tcordle1890
Member
- Messages
- 2
- Location
- Sheffield
Hello,
We're underway with a victorian semi-detached retrofit (diathonite and woodfibre IWI).
I know there's a fair few threads on related topics already and I think i'm familiar mostly with best practice from reading through them... but am having nerves about the architect-defined underfloor specification and wanted a second opinion.
For the underfloor insulation, we wanted to avoid taking up the floorboards so for most of the ground floor are insulating from below, with membrane stapled to the joints. I was assuming we'd end up with something like ecological building systems spec, but because of the intention/requirement to also upgrade the fire rating of the basement ceiling, the final spec has ended up being mineral wool between the joists and magply underneath for the fire protection (and windtightness).
(The basement has limewashed walls and damp floors, which will have proper ventilation but probably still damp floors which I'm also trying to work up to addressing)
The last-minute wobble I'm having about this is the suspicion that because of the incomplete nature of the membrane, we will end up with moisture travelling down through the joists and reaching dew point in the lower portion of the joists (and at the edges with the wall), there'll be no ventilation and it won't necessarily then wick away down through the magply so we'll be putting the aged joists at risk.
I hope I'm missing something (would any condensing moisture would it be naturally drawn back up and dried out higher up in the joists?) and can trust the people i've already paid to specify it.
One option i've been trying to look up is switching to wood wool for the basement ceiling instead of the magply for better breathability and slightly better insulation, as it's also relatively good from a fire perspective (but doesn't look like there's a straightforwardly certified version of this build up).
Had been trying to not worsen the existing headroom but don't like the idea of risking the joists in a way we can't easily detect or track.
Does anything have experience of anything similar?
We're underway with a victorian semi-detached retrofit (diathonite and woodfibre IWI).
I know there's a fair few threads on related topics already and I think i'm familiar mostly with best practice from reading through them... but am having nerves about the architect-defined underfloor specification and wanted a second opinion.
For the underfloor insulation, we wanted to avoid taking up the floorboards so for most of the ground floor are insulating from below, with membrane stapled to the joints. I was assuming we'd end up with something like ecological building systems spec, but because of the intention/requirement to also upgrade the fire rating of the basement ceiling, the final spec has ended up being mineral wool between the joists and magply underneath for the fire protection (and windtightness).
(The basement has limewashed walls and damp floors, which will have proper ventilation but probably still damp floors which I'm also trying to work up to addressing)
The last-minute wobble I'm having about this is the suspicion that because of the incomplete nature of the membrane, we will end up with moisture travelling down through the joists and reaching dew point in the lower portion of the joists (and at the edges with the wall), there'll be no ventilation and it won't necessarily then wick away down through the magply so we'll be putting the aged joists at risk.
I hope I'm missing something (would any condensing moisture would it be naturally drawn back up and dried out higher up in the joists?) and can trust the people i've already paid to specify it.
One option i've been trying to look up is switching to wood wool for the basement ceiling instead of the magply for better breathability and slightly better insulation, as it's also relatively good from a fire perspective (but doesn't look like there's a straightforwardly certified version of this build up).
Had been trying to not worsen the existing headroom but don't like the idea of risking the joists in a way we can't easily detect or track.
Does anything have experience of anything similar?