Will the 2024 favour the homebuyers or the sellers? London housing market through the lens of time. Moisture meter Salts test Carbide moisture test Thermal camera Buying a house in simple steps Tricks some sale agents use to make you buy a property Poor pointing between bricks and dampness inside a house Salts analysis test sheet Gas and Electrical Safety Checks - Is it Important Before Property Purchase? Discover the Real World of Surveying: Shadow a Pro! The Leasehold and Freehold Reform Bill 2024 UK Residential Housing Market Outlook for 2025: Navigating Economic Challenges and Opportunities Practical Tips for Annotating Survey Photographs: CLEAR The short story about the Toasty Terrace and Drafty Dwelling Building Surveyors and AI: The Question That Matters Most Decoding the UK Property Market: Is Now the Time to Buy, or Should You Wait? The Hidden Costs of Homeownership: What the Latest English Housing Survey Reveals How to insulate solid walls so they are breathable and keep original features
How to insulate solid walls so they are breathable and keep original features
“Did I make a mistake? Did I mess up this old building?”
These are the questions architect Níall Hedderman posed on his Youtube channel, Real Life Architecture, about an internal wall insulation specification for one of his projects. His search for answers led him on a journey through retrofit best practice to learning more about an insulation material that he describes as “supernatural” in terms of its performance properties.
It led to Níall and Proctor Group working together to explain how aerogel insulation can help to improve the energy efficiency of traditional buildings without covering up historic features, or taking up too much internal space.
The problem with “destructive” internal insulation
In 2020, Níall specified an internal insulation solution for a building conversion project. Inside the 600mm sandstone walls, he detailed a 50mm clear cavity, then a timber stud frame with PIR insulation fitted between the studs.
Originally, he intended the insulation to be applied directly to the face of the wall, but the Building Standards Officer requested the cavity in accordance with the Technical Handbooks (Scotland’s equivalent to the Approved Documents used in England and Wales).
Two years later, delayed by the Covid pandemic, the project was on site. Níall filmed a YouTube short – which has now been viewed over 200,000 times – showing the insulation solution in place. The video wasn’t a comment on the type of insulation, but on the thickness of the build-up required and how it meant none of the building’s original features could be retained.
Due to this loss of character, Níall characterised the method as “destructive.”
The type of insulation matters more than its thickness
In early 2025, Níall created a full YouTube video called ‘How to insulate a solid wall in the UK.’ He looked at issues like how thick solid wall insulation should be, and what best practice is for insulating old buildings internally. In the video, he referenced his original Short and admitted that, were he to do the project again, he would not insulate the walls the same way.
What matters most is not the thickness of the insulation, but the type of insulation and the method of construction, he recognised.
That’s because knowledge and understanding around solid wall insulation had changed a lot since 2020, when he first specified the project. In 2021, for example, the UK Government published ‘Retrofit Internal Wall Insulation – Guide to Best Practice.’
The guide documents how traditional solid walls don’t rely on drying to the outside only. Sun and wind are an important part of helping wet walls to dry, but traditional internal finishes, like lath and plaster, are also ‘breathable.’ That is, they allow the passage of moisture vapour, meaning walls can also dry to the inside when required.
Fitting ‘non-breathable’ (i.e., vapour closed) insulation materials to the internal face of a solid wall inhibits the wall’s ability to dry to the inside. The face of the wall is colder and potentially damp, increasing the risk of mould and eventual decay. While that might not happen on every building, there’s no way to be sure of what is going on behind an insulation system.