Internal Wall Insulation (IWI) for Solid Walls
Solid Wall Insulation offers the greatest carbon savings of all energy-saving measures for buildings and, given this technology has been around for decades. I have always been astonished by how little progress is made in insulating our huge solid wall building stock, around 30% of the housing stock and around 15% of commercial property.
In the average solid wall property, approximately 45% of heat is lost through walls (DCLG, 2006b, p.3), more than through roofs and windows.
I’ve been working with IWI 2009, when I commenced a detailed research project as part of his MSc Building Surveying Course, and the materials and assistance available have not changed much since then.
Solid walls may be insulated internally or externally. Both come with pros and cons. You might select to insulate internally if regulations prevent you insulating externally, or if you wish to insulate room by room.
An array of products, designs and materials is available for retro-fitted IWI, and which product you choose really depends on the importance you attach to:-
- How much internal floor area you can sacrifice to meet the desired thermal performance / regulations of the time (Part L1B requires a U-value of 0.35 W/m2K).
- Embodied energy of the material – highly processed oil-based products will contain more embodied carbon that products such as hemp or wood-fibre.
- Cash remaining in your pocket after installation.
Insulation may be the common sense solution to reducing heat loss, but IWI comes with challenges. The general reticence to install IWI can be explained by the complications and risks of installation. Ignore these at your peril:-
- • Moisture Management needs careful consideration depending on the insulation material and design to avoid interstitial condensation.
- • Cold Bridging can be avoided with attention to detail at junctions, for example corners, window reveals and joist ends.
- • Other technical or practical considerations such as fire resistance health & wellbeing, acoustics, location of services and internal fixing points, and ease of installation and maintenance, inconvenience to tenants and loss of income to landlords.
