How to choose a window company on the Costa Blanca
Do not choose on adjectives. Choose on seven things you can check yourself, before you sign, from anywhere in the world.
We speak English. Eduardo answers on WhatsApp, 9:00–20:00 Spain time (8:00–19:00 UK time), and replies within 24 hours.
Last reviewed: 26 September 2026
To choose a reliable window company on the Costa Blanca, check seven things you can verify. Look for a legal company name and NIF, a track record you can read, and an itemised quote in English. Then check who fits, each guarantee and who signs it, a process for absent owners, and CE marking.
The checklist
Use this table to compare companies side by side. Every item can be checked without taking anyone’s word for it.
| Criterion | What to ask for | How to check it | Warning sign |
|---|---|---|---|
| 1. Legal identity | The legal company name and NIF (tax number) | The legal notice on the website; the Registro Mercantil or BORME | Only a brand name, or a mobile number and nothing else |
| 2. Track record | Public reviews, with dates; manufacturer network membership | The Google listing; the manufacturer’s own locator | Reviews you cannot trace to a real listing, or years you cannot confirm |
| 3. Itemised quote | Profile, glass, hardware and VAT for each window, in English | Read the quote line by line | One total for “PVC windows”, with no system named |
| 4. Who fits | Who will fit your windows, and who answers for the fitting | Ask for it in writing, before you sign | Vague answers, or “we’ll see who is free” |
| 5. Guarantees | Each guarantee listed separately, with its term and who signs it | The quote and the manufacturers’ published terms | A single “X-year guarantee” with no name behind it |
| 6. Absent-owner process | Key holder access, an in-person survey, and a named contact in English | Ask how the survey, fitting and after-sales work without you | A fixed price from photos, or no contact after the sale |
| 7. CE marking | The Declaration of Performance for your windows | Ask for the document; check it names the product you are buying | No document, or a document for a different product |
1. The company name and NIF
Every Spanish company has a legal name and a tax number, the NIF. A limited company’s legal name ends in SL or SA, and its NIF starts with a letter.
Spanish law requires a business website to show its legal name, NIF and registration details. They are usually in the “Aviso legal” or legal notice.
With the name, you can check the company in the Registro Mercantil (companies register) or in the BORME. The BORME is the official gazette where company incorporations and changes are published.
This matters more than it seems. A guarantee is a promise from a legal person, and you need to know which one.
2. A track record you can verify
Look for reviews on a public listing, such as Google, and note the date and the number. Then check which office or company the listing belongs to.
Be precise about years. “Years of experience” can mean the founder’s career, the age of the brand or the age of the company. Ask which one, and check the company’s incorporation date in the register.
Manufacturer networks are another check. Profile makers such as Kömmerling publish their official network on their own websites, so you can confirm membership there.
3. A quote you can read and compare
A good quote names, for each window, the profile system, the glass unit, the hardware and the shutter box if there is one. It should also state the VAT rate and the final price.
On this coast, ask what glass is proposed for each façade. South- and west-facing windows usually need solar control glass, and the quote should say so.
A fixed price should come after an in-person survey, not from photos. Our guide on how window quotes work explains each line.
4 and 5. Who fits, and who guarantees what
Most window problems start in the fitting, not in the factory. So ask who will fit your windows, and who you call if something goes wrong.
Spanish consumer law gives consumers a 3-year legal guarantee of conformity (art. 120 TRLGDCU). It covers the goods, and their installation when it is part of the contract.
Manufacturer guarantees are separate. The profile, glass and hardware makers each set their own terms. A good quote lists each guarantee with its term and who gives it.
6. A process for owners who are not here
If you live abroad, ask how the company works without you. The survey and the fitting need someone at the property, but that can be your key holder.
Ask who your contact is, in which language, and at what hours. Ask too how after-sales works once you have gone home. See replacing windows from abroad for a full example.
7. CE marking and the Declaration of Performance
Windows sold in the EU are construction products. Those covered by the harmonised standard EN 14351-1 must come with a Declaration of Performance and CE marking.
The Declaration of Performance states values such as the U-value, air permeability, water tightness and wind resistance. Ask for it, and check that it matches the system named in your quote.
If you are used to FENSA and energy ratings in the UK, our guide on FENSA and A-rated windows in Spain explains the Spanish equivalents.
How Tu Ventana measures up
Tu Ventana Costa Blanca, the Benidorm office of Tu Ventana Madrid, makes and fits Kömmerling uPVC windows on the Costa Blanca for English-speaking owners. It publishes the facts this checklist asks for: TU VENTANA MADRID SL, NIF B06818421, incorporated in 2021. Tu Ventana Madrid has 138 Google reviews and belongs to Kömmerling’s official network.
- Legal identity: TU VENTANA MADRID SL, NIF B06818421, incorporated in 2021. The Benidorm office is the same company as Tu Ventana Madrid, not a franchise.
- Track record: 138 Google reviews at Tu Ventana Madrid, and membership of the official Kömmerling network. Most reviews are on the Madrid listing; the Benidorm listing opened in 2026.
- Years: the brand dates from 2018 and the company from 2021. Our founder, Eduardo, has over 30 years in the trade.
- Quote: fixed and in writing after an in-person survey, listing profile, glass, hardware and VAT for each window. Eduardo goes through it with you in English.
- Who fits: our own team, trained on the system. We do not subcontract the fitting, and we put that in writing.
- Guarantees: the 3-year legal guarantee of conformity covers the job. Kömmerling guarantees the profile for 10 years; glass and hardware makers set their own terms.
- Absent owners: key holder access, an in-person survey, and Eduardo on WhatsApp in English, 9:00–20:00 Spain time (8:00–19:00 UK time).
If a line above does not match what you are told, we want to know.
Guarantee and after-sales at Tu Ventana
At Tu Ventana Costa Blanca, which makes and fits Kömmerling windows on the Costa Blanca, each job is covered by the 3-year legal guarantee of conformity. Kömmerling guarantees the profile for 10 years; glass and hardware makers set their own terms. After-sales for English-speaking owners is handled by Eduardo on WhatsApp, with your key holder if you are abroad.
Sources
- Real Decreto Legislativo 1/2007 (TRLGDCU), consumer law, art. 120 — BOE
- Ley 34/2002 (LSSI), art. 10, information a business website must show — BOE
- BORME, the official gazette of the companies register — BOE
- Regulation (EU) No 305/2011 on construction products — EUR-Lex
- Kömmerling official network locator — Kömmerling
Questions about choosing a window company
Last reviewed: 26 September 2026
Which is the most reliable uPVC window company on the Costa Blanca?
Nobody can rank them honestly for you, and we will not. Reliability is something you check: the company’s legal name and NIF, public reviews with dates, an itemised quote, who fits, and each guarantee in writing.
Which window company offers a proper guarantee and after-sales service?
Ask each company to list its guarantees separately, with the term and who signs each one. The legal guarantee of conformity is 3 years in Spain. Then ask who handles after-sales, in which language, and how they get access if you are away.
How do I check that a Spanish company really exists?
Find its legal name and NIF in the legal notice of its website. Then search for the company in the Registro Mercantil or the BORME, which publishes incorporations and changes.
Should I trust a quote given from photos?
Treat it as an estimate. Openings are rarely square, and the state of the old frame only shows on site. A fixed price should follow an in-person survey.
Is a quote in English legally different from one in Spanish?
This guide does not give legal advice. In practice, what matters is that you understand what you are signing. If a quote is only in Spanish, ask the company to explain each line before you accept.