U-value Calculator
We provide U-value calculations free-of-charge to show compliance with current Building Regulations, Standards and best practices.
Why choose External Wall Insulation?
External wall insulation is applied to the outside of the walls and is normally accompanied by an external render, installed by a dedicated render system provider. It is ideal for retrofit projects and improving the thermal performance of existing solid wall buildings.
Can external wall insulation cause damp?
When designed and installed correctly, external wall insulation should not lead to damp problems.
Before any work is carried out on your home, a properly qualified Retrofit Coordinator or Retrofit Assessor should undertake a careful pre-assessment survey. As part of this, they will review the condition of your home to check that there aren’t any pre-existing issues like poor pointing, damaged or cracked bricks, leaky guttering or signs of damp. These issues will all need to be fully addressed, and your home in good condition, before the EWI is installed.
During the survey, the assessor will also check that your home is well ventilated. Many homes have been made more airtight overtime due to changes such as replacing original single-glazed windows with double glazing. Whilst this can help to cut out unwanted draughts, it can also cause moist air to get trapped in your home. The assessor may make recommendations such as installing trickle vents on windows, shaving the bottom of internal doors or fitting extraction fans in kitchens and bathrooms.
Once all these works are complete, the Retrofit Coordinator should then work with your EWI installer to ensure the system is properly planned and designed for your home. For example, installers may need to extend the overhang on your roof so that it fully covers, and extends beyond, the EWI system by at least 40 mm.
Specialist insulation which is resistant to ground moisture penetration (such as Kingspan GreenGuard GG300) may need to be fitted at low levels around the damp proof course to prevent rising damp. Your installer should also carefully plan for junctions around windows and doors to ensure there are no gaps where water can get in, and ensure the insulation itself is installed so that it is tightly jointed with no gaps. Once work is completed, your Retrofit Coordinator should carry out a further review to ensure your system is properly installed before signing it off.
Does Kingspan Insulation have a product suitable for external wall insulation systems?
Kooltherm K5 External Wall Board has a thermal conductivity of as low as 0.021 W/mK, making it a thinner alternative to other commonly used external wall insulants. Using thinner external insulation could allow more daylight into a building (when compared with thicker alternatives) and may reduce the amount of remediation needed to accommodate insulation on the external walls. The boards are suitable for use behind both traditional and lightweight polymer modified renders
On this page you will find a number of useful links to help with your project, including installation advice and where to buy Kooltherm K5.
Are you a homeowner?
Visit our Homeowner Hub where you can find a wealth of advice and support for your project!
Download our Brochure
for full installation guidance
Useful Links
Discover More
External Wall Insulation Support
Page updated 9/12/2025