Summary
Existing solid floors in Letchworth homes are most likely made of concrete. Only those installed in the last 25 years will have any insulation. Digging out concrete floors to add insulation is a major building project and can be high cost.
Insulating concrete floors may require raising the floor level, therefore special consideration should be given on the impact on door heights and staircase levels.
Material options include:
- High performing aerogel insulation as this can be as thin as 30mm.
- Lower performing phenolic foam insulation could also be used, either installed between timber battens or directly ‘floated’ over the existing concrete.
- Bio-based wood fibre boards laid to the required depth over a concrete slab and DPC (damp proof course), staggering joints between the layers, with a vapour control layer membrane over the top for airtightness and to prevent condensation.
Alternatively, if cost is a barrier, a high-quality carpet with quality underlay will provide good thermal benefit.
Cost/difficulty
MEDIUM/HIGH COST
HIGH DIFFICULTY
Applicability in Letchworth
Applicable – No specific requirements.
Insights from ASBP
“If you are keen to take a low embodied carbon approach for your retrofit, consider using woodfibre boards instead of phenolic foam or aerogel.”
Links to further information
- Energy Efficiency Guide for Letchworth Garden City residents (2024), page 5
- HCCSP Retrofitting Your House Guide (2024), page 21
- Retrofitting Your Home – Cambridge Guide (2022), page 19
- The Surrey Home Energy Improvement Guide (2025), page 52
This guidance is part of Floors
See more guidance notes on this topic below: