Cavity Wall Insulation New Build

horsenaughton

I've the foundations in and hoping to start building soon and just looking for advice on insulation. I've a 150mm cavity and initially thought of 100mm insulation and dry lining on internal face of all external walls. I've been told that there is a 110 cavity insulation which has the same uvalue as what I mentioned first. Has anyone used it or any positive/negative views on this! I'd rather not have to use dry lining but do not want the cavity to be completely filled with insulation. Another question is people view on insulation brands. I'm between xtratherm and kingspan?

MicktheMan

horsenaughton wrote: »

but do not want the cavity to be completely filled with insulation.

Why not?

horsenaughton

MicktheMan wrote: »

Why not?

Just prefer to have a bit of cavity so reduce chance of cold bridging nd moisture coming through.

horsenaughton

MicktheMan wrote: »

Why not?

Just prefer to have a bit of cavity so reduce chance of cold bridging nd moisture coming through.

hexosan

horsenaughton wrote: »

Just prefer to have a bit of cavity so reduce chance of cold bridging nd moisture coming through.

I think you need to do a bit of reading up on what cold bridging means. It has nothing got to do with the cavity been full of insulation.
Why not go with 200mm full fill pumped bead insulation. No need for dry lining and cheaper that Kingspan.

Also the only real difference between Kingspan, xtratherm or ballytherm is the price. It's the same insulation with a different name.

Doorcase

Architect has 100mm cavity with kingspan 60mm cavity wall insulation inside. Also 62.5 mm internal plaster board. Just wondering is this sufficient for a modern house. Will it keep it warm or do i need to ask builder to put in more insulation in cavity

BryanF

hexosan wrote: »

I think you need to do a bit of reading up on what cold bridging means. It has nothing got to do with the cavity been full of insulation.
Why not go with 200mm full fill pumped bead insulation. No need for dry lining and cheaper that Kingspan.

Also the only real difference between Kingspan, xtratherm or ballytherm is the price. It's the same insulation with a different name.

Doorcase wrote: »

Architect has 100mm cavity with kingspan 60mm cavity wall insulation inside. Also 62.5 mm internal plaster board. Just wondering is this sufficient for a modern house. Will it keep it warm or do i need to ask builder to put in more insulation in cavity

.

hexosan

Doorcase wrote: »

Architect has 100mm cavity with kingspan 60mm cavity wall insulation inside. Also 62.5 mm internal plaster board. Just wondering is this sufficient for a modern house. Will it keep it warm or do i need to ask builder to put in more insulation in cavity

Get a new architect

Doorcase

So your saying it's not sufficient. Will go on builders advice at this stage as it is an opt out

Gumbo

Doorcase wrote: »

So your saying it's not sufficient. Will go on builders advice at this stage as it is an opt out

What's the builders advice?
Will he stand over the air tightness and any condensation/mould issues?

hexosan

Doorcase wrote: »

So your saying it's not sufficient. Will go on builders advice at this stage as it is an opt out

Don't use the insulated slabs internally at all. If build or arch is recommending it run a mile. Much cheaper and better (in my opinion) 200mm wide cavity pumped with full fill bead insulation.
Easier for block layer so expect a discount on the block price as he'll be much quicker not having to fit insulation boards in the cavity.

hexosan

Look up dry lining mould problems and thermal looping of insulated board in cavities.
You'll see why I suggest full fill bead.

Bonzo Delaney

Doorcase wrote: »

Architect has 100mm cavity with kingspan 60mm cavity wall insulation inside. Also 62.5 mm internal plaster board. Just wondering is this sufficient for a modern house. Will it keep it warm or do i need to ask builder to put in more insulation in cavity

Had to re-read the date on that post that method went out the window about 10 years ago

Doorcase

Suggestions welcome. There is bad reports on blown in insulation also.

Doorcase

60 mm kingspan tw50 in plans

hexosan

Doorcase wrote: »

Suggestions welcome. There is bad reports on blown in insulation also.

Can you link to the reports on blown bead. I'm not aware of any in a wide cavity construction.

If your site isn't in an exposed position and subject to continuous driving rain I can't see an issue.

hexosan

I still stand over my suggestion for full fill from a cost/ ease of construction and end result I don't reckon it can be beaten.

Doorcase

Thanks for your reply. Would you have anything against the proposed 60mm kings pan tw50 in 100mm if it's well build house.

hexosan

Doorcase wrote: »

Thanks for your reply. Would you have anything against the proposed 60mm kings pan tw50 in 100mm if it's well build house.

Yes I still would because you won't get the values Kingspan report, with 99% certainty it won't be installed perfectly and I refer you back to thermal looping.

hexosan

I built with a 250mm full fill cavity but if I was doing it again I'd only go 200mm. The difference between the two is minimal and for the extra cost I'll never see it back in a saving in heating cost.

Handsandtools

BryanF wrote: »

.

Internal insulation can't be more than 1/3 of all insulation thickness, as that will move dew point inside inside the wall between insulation.
I'm using DOF-THERM software to calculate insulation needed and dew point location depending on temperature and moist levels.

BryanF

Handsandtools wrote: »

Internal insulation can't be more than 1/3 of all insulation thickness, as that will move dew point inside inside the wall between insulation.
I'm using DOF-THERM software to calculate insulation needed and dew point location depending on temperature and moist levels.

What post is this in response to ?

Is this just an advert?

Handsandtools

I reply to the comment about insulation 100mm cavity and 62 internal, it will cause problems inside the structure if dew point will not be looked after. that software is free to use for everyone who need it, I got it true internet from Finland, so it's nothing to do with my services, it's more an advise!

BOARDHOG

I am currently at floor level and would appreciate advise on
Insulation for my walls. There is a tight budget so I was thinking 140mm insulation in the cavity. Is this sufficient.

MicktheMan

BOARDHOG wrote: »

I am currently at floor level and would appreciate advise on
Insulation for my walls. There is a tight budget so I was thinking 140mm insulation in the cavity. Is this sufficient.

Your ber assessor is the person to ask. What was specified in the prelim ber?

BOARDHOG

140mm in cavity and 50 mm on the inside. Seems a bit excessive.

MicktheMan

BOARDHOG wrote: »

140mm in cavity and 50 mm on the inside. Seems a bit excessive.

That is a woeful spec. Chances are you will be cold in that house and have high fuel bills.

Your problem will not be the amount of insulation but rather the effectiveness of the insulation on top of very poor airtightness.

Read back through the many threads on insulated drylining and cavity wall insulation boards to understand why.

BOARDHOG

A main goal would be to have it air tight as much as possible. Why is this woeful spec ? The 50 mm is 50 mm dry lining board.

sydthebeat

BOARDHOG wrote: »

A main goal would be to have it air tight as much as possible. Why is this woeful spec ? The 50 mm is 50 mm dry lining board.

on a new build thats a bad specification, not only has its been explained loads of times here why its bad... but we've already had threads on issues which have resulted from this spec., including black staining on internal walls

MicktheMan

What is your airtightness target?
Where is the AT barrier of the wall?
Yes, i know the 50mm is drylining.

To understand why it is a bad spec, I have already suggested you:

MicktheMan wrote: »

Read back through the many threads on insulated drylining and cavity wall insulation boards to understand why.

Top tip: use the "search this forum" function.

BOARDHOG

What would you recommend. My cavity is 150mm. It seems it's not advisable to have internal insulation.