Insulation Needed ?

[Ahmiccc]

Hi all,

 

just bought a 1965 house has a 60mm cavity wall insulation and double glazing windows but all will have to changed for new, it’s a full refurb the only thing it don’t need is to be bulldozed down and re built that’s how big the project is, anyway it’s our first home and wanting to make it a forever home so we want to install underfloor heating system on both floors.

 

Upstairs and downstairs are both suspended floors on.

downstairs I was planning on putting 100mm PIR insulation this is us having to pull the joists out and put bigger ones in then have UFH fitted on that

upstairs I was going to have 75mm insulation in joists and electrics below the insulation and UFH Above of course. The attic is fully insulated aswel I believe with 75mm insulation but this isn’t a problem too much if needs more

 

is this enough is more needed? Obviously money comes into factor, but is the upstairs insulation as important as the downstairs insulation, as downstairs there is air bricks upstairs there isn’t. So am I able to cut the upstairs insulation a bit more form 75 to maybe 50 and have a 125 or 150 in downstairs ?

 

when it comes to flooring it’ll all be laminate throughout entire house.

[SteamyTea]

10 hours ago, Ahmiccc said:

is this enough is more needed

You need more on the ground floor. Can you get 200mm in.

The reason is that UFH will be at about 35⁰C, so a ∆T of at least that when 0⁰C outside (assuming a ventilated void).

 

Also look at making the structure airtight, with the airtightness layer on the exterior side of the insulation. No point putting in loads if cold air can bypass it.

[Bitpipe]

Is it a detached house?

 

Have you considered demolition and rebuild? You say the project is all but this step so you should think it through.

 

We wrestled with the same decision before knocking down our 1950s detached and building a new, airtight and well insulated replacement (with 50% more space).

 

The big advantage is 0% VAT on the project (excluding professional fees).

 

Your build is more likely to stay on budget as there are fewer unknowns compared to a refurb - you also don't need to compromise on the layout and work around the existing.

 

Demolishing a house costs about £5k, you'd need to calculate if the new costs would be addressed by the 20% overall budget saving. I know that in our build, the frame and exterior finish probably accounted for 25% of the overall budget.

[A_L]

13 hours ago, Ahmiccc said:

upstairs I was going to have 75mm insulation in joists and electrics below the insulation and UFH Above of course. The attic is fully insulated aswel I believe with 75mm insulation but this isn’t a problem too much if needs more

 

is this enough is more needed?

 

Unless the ground floor ceiling insulation is for sound insulation then I would reduce it to 25mm of insulation or perhaps an aluminised membrane with a 25mm airspace above the upward facing shiny layer as heatloss downward to a heated volume is very limited and is largely radiative loss. If the first floor ceiling really only has 75mm of insulation I would double it if PIR or make up to 250mm if fibrous insulation.

[Ahmiccc]

43 minutes ago, A_L said:

 

Unless the ground floor ceiling insulation is for sound insulation then I would reduce it to 25mm of insulation or perhaps an aluminised membrane with a 25mm airspace above the upward facing shiny layer as heatloss downward to a heated volume is very limited and is largely radiative loss. If the first floor ceiling really only has 75mm of insulation I would double it if PIR or make up to 250mm if fibrous insulation.

Okay that’s great so I’m sure I’d like maybe more than 25mm maybe 50mm at the very least in the ground floor ceiling and then the first floor ceiling I can easily do more not a problem and probably fibrous insulation too

also the ground floor, the floor will be ripped out cause can’t put in 100mm let alone 200mm which is why I’m doing the research first so I know to order the right thing first

[Ahmiccc]

1 hour ago, Bitpipe said:

Is it a detached house?

 

Have you considered demolition and rebuild? You say the project is all but this step so you should think it through.

 

We wrestled with the same decision before knocking down our 1950s detached and building a new, airtight and well insulated replacement (with 50% more space).

 

The big advantage is 0% VAT on the project (excluding professional fees).

 

Your build is more likely to stay on budget as there are fewer unknowns compared to a refurb - you also don't need to compromise on the layout and work around the existing.

 

Demolishing a house costs about £5k, you'd need to calculate if the new costs would be addressed by the 20% overall budget saving. I know that in our build, the frame and exterior finish probably accounted for 25% of the overall budget.

Yeah sorry this isn’t a option sadly due to budget.

[SteamyTea]

3 hours ago, Ahmiccc said:

the floor will be ripped out cause can’t put in 100mm let alone 200mm

Put in 250mm.

 

What you want to do is reduce the losses to 0.1 to 0.15 W/m².K.

As the floor going to be warmer that the air in the room, you have to calculate on a greater ∆T.

 

Ignore building regulations and get your U-Values and air change per hour figures as low as possible.

And remember that your floor and loft areas are probably your greatest areas, so they have the greatest overall losses.

Don't fret over a door or window that has a 0.05 difference. The areas are too small to make a measurable difference.

 

[Ahmiccc]

15 minutes ago, SteamyTea said:

Put in 250mm.

 

What you want to do is reduce the losses to 0.1 to 0.15 W/m².K.

As the floor going to be warmer that the air in the room, you have to calculate on a greater ∆T.

 

Ignore building regulations and get your U-Values and air change per hour figures as low as possible.

And remember that your floor and loft areas are probably your greatest areas, so they have the greatest overall losses.

Don't fret over a door or window that has a 0.05 difference. The areas are too small to make a measurable difference.

 

Oh yeah I was meaning 220m joists with 200m insulation with 250m insulation Its a very tight fit to the concrete on below

With 175 insulation I get a u value of 0.14 and I heard between 0.13 and 0.25 is good so having the 200m insulation I think is perfect really it’ll be 0.13 u value

[SteamyTea]

16 minutes ago, Ahmiccc said:

Oh yeah I was meaning 220m joists with 200m insulation with 250m insulation Its a very tight fit to the concrete on below

With 175 insulation I get a u value of 0.14 and I heard between 0.13 and 0.25 is good so having the 200m insulation I think is perfect really it’ll be 0.13 u value

Calculate the total energy losses over a year. U-Value is power loss, not the same thing.