Sjk Posted August 19, 2019 Share Posted August 19, 2019 (edited) 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 Link to comment Share on other sites More sharing options...
Mr Punter Posted August 19, 2019 Share Posted August 19, 2019 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. Link to comment Share on other sites More sharing options...
Sjk Posted August 19, 2019 Author Share Posted August 19, 2019 Well colour me embarrassed, it looks like aerogels are not suitable for cavity walls! Link to comment Share on other sites More sharing options...
Sjk Posted August 19, 2019 Author Share Posted August 19, 2019 7 minutes ago, 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. Thanks, is that the same as the K106 panels? Link to comment Share on other sites More sharing options...
Mr Punter Posted August 19, 2019 Share Posted August 19, 2019 1 minute ago, Sjk said: Thanks, is that the same as the K106 panels? 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. 1 Link to comment Share on other sites More sharing options...
Sjk Posted August 19, 2019 Author Share Posted August 19, 2019 3 minutes ago, 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. What don't you like about lightweight blocks? I was considering these along with aerated blocks. Link to comment Share on other sites More sharing options...
Mr Punter Posted August 19, 2019 Share Posted August 19, 2019 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. Link to comment Share on other sites More sharing options...
the_r_sole Posted August 19, 2019 Share Posted August 19, 2019 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
Sjk Posted August 19, 2019 Author Share Posted August 19, 2019 6 minutes ago, 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 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? Link to comment Share on other sites More sharing options...
the_r_sole Posted August 19, 2019 Share Posted August 19, 2019 (edited) . Edited September 26, 2019 by the_r_sole Link to comment Share on other sites More sharing options...
Declan52 Posted August 19, 2019 Share Posted August 19, 2019 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. 2 Link to comment Share on other sites More sharing options...
Sjk Posted August 19, 2019 Author Share Posted August 19, 2019 19 minutes ago, 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. 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. Link to comment Share on other sites More sharing options...
Sjk Posted August 19, 2019 Author Share Posted August 19, 2019 26 minutes ago, 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 Thanks, it would be designed from the outset this way, so I would hope some of these issues would be limited. Link to comment Share on other sites More sharing options...
ADLIan Posted August 19, 2019 Share Posted August 19, 2019 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. 1 Link to comment Share on other sites More sharing options...
Declan52 Posted August 19, 2019 Share Posted August 19, 2019 25 minutes ago, 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. 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. Link to comment Share on other sites More sharing options...
Sjk Posted August 19, 2019 Author Share Posted August 19, 2019 (edited) 1 hour ago, 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. 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 Link to comment Share on other sites More sharing options...
the_r_sole Posted August 19, 2019 Share Posted August 19, 2019 (edited) . Edited September 26, 2019 by the_r_sole 1 Link to comment Share on other sites More sharing options...
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