Two thirds of our loft, the two sections in the outermost/lowest parts of the eaves, is insulated properly with two layers of standard glasswool stuff.

The middle section was boarded by the previous owners, and the only insulation there is some really old, fairly degraded, insulation under the boards, between the joists. We don’t store anything on these boards, as we use the mini-loft in the garage for our hoarding needs.

I assumed that this middle section could do with some insulation so had a chap round a couple of years ago from the power company to look at it as part of their cheap/subsidised insulation deals. He was convinced it didn’t need doing, as, according to him, oldish insulation under a chipboard board is as good as, if not better than, any extra insulation that might be added on top.

I took him for his word at the time, but I’m still not quite convinced. Surely it’d be better if I stumped up for some rolls of insulation and just put them in place over the existing boards?

The key is how much the boards are crushing the insulation as that degrades its capabilities.

There would be no harm in laying insulation over the boards but I would also question its effectiveness against cost. Especially if the central section of the loft is like mine and over the stairs and landing and not over the main heated bedroom areas.

It’d be better if you lifted the boards and insulated directly on top of the ceiling below.

If you insulate on top of the boards you might get interstital condensation on the underside of the boards which wouldn’t be ideal.

He was convinced it didn’t need doing, as, according to him, oldish insulation under a chipboard board is as good as, if not better than, any extra insulation that might be added on top.

He was convinced it didn’t work with  the calculation required to satisfy his government funding requirements, more likely

My guess is that the effective insulation will of the glasswool etc depend mostly on its height rather than type.

Chipboard isn’t generally used as insulation 😉