Full fill cavity vs Aerobord 190 mm with brick

J

jonnykerry

Registered User
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Hi all,

I'm stuck on where to move from here I've made my mind up on a insulated footing & slab circa U-value: 0.10-.12 , roof about the same. But this is where the dilemma is do I : A) Go for 200 mm or 250 mm pumped cavity with say K/span or B) my original and in my mind safe bet of 190 mm aerobord platinum for a 200 mm cavity. It is quoting a U value of 0.16.

Points to bare in mind are that the house has a ridge height of 9.5 meters and is brick on the upper elevations so have concerns about weeping causing damp if I go with pumped insulation.
Also if I go with the aerobord would this by default mean the house would be limited to achieving an "A-2" rating (A-1 calls for U value of .12 in walls), or is the calculation based on the overall performance of the building.

Suggestions welcome.
 
jonnykerry said:
Hi all,

I'm stuck on where to move from here I've made my mind up on a insulated footing & slab circa U-value: 0.10-.12 , roof about the same. But this is where the dilemma is do I : A) Go for 200 mm or 250 mm pumped cavity with say K/span or

  1. B) my original and in my mind safe bet of 190 mm aerobord platinum for a 200 mm cavity. It is quoting a U value of 0.16.Points to bare in mind are that the house has a ridge height of 9.5 meters and is brick on the upper elevations so have concerns about weeping causing damp if I go with pumped insulation.
  2. Also if I go with the aerobord would this by default mean the house would be limited to achieving an "A-2" rating (A-1 calls for U value of .12 in walls), or is the calculation based on the overall performance of the building.
Click to expand...
  1. go with the board type insulation due to the brick - (for confirmation of this, review some Iab certs for pumped bead in brick outer-leaf walls) - note that the board option in such a cavity will slow down the block construction and will demand a top quality 'informed' blocklayer. & please please dont under estimate the need for detailed 1:5 drawings for junctions in your new build!
  2. thats rubish - have you done your provisional BER? calculations are not elemental. you'll be consulting your arch / arch tech on this id assume?
 
+1 to all lowCo2designs comments, and to add the following:

Are you sure that the aeroboard insulation is approved (ie what does it say in its Agreement Certificate) for a 10mm cavity? Theres little margin for error, and you will need to look up 'thermal looping' to see what can happen if board insulation is not tightly fitted to the inner leaf.

Suggest to your blocklayer that the best way to get a correct fit with this type of insulation is to build the inner leaf first, fitting the insulation tightly as you go, and not constructing the outer leaf of block/brick until you have finished the inner leaf (he wont want to do it).

It seems a bit of a shame not to be hitting the 0.12 u value zone with the walls when you are going for such a high spec on the floor and roof.

Your BER rating will be a result of the combination of many factors, and if your BER assessor gave you the information you posted, fire them and get one who knows what he/she is talking about. You are aiming for a high spec, don't undermine it by getting poor advice.


www.studioplustwo.com
 
Food for thought..
Thanks for the reply's, and I have been consulting my architect, he is also of the belief that with the brick featuring in the upper elevations and that the house is being built on the west coast, that the 190 mm aerobord is the safest option coupled to a really good brick layer going as you said up on the inner leaf first, than insulation, than outer.
The working drawings are in the process!

Is the such a produce as 240 mm - 250 mm full fill cavity insulation board?
 
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