Thinnest useful internal wall insulation thickness

Esho

I'm putting panels to headboard height around a bed, and want to put some insulation against the external walls.

It'll need to be thin as it's a small room.

I found a product called Kilima board on Screwfix that is 10mm thick that fits the width.

Is this worth it do you reckon?

10-10-20

https://www.boards.ie/discussion/2058342925/thinnest-useful-internal-wall-insulation-thickness

Those Klima boards appear to be backing boards for tiles. They don't have significant insulation performance.

The closest I know of are 25mm rigid foam boards.

https://brooksonline.ie/insulation/insulation-boards

Whether they will contribute much to the overall thermal performance of the wall is debatable.

listermint

As above 27mm is the lowest realistic obtainable one in providers. But frankly I'd only use it in a punch or around Opes like door frames or window frames.

The minimum I'd personally be getting would be 50mm for anything usable and 70+ on north facing / large gable walls.

10-10-20

https://www.boards.ie/discussion/comment/121925370#Comment_121925370

That one I linked to is just an insulation board at 25mm and not insulated plasterboard. Insulated plasterboard starts at 26.5mm, 12.5mm PB and 12mm PIR.

Esho

https://www.boards.ie/discussion/comment/121925370#Comment_121925370

Wow that thick - thanks for that

Odelay

Are you looking for sound or thermal insulation?

TimHorton

https://www.boards.ie/discussion/comment/121927803#Comment_121927803

I put 100mm Insulation Boards + 12.5 mm Plasterboard on my North Facing Bedroom External Walls (Each room had 2 external walls) - Rooms are now very comfortable and easy to heat.Pay attention to remove any draughts and make airtight. I removed window boards and sealed all around Light Switches Sockets etc and also used 25mm Insulation around Window Reveals. Also ensure there is ventilation.

Shoog

There is no substitute for thickness in insulation. Take the hit on space or live with the cold - those are the only two choices.

Lumen

https://www.boards.ie/discussion/comment/121930155#Comment_121930155

There is no substitute for thickness in insulation.

Well there's aerogels and vacuum insulation panels if money is no object.

lawred2

https://www.boards.ie/discussion/2058342925/thinnest-useful-internal-wall-insulation-thickness

Saucy

10-10-20

https://www.boards.ie/discussion/comment/121933130#Comment_121933130

I went looking for aerogel once to see if I could use it in the corners of a hipped-roof where the rafters create that annoying insulation black-hole. The hint for me in terms of the cost was on the UK websites where you would see "POA" and had to register to see pricing... so I did. They wanted around £300 per square foot with a minimum order of around 10sq.

There are far more aerogel products available now, here's a very good use-case and a reasonable price too:

https://mybuildingsupplies.ie/shop/building-supplies/insulation/foil-insulation/spaceloft-aerogel-strip-insulation-for-posts-windows-doors/

Maybe I should re-look at it.

Esho

https://www.boards.ie/discussion/comment/121928279#Comment_121928279

Thermal. Two external block walls with just plasterboard at the moment. Very cold in winter

Esho

https://www.boards.ie/discussion/comment/121929759#Comment_121929759

Thanks, the room I want to insulate is similar. Looks like it'll need to be 100mm so

10-10-20

https://www.boards.ie/discussion/comment/121933912#Comment_121933912

Over the whole wall, I presume you mean? No point in just doing the headboard in 100mm.

TimHorton

https://www.boards.ie/discussion/comment/121930155#Comment_121930155

Totally agree with this , The Rooms are now a but smaller but so much more comfortable and easy to heat..

Goldengirl

Following this .

Have North East facing room that already has 100mm insulation but still colder than other aspect facing rooms and was thinking about an insulated back wall behind the bed.

Would it be overkill to redo or should I just pay attention to the sockets and switches?

Shoog

https://www.boards.ie/discussion/comment/121934130#Comment_121934130

You can't expect the wall insulation to do all the heavy lifting. Floor insulation and ceiling insulation has a big roll to play. Airtightness is also critical.

Goldengirl

https://www.boards.ie/discussion/comment/121934306#Comment_121934306

Yes. Unfortunately have tried unsuccessfully to get the builder to come back to review and others . Meant to have attic and wall insulation, windows and all up to B 3 level but it's very much colder than the rest of the house .

Rest are toasty enough .

Edit typo

Shoog

https://www.boards.ie/discussion/comment/121934328#Comment_121934328

Over-ventilated possibly ?

It seems that putting in stupid amounts of uncontrolled ventilation is a requirement of the building code.

Esho

https://www.boards.ie/discussion/comment/121933945#Comment_121933945

Yes abso whole wall. I have 16 cm to play with on the very cold external wall.

The other wall is with the bathroom, which has 3 external walls and is a lost cause, I think.

TimHorton

https://www.boards.ie/discussion/comment/121934512#Comment_121934512

Did you consider External Insulation on the Bathroom walls ?

Esho

https://www.boards.ie/discussion/comment/121934640#Comment_121934640

It's possible on two sides, but the other is the side entrance to the back garden. It will just take the wheelie bins width as it is.

listermint

https://www.boards.ie/discussion/comment/121934328#Comment_121934328

What's the heating/ventilation situation in the room

You can insulate a box. But unless it has a source of heat it can just as easily be a fridge or an oven.

Think of a beach thermos..

Airtightness has been for years neglected by lads doing this type of work. Some still do. Sockets, windows , and most of all window sills pissing air. - attention to detail.

GreeBo

OP have or are you taking the walls back to block work?

If not then I wouldnt bother doing anything, its a waste of effort.

One the other hand you will see significant improvement by stripping back to blockwork and using 50mm PIR, VB and the reboarding over the lot.

/edit to add that you probably wont even lose any room space with the above approach as you existing plasterboard is either on battens or dot/dap which are both effectively 50mm.

Esho

https://www.boards.ie/discussion/comment/121936562#Comment_121936562

I think the blocks were just slabbed and plastered over - is that dot/ dap?

There are no battons,space behind the wall.

The whole place was done on the mega cheap in the 80s, I reckon.

I'm happy to lose the space, if it'll help.

But I can only insulate two walls - the wall with window I can do nothing with internally, because the door frames are flush to the wall, or externally because it is the side passage to the back of the house.

GreeBo

https://www.boards.ie/discussion/comment/121936663#Comment_121936663

There must be some sort of gap unless the walls are wet plastered and not plasterboard at all? Even dot and dab will give you 20-30mm typically.

The problem with not doing all the walls, especially the external ones is that you are now reducing the space for condensation, which may/will increase the likelihood of wet walls, especially down the bottom and behind any furniture.

A picture might help with some alternative suggestions as its hard to know exactly what the issue is.

Really you can put as much or as little PIR as you want on the walls, but doing it on the internal walls isn't going to achieve much at all tbh, doing the ceiling would help, unless your attic is very well insulated already?

Goldengirl

https://www.boards.ie/discussion/comment/121936392#Comment_121936392

Hole in the wall Passivent sliding thing with insulated tube going from inside to out.

Long double rad under the window.

Attic insulated. Think gaps everywhere though.

We have been talking about getting someone to check it all out to see what the isdue is for a few years now but something else always takes priority time and money wise.

Somebody here mentioned an airtightness test but to be honest when we looked into it, nobody was interested unless we were getting a big job done.

And I am hoping its not going to be a big job!

listermint

https://www.boards.ie/discussion/comment/121938565#Comment_121938565

Can do basic airflow test yourself with something like an incense candel, plenty of quick how to on YouTube. Give you some idea of possible airflow.

Shoog

https://www.boards.ie/discussion/comment/121936663#Comment_121936663

Its potentially a significant issue if you fail to do the bathroom as well, you will have created a a cold space with very high moisture content right next to a warm space. The warm space generates a much higher air moisture content and it will migrate to the bathroom and condense on the walls, add to this the frequent super saturated air when showering/bathing and your walls will be constantly running with condensation. Expect everything in the bathroom to be black with mould in very short order.

You have to create a strategy for the whole house not just a part otherwise you just shift the problems from room to room.

Goldengirl

https://www.boards.ie/discussion/comment/121938730#Comment_121938730

Have done that and not drafty. But not sure how rigorous a test that is tbh.

No offence.

Have a thermometer thing with a central and another on a string. For a car dashboard I think.

It reads at least about 1degree lower at the wall than the central temp.. But again not sure on accuracy.

I feel a coolness in the corner where the two outside walls meet constantly but my husband is always fine.. Maybe switch places with him 😊

Esho

https://www.boards.ie/discussion/comment/121938783#Comment_121938783

Good point, thanks for that.