Insulation of sub floor

[Steveb21]

1950s bungalow - dormer converted in the 80s.

Cavity walls - 40cm - not filled
Sub floor

Property always feels cold and my heating bills (now I have a smart meter fitted) are higher than what I think they should be.

I was thinking of lifting the floor boards (tongue and groove) and laying a net between the joists and filling with insulation.
Like - https://great-home.co.uk/insulating-a-suspended-timber-floor-from-above-floor/

Has any one done a similar job? what was the outcome?

 

[foxhole]

1950s bungalow - dormer converted in the 80s.

Cavity walls - 40cm - not filled
Sub floor

Property always feels cold and my heating bills (now I have a smart meter fitted) are higher than what I think they should be.

I was thinking of lifting the floor boards (tongue and groove) and laying a net between the joists and filling with insulation.
Like - https://great-home.co.uk/insulating-a-suspended-timber-floor-from-above-floor/

Has any one done a similar job? what was the outcome?

What difference does s smart meter make ?

loft insulation would be first place to check, needs around 300mm. Double glazed windows ?

 

[Steveb21]

What difference does s smart meter make ?

loft insulation would be first place to check, needs around 300mm. Double glazed windows ?

Smart Meter - Well now I actually know how much energy I am consuming per day

Windows I have are what I would class as very old double glazed. Don't seem as thick as most in most houses, majority of the frame is made of wood.

I guess I should be looking at
Loft insulation
Windows
Subfloor insulation

In that order?

Surely the only way to resolve the cold floor is to insulate between the joists?

 

[IT Minion]

Typically the loft is first and then cavity wall is the second thing on the list. Under floor insulation is a fair bit of work and disruption.

 

[JohnD]

1) draughtproofing

2) close the doors

3) loft

4) CWI

How many kWh of gas are you using per day, averaged over the last month or two?

Have you got bare boards? Or carpets?

Your loft conversion is quite likely to have terrible insulation. Get a copy of the Building Regulations plans from your local council. You did verify, when you bought it, that the conversion had approval... didn't you?

Windows are the most expensive and have the slowest payback (if any) second only to a plastic door.

 

[cdbe]

You will more than likely ruin your t&g getting it up - you'll have to saw all the tongues off, it will more than likely be dry and brittle and split when you lever it up etc. To get full lengths up you'll have to remove skirtings or cut all the boards in half.
I considered it for my house, even bought the chicken wire, but have decided to only do those areas I can access from underneath (my house is built on a sloping site so I can fit under some parts but not others). The rest will just be well draftproofed with caulk.

 

[JP_]

I've been doing this in my 1930s bungalow, it is making a huge difference.

My preferred method - remove all floorboards, clean out subfloor, clean out air bricks, update electrics and lag pipes if need be.
Use trellis poles (because i had loads spare) and fix under the joists, then lay 50mm kingspan over them, then 50mm rockwool on top.
In bathroom I put in 100mm kingspan, just in case if there was ever a leak it would get soaked up into the insulation. Seal it all in with expanding foam or insulation tape.

My son's bedroom:

I also insulated the walls, but had no cavity to use:

Finished:

Lots of work but turned cold and damp room into cosy, warm and dry.

 

[foxhole]

Any meter can give you a daily usage figure .

 

[Steveb21]

Thanks for all the useful responses.

The dormer was converted back in the 80s, so I am guessing building regs were different at the time.

As the current cavity wall is only 40mm gap I have been previously told that filling this with polly beads would not make much difference? Is this true?

I have annoying draughts coming from some where, either it be from the
ceiling (lack of dormer/loft insulation)
Sub floor
Windows
Cavity walls

Forgetting about which job is the hardest which would have the most effect?

I will post up figures on how much gas I am going through - approx. I am using £8 a day, even with this the property does not get warm enough, some rooms are still cold. I will add kwh later this evening.

 

[Steveb21]

I've been doing this in my 1930s bungalow, it is making a huge difference.

My preferred method - remove all floorboards, clean out subfloor, clean out air bricks, update electrics and lag pipes if need be.
Use trellis poles (because i had loads spare) and fix under the joists, then lay 50mm kingspan over them, then 50mm rockwool on top.
In bathroom I put in 100mm kingspan, just in case if there was ever a leak it would get soaked up into the insulation. Seal it all in with expanding foam or insulation tape.

My son's bedroom:
View attachment 178687

I also insulated the walls, but had no cavity to use:
View attachment 178688


Finished:
View attachment 178689


Lots of work but turned cold and damp room into cosy, warm and dry.

Great job!
How did you fix the wall insulation? Was this a cavity or solid brick wall? Any reason why you did not consider external wall insulation?

 

[JP_]

Great job!
How did you fix the wall insulation? Was this a cavity or solid brick wall? Any reason why you did not consider external wall insulation?

Thanks.

Solid walls, fixed with Everbuild pink drywall foam, with a few mechanical fixings for good measure. I did consider external wall insulation, but as also had an extension put on the back and was removing chimneys and putting in new windows, and money was tight, it worked out better to do internal. Meant I could do a little at a time and more importantly DIY to save a lot of money. The walls needed plastering anyway, and old electrics ripped out in some rooms. Plus I was a bit unsure about cables outside - I have gas pipes, electric and telephone cables running under soffits and was not sure how external insulation would work around those. Internal just seemed simpler and cheaper.

Although, I do need to get the house re-rendered at some point, and was considering having a thin layer of insulation put on externally, but probably won't bother.

 

[JohnD]

As the current cavity wall is only 40mm gap I have been previously told that filling this with polly beads would not make much difference? Is this true?

No.

 

[Steveb21]

4 Sept > 2 Dec (90 days)
Gas usage 7456kwh @ 2.88p each = £215.11
Standing charge @ 17.6p

 

[Steveb21]

Thanks.

Solid walls, fixed with Everbuild pink drywall foam, with a few mechanical fixings for good measure. I did consider external wall insulation, but as also had an extension put on the back and was removing chimneys and putting in new windows, and money was tight, it worked out better to do internal. Meant I could do a little at a time and more importantly DIY to save a lot of money. The walls needed plastering anyway, and old electrics ripped out in some rooms. Plus I was a bit unsure about cables outside - I have gas pipes, electric and telephone cables running under soffits and was not sure how external insulation would work around those. Internal just seemed simpler and cheaper.

Although, I do need to get the house re-rendered at some point, and was considering having a thin layer of insulation put on externally, but probably won't bother.

What was the reasoning behind have 50mm Kingspan and the rockwool on top? I was thinking of just using 100mm Kingspan.

Were your boards T&G? Any special tools you used to get them up?

What did you use to sit the Kingspan on to prevent it dropping through?

 

[JP_]

What was the reasoning behind have 50mm Kingspan and the rockwool on top? I was thinking of just using 100mm Kingspan.

Were your boards T&G? Any special tools you used to get them up?

What did you use to sit the Kingspan on to prevent it dropping through?

Not much reasoning, money really. 100mm kingspan is probably the best idea, I was thinking of doing that for the last room and hallway.
Boards not T&G, I just used to utlity bars.
Trellis poles were fixed under the joists, although the 3 wall plates supported most.

Can see the poles in this pic: