Summary

For unheated loft spaces (cold roofs) installing insulation at joist level is often the simplest approach. It is important to ensure the loft space is suitably ventilated to prevent condensation.

Cost/difficulty

MEDIUM COST – Estimated £1500-£5000 depending on house size.

LOW/MEDIUM DIFFICULTY – This is a relatively simple measure but it is recommended to consult a professional to carry out the works, especially if there is existing insulation which needs to be removed first. Insulations such as fibreglass can be harmful if loose particles are inhaled, and some older loft insulations may include asbestos.

Applicability in Letchworth

Applicable – No specific requirements.

Insights from ASBP

“Consider using a natural loft roll insulation such as sheep’s wool, hemp or wood fibre, which are easier and safer to handle compared to mineral wool.

An alternative approach to loft roll is to use a loose fill insulation such as cellulose.”

Case study

Links to further information

• Energy Efficiency Guide for Letchworth Garden City residents (2024), page 5
• HCCSP Retrofitting Your House Guide (2024), page 14
• Saltaire Retrofit Handbook (2024), page 38
• Retrofitting Your Home – Cambridge Guide (2022), page 13
• The Surrey Home Energy Improvement Guide (2025), page 52

Image credits – Thermafleece

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This guidance is part of Roofs, Ceilings and Loft Spaces

See more guidance notes on this topic below:

• Insulation between rafters
• Photovolatics {link}