0330 124 6585 info@inca-ltd.org.uk

External Wall Insulation
A Guide For Homeowners

Adding insulation to your home can be done on one of three ways – internally, within the cavity or externally.

If you live in a solid wall property or a non-traditionally constructed house then cavity insulation is not or may not be an option. In addition, your preference may not be to insulate internally because of the loss in living space this will result in (not to mention the cost of moving fitted furniture and redecoration). For these reasons retrofitting with an external wall insulation system may be your preferred option.

As a result INCA have put together a short external wall insulation or EWI guide for homeowners to answer the basic questions we are commonly asked.

The Benefits of External Wall Insulation

As a homeowner, the benefits of refurbishing and thermally upgrading your home using external wall insulation are significant – we’ve covered these in more detail in our feature The Benefits of EWI but, to summarise, the main benefits are as follows:

  • Improves thermal performance
  • Reduces carbon footprint
  • Energy bills drop
  • Thermal comfort improves
  • Adds acoustic insulation
  • Reduces condensation and damp risk
  • Minimises thermal bridging
  • Transforms the look of your property
  • Protects the existing fabric
  • Adds value to your property

Find An INCA Member

Whatever the nature of your involvement in an EWI project, whether it be new build or refurbishment, small or large, INCA have members who can help.

  • Home Owners
  • Social Landlords
  • Specifiers
  • Main Contractors

Insist on EWI system quality and technical competence – choose INCA.

EWI – Planning Permission And Regulations

In most cases you won’t require planning permission from your local council to install an EWI system to your home. You should always check with your local planning office first though as there may be restrictions.

However, if you live in a listed building, if you’re in a conservation area or if the thickness of the insulation you’re proposing infringes into someone else’s land or a public walkway or road you will require permission. In addition, certain local authorities stipulate that planning permission is required if the outside of your house is going to change in colour or texture.

As a rule, we would always recommend that you check with your local planning office before EWI is installed on your property.

It goes without saying that all INCA member EWI systems are covered by British Board of Agrément certification, accredited to ISO9001 quality management standards and conform to all current building and EWI fire regulations. Consult your chosen system designer’s website for full details and links to certification.

Can EWI Be Used On Any Property

EWI is a highly effective way of thermally upgrading a property which can be used on many properties and most construction types … but not all. It’s not the appropriate solution in every case so it’s vital that each project is assessed by an INCA member EWI system manufacturer or contractor first. prior to specification.

Our feature entitled The Suitability Of EWI will explain the restrictions in more detail.

Specifying The Right External Wall Insulation System

Contact an INCA System Designer or a local INCA Contractor member in the first instance. They will organise for your property to be surveyed in order that the correct EWI system can be specified.

The system will depend on the property and your own requirements. The insulant will typically be EPS or mineral fibre with a thickness depending on the thermal improvement you’re looking to make and the options for how think the insulation can be compared to existing overhangs and without infringing on other properties, walkways or public land. Read more about Specifying EWI Insulation. Fixings will be dependent on the thickness of insulant and the substrate they will be fixed in to and the finish effect, texture and colour will be down to personal preference and taking into account any local restrictions.

You’ll see, there are many variables which is why you should always work with a professional organisation who will guide you through every step of the process.

How Will My Property Look?

A tired looking, cold and expensive to heat property can be completely transformed into a warm, energy efficient and stunning looking home. Basically, it can look however you want it to (within reason and any local authority restrictions).

If you want it to have a brick effect finish it can, a thin coat render, a thick coat render, a dry dash using local stone chips, stone effect – even a timber panel effect … all of this is possible.

As for colour, modern renders are designed for EWI systems and often come ready mixed and through colour with a choice of hundreds of different colours.

Then of course, you can mix and match. A brick effect to first floor and a render above for just one example.

You can design the finish to ensure your property looks exactly the way you want it to and completely transform it if you wish. Find out more about finish options >.

External Wall Insulation – What Does It Cost And Is It Worth It?

Cost depends on your property and the system specified. As a very general guide only, for a standard EWI system comprising of a 90mm EPS insulation board fixed to a masonry substrate and finished with a lightly textured silicone render the cost will likely be somewhere between £65 and £95 per square meter. Thicker insulation will increase material costs and different finishes will also increase the overall cost.

So, purely for general guidance, you’re looking at anything from around £4,000 – £6,000 for a small terraced property, £8,000 – £10,000 for an average semi and up to £12,000 – £14,000+ for larger detached homes.

In the recent Spring Statement in 2022 the Chancellor announced a VAT reduction to 0% until 2027 in respect of all energy efficiency measures … including EWI … which will help incentivise.

Funding and grants MAY be available depending on you, your property and the area you live in. Again, your local INCA member contractor will advise you on this.

As for benefits … by installing EWI you can expect a reduction in energy usage of up to 40% and the Energy Savings Trust estimate a saving of up to £455 per year (prior to the 2022 energy price rises).

In addition to annual savings on energy the value of your property should increase by an average of £16,000 (in England) due to the improved EPC rate and the aesthetics.

How Long Does It Take To Install EWI?

This really depends on your property and the system being installed.

By way of a guide, it starts with a survey prior to works commencing. This checks for things such as:

  • Suitability of the existing wall for mechanical fix – this will consist of a pull-out test.
  • Reveals, windows and doors to check for any issues
  • Overhang on cills, soffits and such like
  • What will need to be taken down and re-fixed – satellite dishes, meter boxes, gates etc
  • Soil pipes which may need to be moved
  • Any existing coating which will affect the adhesion of the system

Any issues identified will first need to be addressed as part of the preparatory works.

Once the substrate is prepared there are three main stages to the actual works:

  1. Boarding and beading: on an average size property this will take up to two days
  2. Basecoat and reinforcing mesh: This will take a couple of days to apply with a further drying time of up to 72 hours
  3. Top coat or finish: This completely depends on the finish selected – anything from a single day (for a basic thin coat render).

We have put together a short, generic EWI Installation Guide to explain the process in more detail.

Scheduling The EWI Installation

There are certain weather-related restrictions when it comes to installing an EWI system. Render should not be applied in temperatures of 5 degrees and falling, not should they be applied in direct sun when the temperature is too high (usually around 25 degrees plus).

Wet weather can also present a problem so you may want to consider sheeting scaffolding to add protection from the elements and even adding heaters depending on the time of year and conditions.

How Long Will EWI Last?

EWI is a long-term investment. Most system designers will be able to provide a warrantee of, or in excess of 25 years. In addition, your chosen INCA member contractor will also be able to provide an insurance backed guarantee for a small additional cost.

No EWI system is maintenance free but all are described as low-maintenance. Whilst renders and finishes are through coloured and won’t require painting, they will always benefit from a gentle power-wash periodically in order to remove dirt and airborne pollutants.

External Wall Insulation Refurbishment – Where To Start

Contact any INCA system designer or one of the INCA Contractors members who specialise in the refurbishment of private properties below.

Use the filters in the search boxes below which will help you select the right INCA contractor member who will help you specify the optimum system, provide an accurate quotation and guide you through the process without obligation:

External Wall Insulation
All You Need To Know

Name/WebsiteTown/CountyPostcodeTelephoneEmail Address
A.C. Whyte & Co LtdGlasgowG78 1BF0141 881 9519info@acwhyte.co.uk
A2O LimitedBrentwood, EssexCM15 0LA01277 369555Ashley.brew@a2ogroup.co.uk
AFS (Scotland) LtdStirlingFK7 7UW01786 450409reception@afs-scotland.co.uk
Ailsa Building Contractors LtdNorth LanarkshireML5 4AU01236 422615queries@ailsabuilders.co.uk
AMJ Contracts LtdOrpington, KentBR5 3NF020 3633 1074info@amjcontracts.co.uk
Aspiration Façades LimitedNorfolkIP22 4GT01379 658 959sales@aspirationfacades.co.uk
Baxter Kelly LtdStaffordST16 3HS0800 061 4991info@baxterkelly.co.uk
Bell Group LtdAirdrie, ScotlandML6 9BG01236 766878a.eaton@bellgroup.co.uk
Broad Oak Properties LtdStoke-on-Trent, StaffordshireST10 2EL01782 550371info@broadoakgroup.com
BuildX (SW) LtdPlymouthPL6 5DS01752 546525hello@buildxsw.co.uk
Complete Wall Solutions LtdRadcliffeM26 4BG0161 757 3200info@cwsolutionsltd.com
Frank Rogers Building Contractor LtdLiverpoolL13 9BR0151 226 0323greenersolutions@frankrogers.co.uk
FRT Property Services LtdRomford, EssexRM1 3NH01708 540 979info@frtps.co.uk
Fullers Plastering LtdBrightonBN2 6NX01273686368info@fullers-plastering.co.uk
Gaffney & Guinan Contractors LtdCoventryCV2 1EQ02476449066info@ggcltd.co.uk
GMG Contractors LimitedGlasgowG69 6DW0141 771 1288info@gmgcontractors.co.uk
GPD Contracts LtdUpton-on-Severn, WorcestershireWR8 0SW01684 593431enquiries@gpdcontractsltd.com
Guildmore LtdBromley, KentBR1 3AA0208 313 5050enquiries@guildmore.com
Hamilton (Building Contractors) LtdBaildon, West YorkshireBD17 7AX01274 666166enquiries@hamiltonfirst.co.uk
HLS McConnell LtdKilmarnockKA1 2RL01563 526397info@hlsmcconnell.com
Independent Energy Savers LtdConwyLL299PR01492 516997lee@iesukltd.org
Insulated Render Systems (Scotland)North LanarkshireML6 9AS01236 754 500office@irsscotland.com
Jefferies Contractors LtdPontyclun, WalesCF72 9EW01443 858710enquiries@jefferiesltd.co.uk
Joyner GroupNewportNP11 6AN01633 614460LukeJoyner@joynergroup.co.uk
Kooka Developments LtdWollaston, NorthamptonshireNN29 7RQ01933717129info@kookadevelopments.com
Lawtech Group LtdRochester, KentME2 4LT01634 290500reception@lawtechgroup.co.uk
Next Energy Solutions LtdLiverpoolL33 7UY0800 021 3145info@nextenergyuk.co.uk
P J Mear LtdHuntingdonPE29 6EF01480 431117sales@pjmear.co.uk
Pic Construction Group LtdBrentwood, EssexCM13 3FR01277725120ipendus@picgrp.co.uk
Primars Coatings Services LtdLondonWD24 4AS0203 976 4313julian@primars.co.uk
Procast Building Contractors ltdStrathavenML106LT01355209300contact@pro-cast.co.uk
Quality Fast FacadesLancashireBL2 5RH0161 797 7662amy@qffacades.co.uk
Rateavon LtdBristolBS32 4EU0117 982 0033estimating@rateavon.co.uk
Rendserve LtdLoughborough, LeicstershireLE11 1QJ01509 768 838info@rendserve.co.uk
Rockwarm Insulation LimitedNuneatonCV11 4PN02476 345554info@rockwarm.co.uk
SERS Energy Solutions Group LtdCaerphillyCF83 3GX01443821349info@sersltd.co.uk
SERS Energy Solutions Group LtdLivingstonEH54 6TS01506333213info@sersltd.co.uk
SFP Contracts LtdLeicesterLE3 8DX0116 287 4649contact@sfp-contracts.co.uk
Sustainable Building Services (UK) LtdSkelmersdale, LancashireWN8 9TW01695 553 920enquiries@sustainablebuildinguk.com
Sykes Specialist Contracting LtdNewcastle upon TyneNE6 5DE0191 303 7151chris@sykessc.com
Thomas Niamh Contracting LtdOssettWF5 9ND01924 562251info@thomasniamh.com
TLS Construct South-West LtdExeterEX5 7HW07774622535Office@TLSconstructSW.co.uk
UKR Facades LtdSalford, ManchesterM50 3UP07977138987sb@ukrfacades.co.uk
Warmhouse LtdBellshill, LanarkshireML4 3NP01236710192info@warmhouseltd.co.uk
Westdale ServicesDoncasterDN6 9JD01302 700700malcolm@westdaleservices.co.uk
Westville LtdDerbyshireNG20 8GB0800 454419contact@westville.ltd
WSF Contracts LtdRugbyCV22 5BD01788 220023info@wsfcontracts.co.uk