Wall insulation- overkill?

Santos L. Halper

Hey all,
I am doing an extension to my home- we got planning and our engineer is now doing the drawings for builder. He is calling up the external walls of the new as

18 plaster
100 block outer
150 cavity filled with insulation
100 inner block

and 50mm insulated drylining inside. Is this overkill for the walls? and surely if he wants to dryline all inside I can't hang anything up, as I will be nailing into insulation!

sydthebeat

what insulation is in the cavity?

Santos L. Halper

sydthebeat wrote: »

what insulation is in the cavity?

Full-fill bead insulation I think

sydthebeat

Santos L. Halper wrote: »

Full-fill bead insulation I think

change the bead to 150mm board insulation, then no need for internal drylining, which is a bad specification for a new build anyway.

Santos L. Halper

sydthebeat wrote: »

change the bead to 150mm board insulation, then no need for internal drylining, which is a bad specification for a new build anyway.

Whats the difference between bead and board? Someone told me I should keep the drylining to future proof the extension, but will it really make much difference?

sydthebeat

Santos L. Halper wrote: »

Whats the difference between bead and board? Someone told me I should keep the drylining to future proof the extension, but will it really make much difference?

using the board only will give the same thermal resistance as using the dry lining board, but you get the extra benefits of less thermal bridges, better air tightness and better thermal mass.

drylining does not "future proof" you

Santos L. Halper

sydthebeat wrote: »

using the board only will give the same thermal resistance as using the dry lining board, but you get the extra benefits of less thermal bridges, better air tightness and better thermal mass.

drylining does not "future proof" you

Ah, but whats the cost?

loyatemu

Santos L. Halper wrote: »

and surely if he wants to dryline all inside I can't hang anything up, as I will be nailing into insulation!

90% of houses built in the last 20 years are plasterboarded on the inside, of course you can still hang things up.

covey09

You really need to Assess what you want your self, do you want a gallery or somewhere warm and easy to heat

overshoot

Santos L. Halper wrote: »

Ah, but whats the cost?

in general we have found marginal price differences for board insulation vs pumped & drylined. If you want to pump it alone, to meet regulations you need a 200mm cavity.
Added to syds post, id recommend a higher spec board that you can leave a bit of a cavity eg 120mm kingspan k106. Again it will work out a similar price as it is easier to install & build around that a full fill-you lose money in one place make up in another (still may be marginally dearer). It also reduces the risk of water tracking across. Full fill board insulation really needs to be done right or not at all - it depends on the competency of builders.
You friends have mentioned "future proof", all the options above give the same u-value.

edit-drylining removes the thermal mass, so your house will heat up/cool much quicker. Think getting up in the morning - its warmer with all cavity insulation as the blocks will retain & then radiate the heat - providing proper detailing

Santos L. Halper

loyatemu wrote: »

90% of houses built in the last 20 years are plasterboarded on the inside

Not where I'm from mate.

Santos L. Halper

Thanks for the help guys, I just had a phone call with my engineer where I went ballastic at him for suggesting the internal drylining- still cooling down here!

Gumbo

Santos L. Halper wrote: »

Not where I'm from mate.

Where are you from

893bet

Santos L. Halper wrote: »

Thanks for the help guys, I just had a phone call with my engineer where I went ballastic at him for suggesting the internal drylining- still cooling down here!

Going ballistic with your engineer won't help.

Given its an extension it is a pretty common detail. Not ideal but very common even in new builds (several of my friends currently building and using slabs on external walls).

Gumbo

893bet wrote: »

Going ballistic with your engineer won't help.

Given its an extension it is a pretty common detail. Not ideal but very common even in new builds (several of my friends currently building and using slabs on external walls).

Extremely common on new builds on Dublin ranging from housing estates in north Dublin to large one off builds in plusher areas such as Clontarf etc, it's not a detail I like myself but there's nothing wrong with it per say either.

Poor Uncle Tom

Santos L. Halper wrote: »

I just had a phone call with my engineer where I went ballastic at him for suggesting the internal drylining- still cooling down here!

Very short sighted, given that you are a novice to this and your engineer is the indemnified professional and the detail you describe is very common.

BryanF

Santos L. Halper wrote: »

Hey all,
I am doing an extension to my home- we got planning and our engineer is now doing the drawings for builder. He is calling up the external walls of the new as

18 plaster
100 block outer
150 cavity filled with insulation
100 inner block

and 50mm insulated drylining inside. Is this overkill for the walls? and surely if he wants to dryline all inside I can't hang anything up, as I will be nailing into insulation!

May I ask,
1. what is the wall buildup
2, and m2 of the existing house
3. m2 is the extension?
4. Budget?
.

MicktheMan

893bet wrote: »

Given its an extension it is a pretty common detail. Not ideal but very common even in new builds (several of my friends currently building and using slabs on external walls).

kceire wrote: »

Extremely common on new builds on Dublin ranging from housing estates in north Dublin to large one off builds in plusher areas such as Clontarf etc, it's not a detail I like myself but there's nothing wrong with it per say either.

What about air tightness, or more to the point, lack thereof?

Common doesn't make it right or acceptable:)

ht9zni1gs28crp

Imagine being that engineer and a client has read online somewhere of a better option from people who don't know the full story......


hmmmmmmm

Santos L. Halper

BryanF wrote: »

May I ask,
1. what is the wall buildup
2, and m2 of the existing house
3. m2 is the extension?
4. Budget?
.

None of your business.

Santos L. Halper

BryanF wrote: »

May I ask,
1. what is the wall buildup
2, and m2 of the existing house
3. m2 is the extension?
4. Budget?
.

67

fred funk }{

Santos L. Halper wrote: »

None of your business.

What the hell.

BryanF

Santos L. Halper wrote: »

None of your business.

What's with the attitude?

In order to help, it would be useful to know what the increased footprint relative to the existing is. And Also what the existing construction is like - in order to ascertain whether additional drylining is worth considering.

Gumbo

Santos L. Halper wrote: »

None of your business.

Good luck with the advice mate. Bryan is one of the most experienced posters n this forum, and with that attitude towards him, the rest just won't bother.

Best of luck on site.

ht9zni1gs28crp

Even more so I bet every engineer reading this is breathing a sigh of relief they haven't you on their books.......