed windows. These units consist of two panes of glass separated by a spacer bar, sealed around the edges to create an insulating barrier filled with argon gas. If you’re dealing with faulty uPVC window parts, understanding sealed units helps you pinpoint issues before calling in professionals like us at Window Repairs Sutton.
What It Is
A sealed unit, also known as a double glazed sealed unit, forms the glass component of modern double glazing. It traps a layer of air or inert gas between two glass sheets, bonded with a primary and secondary sealant to prevent moisture ingress and maintain thermal efficiency.
These replacement window parts are factory-assembled to precise standards, with the spacer bar often aluminium or warm-edge for better performance. Over time, seals can fail, leading to problems that affect your home’s comfort.
How To Identify It
Spotting a sealed unit is straightforward if you know where to look. Examine the space between your inner and outer glass panes on any double-glazed window – that’s your sealed unit.
Key identifiers include:
- A narrow aluminium or plastic spacer bar at the edges, visible when looking closely at the glass perimeter.
- Laser-etched markings on the glass corner, showing manufacturer details, glass type (e.g., toughened), and installation date.
- Uniform gap (typically 12-16mm) between panes, unlike single glazing.
If condensation appears inside this gap, it’s a telltale sign of failure – more on that later.
Compatibility Factors
Not all sealed units fit every window, so compatibility matters when sourcing replacement glass units. uPVC frames from standard casement or fixed designs are our focus, as we specialise in those at Window Repairs Sutton.
Consider these factors:
- Frame material and style: Matches uPVC frames only; we exclude sash, sliding, tilt-and-turn, or inward-opening windows.
- Glass specifications: Toughened, laminated, or low-E coated glass must align with original for safety and performance.
- Energy ratings: Modern units may have higher U-values, but retrofits need to fit existing rebates without frame alterations.
- Beading type: Clip-in or friction beading affects removal and installation ease.
Public liability insured and DBS-checked technicians ensure safe handling during any related work.
Measurements That Matter
Accurate measurements prevent costly errors with sealed units for double glazing. Always measure the existing unit after careful removal, not the frame opening.
Critical dimensions include:
- Width and height: Overall size in millimetres, measured edge-to-edge on the internal faces.
- Spacer bar width: Typically 11mm to 20mm, dictating the air gap and insulation properties.
- Unit thickness: Total depth (glass + spacer + seals), usually 24-36mm for double glazing.
- Glass thickness: Each pane often 4mm, but varies (e.g., 6mm for acoustic units).
Use a tape measure and note any bevels or steps. For precision, our local Sutton team can assist after initial contact.
Common Naming Confusion
Sealed units spark frequent mix-ups in searches for replacement window parts. People often call them “double glazed sealed units,” “IGUs” (insulated glass units), or simply “glass packs.”
Other confusions:
- Blown double glazing: Refers to a failed sealed unit, not the whole window.
- Misted unit: Same as a sealed unit with internal condensation.
- Double glazing glass: Broad term, but technically it’s the sealed unit inside.
This jargon can complicate DIY fixes – stick to pros for misted unit replacement or blown unit replacement.
Symptoms It Can Cause
A failing sealed unit impacts your home noticeably, often starting subtly. Internal moisture is the classic red flag, linked to our misted double glazing symptoms page.
Common signs include:
- Condensation between panes: Frosty or misty appearance inside the unit, worsening in cold weather.
- Draughts and cold spots: Lost insulation lets heat escape, raising energy bills.
- Noise increase: Reduced soundproofing as the airtight seal breaks.
- Visual distortion: Water droplets or black spots from desiccant failure.
- Foxing or discolouration: Spacer bar corrosion visible at edges.
Early detection avoids escalation – our 10+ years’ experience handling uPVC repairs spots these quickly.
Related Repairs
When sealed units fail, double glazed unit replacement is the go-to fix among our core services. This involves removing the old replacement glass unit, fitting a matching new one, and resealing into the uPVC frame.
We handle misted, blown, or cracked units with:
- Precise matching to your measurements.
- Draught proofing checks during the process.
- No glass clean-up promises, but efficient replacement.
As liability insured locals in Sutton, we focus on practical uPVC solutions. Contact us on 020 8138 0796 or info@window-repairs-sutton.co.uk for advice.
FAQs
What causes sealed units for double glazing to fail?
Seal degradation from temperature extremes, poor installation, or manufacturing defects allows moisture in. Expect 10-25 years lifespan, depending on quality.
Can I replace a double glazed sealed unit myself?
DIY is possible for handy homeowners with tools, but risks frame damage or mismatched units. Pros ensure compatibility and safety.
How much does misted unit replacement cost?
Costs vary by size and specs – get a quote tailored to your uPVC windows. We provide transparent pricing post-inspection.
Do you repair wooden or sash windows?
No, our services exclude wooden, sash, sliding, tilt-and-turn, or inward-opening windows – uPVC only.
How do I measure for a replacement glass unit?
Remove beading, measure the unit’s width, height, and depth internally. Note glass type from etchings for exact matches.
Is warm-edge spacer better than aluminium?
Warm-edge reduces cold bridging for improved efficiency, but both work if seals hold. Discuss options during repairs.
For Sutton uPVC window issues, reach out via /contact/ – our team is ready to help.
