Why should I insulate my walls?
Energy use in homes contributes a staggering 10.9% to global greenhouse emissions[1]. Properties can lose one-third of their heat through the walls[2], so that’s a huge opportunity to save money, save energy and stop contributing to climate change. Installing wall insulation is an effective, do-it-once-and-forget-about-it climate change action that keeps on working, and there may even be grants available to help with the cost.
Can you insulate cavity walls?
In the UK, most houses built since 1920 have cavity walls. Some, but not all, cavity walls can be insulated, usually with mineral wool, polystyrene beads, or polyurethane foam.
Cavity wall insulation should be suitable for your property if:
- Your external walls have an unfilled cavity between the inner and outer layers
- The cavity is at least 50mm (2 inches) wide
- The cavity is clear of rubble (it may not be, as the “cavity” was often a convenient place for previous generations of builders to dump waste)
- The brickwork or stone is in good condition
- The walls are not exposed to driving rain (rain that falls hard and fast, and is forced into the fabric of the building by strong winds)
- The property is not at risk of flooding
- The masonry or stone surface inside the cavity is fairly smooth (otherwise the insulation won’t fill evenly and you’ll get damp patches)
If you have a cavity wall that can’t be insulated, you may still be able to add insulation on the inside – see the solid wall section below for more details.
For more information on cavity wall insulation, visit The Energy Saving Trust (cavity wall insulation).
Can you insulate solid walls?
In the UK, houses built before 1920 are likely to have solid walls, i.e. a single wall made of just one material, usually brick or stone. Heat loss is slowed down by changes in materials, so walls made of just one material are likely to leak heat faster. Adding a layer of a different material slows this “thermal bridging” effect.
Not all solid walls can be insulated. Adding insulation to very old properties can prevent them from “breathing” and cause problems with damp, condensation and mould. If you’re thinking about insulating an older property, take advice from a reputable company – ideally one that’s been around for a long time and specialises in older buildings.
If they’re suitable, solid walls can be insulated on either the inside or the outside of the wall. Unfortunately, fitting solid wall insulation is more expensive and disruptive than installing cavity wall insulation.
Fitting solid wall insulation on the inside is disruptive and expensive because the extra thickness of the insulation forces you to move the positions of electrical sockets and doorframes.
Fitting solid wall insulation on the outside means the depth of the window reveals and the eaves will be reduced, which can look a bit strange (not that that should really be a consideration when the climate is at stake!). Depending on where you live you may also need to get planning permission, as you will be changing the external appearance of your property.
As a result, solid wall insulation will be least disruptive and costly if it’s done at the same time as other work, e.g. internal decoration, roof repairs or an extension. Landlords will probably want to do the work between tenancies to avoid disruption to tenants.
For more information on solid wall insulation, visit The Energy Saving Trust (solid wall insulation).
Insulation for new builds and extensions
If you are building from scratch, there’s a huge choice of modern, sustainable insulating boards and natural products available, including sheep’s wool, recycled insulation, straw bales, hemp, cork, wood fibre, recycled newspaper (cellulose) and cotton (recycled fabrics).
Check out Homebuilding and Renovation and GreenSpec for more details.
Grants to fund insulation upgrades
Grants for insulation may be available through government schemes, your local council, or your energy supplier. The grants and rules change often so we recommend searching for “insulation grants” followed by the name of your country, county or energy supplier, to find out what’s currently available.
How can I encourage other people to improve their wall insulation?
As energy prices remain high, it’s a great time to talk to friends, family and colleagues about improving their insulation.
Look for information about grants that may be relevant to them, even if they aren’t relevant to you; for example, grants for low-income families, landlords, or people who live in council properties.
If you’re good with forms, help other people make their grant application. If you’ve already gone through the process, help them avoid any delays or pitfalls you experienced.
If you’ve had insulation fitted, look back through your energy bills for the year before you got insulation, and note down how much energy you used. The number of units or kWh is most useful, as that isn’t affected by price changes. Then collect the same information for the year after the insulation was fitted. Hopefully, you should see a significant reduction in the amount of energy you used, which is great evidence to give to other people who are thinking about it.
Improving your wall insulation is just one of many ways to save energy at home – don’t forget to check out our other ideas!
[1] Ritchie, H., Roser, M. and Rosado, P. (2020) Emissions by sector. Our World in Data. Available at: https://ourworldindata.org/emissions-by-sector (Accessed: March 22, 2023).
[2] Cavity Wall Insulation (2022) Energy Saving Trust. Available at: https://energysavingtrust.org.uk/advice/cavity-wall-insulation/ (Accessed: February 5, 2023).
Photo credit: Chris Barbalis on Unsplash