Sophiae Posted June 8, 2023 Share Posted June 8, 2023 Apologies for the intrusion (me again), didn’t want to start a new topic as this one may very well address my ongoing dilemma. so working on building regs and trying to optimise my drawings and attempting to make better choices for the structure. The SE specified 7.3N blocks (u-value 0.18) for the extension cavity wall. Initially he proposed a block/brick cavity wall and I was ok. With new regs requiring a lower u-values I thought to get the thickness a little smaller we can use this make up: 100mm blocks rendered external leaf 50mm cavity 100mm PIR insulation 100mm blocks internal leaf 12.5mm plasterboards The problem I am reading here is that placing the PIR boards can be a problem with heat loss? What are the other alternatives that are with similar budget? what does everyone think of a solid block wall with external insulation instead of the cavity? Would it work better? Cost? U-Value? Link to comment Share on other sites More sharing options...
Temp Posted June 8, 2023 Share Posted June 8, 2023 If the outside is rendered perhaps a fully filled cavity might be an option? There is a 140mm Celotex Thermaclass Cavity Wall 21 that has T&G edges so should be easier to install without gaps? Possibly expensive though. Link to comment Share on other sites More sharing options...
Dave Jones Posted June 8, 2023 Share Posted June 8, 2023 On 08/04/2023 at 07:45, Brickie said: 100% agree. Never going to get the states U value due to the realities of installation,even if you had the most conscientious bricklayers in the world. The detailing at reveals & lintols would require surgical precision to be anything other than leaky. not really with thermally broken lintels etc. Yes the new regs demand much higher attention to detail but that's not a bad thing. Link to comment Share on other sites More sharing options...
Nickfromwales Posted June 8, 2023 Share Posted June 8, 2023 3 hours ago, Sophiae said: 50mm cavity 100mm PIR insulation 150mm of blown, bonded beads? 1 1 Link to comment Share on other sites More sharing options...
ETC Posted June 8, 2023 Share Posted June 8, 2023 17 minutes ago, Nickfromwales said: 150mm of blown, bonded beads? Yep. Link to comment Share on other sites More sharing options...
Sophiae Posted June 9, 2023 Share Posted June 9, 2023 3 hours ago, Nickfromwales said: 150mm of blown, bonded beads? What is that? Any pictures to understand? Link to comment Share on other sites More sharing options...
Nickfromwales Posted June 9, 2023 Share Posted June 9, 2023 3 hours ago, Sophiae said: What is that? Any pictures to understand? Random internet grab = https://springvale.com/ecobead/ Ask on here for possible recommendations for installation companies. 1 Link to comment Share on other sites More sharing options...
PeterW Posted June 9, 2023 Share Posted June 9, 2023 Yeh +1 to blown bead and at wider cavities too. Got a couple of installers we have used in the past 1 Link to comment Share on other sites More sharing options...
Dave Jones Posted June 9, 2023 Share Posted June 9, 2023 beads are not better than cavity batts, both rely on the inner block being good enough (0.11)to get a pass. Batts cheaper and better at keeping the cavity clean. 1 Link to comment Share on other sites More sharing options...
HughF Posted June 9, 2023 Share Posted June 9, 2023 I’d go full fill fluffy (something from rockwool, probably) on 150 cavity…. Standard method that every builder knows and understands. We’re about to start a rear ex next week in this exact buildup. Rendered conc, 150, cellcon inner. 1 1 Link to comment Share on other sites More sharing options...
Sophiae Posted June 11, 2023 Share Posted June 11, 2023 On 09/06/2023 at 07:57, Dave Jones said: beads are not better than cavity batts, both rely on the inner block being good enough (0.11)to get a pass. Batts cheaper and better at keeping the cavity clean. What are batts? Link to comment Share on other sites More sharing options...
Sophiae Posted June 11, 2023 Share Posted June 11, 2023 On 09/06/2023 at 08:13, HughF said: I’d go full fill fluffy (something from rockwool, probably) on 150 cavity…. Standard method that every builder knows and understands. We’re about to start a rear ex next week in this exact buildup. Rendered conc, 150, cellcon inner. Isn’t rockwool not a great insulation compared to rigid PIR? Link to comment Share on other sites More sharing options...
HughF Posted June 12, 2023 Share Posted June 12, 2023 7 hours ago, Sophiae said: Isn’t rockwool not a great insulation compared to rigid PIR? Ah, the great PIR con….. PIR is great stuff, don’t get me wrong, but the manufacturers have spent an enormous amount of time and money marketing the stuff as the only product worth using. The reality is, other products are perfectly decent when applied to the correct thickness, and they bring other benefits. Specifically in the case of cavity wall insulation, the ability for the product to completely contact the inner skin, flowing around the mortar snots. All insulation has a U value, so one product can give just the same performance as another, it just might need to be thicker. 1 Link to comment Share on other sites More sharing options...
Sophiae Posted June 12, 2023 Share Posted June 12, 2023 3 hours ago, HughF said: Ah, the great PIR con….. PIR is great stuff, don’t get me wrong, but the manufacturers have spent an enormous amount of time and money marketing the stuff as the only product worth using. The reality is, other products are perfectly decent when applied to the correct thickness, and they bring other benefits. Specifically in the case of cavity wall insulation, the ability for the product to completely contact the inner skin, flowing around the mortar snots. All insulation has a U value, so one product can give just the same performance as another, it just might need to be thicker. Agreed, and that’s the situation most people are in. i started this journey thinking I would get 4 meters extension under PDR. Found out the wall will nearly come to 40cms with all layers to be complaints and fit for purpose, taking those from my inner space. So now left with 3.6 meters, and have to find furniture to fit. This is why I am trying to see what will work instead of going back to application process. Link to comment Share on other sites More sharing options...
HughF Posted June 12, 2023 Share Posted June 12, 2023 1 hour ago, Sophiae said: Agreed, and that’s the situation most people are in. i started this journey thinking I would get 4 meters extension under PDR. Found out the wall will nearly come to 40cms with all layers to be complaints and fit for purpose, taking those from my inner space. So now left with 3.6 meters, and have to find furniture to fit. This is why I am trying to see what will work instead of going back to application process. 4m, lucky you…. We’re end of terrace so we’re limited to 3m external. Link to comment Share on other sites More sharing options...
Nickfromwales Posted June 12, 2023 Share Posted June 12, 2023 On 09/06/2023 at 07:57, Dave Jones said: beads are not better than cavity batts, both rely on the inner block being good enough (0.11)to get a pass. Batts cheaper and better at keeping the cavity clean. They minimise airflow (convection) so would be my choice. The cavity can be fully blown, and very few gaps/cavities are left when done by a good company. Link to comment Share on other sites More sharing options...
Sophiae Posted June 12, 2023 Share Posted June 12, 2023 1 hour ago, Nickfromwales said: They minimise airflow (convection) so would be my choice. The cavity can be fully blown, and very few gaps/cavities are left when done by a good company. I read a few articles and seen the videos and I have to agree they are a better option for all my pre-existing cavity walls with no insulation. Do you believe they are a good option for my new extension walls? Link to comment Share on other sites More sharing options...
Nickfromwales Posted June 12, 2023 Share Posted June 12, 2023 1 hour ago, Sophiae said: I read a few articles and seen the videos and I have to agree they are a better option for all my pre-existing cavity walls with no insulation. Do you believe they are a good option for my new extension walls? Will be easier to employ one company (imo) to just do the lot in one visit? Link to comment Share on other sites More sharing options...
Sophiae Posted June 12, 2023 Share Posted June 12, 2023 10 minutes ago, Nickfromwales said: Will be easier to employ one company (imo) to just do the lot in one visit? Yes that would be the plan, but as I get building regs done for approval, do you believe they will give me the same U-value for the new walls as the new regs? Link to comment Share on other sites More sharing options...
Sophiae Posted June 12, 2023 Share Posted June 12, 2023 On 08/06/2023 at 19:50, Temp said: If the outside is rendered perhaps a fully filled cavity might be an option? There is a 140mm Celotex Thermaclass Cavity Wall 21 that has T&G edges so should be easier to install without gaps? Possibly expensive though. Too expensive for my budget Link to comment Share on other sites More sharing options...
Sophiae Posted June 12, 2023 Share Posted June 12, 2023 On 08/06/2023 at 19:50, Temp said: If the outside is rendered perhaps a fully filled cavity might be an option? There is a 140mm Celotex Thermaclass Cavity Wall 21 that has T&G edges so should be easier to install without gaps? Possibly expensive though. On another note. How would I calculate how much I need? I suppose no harm in punching the numbers. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted June 12, 2023 Share Posted June 12, 2023 17 minutes ago, Sophiae said: Yes that would be the plan, but as I get building regs done for approval, do you believe they will give me the same U-value for the new walls as the new regs? https://www.kore-system.com/insulation-series-using-eps-for-cavity-wall-insulation-applications/ 1 Link to comment Share on other sites More sharing options...
Temp Posted June 12, 2023 Share Posted June 12, 2023 3 hours ago, Sophiae said: On another note. How would I calculate how much I need? I suppose no harm in punching the numbers. For Thermaclass Cavity Wall 21 the board size installed is 1190 x 450mm (installed). That's an area of 1.19 x 0.45 = 0.53 sqm. So work out the area of your walls and divide by 0.53 to get the number of boards needed. In the 140mm thickness there are 64 boards per pallet so divide the number of boards by 64 to get the number of pallets. Perhaps add 5% for cutting/wastage? Shop around/haggle. 1 1 Link to comment Share on other sites More sharing options...
Dave Jones Posted June 13, 2023 Share Posted June 13, 2023 On 12/06/2023 at 12:22, Nickfromwales said: They minimise airflow (convection) so would be my choice. The cavity can be fully blown, and very few gaps/cavities are left when done by a good company. minimal upside, more downsides. more expensive, no batts to keep cavity clean while being built etc. For retrofit they have a place, wouldn't bother with new build. 1 Link to comment Share on other sites More sharing options...
Dave Jones Posted June 13, 2023 Share Posted June 13, 2023 On 12/06/2023 at 00:02, Sophiae said: What are batts? https://www.superglass.co.uk/products/superwall-32-cavity-wall-batt/ 1 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now