Post and beam Posted November 9, 2023 Share Posted November 9, 2023 I noticed that the magic purple airtight paint was used on the entire surface of his OSB. i understood that OSB is regarded as airtight by design. Is this not so or did he just get carried away? Link to comment Share on other sites More sharing options...
markc Posted November 9, 2023 Share Posted November 9, 2023 26 minutes ago, Post and beam said: I noticed that the magic purple airtight paint was used on the entire surface of his OSB. i understood that OSB is regarded as airtight by design. Is this not so or did he just get carried away? OSB is not airtight Link to comment Share on other sites More sharing options...
Galileo Posted November 9, 2023 Share Posted November 9, 2023 Quite like the idea of the zip board you get in the US with the air tight waterproof coating already made. It's always seemed to me that our building material technology is a bit behind others, you can get ply coated (like "Smartply"), but coated OSB seems to be a mystery product. Link to comment Share on other sites More sharing options...
SteamyTea Posted November 9, 2023 Share Posted November 9, 2023 No idea of the price. https://mdfosb.com/en/products/smartply-propassiv Link to comment Share on other sites More sharing options...
Gone West Posted November 9, 2023 Share Posted November 9, 2023 50 minutes ago, Post and beam said: I noticed that the magic purple airtight paint was used on the entire surface of his OSB. i understood that OSB is regarded as airtight by design. Is this not so or did he just get carried away? OSB can be airtight, it depends on the thickness and how well made it is. I would be very surprised if a thick SIPs panel wasn't airtight to the degree required for an airtightness test. With the the way the SIPs panels are joined I would have thought the purple paint wasn't really required. I achieved an average airtightness on my house of 0.47ACH without any airtightness tapes, membranes or paints. I just had 15mm OSB3 and 350mm Icynene foam. The window and door frames were sealed in the openings with two rows of Compriband and Soudal SWS foam. There were no openings in the walls or roof other than the two ducts for MVHR. 2 Link to comment Share on other sites More sharing options...
SteamyTea Posted November 9, 2023 Share Posted November 9, 2023 18 minutes ago, Gone West said: I achieved an average airtightness on my house of 0.47ACH without any airtightness tapes, membranes or paints Do you think, if time and price were no object, you could have improved it much. That is without getting silly and casting a block of concrete over it. Link to comment Share on other sites More sharing options...
joe90 Posted November 9, 2023 Share Posted November 9, 2023 22 minutes ago, Gone West said: I achieved an average airtightness on my house of 0.47ACH without any airtightness tapes, membranes or paints. I just had 15mm OSB3 and 350mm Icynene foam. Very commendable, just shows what can be done, I have my doubts about the longevity of tapes 🤷♂️ 1 Link to comment Share on other sites More sharing options...
Alan Ambrose Posted November 9, 2023 Share Posted November 9, 2023 >>> 350mm Icynene foam Sprayed in? Link to comment Share on other sites More sharing options...
Gone West Posted November 9, 2023 Share Posted November 9, 2023 16 minutes ago, SteamyTea said: Do you think, if time and price were no object, you could have improved it much. That is without getting silly and casting a block of concrete over it. I don't know what I could have done to improve it other than not have a lift slide door, which leaked a bit. Link to comment Share on other sites More sharing options...
Gone West Posted November 9, 2023 Share Posted November 9, 2023 15 minutes ago, Alan Ambrose said: >>> 350mm Icynene foam Sprayed in? Yep. Link to comment Share on other sites More sharing options...
Post and beam Posted November 9, 2023 Author Share Posted November 9, 2023 53 minutes ago, Gone West said: I don't know what I could have done to improve it I suppose you would have to do a smoke test to see if any issues became apparent. Rather than theorise where improvements might be possible. Link to comment Share on other sites More sharing options...
Post and beam Posted November 9, 2023 Author Share Posted November 9, 2023 1 hour ago, Gone West said: I would be very surprised if a thick SIPs panel wasn't airtight to the degree required for an airtightness test. This is what i am expecting. My Potton home, if it ever happens,( sale chain has fallen through) will be Sips. I am happy to tape the joints but dont fancy purple painting the entire panel area. Link to comment Share on other sites More sharing options...
Gone West Posted November 9, 2023 Share Posted November 9, 2023 2 hours ago, Post and beam said: I suppose you would have to do a smoke test to see if any issues became apparent. Rather than theorise where improvements might be possible. We did smoke tests, and the lift slide door was the only one showing a 'significant' leak, although nothing compared to most houses. 2 hours ago, Post and beam said: This is what i am expecting. My Potton home, if it ever happens,( sale chain has fallen through) will be Sips. I am happy to tape the joints but dont fancy purple painting the entire panel area. I can't imagine even the joints would need taping, but it comes down to how carefully the panels are joined together. Link to comment Share on other sites More sharing options...
Post and beam Posted November 10, 2023 Author Share Posted November 10, 2023 16 hours ago, Gone West said: it comes down to how carefully the panels are joined together Agree, and i would be happy if my taping efforts are redundant. But once done i wont know either way. The size of the task is worth it to me. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted November 10, 2023 Share Posted November 10, 2023 45 minutes ago, Post and beam said: The size of the task is worth it to me. We all look forward to the ACH figure from the leakage test, no pressure. Link to comment Share on other sites More sharing options...
Square Feet Posted November 10, 2023 Share Posted November 10, 2023 I've been very surprised that Booglehead (a guy I follow on YouTube) and Glyn Hudson (same) both passed their pressure tests without doing what I would have thought necessary. Booglehead hadn't taped around his windows at all it seemed and hadn't taped the insides of his SIPS. The outsides didn't look very carefully taped either. He also put a lot of screws right through everything in a way that I thought would have caused leaks. Glyn Hudson got his regular town house (not sure when built, but quite old) pressure tested and that passed too. I was really surprised by that one. Made me wonder what all the fuss is about. Link to comment Share on other sites More sharing options...
SteamyTea Posted November 10, 2023 Share Posted November 10, 2023 12 minutes ago, Square Feet said: I've been very surprised that Booglehead (a guy I follow on YouTube) and Glyn Hudson (same) both passed their pressure tests Passed at what level. 0.2 or 5? I passed my driving test, crashed sister's car 2 nights later, then my motorbike, twice, then my father's brand new car, got banned twice for my troubles. Then, at 20 years old, I got glasses and it all seemed to stop happening. 2 Link to comment Share on other sites More sharing options...
Post and beam Posted November 10, 2023 Author Share Posted November 10, 2023 2 hours ago, SteamyTea said: Passed at what level. 0.2 or 5? This is the vital question of course. Link to comment Share on other sites More sharing options...
saveasteading Posted November 10, 2023 Share Posted November 10, 2023 On 09/11/2023 at 11:42, joe90 said: I have my doubts about the longevity of tapes Each January, I pack away the decorations, tape the tops shut and store in the attic. Each December I find all tapes are unstuck. It must be the February chill or the summer heat. I regard tapes as temporary fixings. 1 Link to comment Share on other sites More sharing options...
IanR Posted November 10, 2023 Share Posted November 10, 2023 On 09/11/2023 at 12:56, Post and beam said: This is what i am expecting. My Potton home, if it ever happens,( sale chain has fallen through) will be Sips. I am happy to tape the joints but dont fancy purple painting the entire panel area. I followed the Potton PassivHaus case Study using Kingspan SIPs panels when it was being built 5 - 10 years ago. They were running a blog that was regularly updated. I remember they struggled a bit with the air tightness, failing the first air test they did, and later commenting that an internal membrane was required to get it below the 0.6 ACH target. I thought the blog was quite honest of them. SIPs are considered "airtight" in a standard building regs environment, but the shortfalls need to be mitigated for PassivHaus levels of airtightness. Link to comment Share on other sites More sharing options...
Square Feet Posted November 11, 2023 Share Posted November 11, 2023 On 10/11/2023 at 09:56, SteamyTea said: Passed at what level. 0.2 or 5? I passed my driving test, crashed sister's car 2 nights later, then my motorbike, twice, then my father's brand new car, got banned twice for my troubles. Then, at 20 years old, I got glasses and it all seemed to stop happening. 0.45 if I remember correctly. I think Glyn Hudson's was even lower, which was very strange. Here's the links. https://www.youtube.com/watch?v=tFMlJmRiaqo&list=PLzJHPUKEmzWVlbuMLwIeT_52SooH5ROrB&index=4&ab_channel=Booglehead I think Glyn has done the numbers wrong tbh, though he is a techiehead and loves this sort of thing so it seems unlikely, but I just can't wrap my head around how he has calculated it - he claims it's 0.3Ach. https://www.youtube.com/watch?v=kkNx2oSO-S4&t=383s&ab_channel=GlynHudson Link to comment Share on other sites More sharing options...
S2D2 Posted November 11, 2023 Share Posted November 11, 2023 16 minutes ago, Square Feet said: 0.45 if I remember correctly. I think Glyn Hudson's was even lower, which was very strange. Here's the links. https://www.youtube.com/watch?v=tFMlJmRiaqo&list=PLzJHPUKEmzWVlbuMLwIeT_52SooH5ROrB&index=4&ab_channel=Booglehead I think Glyn has done the numbers wrong tbh, though he is a techiehead and loves this sort of thing so it seems unlikely, but I just can't wrap my head around how he has calculated it - he claims it's 0.3Ach. https://www.youtube.com/watch?v=kkNx2oSO-S4&t=383s&ab_channel=GlynHudson 0.3 for the heat loss calculation, not the blower test. Shows in the thumbnail that's after dividing by 20 and the actual blower test result of 6.4@50Pa 1 Link to comment Share on other sites More sharing options...
JohnMo Posted November 11, 2023 Share Posted November 11, 2023 4 hours ago, Square Feet said: but I just can't wrap my head around how he has calculated it - he claims it's 0.3Ach. He is playing with numbers, his house leaks like a seize. A passivhaus is also tested at 50Pa, they have to score 0.6 ACH or better from that test, he scored 6.4m3/m2 at the same pressure. Not quite the same scale, but close enough in this case. So using his example of dividing by 20 a passivhaus would leak at a rate 0.03 ACH. 2 Link to comment Share on other sites More sharing options...
Dan F Posted November 11, 2023 Share Posted November 11, 2023 On 09/11/2023 at 10:58, SteamyTea said: No idea of the price. https://mdfosb.com/en/products/smartply-propassiv MBC used this on ours. Joints get taped, but the board itself is airtight. Link to comment Share on other sites More sharing options...
ProDave Posted November 11, 2023 Share Posted November 11, 2023 I thought the conversion from m3/m2 to ACH was very approximately 1:1 but there is no simple universal conversion because it depends on the geometry of the house, i.e is it single storey, 2 storey, vaulted ceilings etc. If it really was divide by 20 them my 1.4 m3/m2 would be 0.07ACH. No way is that the case. Link to comment Share on other sites More sharing options...
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