§ Free quote
What does replacing windows cost?
Information checked on 20 August 2026
Nobody can give a price over the phone, and an installer who does is guessing. The figure depends on the material, the dimensions, the glazing, access to the site and the finishing — six things visible on site in twenty minutes. Here is what moves the price, what a serious quote contains, and the questions to ask before you sign.
Why a price over the phone does not exist
Two flats on the same street, six windows each, can differ by a factor of two. One has straight openings on the first floor, the other arched ones on the fourth with no lift, and a reveal that has to be rebuilt from scratch.
An installer who names a figure without seeing the openings is doing one of two things: quoting the simplest case to win the appointment, or padding the number to stay safe. Either way it has nothing to do with your job.
The six things that set the price
- The material. PVC, aluminium, wood: at equal size the gap is wide, and it is not only the purchase price — fitting and finishing differ too.
- Size and shape. A three-metre sliding unit is not three one-metre windows. Arches, transoms and corners mean bespoke fabrication.
- The glazing. Double or triple, acoustic or not, with or without solar control. This is where people save most easily — and regret most often.
- Access. Fourth floor without a lift, narrow street with no parking, façade on the pavement: hoisting, a platform and a permit to occupy the road are real lines on a quote.
- The state of the reveal. If the edge is sound, finishing is quick. If it is cracked, damp or patched up before, it has to be redone — often exactly the difference between two quotes that looked close.
- Finishing and disposal. Silicone, wood or plasterboard, repainting or not, taking the old frames away: these exist on every job but do not appear on every quote.
VAT at 6 % instead of 21 %
For a home first occupied at least ten years ago and used mainly as private housing after the work, replacing windows falls under the reduced rate of 6 %. Across a full job, the gap with 21 % is worth considerably more than one window.
Two practical conditions people often discover too late: the contractor must supply and invoice the materials together with the fitting — if you buy the windows yourself, only the labour goes to 6 %. And since 1 July 2022 the invoice must carry a statement that the conditions are met.
We apply the reduced rate as soon as your situation allows, and we check it before drawing up the quote, not after.
What our quote contains
- The exact number of openings with dimensions measured on site, not estimated.
- The profile system and glazing type, named precisely.
- Removal of the old frames and their disposal.
- Interior and exterior finishing, in the material stated.
- Manufacturing lead time and the length of the job.
- The VAT rate applied and why.
- The final figure. The one on the quote is the one on the invoice: any extra work is agreed with you before it happens.
Comparing two quotes without being in the trade
The cheapest quote is usually the least complete. These questions expose the difference in five minutes, whoever the installer is.
- 01Is disposal of the old frames included, or billed separately?
- 02Is finishing of the reveals in the price? In which material?
- 03Which glazing exactly — thicknesses, gas, coefficient?
- 04Which VAT rate applies, and on what basis?
- 05What happens if the reveal turns out to be damaged once the old frame is out?
- 06Who fits: your own teams or a subcontractor?
- 07What guarantee on the fitting, and what manufacturer guarantee on the window?
- 08Can the figure change after signing, and in which cases?
Questions about price
Is the quote free?
Yes. The visit, the measurements and the written quote are free and carry no obligation, in Brussels and elsewhere in Belgium.
Can you give a ballpark before the visit?
On the phone we can tell you which material and glazing suit your situation and what will weigh on the budget. A figure, no — it would be invented.
Does everything have to be replaced at once?
No. Many jobs run in two phases: the most exposed façade first, the rest the following year. The price per window is slightly higher, but spreading it is sometimes wiser than borrowing.
Is triple glazing worth the price?
Not always. In Brussels renovation the comfort gap between good double and triple is small if the walls do not keep up, while the extra cost is real. We say so when that is the case.
Are there still grants?
Rénolution grants no longer exist for work invoiced in 2025 or 2026, but four mechanisms remain open. The detail is on our dedicated page.
Also worth reading: Grants and reduced VAT
A figure for your job, not for an average one
We come and measure, look at the state of the reveals and the access, and you receive a written quote with the final figure. Free, no obligation.
The VAT conditions described here are those in force on the date shown and fall under Belgian federal rules. They do not replace advice from your accountant.
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