davejura Posted March 12, 2021 Author Share Posted March 12, 2021 On 10/03/2021 at 14:58, Iceverge said: Have a price up of the below buildup. If you're DIYing it I can't see a cheaper way. Remember increasing your insulation much beyond building regs isn't worth much unless you're taking care of thermal bridging and airtightness. I'll look into that, thanks. As long as I don't have to go back to the architect again, it shouldn't be a problem! Is the Glasswool 35 cheaper than PIR insulation? And what site did you use for the calculations please? My local supplier of PIR has just quoted me for IKO Enertherm and Recticel boards, and has said there will be a 17% price increase on 1st April! Link to comment Share on other sites More sharing options...
the_r_sole Posted March 12, 2021 Share Posted March 12, 2021 1 minute ago, davejura said: I'll look into that, thanks. As long as I don't have to go back to the architect again, it shouldn't be a problem! Is the Glasswool 35 cheaper than PIR insulation? And what site did you use for the calculations please? My local supplier of PIR has just quoted me for IKO Enertherm and Recticel boards, and has said there will be a 17% price increase on 1st April! Be aware that if you change anything you will have to provide an update SAP calc and amendment to warrant before you get your completion certificate, so you should run any changes to the specifications past your architect asap - you'd be amazed how many times builders "rules of thumb" which get rid of the "expensive, over-specced architects insulation", mean that you no longer comply with the regs! Link to comment Share on other sites More sharing options...
davejura Posted March 12, 2021 Author Share Posted March 12, 2021 7 minutes ago, the_r_sole said: Be aware that if you change anything you will have to provide an update SAP calc and amendment to warrant before you get your completion certificate, so you should run any changes to the specifications past your architect asap - you'd be amazed how many times builders "rules of thumb" which get rid of the "expensive, over-specced architects insulation", mean that you no longer comply with the regs! Going to have a few amendments to warrant anyway, so that shouldn't be a problem! Yes, architects do tend to over spec things and I'm sure they have shares in Kingspan! Link to comment Share on other sites More sharing options...
Moonshine Posted March 12, 2021 Share Posted March 12, 2021 12 minutes ago, davejura said: Yes, architects do tend to over spec things and I'm sure they have shares in Kingspan! Do you @the_r_sole? ?? Link to comment Share on other sites More sharing options...
the_r_sole Posted March 12, 2021 Share Posted March 12, 2021 (edited) 14 minutes ago, Moonshine said: Do you @the_r_sole? ?? I backed the wrong horse and went for celotex.... what a melon when everyone else went for kingspan! (it's always funny to see what people take from the posts, seems you cannot be explicit enough) Edited March 12, 2021 by the_r_sole 1 Link to comment Share on other sites More sharing options...
Iceverge Posted March 12, 2021 Share Posted March 12, 2021 (edited) 1 hour ago, davejura said: I'll look into that, thanks. As long as I don't have to go back to the architect again, it shouldn't be a problem! Is the Glasswool 35 cheaper than PIR insulation? And what site did you use for the calculations please? My local supplier of PIR has just quoted me for IKO Enertherm and Recticel boards, and has said there will be a 17% price increase on 1st April! I reckon your original buildup had a u value of 0.2 W/mK so the mineralwool 35 betters at 0.19 it albeit with an additional 20mm wall thickness. A quick Google suggests material only the PIR is £23.65/m2 and dritherm 35 is £8.60 ex vat for the above buildups. This excludes the faf of cutting foaming and fitting the boards. It's worth getting a handle on the numbers or you risk just doing whatever makes the architects life easiest. When it comes to insulation architects very rarely overspec the design. Many were educated in the oil era when infinite cheap energy was the solution. They can often outsource SAP calculations with a "just make it pass " requirement. Edited March 12, 2021 by Iceverge Link to comment Share on other sites More sharing options...
Iceverge Posted March 12, 2021 Share Posted March 12, 2021 By the way dritherm/frametherm are trade names for various mineral wool and glass wool products. The site I used is Ubakus. Link to comment Share on other sites More sharing options...
davejura Posted March 12, 2021 Author Share Posted March 12, 2021 7 hours ago, Iceverge said: I reckon your original buildup had a u value of 0.2 W/mK so the mineralwool 35 betters at 0.19 it albeit with an additional 20mm wall thickness. Interesting. Thanks for this. Where do you get the extra 20mm wall thickness? If I put 140mm of mineral wool 35 in instead of 100mm PIR, that could work. Here is the build make up. Link to comment Share on other sites More sharing options...
davejura Posted March 12, 2021 Author Share Posted March 12, 2021 Would there be an issue with air tightness using minerwool 35? Link to comment Share on other sites More sharing options...
Iceverge Posted March 12, 2021 Share Posted March 12, 2021 Looking at your whole wall build up it is actually 5 mm narrower with my suggested buildup as I didn't realise you had a service cavity. Insulation has little to do with airtightness. It's the vapour control layer that does that in your case. How much of the work do you intend to do yourself? Do you have anyone with a good knowledge of the main principles to hand? Link to comment Share on other sites More sharing options...
davejura Posted March 13, 2021 Author Share Posted March 13, 2021 9 hours ago, Iceverge said: Do you have anyone with a good knowledge of the main principles to hand? I do actually. I'm lucky in that I have secured the services of a local builder on an advisory basis. I'm doing some fencing for him as a trade off! He is also going to mark out and supervise the foundations. Thanks for all your advise. I'm just going to email my architect and get her take on it all. 1 Link to comment Share on other sites More sharing options...
the_r_sole Posted March 13, 2021 Share Posted March 13, 2021 Your architect is going to love being told to change their drawings based on what you've been told on an Internet forum ? 1 Link to comment Share on other sites More sharing options...
davejura Posted March 13, 2021 Author Share Posted March 13, 2021 21 minutes ago, the_r_sole said: Your architect is going to love being told to change their drawings based on what you've been told on an Internet forum ? I presume you are talking from experience? ? Just pinged her now to make her Saturday! Actually, hoping if we don't change the make up, just use the 140mm of ThrameTherm or similar instead of the 100m of PIR, it can just go through as an amendment to warrant at the end. Obviously, will need a new SAP calculation. Link to comment Share on other sites More sharing options...
the_r_sole Posted March 13, 2021 Share Posted March 13, 2021 Have you got a load of pv or something to balance out the sap? Just doubled checked a recent sap where we looked at similar insulation and needed 50mm pir inside to get to 0.19, even then we needed to add more renewable to get through, ended up being cheaper to rever back to 140 pir between the studs... Link to comment Share on other sites More sharing options...
davejura Posted March 13, 2021 Author Share Posted March 13, 2021 No PV, just ASHP with UF heating. Our SAP is passing with 100mm plus 25mm of PIR, but would obviously like to improve on that. Link to comment Share on other sites More sharing options...
the_r_sole Posted March 13, 2021 Share Posted March 13, 2021 Have you got no windows or something? Your spec sounds like what we were doing 10 years ago to get a pass! Link to comment Share on other sites More sharing options...
davejura Posted March 14, 2021 Author Share Posted March 14, 2021 On 13/03/2021 at 14:36, the_r_sole said: Have you got no windows or something? Your spec sounds like what we were doing 10 years ago to get a pass! I'm not kidding on I have a clue when it comes to this. Just going by what the architect and company that did the SAP calc came up with! Link to comment Share on other sites More sharing options...
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