Which high performance CWI?

[Sjk]

Hi all,

 

Would appreciate your thoughts.

 

I am looking to keep the wall thickness to a minimum (withing reason), while meeting BR, which I think is 0.18 W/m2.K?  

 

Traditional brick and block construction, hoping  at worst to have a 100mm cavity which would mean 302.5mm. 

 

I've asked for a price of Spacetherm which is a silica gel product and I'm considering Kingspan's OPTIM-R, lastly injected polyurethane foam would really suit the build but I think the performance isnt great?

 

Many thanks

Edited August 19, 2019 by Sjk

[Mr Punter]

Full fill rigid (PIR type) insulation will meet the u-values and work out cost effective. Correct installation is critical, so you need to make sure your bricklayers follows the instructions to the letter.

[Sjk]

Well colour me embarrassed, it looks like aerogels are not suitable for cavity walls!

[Sjk]

  On 19/08/2019 at 13:27, Mr Punter said:

Full fill rigid (PIR type) insulation will meet the u-values and work out cost effective. Correct installation is critical, so you need to make sure your bricklayers follows the instructions to the letter.

Expand  

 

Thanks, is that the same as the K106 panels?

[Mr Punter]

  On 19/08/2019 at 13:35, Sjk said:

 

Thanks, is that the same as the K106 panels?

Expand  

 

Yes.  A few others do similar.  Celotex suspended theirs, which was a shame as theirs had a better interlock to prevent water ingress. Be aware that some u-value claims include for insulated plasterboard and lightweight blocks, neither of which are my favourite.

[Sjk]

  On 19/08/2019 at 13:40, Mr Punter said:

 

Yes.  A few others do similar.  Celotex suspended theirs, which was a shame as theirs had a better interlock to prevent water ingress. Be aware that some u-value claims include for insulated plasterboard and lightweight blocks, neither of which are my favourite.

Expand  

 

What don't you like about lightweight blocks? I was considering these along with aerated blocks.

[Mr Punter]

They are not as good to fix into or to plaster. I like to use 7 newton medium density aggregate blocks throughout, rendered and set. No confusion over different block types and fairly economical.

[the_r_sole]

.

Edited September 26, 2019 by the_r_sole

[Sjk]

  On 19/08/2019 at 14:22, the_r_sole said:

Cavities are there for a reason, filling them is a terrible idea, either design out the need for one or put insulation elsewhere imo

Expand  

 

Apart from polyurethane foam they would all have a cavity, okay maybe some will be small, say 10mm.

 

What's the problem with no cavity and injected polyurethane?

[the_r_sole]

.

Edited September 26, 2019 by the_r_sole

[Declan52]

Why are you set on a 100mm cavity???

If you go down the route of cavity boards then you really are at the mercy of the guy putting them in. Any snots that fall onto the tongue or motar pushed out when he is lifting a block on will have a major impact on how your house performs. A 100mm cavity with boards in a lab will give great results. On a building site its a toss of a coin. Are you able to stop by the site each day to look down the cavity to see if any boards aren't right. And if you do notice some with gaps are you prepared to pull the brickies up on it. 

 I used them in mine but I built it myself so spent time cutting boards with a hand saw for each corner and door and window junction. The boards have small fins on them so there is about 10mm of a cavity. But I made mine an extra 10mm wider as if you get a thicker batch of blocks then you ain't got no room to manoeuvre and the wall will be out of plumb. My build was block and block so I was able to use additives in my render to help keep the wet stuff out. Very few facing bricks will stop rain penetrating into the cavity.

If you can increase the width to at least 150mm you can use graphite EPs beads blown into the cavity so no gaps anywhere. It will be one less thing to worry about on the long list of things to stress out over.

[Sjk]

  On 19/08/2019 at 14:47, Declan52 said:

Why are you set on a 100mm cavity???

If you go down the route of cavity boards then you really are at the mercy of the guy putting them in. Any snots that fall onto the tongue or motar pushed out when he is lifting a block on will have a major impact on how your house performs. A 100mm cavity with boards in a lab will give great results. On a building site its a toss of a coin. Are you able to stop by the site each day to look down the cavity to see if any boards aren't right. And if you do notice some with gaps are you prepared to pull the brickies up on it. 

 I used them in mine but I built it myself so spent time cutting boards with a hand saw for each corner and door and window junction. The boards have small fins on them so there is about 10mm of a cavity. But I made mine an extra 10mm wider as if you get a thicker batch of blocks then you ain't got no room to manoeuvre and the wall will be out of plumb. My build was block and block so I was able to use additives in my render to help keep the wet stuff out. Very few facing bricks will stop rain penetrating into the cavity.

If you can increase the width to at least 150mm you can use graphite EPs beads blown into the cavity so no gaps anywhere. It will be one less thing to worry about on the long list of things to stress out over.

Expand  

 

Im not set on a 100mm, if it can be reduced I'm all for that. It is just I am told 100mm will be sufficient for the insulation panels I was looking at. 

 

 

[Sjk]

  On 19/08/2019 at 14:42, the_r_sole said:

cavities are designed to be empty (hence the name) - they are meant to ventilate out humid air and stop it condensing in the building structure, if you fill the cavity and restrict it's ability to ventilate, you are increasing the potential for moisture build up in the structure, make sure that you do a proper dew point analysis with the manufacturer of the product you choose

Expand  

 

Thanks, it would be designed from the outset this way, so I would hope some of these issues would be limited.

[ADLIan]

Assuming you only want to comply with the Regs check the required U-value with your SAP assessor (for new build) as SAP gives a lot of design flexibility. The 0.18 mentioned in the Regs is not cast in stone. For better than Regs you may have to increase the cavity to 125mm or 150mm, or even wider, depending upon block and insulation. I'm not a fan of injected cavity wall insulation in new build as there is no way of checking for the presence of voids. At least with built in products you can see any problems and correct them.

 

The 'clear' cavity in cavity walls has nothing to do with condensation issues, it is to minimise the risk of rain penetration. Most insulation products for this application, partial and full fill, are BBA approved as required by the Regs.

[Declan52]

  On 19/08/2019 at 15:09, Sjk said:

 

Im not set on a 100mm, if it can be reduced I'm all for that. It is just I am told 100mm will be sufficient for the insulation panels I was looking at. 

 

 

Expand  

Who told you 100mm is sufficient???

Price up the 100mm cavity boards and then don't forget the brickies will want some of you £s per sheet as to put them in right is slow. 

[Sjk]

  On 19/08/2019 at 15:37, Declan52 said:

Who told you 100mm is sufficient???

Price up the 100mm cavity boards and then don't forget the brickies will want some of you £s per sheet as to put them in right is slow. 

Expand  

 

Insulation provider and my builder. 

 

I wouldn’t have time to check they have been installed correctly, I trust my builder though. I understand your point though.

 

I’m not too price sensitive, and the increased floor space would be welcome and valuable. 

 

 

Edited August 19, 2019 by Sjk

[the_r_sole]

.

Edited September 26, 2019 by the_r_sole