FAQ – About External Wall Insulation

1. What is external wall insulation?

EWI is an insulation process that wraps the outside of your property with insulation boards and is finished with a lightly-textured waterproof render. The render is available in a wide choice of colours. It is most effective on solid-walled properties, i.e. those without a cavity. It is very effective, however, on cavity-walled properties also. It makes your home warmer by dramatically reducing the amount of heat lost through your walls, and reduces condensation/mould and the transfer of noise through your walls. You can find out more here or by contacting Greenhus on 01822 819 911 or by using our contact form.

2. How is external wall insulation installed?

EWI is installed in stages, starting with preparing your walls. (See our section How is EWI installed – step-by-step for full details.) Insulation boards are then fixed to your walls, with various render-layers then applied and finished with a lightly-textured through-colour waterproof render. It’s a highly-skilled, specialist process. Greenhus only does EWI, so talk to us on 01822 819 911 to fid out more, or use our contact form.

3. Is external wall insulation suitable for any property?

EWI suits a wide range of properties, both existing and new-build. If fitting to an existing property, you’ll achieve the best results on a solid-walled (i.e. non-cavity) property, although considerable improvements in heat retention can also be achieved on properties with cavities. As the insulations boards need to sit on a flat surface, the best surfaces are rendered walls, concrete panel/cast-concrete, brickwork or blockwork. We also have systems for new-builds and extensions. Stone-built walls with exposed stone surfaces are not generally suitable because of the uneven nature of the surface. For a free consultation to explore whether your property is suitable for EWI, call Greenhus on 01822 819 911, or use our contact form.

4. How long does it take to install external wall insulation?

This will depend on the size of your property. As a guide, an average 3-bed semi-detached home would take approx. 2-3 weeks, a small terraced home would take approx. 2 weeks and a large detached home would take approx. 4 weeks. Your free survey will establish this. Call Greenhus on 01822 819 911, or use our contact form to discuss your needs and to arrange your survey.

5. How thick is external wall insulation?

When applying EWI, Greenhus always aims to improve the thermal performance of your walls to the same standards as a new-build (i.e. a u-value of 0.3 W/m2K or less.) For the majority of wall constructions, this can be achieved using a 90mm insulation board. The total thickness, including the 12mm of associated and render, will be 102mm (4”). We provide calculations to establish the exact thickness as part of our free quotation. To arrange yours, call Greenhus on 01822 819 911, or use the contact form.

6. How long will external wall insulation last?

Greenhus installs only BBA-approved systems. To obtain BBA approval, an EWI system has to demonstrate a life expectancy of at least 25 years. This means your home will be protected by a waterproof jacket for a long, long time. As the materials used in your system are protected from the weather by the waterproof final render, your system could enjoy a lifespan much longer than 25 years – the earliest known example of EWI still performing as installed is in Germany, and dates from 1957. If you’re interested in protecting your home as well as being warmer and saving money on heating costs, call Greenhus on 01822 819 911, or use our contact form.

7. What warranty/guarantee do I get with external wall insulation?

You will receive a 25-yearinsurance-backed warranty against material and workmanship defects.

8. How do I maintain external wall insulation?

Each installation comes with a manufacturer’s maintenance guide, which is very simple. EWI requires annual visual checks to look for impact damage. Sealing around window and door openings should also be checked. In the highly unlikely event that you believe your installation might need repair, contact Greenhus for advice.

9. Can external wall insulation be painted a different colour or touched-up?

Yes. Whilst the colour you choose for your finishing render will never “wash-out”, you may decide to change the colour of your home as part of a future makeover. If so, contact Greenhus – you’ll need compatible paints designed to work with the render. These paints are no more expensive than conventional exterior-grade paints.

A pot of touch-up paint is provided with each installation.

10. Can external wall insulation be repaired?

Yes. In the unlikely event of impact damage, contact Greenhus for advice. Due to the specialist nature of the installation and the products used, DIY repairs are not recommended.

11. Can I still live in my property while external wall insulation is installed?

Yes. All works take place outside your property, and well keep paths and other access points clear for you to come and go as normal. Where it’s not practical to do so, we will minimise any impact. In practice, you’ll be aware of the installation taking place but it will have minimal effect on your day-to-day activities.

12. Can I fix things to external wall insulation?

Yes. Where we know in advance about existing fixtures and fittings that will be replaced following the installation, we will insert fixing points within the system. For items you may decide to fix in the future, we can offer different methods depending on the weight of the item. A competent DIY-er will be able to easily use these methods. Our free survey takes account of existing fixtures and fittings. Call Greenhus on 01822 819 911, or use our contact form to discuss your needs and to arrange your survey.

13. How much does external wall insulation cost?

There is no easy answer to this question. Each property is individual and with different needs. Greenhus offers a turnkey service that meets all your specific needs, so we need to take account of everything before conforming your installation price. Your best action is therefore to contact us. We will arrange a free survey and quotation (not an estimate) and you will quickly have an exact cost to consider. Call Greenhus on 01822 819 911, or use our contact form to discuss your needs and to arrange your survey.

14. How long does it take for external wall insulation to pay for itself?

EWI is not like a solar photovoltaic (PV) installation. It does not attract a tariff. With solar PV, you can forecast the likely tariff payments and calculate the “break-even” date. EWI will generate savings, but these will depend on factors such as how you heat your home, when you heat your home and the size of your home. It’s not therefore fair to try and forecast when it will pay for itself, because too many factors are at play. Instead, concentrate on the benefits – you’ll be warmer and healthier, your home will get a great new look and be more appealing to potential buyers due to its increased energy efficiency, and it will be protected by its waterproof jacket. It’s much more of an emotional decision; ask yourself if you want the benefits, and then weigh these against the cost. Our customers’ experiences to date suggest payback dates somewhere in either the second or third decade. We would stress, however, that not all life’s choices can be thought of in terms of payback – does that nice car on your drive pay itself back? Do your nice clothes pay themselves back?

15. Are there any extra costs when installing external wall insulation?

Your Greenhus quotation will be a fixed price – what you see is what you pay. We take care at survey stage to ensure there are no surprises. Get an exact cost for this energy-efficient home improvement by calling Greenhus on 01822 819 911, or email us here [link to contact form] to discuss your needs and to arrange your free survey and quotation.

16. What does my quotation for external wall insulation include?

Your quotation from Greenhus will include the following:

  • BBA approved external wall insulation system (including coloured
  • render if required, at no extra charge).
  • Window sill extensions to the design of your choice.
  • Replacement of all wall-mounted pipework (if you’ve recently had new downpipes, we may re-use these. We’ll agree this with you and your quotation will be adjusted accordingly).
  • Building Notice application fee, and liaising with the Building Control department of your local authority until the issue of the Completion Certificate.
  • Liaising with other service providers (e.g. Western Power, if your wall-mounted mains electricity supply cable needs moving).
  • All necessary enabling works (e.g. boiler flue extension to accommodate the increased thickness of your walls).
  • Homeowner Pack (including maintenance instructions).
    25-year insurance-backed warranty.
  • Removal of all waste, and a thorough clean down before we leave.
    An ongoing relationship, including free advice, for the lifetime of your system.

Get your own comprehensive, inclusive quotation by calling 01822 819 911 or by using our Contact Form.

Discover how External Wall Insulation from Greenhus can transform your home or business premises - complete our Contact Form and we’ll call you back, or speak to us on 01822 819 911

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