Insulating 1st floor on 1930's house

[happyhero]

Hi I have a typical draughty 1930's house with suspended floors and I understand a fair bit about insulating the ground floor. We have air bricks back and front on both floor levels and of course it gets pretty draughty under the ground floor and there is a void of about 10inches under the ground floor joists but what about the 1st floor?

I am not sure how the air bricks can do that much on the 1st floor as the joists are sandwiched between the ceiling below and the floor above so surely they can only ventilate within the 2 joists that they are located what do you think?

I am thinking of insulating the 1st floor as I am decorating there now. I realise that some heat may come up from below and insulating will stop this but surely this is a good thing, as heat from below is lost heat below and the air bricks in the 1st floor will be allowing cold in so insulating from this and thus preventing so much heat being stolen from below will be a good thing, wont it?

I was trying to find a good thin insulator with a good R value that I could place on top of the floorboards (and not create too much height) but other than a really crazily expensive one none seem that good so I then considered putting in Kingspan just under the floorboards, which would be a lot of work but seems my only option to insulate well, any ideas?

What do you think about me insulating the 1st floor, good or bad idea and reasons, any advice appreciated.

 

[JohnD]

for an irregular gap in an older houe. stuffing mineral wool between the joisrs will fill the gap tight enough to prevent draughts. Kingspan is unlikely to be a close fit.

but why do you want to do it?

have you got cavity walls?

have you got a porch roof or bay window roof allowing draughts to come up under the first floor?

The airbicks under the ground floor are to allow cool dry air to flow through and take away damp.

 

[happyhero]

Hi JohnD thanks for that, so are you saying to fill the cavity completely, is it ok to fill between the joist on the first floor to fill completely with mineral wool, I have seen it done before I must admit?

The reason I am thinking of doing it is because I have access to it better than I ever will do again in the future because we are decorating etc, and I thought insulating will improve things, but no I am not aware of any draughts coming through on the first floor or at least not in our bedroom which I am working on now. Do you think it is a waste of time and money to do anything insulation-wise with this room?

Should I forget about insulating the floor and just carry on with our floor plans as normal, i.e. we are thinking of either laminate or hard wood floor more likely in this room?

What do the first floor airbricks do I cannot see them coming through into the 1st floor gaps between the joists?

 

[JohnD]

if you have airbricks on the first floor as well as the ground floor, they are probably intended to ventilate the cavity. This is no longer considered nmecesary and they will probably be sealed when you get cavity wall insulation.

packing mineral wool between the joists will slightly reduce airbourne sound such as conversations or tv.