Never been a fan of yankee gutters. I did a exterior shell with warm roof. Mineral wool batt and board. Then added green board rafter tails. I have masonry veneer. I ran sofit at angle too. Mono slope roof so my north wall never gets sun. All the snow dumps there too. 70 psf snow loads and 6 foot frost depths. I understand yankee gutters do work for ice dams in warmer climates. We are no stranger to sip panels as we build a lot of post and beams, and heavy timber frames. High humidity houses we use low perm barriers and mineral wool. I am looking forward to the day we can get sip walls with mineral wool in them.
Thanks for yhe video. Many very interesting facts here. Especially the small roof air gap vs the larger ground-level gap. I'm in Madrid where it does get colder in winter than Melbourne, but i think the climate is pretty similar.
I noticed this a few years ago, looking at like prebuilt or cheap type or mobile buildings, that used siding, like manufactured siding, etc, There are spots where it starts to separate or peel back at the peaks of gables, gable ends, or end walls. Where ever the sun gets to it, or on the north sides where there is always shade. whatever causes warping or freeze thaw. But then once it starts, more wind, more moisture and more cold gets in. Sometimes just a small crack lets in a prevailing wind and the whole envelope is compromised. But I have only started to pay attention and observe these things recently despite always having worked on stuff of a variety of building related jobs.
This is crazy... house insulation works by slowing and trapping pockets of air and disrupting conduction of heat.... It's not supposed to be airtight otherwise you get mold buildup like when you don't air out your Eski... The building still needs to breathe including the inside... Putting insulation against the footing is another recipe for mold... And that plywood under you roof sheets better have a membrane otherwise condensation will rot it out... How did you get engineering approval? Cathedral ceiling no rafters... what's the live load on that SIP?... as a carpenter and roof plumber this looks like dodgy American madness....
Thanks for the comment. Much of what you say is absolutely correct in certain circumstances and it could be that I didn’t provide enough clarity to answer these issues in the video. It is a fine line between providing information and providing too much so that it overwhelms. Let me respond to your comments. The proposed structure is airtight but only in one direction as the membranes are smart enough to allow it to breathe from the inside to the outside but not the other way around. The insulation has air trapped within it but the membranes protect it from incoming moisture from both sides. No moisture = no mould but optimal insulation performance. Also if you leave the insulation open to the air it reduces its performance from wind washing and moisture penetration. With insulation in contact with the ground you need to use a different type of insulation which is called closed cell such as XPS. This doesn’t have gaps to allow moisture in so it wont rot or mould. Finally SIPs panels can span up to 6m without support subject to engineering. Obviously this depends on thickness, live and dead load, allowable deflection etc. it all works as a very efficient structural system reducing the need for a lot of additional structure.
You're conflating "airtightness" with "vapour blocking", which are two different things. A material can be perfectly airtight whilst still being very permeable to water vapour. The video mentions this detail being designed for a (sub-)tropical climate. Meaning that water vapour will be moving from the outside to the inside for most, if not all, of the year. Hence the only condensation to worry about will be on the outside face of the inside OSB sheet and the insulation directly behind it (depending on the insulation material used). Not the weather barrier atop the roof. Having said that: this roof detail will likely still work fine in a temperate climate. Because it's ventilated, so there's no differential in vapour pressure between the two sides of the roof. Though I can imagine a membrane may be warranted between the plywood/OSB and the metal of the roof if thawing water on the underside of the steel is too be expected. (I'm not knowledgeable enough about metal roofs to say anything definitive about that).
@@borlandarchitecture You're making my point.... houses create humidity from the inside and this usually is dissipated into the roof space by ceiling fans.... This house has no ceiling space and the XPS (in the SIP's) is not vapor permeable past 25mm.... The issue with the foundation insulation is water pooling behind it... where does the inside humidity go?... why would you want a house with stale air?
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Never been a fan of yankee gutters. I did a exterior shell with warm roof. Mineral wool batt and board. Then added green board rafter tails. I have masonry veneer. I ran sofit at angle too. Mono slope roof so my north wall never gets sun. All the snow dumps there too. 70 psf snow loads and 6 foot frost depths. I understand yankee gutters do work for ice dams in warmer climates. We are no stranger to sip panels as we build a lot of post and beams, and heavy timber frames. High humidity houses we use low perm barriers and mineral wool. I am looking forward to the day we can get sip walls with mineral wool in them.
Thanks for yhe video. Many very interesting facts here. Especially the small roof air gap vs the larger ground-level gap.
I'm in Madrid where it does get colder in winter than Melbourne, but i think the climate is pretty similar.
appreciate the comment Mark, glad you got some value from it
I noticed this a few years ago, looking at like prebuilt or cheap type or mobile buildings, that used siding, like manufactured siding, etc, There are spots where it starts to separate or peel back at the peaks of gables, gable ends, or end walls. Where ever the sun gets to it, or on the north sides where there is always shade. whatever causes warping or freeze thaw. But then once it starts, more wind, more moisture and more cold gets in. Sometimes just a small crack lets in a prevailing wind and the whole envelope is compromised. But I have only started to pay attention and observe these things recently despite always having worked on stuff of a variety of building related jobs.
I tell everyone, walk around your building twice a year and seal up every crack with proper sealant. I try and do this myself. Lots of maintenance.
This is crazy... house insulation works by slowing and trapping pockets of air and disrupting conduction of heat....
It's not supposed to be airtight otherwise you get mold buildup like when you don't air out your Eski...
The building still needs to breathe including the inside...
Putting insulation against the footing is another recipe for mold...
And that plywood under you roof sheets better have a membrane otherwise condensation will rot it out...
How did you get engineering approval?
Cathedral ceiling no rafters... what's the live load on that SIP?...
as a carpenter and roof plumber this looks like dodgy American madness....
Thanks for the comment. Much of what you say is absolutely correct in certain circumstances and it could be that I didn’t provide enough clarity to answer these issues in the video. It is a fine line between providing information and providing too much so that it overwhelms. Let me respond to your comments. The proposed structure is airtight but only in one direction as the membranes are smart enough to allow it to breathe from the inside to the outside but not the other way around. The insulation has air trapped within it but the membranes protect it from incoming moisture from both sides. No moisture = no mould but optimal insulation performance. Also if you leave the insulation open to the air it reduces its performance from wind washing and moisture penetration. With insulation in contact with the ground you need to use a different type of insulation which is called closed cell such as XPS. This doesn’t have gaps to allow moisture in so it wont rot or mould. Finally SIPs panels can span up to 6m without support subject to engineering. Obviously this depends on thickness, live and dead load, allowable deflection etc. it all works as a very efficient structural system reducing the need for a lot of additional structure.
You're conflating "airtightness" with "vapour blocking", which are two different things.
A material can be perfectly airtight whilst still being very permeable to water vapour.
The video mentions this detail being designed for a (sub-)tropical climate. Meaning that water vapour will be moving from the outside to the inside for most, if not all, of the year. Hence the only condensation to worry about will be on the outside face of the inside OSB sheet and the insulation directly behind it (depending on the insulation material used). Not the weather barrier atop the roof.
Having said that: this roof detail will likely still work fine in a temperate climate. Because it's ventilated, so there's no differential in vapour pressure between the two sides of the roof. Though I can imagine a membrane may be warranted between the plywood/OSB and the metal of the roof if thawing water on the underside of the steel is too be expected. (I'm not knowledgeable enough about metal roofs to say anything definitive about that).
@@borlandarchitecture You're making my point....
houses create humidity from the inside and this usually is dissipated into the roof space by ceiling fans....
This house has no ceiling space and the XPS (in the SIP's) is not vapor permeable past 25mm....
The issue with the foundation insulation is water pooling behind it...
where does the inside humidity go?...
why would you want a house with stale air?