Window and door quotes: what to check before you sign

A windows and doors quote should be a technical document, not a slip of paper with a lump-sum price and two lines of description. Yet it’s common for a customer to receive three very different offers with no real idea of what they’re actually comparing: different profiles, different glazing, installation included in one and excluded in another. The result is that people end up choosing the lowest number, which is almost always the lowest precisely because something is missing.

This article is an operational checklist: which line items must appear in black and white before you sign, how to spot a quote that’s too vague or suspiciously cheap, and how to put three offers on the same comparison basis. This isn’t about how to choose the product (you’ll find that in our guide to choosing the right windows and doors): here the focus is the document you’re holding just before putting pen to paper.

Why the quote is where everything is decided

When you sign, you’re accepting exactly what’s written. Not what you were told verbally in the showroom, not what you think you understood: what’s written. If the quote doesn’t state that the glass is triple-glazed, you might end up with double glazing. If it doesn’t state “installed to UNI 11673”, the installation could turn out to be nothing more than a few screws and a bead of silicone.

There’s one underlying rule: everything that matters must be written down and quantified. A serious quote isn’t afraid of detail, because the supplier already knows exactly what they’re going to install. A vague quote, by contrast, leaves room for manoeuvre for whoever wrote it — not for you.

The line items that MUST appear in black and white

Here are the items a complete quote should state explicitly. Use this table as a reading grid: for each row, check whether the information is there and whether it’s specific.

Item	What must be written	Why it matters
Material and profile system	Material (PVC, aluminium…) and exact name of the system/series (e.g. a specific Salamander series)	“PVC” on its own says nothing: profiles vary enormously
Thickness and chambers	Frame depth in mm and number of chambers	Indicates the profile class and affects insulation
Declared Uw value	Thermal transmittance of the finished window (Uw), not just the glass	Uw is the figure for the complete product; Ug is the glass alone
Type of glazing	Composition (e.g. double/triple, low-emissivity, gas fill, warm edge) and Ug	The item most easily “saved on” by lowering quality
Hardware and brand	Manufacturer and type (tilt-and-turn, locking points, any burglary-resistance class)	Determines security, durability and ease of operation
Installation	Installation to UNI 11673, with detail on tapes/sealants and disposal of old windows	Installation matters as much as the window itself: see below
CE marking / DoP	Reference to CE marking under EN 14351-1 and availability of the Declaration of Performance	A legal obligation for construction products, not an optional extra
Quantity and dimensions	Number of units, sizes (even if subject to confirmation on final survey), opening type	Without dimensions, prices aren’t comparable
Timescales	Indicative delivery and installation times	Avoids surprises with site planning
Warranties	Duration and scope (profile, hardware, installation)	A generic “guaranteed” claim isn’t a warranty
Payment terms	Deposit, balance, method, any penalties	Protects both parties

Some of these items deserve a closer look.

Uw, not just Ug

This is the most common misunderstanding. Ug is the thermal transmittance of the glass alone; Uw is that of the complete window (glass + frame + spacers). A quote that only flaunts a very low Ug is showing you the best figure, not the real one: the frame and thermal bridges always worsen the overall value. Insist on the Uw of the finished window. If you want to understand why this number matters and how much it changes depending on climate zone, there’s a dedicated deep dive on thermal insulation and climate zones.

UNI 11673 installation

This is the item that most often disappears from discount quotes. Installation to the UNI 11673 code of practice requires correct sealing at three levels (internal, central, external) using suitable tapes and materials, not just foam and silicone. A poorly done installation undermines even the best window: condensation, draughts, mould in the corners. If the quote just says “installation included” with no reference to the standard, ask for it to be specified. What actually changes is explained in our article on what UNI 11673 installation means.

CE marking and DoP

External windows and doors are construction products and fall under Regulation (EU) 305/2011 (CPR). They must carry CE marking under the harmonised standard EN 14351-1 and be accompanied by a Declaration of Performance (DoP). This isn’t a commercial nicety, it’s a requirement. A supplier who doesn’t know what a DoP is, or who gets uneasy when you ask for one, has already told you something about themselves.

The lines that are often missing (and that you should insist on)

Beyond the main items, there are details that an honest quote includes and a rushed one leaves out. Not because they’re expensive, but because they define who does what.

• Disposal of old windows: included, or at your expense?
• Finishing work: who repairs the plaster or shutter boxes after installation? This is often the item that blows the budget at the end of the job.
• Accessories: sills, trims, low thresholds, any insect screens or shutters — if you take them for granted, you risk finding them billed as extras.
• Exact number of units and size/room matching: a serious quote lists window by window, not “windows, lump sum”.
• Conditions in case of different measurements at the final survey: the final technical survey can change things; it’s better to know in advance how this is handled.

How to spot a vague or suspiciously low quote

A price much lower than the others isn’t a stroke of luck: it’s information. It almost always means something is missing from the comparison, or that the supplier has cut a corner you can’t see. Here are the red flags to watch for.

Red flag	What it could be hiding
A lump-sum price with no itemisation	Impossible to know what you’re paying for and what’s missing
Only Ug given, no Uw	A lower-quality frame or assembly
”Installation included” with no reference to UNI 11673	A quick installation, not done to standard
Profile stated only as “PVC” or “aluminium”	No guarantee on the actual system
No mention of CE marking / DoP	Possible non-compliance or a poorly structured supplier
No timescales or warranties given	Room for excuses later
A price well below the other two	Cheaper glass, basic hardware, installation excluded or disposal at your cost

Watch out for the sales pitch too. Be wary of anyone selling “the lowest price in Italy” without explaining how they get there: behind an overly aggressive offer there’s almost always a compromise on the product, the installation or after-sales support. We are an Italian manufacturer under Italian management working with German Salamander systems bearing CE marking — the price reflects what’s written down, not a clearance-sale label.

How to compare 3 quotes on the same basis

Three quotes are of little use if they’re comparing different things. The aim is to reduce them to a common basis before you even look at the total. Proceed like this:

1. Align the product. Check that all three propose the same profile class (same thickness/chambers or equivalent), the same type of glazing and a comparable Uw. If one offers double glazing and the others triple, you’re not comparing the same thing.
2. Align the installation. Make sure all three include installation to UNI 11673 and disposal. If one excludes it, mentally add that cost before comparing.
3. Align the scope. Same number of units, same sizes, same accessories (sills, trims, etc.).
4. Reduce everything to a comparable unit. In the industry, the reasoning is often in terms of €/m² fully installed: for the same product and installation, it’s the cleanest way to compare. The criteria are set out in our article on how much it costs to replace all the windows and doors in a house.
5. Only then look at the total. If, on an aligned basis, one quote is still far lower, ask for an explicit explanation: where’s the difference coming from?

A simple comparison table, row by row, helps more than any gut feeling. List the three suppliers in columns and the items from the first table of this article in rows: you’ll immediately see who’s left gaps.

When it’s NOT worth it

Checklists are useful, but they should be applied with common sense. There are cases where the level of rigour needs calibrating.

• When you don’t need five quotes. Three well-detailed offers, reduced to the same basis, already give you a reliable picture. Multiplying quotes endlessly only lengthens the process and adds confusion, without improving the decision. Three complete quotes beat eight vague ones.
• When the lowest price is justified. The cheapest doesn’t always hide a catch. If, on an aligned basis, a supplier costs less because they work with fewer intermediaries (for example a direct manufacturer versus a reseller), the saving is real and legitimate. The difference lies in the why: if the supplier can explain it with concrete line items, it’s credible; if they can’t, it’s a warning sign.
• When the project is simple and standard. For a single, standard-sized window, demanding the same level of documentation as for a full renovation can be disproportionate. The essential items (product, Uw, glazing, installation, CE) remain non-negotiable regardless.

FAQ

How many items does a windows and doors quote need to be considered complete? There’s no magic number, but the non-negotiable items are: profile system and thickness, window Uw, type of glazing with Ug, hardware and brand, installation to UNI 11673, reference to CE marking/DoP, quantity and dimensions, timescales, warranties and payment terms. If more than one or two of these are missing, ask for the quote to be completed before evaluating it.

Is the lowest price always the one to reject? No. The lowest price should be understood, not rejected on principle. If, on an aligned basis, it remains cheaper for concrete, explainable reasons (a shorter supply chain, direct production), it’s legitimate. It only becomes a problem when the supplier can’t or won’t explain the difference.

What’s the difference between Uw and Ug, and which one should I look at? Ug is the transmittance of the glass alone; Uw is that of the complete window, frame included. To compare products you need to look at the declared Uw, because that’s the figure describing what you’re actually installing. An excellent Ug with a poor frame still gives a mediocre Uw.

What does “UNI 11673 installation” mean and why should I insist it’s written down? It’s the reference code of practice for window and door installation, which requires correct sealing at multiple levels using suitable materials. It needs to be written down because a properly executed installation protects against draughts, condensation and mould, and because without a written specification the supplier isn’t bound to carry it out. The detail is here: UNI 11673 installation, what it means.

Can I ask for the Declaration of Performance (DoP)? Yes, and you should be able to obtain it without difficulty. External windows and doors are construction products subject to the CPR (Reg. (EU) 305/2011) and CE-marked under EN 14351-1; the DoP attests the declared performance. A well-organised supplier will provide it without issue.

Is the quote binding on the final price? It depends on how it’s worded: validity periods, any clauses on variations following the final survey, and payment terms all matter. For the specific contractual and tax aspects, always have the document checked by your trusted professional or accountant: this article is a technical guide, not legal advice.

In summary

A good windows and doors quote isn’t judged by the total at the bottom, but by the detail of the line items. If every item on the checklist has an answer — profile, Uw, glazing, hardware, UNI 11673 installation, CE marking, timescales, warranties, payment — you’re holding a document you can genuinely compare. If pieces are missing, the low price isn’t a bargain: it’s missing information. Always reduce your three quotes to the same basis before deciding.

If you want to understand the product better before comparing offers, you can start with our pages on PVC windows and doors and aluminium windows and doors, or with the complete guide to PVC windows and doors.

Want a detailed, itemised quote you can compare with confidence? Request a free, tailor-made quote: we work from your measurements, explain every line item and put everything that matters in writing — Uw, glazing, hardware, UNI 11673 installation requirements and CE marking included.