2 Storey House, Insulating Under Upstairs Floor

[Click4]

hi,

Going to be pulling up most of the upstairs floors in a 2 storey house to get a rewrire done and install underfloor heating throughout.

While floor is up and before rewiring is done, considering installing insulation under the floor to minimise heat from downstairs rising upstairs. Especially with the low heat output underfloor heating want to keep as much as Possible heat wise downstairs.

Just wondered if anybody had any suggestions on insulation to use?

And is it ok to install flat against the ceiling below without an air gap.

Some things I’ve read suggest it’s ok as there is no cold zone for condensation to form and others suggest no as it effects the breathability of the house... one suggestion to get around this was to use a sheep’s wool type insulation that absorbed condensation while releasing it in a controlled manner without inhibiting breathability?

Otherwise was just going to use rock wool or a foam board insulation, then when required the cables can be laid across the top.

Thanks

 

[ivixor]

Yes, rockwool resting on the plasterboard is pretty standard I think. Cables on top of that.

The heat retention benefits are actually secondary to the noise insulation properties.

 

[^woody^]

There is no condensation risk between two heated spaces. What you have been reading applies to other situations.

Underfloor heating requires specific insualtion type to reflect heat not just insulate.

 

[Click4]

Thanks for the replies,

As it will be upstairs in a retrofit application was looking at the aluminium spreader plates which go between the joists to reflect heat upwards, they also do some with built in insulation but it’s polystyrene and not too keen on polystyrene inside the house due to its toxicity when burnt.

So was thinking rockwool above ceiling, then electrical cables on top, then the spreader plates with heating pipes then boarded over.