Insulating between ground floor and first floor?

[Stephen H]

Hi all,

as part of the central heating upgrade, I've got the floorboards up.

I am putting in 14 rads, 7 downstairs on its own zone valve, and 7 upstairs, also on its zone valve.

The idea is that while we are sleeping upstairs, theres no point heating the downstairs, and equally when we are downstairs during the day, theres no point heating the upstairs.

Now I am thinking about putting in insulation between the ground floor ceiling and the first floor floorboards. I know about making sure all the insulation goes under all power and lighting cables.

The idea is that the heat from downstairs does not inadvertently heat upstairs through convection/conduction and also should hopefully make the upstairs rooms more bearable in the summer.

Now is this OK to do, and should I go for 4 or 8 inches?

Needless to say there will be 12 inches in the loft.

Regards

Stephen.

[Bob Minchin]

Gut feeling is that it would be a waste of effort unless you are going to religiously close all doors in the house to prevent the insulation being bypassed by moving air going up stairs.

Bob

[Doctor Drivel]

Put in Rockwool not glass fibre. this adds sound insulation -well worth it. Thermal insulation will be minimal. Uprate the insulation in the loft.

[Andrew Gabriel]

You won't build up enough temperature differential during those periods for it to matter. If you intended to only heat one or the other for many days on end whilst allowing the other one to get stone cold, then it might be more significant.

You allow for this when doing your heatloss calculations for sizing the radiators.

How?

None at all.

[Stephen H]

Talking of Heat loss calculations, I did this for fabric heatloss and ventilation heatloss.

I found a source of U values on a website somewhere and they are as follows

Surface material W/m2°C plasterboard ceiling with 4in fibreglass, felted & tiled roof 0.3 suspended wood floor 1.7 double skin wall & air cavity 1 Stud & partition 1.8 DG UPVC 1.7 Wood 1.8

I notice that the the U value for a double skin wall with air cavity has a U value of 1.0. Now for a plasterboard ceiling with 4 inches fibreglass has a U value of 0.3 That is suggesting that plasterboard and

4 inches of fibreglass is a better insulator than 4 inch brick, 2 inch air cavity and 4 inch breeze block....

Is that really the case?

If so the mind boggles as to what the U value would be if that 4inches of loft insulation was replaced with 12 inches.......

Stephen.

[The Natural Philosopher]

Yes

Irrelevant.

At some level the dominant heat loss becomes ventilation, and also doors and windows.

Once you are up to 4" of celotex or about 6-8" of rockwool, you are in the position of needing to go triple argon bullshit bollocks, and have double doored porches to the outside world..and heat recovery ventilation.

And probably some form of powered humidity control

Diminishing returns.

The figures suggest that the average poorly built house of 30-300 years ago will be 3-10 times worse than double glazed cavity insulated modern.. but ou could treble the cost of the house of today and still not much more than halve the heatloss.

Better to spend the money on nuclear power stations..;-)

[therustyone]

Plus, if the bathroom/toilets are always heated, for comfort, the doors must be always closed.

rusty

[NT]

The temp difference that occurs over one day is trivial. Insulating the 2 zones only results in more uneven central heating. It also will worsen overheating of upstairs in summer, since heat is no longer being conducted down. Forget it. Do something useful with the insulation instead.

Pouring in a load of runny plaster can help with noise transmission by making the ceiling PB a lot more rigid, and increasing mass some. Once set, adding a very thin sprinkling of loose sand can help things further.

NT