Finding a trustworthy insulation company in the UK means checking credentials, guarantees, and track record before you accept a quote. The best installers are TrustMark-registered and use BBA-certified materials. We have compared national chains, local specialists, and ECO-approved contractors to help you choose the right installer.
Insulation quality depends as much on the installer as the material. A poorly fitted cavity fill can cause damp, and badly installed loft insulation leaves cold spots that waste energy. This guide covers the main types of insulation companies in the UK, what to look for in a good installer, and the red flags that should make you walk away.
- TrustMark registration is the minimum standard for any insulation installer - it is the government-endorsed quality scheme and a requirement for all ECO4 and GBIS grant-funded work
- CIGA membership provides a 25-year guarantee for cavity wall insulation - this covers extraction and re-insulation if problems arise, backed by an independent guarantee body
- Getting 3 quotes saves an average of 30-50% compared to accepting the first offer - prices vary significantly between companies for identical work on the same property
- ECO-approved installers handle grants at no cost to eligible homeowners - they manage the entire process from eligibility check to installation with zero upfront payment
- Cold callers and pressure sellers are the biggest risk in the insulation industry - never agree to work from a doorstep salesperson and always insist on a full property survey before any quote
Types of Insulation Companies in the UK
The UK insulation market includes national chains, local contractors, ECO-approved installers, and spray foam specialists. Each type serves different needs and budgets. Here is how they compare.
1. National Insulation Companies
Large national companies such as Dyson Energy Services (now part of E.ON) and Mark Group handle thousands of installations per year across the UK. They offer the full range of insulation types and have established supply chains.
The main advantage is capacity and consistency. They employ trained teams, carry full insurance, and can usually book you in within 2-4 weeks. The downside is higher pricing than local independents. You may also have less flexibility on scheduling.
National companies are often the primary contractors for ECO4 and GBIS installations, meaning they handle a high volume of grant-funded work. If you are applying for free insulation through a government scheme, the appointed installer will frequently be a national company.
2. Checkatrade and Local Verified Installers
Local contractors on Checkatrade, MyBuilder, and Rated People offer competitive pricing. You deal directly with the people doing the work. Customer reviews provide transparency that larger companies often lack.
Verification is essential with local installers. Check they hold TrustMark registration (not just Checkatrade membership). They should carry at least £2 million public liability insurance and provide references from recent jobs. For cavity wall work, confirm CIGA membership.
Local contractors often quote 15-30% less than nationals for identical work. The trade-off is longer lead times. Their guarantee is backed by their own business, not a corporate entity. Ask for an insurance-backed guarantee (IBG) to protect you if the company ceases trading.
3. TrustMark-Registered Installers
TrustMark is the government-endorsed quality scheme for tradespeople. All installers carrying out work under ECO4 or GBIS must be TrustMark-registered, making it the baseline standard for any insulation installation in the UK.
TrustMark registration requires installers to meet technical competence standards, follow a code of conduct, carry appropriate insurance, and submit to regular audits. It also provides consumers with access to a dispute resolution service if problems arise.
You can search for TrustMark-registered insulation installers in your area at trustmark.org.uk. Filter by “insulation” to see only relevant tradespeople. Every legitimate insulation company should be willing to provide their TrustMark registration number on request.
4. CIGA Members (Cavity Wall Specialists)
The Cavity Insulation Guarantee Agency (CIGA) is the independent body that provides 25-year guarantees for cavity wall insulation. CIGA membership is the gold standard for cavity wall installers, as it means the guarantee is backed by an independent trust fund rather than the installing company alone.
If the installing company goes out of business, CIGA’s guarantee still stands. This is important because many small insulation companies have come and gone over the years, but the CIGA guarantee survives them. After installation, you receive a guarantee certificate directly from CIGA, not from the installer.
Currently over 500 companies are CIGA members. You can verify an installer’s membership at ciga.co.uk. For cavity wall insulation specifically, we recommend only using CIGA-registered installers.
5. ECO Scheme Approved Installers
ECO-approved installers are authorised to carry out grant-funded insulation work under ECO4 and GBIS. They handle the entire process from eligibility assessment through to installation, with zero cost to the homeowner if they qualify.
These companies have contracts with energy suppliers and must meet additional quality standards beyond standard TrustMark registration, including PAS 2030 certification (installation quality) and PAS 2035 compliance (retrofit assessment). This makes them among the most thoroughly vetted installers in the market.
The main consideration with ECO installers is that you typically cannot choose which company does the work – the energy supplier appoints from their approved panel. However, you can request quotes from multiple ECO-approved companies independently to check your eligibility and compare the proposed measures. For full details on how grants work, see our insulation grants guide.
6. Spray Foam Specialists
Spray foam insulation is a specialist market with dedicated companies that focus exclusively on polyurethane foam installation. These firms typically handle loft spray foam and sometimes wall applications using specialist equipment.
The spray foam market is less regulated than traditional insulation, which makes choosing the right company even more important. Always insist on BBA-certified products, check that the installer offers a meaningful guarantee (at least 25 years), and verify their work will not affect your mortgage or home insurance.
The best spray foam companies will conduct a thorough survey, check your mortgage lender’s position on spray foam, and explain both the benefits and risks. Be cautious of companies that dismiss concerns about mortgage lender acceptance or that do not carry out a proper survey before quoting.
How to Choose an Insulation Installer
Choosing the right installer requires checking credentials, comparing quotes, and verifying that the company follows proper procedures. A systematic approach protects you from poor workmanship and ensures the insulation performs as expected for its full lifetime.
– **Check TrustMark registration** – search trustmark.org.uk to verify, not just the company’s website – **Verify CIGA membership for cavity work** – check ciga.co.uk, not just the installer’s claims – **Confirm BBA-certified materials** – the British Board of Agrement certification ensures materials meet performance standards – **Request a written guarantee** – minimum 25 years for cavity wall, with insurance backing – **Get 3 written quotes** – compare scope of work, materials specified, and what is included in the price – **Ask for references** – reputable companies will happily provide contact details for recent customers
A good installer will always complete a full property survey before providing a quote. They will check cavity width, wall condition, exposure level, and existing insulation. Any company that quotes over the phone without visiting the property should be avoided.
Red Flags to Avoid
The insulation industry has improved significantly in recent years, but rogue traders still operate. Knowing the warning signs helps you avoid companies that deliver poor-quality work or charge for free government-funded installations.
- Cold calling or doorstep selling – legitimate insulation companies do not send salespeople door to door. This is the single biggest red flag in the industry.
- No pre-installation survey – any company that quotes without physically inspecting your property is guessing, and guesses lead to problems.
- Pressure to sign immediately – phrases like “this price is only available today” or “we have a team in your area this week” are pressure tactics, not genuine urgency.
- Charging for grant-funded work – ECO4 and GBIS installations are free for eligible households. “Administration fees” or “survey charges” are not part of any legitimate grant scheme.
- No written guarantee – verbal promises have no value. Insist on a written guarantee document specifying the coverage period and what is included.
- Cannot provide TrustMark number – if they claim to be registered but cannot provide the number for you to verify, walk away.
What to Expect During Installation
Installation timelines and disruption levels vary significantly by insulation type. Knowing what to expect helps you plan around the work and identify potential problems during the installation process.
| Insulation Type | Duration | Disruption | Can You Stay Home? |
|---|---|---|---|
| Cavity wall | 2-3 hours | Minimal (external drill holes) | Yes |
| Loft (rolls) | Half day | Low (loft access only) | Yes |
| Loft (blown-in) | 2-4 hours | Low (loft access + machine noise) | Yes |
| External wall | 2-4 weeks | Medium (scaffolding, external noise) | Yes |
| Internal wall | 1-3 weeks | High (room-by-room, furniture moved) | Yes (room by room) |
| Spray foam (loft) | 1 day | Low-Medium (fumes, ventilation needed) | Yes (ventilate well) |
For cavity wall and loft insulation, the work is quick and non-intrusive. External wall insulation is the most disruptive due to scaffolding and the 2-4 week timeframe, but you can live in the property throughout. Internal wall insulation is the most disruptive for daily life as it requires room-by-room access.
After installation, ask for a completion certificate, guarantee document, and before/after thermal images (good installers often provide these as standard). Keep all documentation – you will need the CIGA certificate if you sell the property, and the guarantee protects you against future problems.
For cost comparisons to help you evaluate quotes, see our home insulation cost hub, cavity wall insulation costs, loft insulation costs, and external wall insulation costs.
