Is it Possible to Insulate Solid Walls?
Learn about the advantages and disadvantages of solid wall IWI and EWI for your home
Knowledge Article5 min read
Homeowners Adam Dadeby and Erica Aslett had long dreamed of creating their own low-energy home in the south west of England.
The couple settled on a dilapidated 1970s property and worked with Janet Cotterell from CTT Sustainable Architecture (and now also Passivhaus Homes Ltd.) to make their dream a reality, extending and transforming the detached house.
LOCATIONTotnes, UK
ArchitectCTT Sustainable Architecture
ProductsKooltherm K5 External Wall Board
As the final U-value for the floor was still above the Passivhaus target limit of 0.15 W/m²K, the designers chose to compensate by improving the U-value of the external walls to 0.09 W/m²K.
To achieve this, 180 mm thick Kooltherm K5 External Wall Board was fitted to the outside of the existing walls and finished with a white render. The insulation is suitable for use behind traditional and lightweight polymer modified renders and dry cladding systems and minimised thermal bridging through the property walls. The existing wall cavity was also filled with polystyrene bead insulation.
"The architects and I specified the Kingspan Insulation products for the existing walls because their thermal conductivity was lambda 90/90 CE Mark certified. Without this, we would have had to apply a 20% uplift to the manufacturer’s quoted lambda value". - Adam Dadeby - Owner and Passivhaus Consultant
Page updated 07/01/2026
