Hi, I am being told by people on self build forum in uk that pur is basically rubbish cos it has no deceremental delay. To sum up because pur etc is a solid thing the conduction of heat through the material will cause excessive heat in upper rooms . and that pure "u" value is not be all of a house construction ,as the heat on the roof will cause alot heat to pass qickly through the solid parts of the foam and what we should be doing is using a much less dense substance. I take the view that if using blown foam etc was the right way then cold stroage would be made from that where running costs not initial costs are paramount I look forward to someone explaining to me why what they say is true --and the way to make a livable house that will not overheat in summer. and a sips roof is not the right answer

bearing in mind most sips house in UK are 1.5 floors --EG we live in the roof space with slanted ceilings.
a house with a realattic and flat ceilings could indeed give enough airspace to stop some of the radiation from the roof to pass to living area.
Iam interested how you in US with much bigger heat swings decide which is best

Posted By scottishjohn on 14 Nov 2018 09:44 AM
bearing in mind most sips house in UK are 1.5 floors --EG we live in the roof space with slanted ceilings.
a house with a realattic and flat ceilings could indeed give enough airspace to stop some of the radiation from the roof to pass to living area.
Iam interested how you in US with much bigger heat swings decide which is best

that is totally false information,
I built many 1.5 stories in Florida and the heat gain is minimal.
my own office addition is 1.5 stories and stays at 70 degrees inside in August and 95 outside

Photos of my office

another job:

what air gap are you using above sips roof before roofing material. and are you using air con to keep down

The same applies to any design, single stories , two stories or 1-1/2 stories . the heat gain is minimal thru the EPS core as there is no metal to metal transference in the main field of roof
and a major reason why metal SIPs are used primarily throughout the world for cold storage applications
even the refrigerator in your own home is technically a metal SIP

Posted By scottishjohn on 14 Nov 2018 12:15 PM
what air gap are you using above sips roof before roofing material. and are you using air con to keep down

air gap - NONE!
mostly central forced air ,my addition is a mini-split on second floor , with none on first floor , lower floor stays at 74 degrees with just the cool air moving downward

Posted By scottishjohn on 14 Nov 2018 12:15 PM
what air gap are you using above sips roof before roofing material. and are you using air con to keep down

NONE!

could not do that in uk --too damp --would always need to be cross battons so no ledge for water could sit behind the horizontal battons and no nails peircing the membrane
all good info

Posted By scottishjohn on 14 Nov 2018 01:24 PM
could not do that in uk --too damp --would always need to be cross battons so no ledge for water could sit behind the horizontal battens and no nails peircing the membrane
all good info

I would like you to explain how no nails pierce the membrane?
how are the battens attached to roof deck?

the original discussion was about too much heat gain and now shifted to needing an air gap because of dampness , it's not that you can't use an air gap , but in the southeast US hot humid climate it's simply not needed
your not going to attach any battens without a nail or some fastener piercing the membrane , not that that's a bad thing, many membranes are self sealing

well we are cold and damp -so water will sit behind any directly attached roof material ,hence the need for double battons .
yes nails would piece mebrane to fix battons -but i would use sealer under the first vetical battons as well and not use nails,not much to grip in an osb that will be half thickness or less than the batton , but screws to attach the pre drilled battons ,then roof slates are attached to counter battons ,vertical battons first give clear path for any water to run straight off roof.
air gap will cut down heat transfer from roofing material as there will be a draft under neath them. some roofers even want a second rain barrier on top of counter battons below the slates as well.

Don’t think there’s much difference between cool/damp and warm/damp. Today it’s 68f and 85% humidity. We have heavy dew every morning dripping off roof , in winter frost on roof . Condensation would occur on top of the roofing not below it, unless water is penetrating the slate in either case seems like wood battens constantly exposed to water would rot?

I,m not going to argue with you --just this the way it is done in uk to keep the actual roof surface under the tiles dry .
people just running 1 set of battons will have a much shorter roof life than double battoning and with OSB sips panels that would be a very expensive problem to have for the sake of a few lengths of batton.

Not really a horrendous issue in the era of fluid-applied and peel-&-stick self-sealing membranes.

Is that really a good idea onto OSB you maybe sealing moisture in -breathable is surely the way ?

https://www.greenbuildingadvisor.com/article/how-to-make-a-sip-roof-better
don,t look like it worked well here with stuck on layer

Posted By scottishjohn on 16 Nov 2018 11:01 AM
https://www.greenbuildingadvisor.com/article/how-to-make-a-sip-roof-better
don,t look like it worked well here with stuck on layer

I thought your weren't going to argue
Would have been good if you read the report,
direct roof application had nothing to do with the failure
the report in its entirety is available at sips.org
it would be good to read it before posting a comment
OSB sips are problematic if not installed properly in cold climates
and further the reason why I promote SIPs that will not rot , with no food value for termites and carpenter ants , will not shrink or swell, will not support mold or mildew, the skins are the water/moisture barrier

sorry I didn,t, realsie that asking questions counted as arguing-

Posted By scottishjohn on 16 Nov 2018 10:59 AM
Is that really a good idea onto OSB you maybe sealing moisture in -breathable is surely the way ?

There are vapor open fluid-applied and P&S systems out there.