Start with what you already know is wrong
If you've read our guide on the signs your windows need replacing and ticked off three or more of them, especially draughts plus stiff hardware plus a frame that's twenty years old or more, the diagnostic question is answered. What's left is timing and budget, which is what this guide is for.
If you're only seeing one isolated issue, like a single misted pane, it's worth ruling out a targeted repair before committing to a full replacement decision.
Age is doing more work than people think
A uPVC window fitted in the 1990s was built to a specification that predates modern Building Regulations Part L on thermal performance. Even a window with no visible fault will be losing considerably more heat than a current double or triple glazed unit with a low-E coating and a warm edge spacer, simply because the glass and gasket technology of the time was less capable.
As a rough guide, windows over 20 to 25 years old are worth assessing even without obvious symptoms, because the case for replacing them is increasingly about energy bills and comfort rather than waiting for something to break.
Reading the calendar
Window installation doesn't stop for weather, but it's slower and more disruptive in the depths of winter, when openings are exposed to cold and rain while the old frame is out and the new one is being fitted. Late spring through early autumn gives the most comfortable working conditions and the shortest exposure time per opening.
December is the worst month to try to book in, not because the work can't be done, but because everyone else has decided the same thing at the same time. Installers get booked solid through late autumn for jobs they want finished before Christmas, so if that's your target, get the survey done by late summer.
| Time of year to start | What to expect |
|---|---|
| Late spring to summer | Best working conditions, widest choice of fitting dates |
| Early autumn | Good conditions, book ahead if you want it done before winter |
| Late autumn | Booking pressure builds fast as people target Christmas |
| December | Longest waits, weather dependent scheduling, avoid if you can |
| January to February | Quieter for booking, but exposed openings during colder fitting days |
Whole house or phased, on a real budget
Doing the whole house in one visit is more efficient for the installer, which usually shows up as a better overall price, and it means no more juggling old and new frames side by side. It also means one lump sum, which not every household can find in one go.
Phasing works when you tackle the worst rooms first, typically the ones facing the prevailing weather or the ones with the most symptoms, and complete the rest over one or two further winters. The trade-off is doing more than one survey and fitting visit, and living with mismatched frames for longer. Neither approach is wrong, it comes down to what the budget can absorb this year versus next.
- Whole house: one survey, one fitting visit, typically the better unit price
- Whole house: no mismatched old and new frames sitting side by side
- Phased: spreads the cost over more than one year
- Phased: lets you prioritise the coldest or worst affected rooms first
- Phased: means at least two lots of survey and fitting disruption
Working out your own timeline?
Get a quote and we'll talk you through realistic timing for a survey and fitting, whether that's this month or planned for next spring.
What a 1990s frame is actually costing you now
It's worth separating the emotional case from the financial one. A 1990s frame with a failed gasket and single glazed sealed units, which was common at the time, is losing heat through both the frame material and the glass. That's a bigger factor in a cold room than most people assume, and it's one that gets steadily worse rather than staying constant, because gaskets and profiles continue to degrade with age.
Living with the disruption while you decide
Some households put replacement off simply because they're dreading the mess. In practice a well organised fitting visit deals with one opening at a time, so the rest of the house stays weathertight and usable while the job is under way. Dust sheets, a tidy work area and disposal of the old frames as part of the job are what to expect, not a house stripped bare for a week.
It's reasonable to ask at survey stage roughly how many openings can be done per day, so you can plan around school runs, working from home or anyone in the household who's particularly sensitive to noise and disruption.
Signs it's genuinely urgent rather than just due
Most of this guide is about weighing up timing when there's no emergency. Occasionally there is one: a cracked pane that's become a safety risk, a frame so rotten around the fixings that it's no longer secure, or water actively getting past the seal and into the wall. In any of those cases, the decision isn't really about the calendar any more, it's about getting someone out promptly rather than working through the rest of this framework.
- Urgent: cracked or broken glazing that's become a safety hazard
- Urgent: water penetrating past the seal into the wall or reveal
- Urgent: a frame so degraded it no longer locks securely
- Not urgent: cosmetic yellowing with no draughts or water ingress
- Not urgent: a single stiff handle or one whistling trickle vent
Getting a realistic figure before you commit
Once you've decided replacement makes sense, the next practical step is a survey rather than a guess from a brochure price. Window shapes, opening sizes and access all affect the final figure, and a survey is also the point where you'd raise anything urgent so it's dealt with as part of the same visit rather than separately.