DIY loft insulation improvements questions

[Box Brownie]

Hi all

Our loft insulation needs some updating and I am sure ( ) I can do it the DIY route.

It is a 1970's chalet style property so part pitched roof with flat 'dormer' roof areas over the upstairs rooms (bathroom & bedrooms).

Now the roof and situation...

It seems to me that it would be easier to cut and slide into place (added benefit = pushing the old & thin stuff out of the way) insulation panel material rather than the rolls of material. This especially so where the gap between room ceilings and aforementioned flat roof areas is deep & narrow.
NB I will measure the gaps wherever I can but ideally don't want to have to lift the attic boarding where it is place.

Plus, in regard to the rafters....I read that you should not stuff the spaces i.e. at least a 25mm airgap should be left between the internal roof felt and any insulation material. I had seen that a type of metalised bubble wrap can be stapled to the rafters including across the ridge beam.

My question(s) ~ has anyone done the same and if so what thicknesses of material did you use and how straightforward was it for you???

TIA for your insights

 

[Dave Canon]

Interesting, one day some loft insulating guy came to our house and surprisingly my wife let him look in our loft. Initially, he pointed out that the layer of insulation was too thin by current standards. He then said you will have to empty your loft to allow a new layer to be added. When it was clear that my wife had no intention of emptying the loft, he pointed out that it probably did not matter as the stuff in the loft probably provided equal insulation. I think you need to be careful handling the insulation material by wearing gloves and a mask.

Dave

 

[Tringa]

A few of thoughts

Are there any electrical cables, pipes or just a nail sticking out of a joict in the gaps you want to insulate which would make sliding insulation in difficult or impossible?

I don't know if this would be a problem or not, I'm sure others will know but would you be able to push 'the old thin stuff out of the way'? Or would it just ruck up as the board material was pushed in?

Dave

 

[Nod]

There may well be noggins in the ceiling too and they'll make it impossible to pull out/slide in.

Wear a GOOD mask when dealing with old or new insulation!

 

[bass_junkie83]

There is probably little point in replacing the insulation above the dormers, unless it is in bad condition. Materials haven't changed that much to make a noticeable difference and as you say it is a fixed depth void so you can't increase the thickness over what is there already. Yo could go to a PIR rigid board to get some improvement, but I am not a fan of flammable insulation and it still seems a lot of faff. You will want to put in a perimeter of mineral wool insulation first that you can compress with the PIR so that there are no voids left as these will mitigate any benefit from the upgraded insulation and may even lead to damp spots.

For the rest of the loft where it is more accessible, I would just roll out some additional insulation on top of what is already there, assuming that you don't use your loft for storage.

 

[robj20]

I've just done my whole loft.

What I did was sister the current joists doubling their height from 75mm to 150mm. I've glued and screwed these and it's took loads of the bounce out of the loft.

I then used 140mm PIR insulation between the joists, any gaps filled with expanding foam.
Then put 18mm chipboard flooring down.

140mm PIR is about as thin as you can go and still meet the regs.

 

[Box Brownie]

Interesting, one day some loft insulating guy came to our house and surprisingly my wife let him look in our loft. Initially, he pointed out that the layer of insulation was too thin by current standards. He then said you will have to empty your loft to allow a new layer to be added. When it was clear that my wife had no intention of emptying the loft, he pointed out that it probably did not matter as the stuff in the loft probably provided equal insulation. I think you need to be careful handling the insulation material by wearing gloves and a mask.

Dave

Thanks for the insights and yes our loft has a rather large amount of 'stuff' to contend with.

A few of thoughts

Are there any electrical cables, pipes or just a nail sticking out of a joict in the gaps you want to insulate which would make sliding insulation in difficult or impossible?

I don't know if this would be a problem or not, I'm sure others will know but would you be able to push 'the old thin stuff out of the way'? Or would it just ruck up as the board material was pushed in?

Dave

A good point and I would be surveying(?) the job as needed before buying anything materials

There may well be noggins in the ceiling too and they'll make it impossible to pull out/slide in.

Wear a GOOD mask when dealing with old or new insulation!

A good point about PPE and care in handling the old as well the new stuff....though panels are not so injurious as rock wool and it's similar types.

As mentioned above I would thoroughly 'reccy' the job and hopefully spot any such noggins & obstructions?

There is probably little point in replacing the insulation above the dormers, unless it is in bad condition. Materials haven't changed that much to make a noticeable difference and as you say it is a fixed depth void so you can't increase the thickness over what is there already. Yo could go to a PIR rigid board to get some improvement, but I am not a fan of flammable insulation and it still seems a lot of faff. You will want to put in a perimeter of mineral wool insulation first that you can compress with the PIR so that there are no voids left as these will mitigate any benefit from the upgraded insulation and may even lead to damp spots.

For the rest of the loft where it is more accessible, I would just roll out some additional insulation on top of what is already there, assuming that you don't use your loft for storage.

Of the areas I can see there is damn all old stuff in places and IIRC what there is is very thin!

As mentioned the loft is partially boarded & used for storage and that was why I was thinking of using the solid board type materials.

I've just done my whole loft.

What I did was sister the current joists doubling their height from 75mm to 150mm. I've glued and screwed these and it's took loads of the bounce out of the loft.

I then used 140mm PIR insulation between the joists, any gaps filled with expanding foam.
Then put 18mm chipboard flooring down.

140mm PIR is about as thin as you can go and still meet the regs.

In regard to raising the height/spacing I learned that there is a method using "loft feet" but they would not increase the stiffness that mention needing to resolve a bounce.....which ours does not have

PS I am not too sure what the joist height/depth is on ours?

 

[dekeyboy]

What you need to know for Installing loft insulation

As bills rise, energy efficiency will be a priority for homeowners. Installing loft insulation at ceiling level is a quick and practical way to prevent heat loss, so Bradley Hirst, Technical Services

probuildermag.co.uk

This might help.

 

[admirable]

Flat dormer roofs,
you can remove the plasterboard ceiling and replace with insulated plasterboard.
Bit of a messy job but lets you get access to evaluate the condition of the roof and upgrade wiring/lights etc too?
Depends on costs but you could do most of the work yourself and just pay for a taper to finish the job before painting.