What this means in practice
Heat loss, air leakage, vapour movement and ventilation must be designed together. Adding insulation without maintaining the intended air path—or assuming a breathable membrane solves every moisture risk—can move condensation into concealed parts of the roof.
What to check next
- Calculate the whole build-up
- Include repeating thermal bridges
- Do not judge performance by thickness alone
When should you ask a roofer to inspect it?
Seek a build-up-specific assessment when condensation persists, timbers remain damp, insulation has been altered or a reroof changes a thermal element. Compliance is based on the complete construction and target U-value, not an insulation thickness copied from another roof.
Safety first: do not climb onto a roof without suitable access, training and protection. Keep clear of loose coverings, unstable ceilings and water near electrical fittings.
Would you like a property-specific answer?
Request an inspection and written quotation from J&L Welch.
No deposit is required. Payment is due on completion within seven days, with the agreed scope and price confirmed in writing.