Insulating my floor

[Derwydd]

I'm wondering what some of your expert thoughts are on insulating my floor. This is my first little project since we took over the house 5 month and I'm really keen on doing things right, using the correct materials etc.
I have a builder friend who's coming on Thursday to carry out a few jobs for me. We have a utility room which is 2.4m x 2.1m. Within this space is a small WC and basin accessed via a sliding door. This creates a dead space so I've decided to take down the solid non supporting walls to create one room. I will keep the Wc as it's handy for my kids.

The property was built in 1836 and the utility where the work is to be carried out is in an extension, however we are unsure when the extension was built. It has a lathe ceiling so I guess it's been stood a few years.

I was in my head that I'd dig out the floor and insulate and carry this on through the house as I go through each room. My builder recommends I do this but the more I read the more my head is saying not to bother and just leave it alone. He says a visquine as to prevent any damp coming in but my thought was if any damp wanted to come up through the floor would instead find its was to the walls, then 100mm kingsman? Shall I bother digging out as if I do it now I'd feel I'd have to carry it on through potentially damaging skirting boards etc. My only gain is a warmer floor and lowering my overall heat loss- is it worth doing or waste of time? What is the recommended method?

Thank you

 

[88v8]

Hello and welcome.

Leave well alone, is a good thought.

Depending on the age of the house, it may or may not have an effective dpc.
If not, as you say, any damp will be sent into the walls.

In any case, to dig up floors for the sole purpose of insulation, is a dead waste of money. Of course, your builder is keen, however heat loss through the floor is about 10/15%. If you insulate, you might save half that. But the cost, and disruption....... what's your annual heating cost ? (leaving aside hot water) ... completely pointless.

If you're replacing a floor anyway, that may be a different matter of course.

Best payback is insulating the attic.
Hot water tank with integral foam insulation.
Draughts, but be careful not to stop ventilation if the house has a tendency to damp..
And keeping the temp down... the cost difference between heating to 66f and 70f is considerable... wear a wooly.

Ivor

 

[wobs]

Hello and welcome.

Leave well alone, is a good thought.

Depending on the age of the house, it may or may not have an effective dpc.
If not, as you say, any damp will be sent into the walls.

In any case, to dig up floors for the sole purpose of insulation, is a dead waste of money. Of course, your builder is keen, however heat loss through the floor is about 10/15%. If you insulate, you might save half that. But the cost, and disruption....... what's your annual heating cost ? (leaving aside hot water) ... completely pointless.

If you're replacing a floor anyway, that may be a different matter of course.

Best payback is insulating the attic.
Hot water tank with integral foam insulation.
Draughts, but be careful not to stop ventilation if the house has a tendency to damp..
And keeping the temp down... the cost difference between heating to 66f and 70f is considerable... wear a wooly.

Ivor

...and thick curtains, with thermal liners.

 

[Tony.]

Can you clarify all the rooms are of a solid construction?

 

[Tony.]

clearly I meant floor! solid or suspended?

 

[MatthewC]

I'm a fan of limecrete floors, which I think are warmer than ordinary floors, but in this case I agree with Ivor that you should leave it all alone. Certainly putting down Kingspan would drive any damp to the walls, and if you dug out that much then you might as well do limecrete!

If you do the loft then investigate natural insulation such as sheepswool e.g. Thermafleece

BTW, the ceilings are made with "lath", not "lathe" - only a letter different but rather significant!

Matthew

 

[paulc]

I'm a fan of limecrete floors, which I think are warmer than ordinary floors, but in this case I agree with Ivor that you should leave it all alone. Certainly putting down Kingspan would drive any damp to the walls, and if you dug out that much then you might as well do limecrete!

The other danger of digging out the existing floor is you may dig bellow the footings. This could compromise the foundations and end up being even more expense.

 

[Derwydd]

Thanks for you informative responses! (Including the English lesson)

I think I've made up my mind and decided against the floor insulation - cheers for that - it makes sense, which is why I wanted to ask you.
The house has been underpinned in the area in question - which I forgot to mention! - probably a critical piece of information!!
The lounge, utility, kitchen are solid floor - under the carpet in the lounge is parquet which is in only half of the room as it was extended some time ago - shame really as I would have liked it all exposed. The reception and dining room are timber suspended.

 

[88v8]

Mmm, yes. Because something can be done, doesn't mean it should be done.
You could lift the boards, suspend insulation underneath being careful not to block the airflow**, but inevitably it will damage the boards and unless you are lifting the floor anyway I would question whether it's worth the bother. A thick carpet and underlay is pretty insulating.

Not all insulation has to have a payback. Sometimes, it's worthwhile just for the cosiness.
But in considering the notion of payback, one should not forget the opportunity cost, that is to say how one could invest that capital.
Currently one can get around 6% (less dividend tax if applicable) investing in bank Preference shares. So, that notional 6% needs to be deducted in assessing any annual savings. Having made that calculation, one may find that the 'payback' time is never.
Just an observation.

Ivor

** seeing as you are new to the house, before you cover up the floors with some nice new lino or whatever, check that the airbricks are uncovered, indeed check that there are sufficient of them and there are no dead corners where damp/rot may lurk. Lifting a couple of boards at each end of the room may or may not produce a reassuring gale. If not, now is the time to do something. It has even been known for builders to block airbricks when erecting extensions. Gasp horror.

 

[MatthewC]

** seeing as you are new to the house, before you cover up the floors with some nice new lino or whatever, check that the airbricks are uncovered, indeed check that there are sufficient of them and there are no dead corners where damp/rot may lurk. Lifting a couple of boards at each end of the room may or may not produce a reassuring gale. If not, now is the time to do something. It has even been known for builders to block airbricks when erecting extensions. Gasp horror.

On my house there was just one airbrick to the suspended floor in the front lounge, and before I even bought the house I made sure that it was unobstructed. However, when I lifted the floorboards some months later, I found the vent was blocked with cement on the inside and, in any case, the wall supporting the joists was so close to the external wall that the gap had filled with damp muck and completed the blockage. Also, since it was the only vent, it wouldn't be much good anyway.

I installed a second vent in the floor on the far side of the lounge to give some flow, and rebuilt the supporting wall an inch or two back.

Matthew