Case study
Loft Insulation Case Study — Old Insulation Replaced With 300mm in a Bungalow Loft, Ingatestone
This Ingatestone bungalow had a 70m² loft with less than 100mm of old, flattened insulation and no roof ventilation at all. We cleared the old material out, treated the timbers, fitted lap vents and laid new 300mm insulation across the whole loft floor in a single day.
What we found
- •Old fibreglass and mineral wool, 100mm or less
- •Insulation compressed and damaged in places
- •No ventilation in the roof space
- •Downlights and cabling in the ceiling below
The loft
A bungalow has a big loft for the size of the house, because the whole home sits under one roof. Here that meant about 70 square metres of loft floor, with a good two metres of height at the ridge, so there was plenty of room to work.
The insulation up there was a mix of old fibreglass and mineral wool, mostly well under 100mm deep. Years of being walked on and pushed around had flattened it, and some of it was torn. Flattened insulation holds far less warm air, so the loft was doing much less than its depth suggested.
There was also no ventilation in the roof. When warm, damp air from the house meets a cold roof with nowhere to go, condensation follows. The damp meter readings on the day were low, so this was the right time to deal with it, before it became a problem.
What we recommended
Our surveyor, Dean, recommended taking the old insulation out rather than laying new on top. Topping up over compressed, damaged material leaves you with an uneven layer, and it hides the condition of the ceiling and timbers underneath.
With the loft cleared, the plan was to treat the timbers, add ventilation and lay a full new layer of 300mm insulation, which sits above the 270mm benchmark usually recommended for mineral wool.
The work
Our own team did the job the day after the survey. The old insulation was cleared out, back to the joists and ceiling.
The roof timbers were given a mould treatment, and lap vents were fitted so air can now move through the roof space. The downlights and cabling noted on the survey were worked around as the new insulation went down.
The new 300mm layer of Knauf insulation was then laid across the full 70 square metres.
The work helped to
- Replace flattened insulation with a full 300mm layer
- Add ventilation to a roof that had none
- Treat the roof timbers while the loft was clear
- Finish the whole loft in a single day
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