Browse Forums Building A New House Re: New house build - Passive House 27Jun 23, 2023 10:58 am alexp79 ren_ho Actually to clarify - the barrier in place is a vapour permeable barrier, then another airtight later will go on. Yes, this was my whole point - you install vapour permeable barrier in front of much less permeable OSB layer, effectively, shutting down this barrier and causing vapour accumulation and condensation in the inner layer around your insulation and framing. If you are planning to install airtight barrier (which is effectively a vapour barrier) - how will you ensure it won't get punctured/damaged during the plasterboard installation? It an quite sure it will be possible to achieve the right degree of airtightness and pass the blower test even with the punctured barrier, however, I am more concerned about moisture issues I have raised above. You would have to be 100% sure that your always-on ERV will be powerful enough to handle well the additional moisture removal from kitchen and showers. Condensation is a key concern with Passive House and is taken into account with the modelling. Looks like the wall make-up here will involve Proclima Intello as an internal membrane. This is an "intelligent" vapour membrane meaning that vapour permeability is less going into the wall than coming out of the wall. In other words, this reduces vapour entering the wall while still encouraging the wall to dy out. This is a widely adopted solution for Passive House and suitable for much of the country, but not the tropics. Re: New house build - Passive House 28Jun 23, 2023 11:07 am RustedOn alexp79 ren_ho Actually to clarify - the barrier in place is a vapour permeable barrier, then another airtight later will go on. Yes, this was my whole point - you install vapour permeable barrier in front of much less permeable OSB layer, effectively, shutting down this barrier and causing vapour accumulation and condensation in the inner layer around your insulation and framing. If you are planning to install airtight barrier (which is effectively a vapour barrier) - how will you ensure it won't get punctured/damaged during the plasterboard installation? It an quite sure it will be possible to achieve the right degree of airtightness and pass the blower test even with the punctured barrier, however, I am more concerned about moisture issues I have raised above. You would have to be 100% sure that your always-on ERV will be powerful enough to handle well the additional moisture removal from kitchen and showers. Condensation is a key concern with Passive House and is taken into account with the modelling. Looks like the wall make-up here will involve Proclima Intello as an internal membrane. This is an "intelligent" vapour membrane meaning that vapour permeability is less going into the wall than coming out of the wall. In other words, this reduces vapour entering the wall while still encouraging the wall to dy out. This is a widely adopted solution for Passive House and suitable for much of the country, but not the tropics. Yes, as long as it is installed properly and not getting punctured by some crazy gyprockers or plumbers after, this should work. Re: New house build - Passive House 30Jun 23, 2023 1:47 pm RustedOn True. This is why blower door pressure tests are performed during the build of a Passive House. At the end of the build a final blower door test must be passed for certification. This small punctures might not affect blower test significantly, but will still allow vapour through. On the other side, if blower test fails because of this - it will be quite a frustrating exercise to identify where the punctures are, remove plaster, fix and re-install. But let's see, I hope they have experience dealing with all this. Re: New house build - Passive House 32Jun 23, 2023 2:04 pm Pedro4137 How will paint/membrane on outside wall impact all this Alex? Closed cavity construction so no drainage in wall cavity All windows and doors need to caulked externally The vapour from the inside (kitchen, bathrooms etc) can penetrate Proclima through punctures and then will be accumulating near this OSB board trying its best to slowly escape to the outside. Re: New house build - Passive House 33Jun 23, 2023 2:16 pm The purpose of the blower door testing is to identify any leaks and address them. Even a small puncture will cause the test to fail. The first test is performed before gyprock is installed as it will otherwise be very difficult to locate leaks - as you have pointed out. This page will gives an idea of the attention to detail that is required https://efficiencymatrix.com/getting-pa ... tightness/ Re: New house build - Passive House 34Jun 23, 2023 2:30 pm RustedOn The purpose of the blower door testing is to identify any leaks and address them. Even a small puncture will cause the test to fail. The first test is performed before gyprock is installed as it will otherwise be very difficult to locate leaks - as you have pointed out. This page will gives an idea of the attention to detail that is required https://efficiencymatrix.com/getting-pa ... tightness/ Well, puncture in the Proclima is not a leakage per se The air will stay inside the wall, right? Re: New house build - Passive House 36Jun 23, 2023 2:56 pm With the dual interior + exterior membrane solution, the interior membrane is the air-tight layer, so a puncture would be a leakage - if I understand you correctly. Regarding slab insulation requirements, it all depends on the climate. The modelling will indicate whether it is required or not, and whether it needs to be slab edge only or also under slab. For Sydney, it is possible to satisfy the modelling without any slab insulation, it all depends on the design. From memory, the Passivhaus at Asquith has no slab insulation and takes advantage of the thermal mass of the ground. In colder locations, slab edge insulation will almost certainly be needed. Re: New house build - Passive House 38Jun 23, 2023 3:35 pm OSB available in Australia is generally not air-tight. Air will also escape through top plates and any penetrations in the external membrane (assuming it has not been taped and sealed for air-tightness). But if the external surface is air-tight, surely that would also reduce the problem of air flow through any puncture in the internal membrane? That would be like trying to blow into a bottle. Re: New house build - Passive House 40Jun 23, 2023 9:01 pm Ardo I am interested in the external door situation. How they would seal and/or thermal bridging. Buying a door jamb with seals all round is problematic. Hinged doors for Passivhaus use same solution for top and sides as for windows: multiple seals and locking points. Bottom of door can be butted up against a low threshold using a couple of seals. For zero threshold there's a solution involving magnetic strips that rise up from the floor into the door when it is closed to seal the gap: https://siegware.com.au/alumat-barrier- ... c-profile/ I would still ask the question, see if you can get your builder to do it 3 1672 Thank you so much everyone. This all makes a lot of sense. I guess when you talk to a builder who butters up everything to look very polished, you get to start believing… 7 24861 6 60441 |