Which type of Insulation??

WUFF

Hi,

Starting an extention...any opinions which way to go with external walls?

310mm wide Cavity wall with 65mm insulation and insulated slabs internally....or

335mm wide Cavity wall with 80mm insulation and no internal insulation?

sydthebeat

350mm wide cavity wall with 150mm pumped platinum polystyrene bead insulation

best bang for buck in my opinion with least possible problems...

jpfahy

Cavity Wall: In theory this is great but in practice there will always be gaps in the insulation, the amount and size of these depends on the skill/interest of the builder. Any walls I've seen being built are full of gaps. Where there is a gap the cold air just flows through like an open door bypassing the insulation. You also waste heat heating the inner leaf of the wall which consumes energy.

9" Hollow Block with internal drylining: Much more snug and no heat is wasted heating the walls as the insulation is directly behind the plasterboard. Rooms just feel more comfortable too. Also handy that you can run cables and pipes behind the drylining.

Poor Uncle Tom

jpfahy wrote: »

9" Hollow Block with internal drylining.

This is not a good enough method of construction for any part of a house, these days. Unless the 225mm hollow block is the inner leaf of a cavity it will be constantly wet. You cannot have wiring or pipework in this environment. Also it is not good practice to have the insulation in this environment either.

This is sub-standard construction, imo.

sydthebeat

jpfahy wrote: »

9" Hollow Block with internal drylining: Much more snug and no heat is wasted heating the walls as the insulation is directly behind the plasterboard. Rooms just feel more comfortable too. Also handy that you can run cables and pipes behind the drylining.

sorry, i must admit i laughed when i read this....

Dry lining is by far the worst construction method still acceptable in this country. Everything about it is wrong. Every solid wall create a huge thermal bridge. Every intermediate floor is a thermal bridge. Condensation issues are rife. Risk of timber rot is huge. Its highly debatable whether the construction would actually comply with current regs, i personally would purport that it comes no where near compliant.

To the OP....stay away from hollow block construction....

WUFF

Hi,
Thanks for replys.

9" not an option .. external leaf must be brick to match existing.

Sydthebeat, are there any issues with pumped insulation regarding moisture penetration ect.
I known anyone I have spoken to who have used this are very happy with the results regarding heat retention.

The extention is being built on to a timber framed house..can this type of construction also be retro fitted with pumped insulation?

jpfahy

I bought my house twenty years ago. It had been built of 9" hollow block with no insulation in 1969. I was as dry as a bone. I drylined all the inner walls, it's still as dry as a bone. No cold, no rot, no condensation, nada.
The current method of construction is great IN THEORY. Suits builders too as it's easy. Hence the regulations suit them, coincidence that???. Drylining is labour intensive but better.
You'll find more cold bridges is a typical cavity wall than in a drylined house.
In practice I've never seen cavity wall insulation done right.

sydthebeat

WUFF wrote: »

Hi,
Thanks for replys.

9" not an option .. external leaf must be brick to match existing.

1. Sydthebeat, are there any issues with pumped insulation regarding moisture penetration ect.

I known anyone I have spoken to who have used this are very happy with the results regarding heat retention.

2. The extention is being built on to a timber framed house..can this type of construction also be retro fitted with pumped insulation?

1. make sure the product used carries the relevant IAB or BBA certification. This certification includes results of testing to show that moisture penetration is not an issue with this type of insulation.

2. No. A timber frame must have a ventilated space between the outer leaf and the inner timber frame, this should not be compromised.

sydthebeat

jpfahy wrote: »

I bought my house twenty years ago. It had been built of 9" hollow block with no insulation in 1969. I was as dry as a bone. I drylined all the inner walls, it's still as dry as a bone. No cold, no rot, no condensation, nada.
The current method of construction is great IN THEORY. Suits builders too as it's easy. Hence the regulations suit them, coincidence that???. Drylining is labour intensive but better.
You'll find more cold bridges is a typical cavity wall than in a drylined house.
In practice I've never seen cavity wall insulation done right.

we are not going to turn this thread into a cavity versus hollow debate.

If you want to start a new thread please go ahead, although you will find you are in a small minority if you consider hollow block construction to be superior to cavity wall...

gillad

310mm wide Cavity wall with 65mm insulation and insulated slabs internally is the warmest option