Insulation in loft conversions
How roof build-up, ventilation and available rafter depth influence a loft conversion.
This is general information, not a survey, design, legal or Building Control decision. The correct scope and standard depend on the property, work, date and regulatory route.
A conversion normally needs a coordinated thermal envelope around the habitable room, with junctions, fire strategy, ventilation and structure considered together. A product thickness should not be guessed from a photograph: the designer and Building Control route determine the target and build-up.
Insulating between rafters alone may not provide enough depth; an additional layer can help continuity but affects headroom, details and condensation risk. Existing loft-floor insulation and new sloping-roof insulation are different elements with different constraints.