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Is Replacing Double Glazed Units Cheaper Than New Windows?
Last Updated: November 1, 2026
Quick Summary
Replacing double glazed units costs £90-£250 per unit fitted, depending on size and glass specification, while supply-only units are cheaper because you pay for glass rather than labour. Replacing the sealed unit rather than the whole window can cost up to 50% less, according to a supplier claim cited by Williams Windows.
- A failed sealed unit usually takes 30 to 60 minutes per unit to swap once it is on site.
- Misted units cannot be repaired, so replacement is the only durable fix.
- Re-gasketing and resealing a sound window typically costs £40-£120 per window.
- Ask for an itemised quote covering glass specification, access, disposal and warranty.
- Replacement glazing in critical locations must meet Approved Document K of the Building Regulations.
Table of Contents
- What Drives the Cost of Replacing Double Glazed Units
- Cost to Replace Double Glazing Glass: Supply-Only vs Fitted
- Misted Double Glazing Replacement Cost and When Repair Is Possible
- Can You Replace Double Glazing Without Replacing the Frame?
- Double Glazed Unit Replacement Time: What to Expect on the Day
- Itemised Cost Breakdown: Labour, Glass and Extras
- Request a Free, No-Obligation Glazing Quote
- Frequently Asked Questions
What Drives the Cost of Replacing Double Glazed Units
The cost of replacing double glazed units depends on unit size, glass specification, frame condition and whether you buy supply-only or fitted. The glass itself is rarely the expensive part. Access, specification and frame condition decide the final figure.
A sealed unit is the factory-made glass sandwich, two panes held apart by a spacer bar and sealed around the edge. Replacing that unit is a different job from replacing a whole window, and the price difference is large. MyJobQuote's window glass replacement guide puts the average cost of replacing blown windows at around £70, though it does not state whether that figure covers a complete sealed unit or glass-only work.
Quotes vary for several reasons. Below, we break down what moves the number.
Unit Size, Glass Specification and Frame Condition
Three things push a unit replacement quote up or down.
Size. A small box bedroom window unit and a wide bay window unit use different quantities of glass, spacer and sealant.
Specification. Standard clear double glazing is the baseline. Toughened glass is a legal requirement in critical locations under Approved Document K of the Building Regulations, so bathroom and low-level units often cost more than a standard bedroom unit of the same size.
Frame condition. A sound uPVC frame takes a new unit easily. A timber frame with rot, or one twisted out of square, may need repair before any glass goes in.
| Cost factor | Effect on price | Why it matters |
|---|---|---|
| Unit size | Larger = higher | More glass, two-person handling |
| Glass specification | Toughened, laminated, acoustic = higher | Safety rules and performance upgrades |
| Frame condition | Rot or distortion = higher | Repair work before glazing |
| Access (height, obstructions) | Difficult access = higher | Scaffolding or extra labour time |
| Supply-only vs fitted | Fitted = higher | Labour and disposal included |
Cost to Replace Double Glazing Glass: Supply-Only vs Fitted
Supply-only means you buy the sealed unit and fit it yourself. Supplied-and-fitted means a glazier measures, supplies and installs it.
The gap is real. Checkatrade's window glass replacement guide puts supply-only single-pane glass at roughly £25, against around £100 to supply and install the same pane.
For sealed units, the same principle applies. Supply-only suits a confident DIYer with a sound frame and a standard-size opening.
Misted Double Glazing Replacement Cost and When Repair Is Possible
Misted double glazing means the seal has failed and moisture has entered the cavity between the panes. Once that happens, the unit cannot be repaired. Our guide to fixing misted double glazing units covers diagnosis, repair vs replacement and costs. The desiccant is saturated and the insulating gas is gone. Replacement is the usual fix.
How to tell a failed sealed unit from a frame problem
The diagnosis matters more than the quote, because the two faults carry very different prices. A failed sealed unit shows these signs:
- Condensation between the panes, inside the glass sandwich, not on either surface. This is the definitive sign of seal failure.
- A chalky white or grey haze across the inner glass face, caused by the desiccant breaking down.
- A visible mist or water droplets that do not clear on a warm day.
A frame or fitting problem looks different:
- Draughts around the edge of the glass rather than through it, usually perished gaskets or failed sealant.
- Condensation on the room-side surface only, which points to ventilation and humidity rather than the unit.
- Sticking or dropping hinges, which are hardware faults, not glass faults.
If the mist is between the panes, you need a new unit. If the problem is the frame, the hinges or the seal around the glass, a repair may do the job for less.
Typical cost ranges by fault type
| Fault | Typical fix | Indicative fitted cost |
|---|---|---|
| Failed sealed unit (misted) | New sealed unit, frame retained | £90-£250 per unit, depending on size and glass spec |
| Cracked pane in a sound unit | New unit (glass cannot be patched safely) | £90-£250 per unit |
| Perished gasket or sealant | Re-gasket and reseal | £40-£120 per window |
| Dropped or stiff hinge | Hinge replacement or adjustment | £50-£150 per window |
| Frame rot in the rebate | Cut out and splice, or new frame section | £120-£400+ per window |
| Whole-window replacement (frame failed) | New window supplied and fitted | £300-£900+ per window |
Settle the diagnosis before agreeing the quote, because a quote for a new unit will not fix a frame fault and a frame repair will not clear misted glass.
Why a misted unit cannot be repaired
A sealed unit is a closed system. The spacer bar contains desiccant that absorbs residual moisture at manufacture, and the cavity is filled with air or an insulating gas such as argon. When the perimeter seal fails, moisture enters, the desiccant saturates and the gas escapes. There is no practical way to dry the cavity, recharge the desiccant and re-gas a unit on site.
When repair is the cheaper answer
Repair beats replacement when the glass is sound and the fault is in the frame, the hardware or the perimeter seal. A re-gasket and reseal on a sound uPVC window can solve draughts and edge condensation. A hinge replacement restores operation without touching the glass. The rule of thumb most glaziers use: if the mist is inside the glass, replace the unit; if the problem is around the glass, repair the frame.
Can You Replace Double Glazing Without Replacing the Frame?
Yes, you can replace double glazing without replacing the frame in most cases. You can get replacement double-glazed units in Leicester and surrounding areas from JJ's Glass and Glazing.
This is the single biggest saving available. A supplier claim cited by Williams Windows states that replacing the sealed unit rather than the whole window can cost up to 50% less while delivering nearly the same energy-saving benefit.
Frames that usually accept a new unit:
- Sound uPVC frames with intact gaskets
- Aluminium frames without corrosion at the rebate
- Timber frames with solid, dry timber around the opening
Frames that usually do not:
- Frames that are bowed, cracked or out of square
- Timber frames with rot in the rebate
- Old frames where the gasket has perished beyond reuse
Double Glazed Unit Replacement Time: What to Expect on the Day
A double glazed unit replacement typically takes 30 to 60 minutes per unit, according to MyJobQuote's cost guide. That estimate covers the swap itself once the unit is on site.
Here is how the visit usually runs:
- Measure and confirm. The glazier checks the opening against the order, usually a few minutes.
- Protect the area. Floor coverings down, furniture moved back.
- Remove the old unit. Beading or putty comes away, the failed unit lifts out.
- Clean the rebate. Old sealant and debris cleared so the new unit seats properly.
- Fit and seal. New unit set, beading refitted, sealant applied.
- Clean and check. Glass cleaned, operation checked, old unit taken away.
Two things stretch the timeline: lead time on the unit itself, which depends on size and specification, and access. A first-floor window with clear access is quick. A bay window or a unit behind a conservatory roof is not.
Itemised Cost Breakdown: Labour, Glass and Extras
A good glazing quote separates the parts. Ask for it itemised, and you can see exactly what you are paying for. Here is what a fitted sealed unit quote should show.
| Line item | What it covers | Indicative amount | What to check |
|---|---|---|---|
| Glass unit | The sealed unit itself, sized and specified | £45-£150 per unit | Specification stated (toughened, low-E, acoustic, gas fill) |
| Measuring and survey | Site visit, template or dimensions | Often free, sometimes £30-£60 | Whether it is deducted from the order |
| Labour | Removal, fitting, sealing, making good | £40-£90 per unit | Number of units and estimated time on site |
| Sealant and beading | New gaskets or beading where needed | £10-£30 per unit | Whether reuse or replacement is priced |
| Access equipment | Scaffolding, tower or ladders for high or awkward windows | £0-£250+ per job | Whether it is included or extra |
| Disposal | Removal and recycling of the old unit | £5-£20 per unit | Whether the old unit is taken away |
| Frame repair | Any rot or distortion work | £60-£300+ per window | Priced separately, not bundled |
| Call-out or minimum charge | Attendance for small jobs | £0-£80 | Whether it applies and when |
What a quote should state explicitly
A quote you can compare like-for-like will answer these questions on the page:
- Who measures? If you supply dimensions and they are wrong, who pays for the remake? A fitted quote should include the measure.
- What glass specification? "Double glazed" is not a specification. Look for the make-up: pane thickness, cavity width, coating (low-E), gas fill, and whether toughened or laminated glass is required.
- Is access included? First-floor windows, bays and units above a conservatory roof may need a tower or scaffolding. If it is not priced, it is extra.
- Is disposal included? Old units are bulky and not accepted in normal household waste in most areas. Confirm removal is in the price.
- What is the warranty? Ask what guarantee covers the sealed unit and the installation, and get the terms in writing.
- What happens if the frame needs repair? The answer should be a priced contingency, not a shrug.
- Is the work compliant? Replacement glazing in critical locations must meet Approved Document K of the Building Regulations, and replacement units should meet the thermal performance requirements in Approved Document L where applicable. Ask for confirmation that the specification meets both.
Red flags in a quote
- One lump sum with no breakdown. Hard to compare and easy to inflate.
- No specification line. A cheap quote often hides a thinner glass make-up or a missing gas fill.
- Access and disposal excluded. These are real costs that reappear later.
If you have follow-up questions about units, repairs and what we cover, our glazing FAQs for Leicester answer the common ones.
Request a Free, No-Obligation Glazing Quote
Comparing quotes is the only reliable way to know what your job should cost. Get two or three, itemised, and check the specification line on each one.
We offer free, no-obligation quotes across Leicester and Leicestershire for homes and businesses. That includes emergency glazing, replacement double glazed units, glass repairs, bespoke mirrors and splashbacks, and high-security window and door locks.
Frequently Asked Questions
Is it cheaper to replace the glass or the whole window?
Replacing just the sealed unit is almost always cheaper than a full window swap because you keep the existing frame and skip the fitting labour. For a sound frame, replacing double glazed units is generally the lower-cost route.
How much does it cost to replace just the glass in a window?
Costs vary with unit size, glass specification and whether you buy supply-only or fitted. Ask for an itemised quote so you can see the glass, labour and any extras separately.
How long does it take to replace a double glazed unit?
Replacing a sealed unit involves removing the old unit, cleaning the rebate and fitting the new sealed unit. Bay windows, odd-shaped frames or units needing new beading can take longer.
Can misted double glazing be repaired, or does the unit need replacing?
Misting means the seal has failed and moisture has got between the panes. In most cases the sealed unit itself needs replacing rather than repairing, because the insulated glass unit is factory-sealed. A glazier can confirm whether the frame is still sound; if it is, only the unit changes and the frame stays put. If the frame has warped or rotted, a full window replacement may be the better long-term option.
What affects the cost of replacing a double glazed unit?
The main factors are unit dimensions, glass specification, frame condition and access. Larger or non-standard sizes cost more, and upgrades such as low-emissivity glass, acoustic glazing or toughened safety glass add to the price. The number of units replaced in one visit spreads the labour cost. Access matters too: upstairs windows, bay windows and commercial shop fronts take more time. Ask for a free, no-obligation quote based on your actual measurements rather than a phone estimate.
Replacing a misted or failed unit is a smaller job than most homeowners expect, and keeping a sound frame keeps the bill down. The hard part is knowing which quotes are like-for-like. JJ's Glass & Glazing can help you compare properly, with free no-obligation quotes, on-site measuring and a clear specification before any work starts. Get started with JJ's Glass & Glazing and request a quote for your windows today.
