Insulating void between floors

rob w

Hi,

I am doing a bit of renovation at the moment and have all the floors lifted upstairs and will be closing them up shortly. I am wondering should I put some insulation in the void before I do?

We live in a dormer bunglaow, cavity walls and attic are already well insulated. The suspended floor downstairs will be done over the coming months.

Is there any benefit to insulating the void between floors - I would like to do this to dampen sound and keep each floor insulated from one another so I am only heating the zones I want to heat in the house.

Is there any potential issues with breathability, condensation etc doing this? I was planning on using 100mm rockwool in a 200mm void.

Thanks

Interested Bystander

I did it in February Rob but haven't moved back in yet. Used 150mm acoustic isover and rockwool.
From what ive experienced working in the house since with tradesmen roaring at each other up and down the stairs, it has definitely made a difference with sound.
Hopefully in winter we will feel the thermal difference as now heat can only escape to the upper floor quickly via the hall which is double height due to stairwell. Where before there was no insulation whatsoever between floors so the bedrooms were toasty but downstairs was only so-so.

I would do it. Especially if you are happy to lay it yourself. It won't take long especially if you get one or two more bodies to help out. And is far easier to do your way (from above) than how I had to do it. I stuffed between the joists from below before my ceilings were put back up, no PPE can make that a pleasant experience!
So a small investment for a decent return. If I recall, I paid about €10 per m²

BryanF

Rob what is the external wall construction?

rob w

BryanF wrote: »

Rob what is the external wall construction?

Hi,

External walls are cavity blocks rendered on outside and have been pumped with insulation before we bought the place.

It's a dormer so the upstairs floor only meets the external wall at the gable ends. Other walls upstairs are partitions with the attic behind them. Attic is well insulated with earthwool right up to the bottom of these partitions.

rob w

Interested Bystander wrote: »

I did it in February Rob but haven't moved back in yet. Used 150mm acoustic isover and rockwool.
From what ive experienced working in the house since with tradesmen roaring at each other up and down the stairs, it has definitely made a difference with sound.
Hopefully in winter we will feel the thermal difference as now heat can only escape to the upper floor quickly via the hall which is double height due to stairwell. Where before there was no insulation whatsoever between floors so the bedrooms were toasty but downstairs was only so-so.

I would do it. Especially if you are happy to lay it yourself. It won't take long especially if you get one or two more bodies to help out. And is far easier to do your way (from above) than how I had to do it. I stuffed between the joists from below before my ceilings were put back up, no PPE can make that a pleasant experience!
So a small investment for a decent return. If I recall, I paid about €10 per m²

Great, thanks for that info. I certainly wouldn't have fancied doing that job from below! Fair play!

Gumbo

rob w wrote: »

Hi,

External walls are cavity blocks rendered on outside and have been pumped with insulation before we bought the place.

It's a dormer so the upstairs floor only meets the external wall at the gable ends. Other walls upstairs are partitions with the attic behind them. Attic is well insulated with earthwool right up to the bottom of these partitions.

Cavity blocks pumped?
So each block was drilled twice and each cavity pumped?

rob w

Gumbo wrote: »

Cavity blocks pumped?
So each block was drilled twice and each cavity pumped?

Sorry, cavity wall has been pumped! Not the blocks.

Lumen

You might want to go round with an FLIR camera to inspect both upstairs and the ceilings on the ground floor.

I did this in a friend's bungalow and the results were quite surprising. Cold spots all over the place.

Possibly not the best time of year to do a heat loss survey though.