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<DIV><FONT size=2 face=Arial>We detail the airtight membrane stapled to the
ceiling joists for the flat ceiling sections, with ample insulation above. As
noted previously, hats to seal services passing through are critical. However,
if there is space, a nice detail is to allow for a 25 - 40mm (1" - 1.5") service
void below the airtight barrier to avoid concern about services breaking through
(we always use this detail on walls). The plasterboard/T&G is fixed to
a minimal amount of battens. This is particularly beneficial if anyone wants to
add services in the future as they will be independent of the
airtight membrane.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>On the sloped sections, sometimes it is difficult
to get enough insulation within the depth of the rafters. In this situation, we
staple the airtight membrane to the underside of the rafters. Then we fix
semi-rigid wood fibre boards (e.g. Gutex or Steico) through the membrane
into the rafters and fix our plasterboard or T&G to the wood fibre boards.
It is an effective detail and has been tested with very good
results.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV>
<DIV><FONT size=2 face=Arial>We have also fixed very small lath-like battens on
to the membrane in situations where it needed to be a bit more robust, e.g.
horizontal battens fixed through the membrane to vertical studs in a timber
frame wall where cellulose was pumped in after.</FONT></DIV></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I'm a big fan of Intello as it is a cellular
membrane and checks vapour in both directions - so if the weather conditions
mean that reverse diffusion is required, this can happen. The micro-porous
membranes are not so capable.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>You have mentioned being careful at
penetrations/junctions - I still use the pen test every time - can you put pen
to paper and trace around each section of your building. If you need to lift
your pen - this is an area that needs some consideration.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I did hear an interesting point from a services
engineer who also carries out a lot of blower door tests. People worry about
screws/nails/staples diminshing the effectiveness of the airtight membrane. But
the fixings fully fill the holes, so this is not really a concern. However, in
houses where there were multiple blower door tests carried out, it was
noticed that the results were getting slightly worse every time (now - the
figures were probably miniscule). But it turned out that each time the membrane
was put under pressure from the blower test, it moved and strained against
the fixings, enlarging the holes that little more. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Regards</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Feile</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial><A
href="mailto:feile@mudandwood.com">feile@mudandwood.com</A></FONT></DIV>
<DIV><FONT size=2 face=Arial><A
href="http://www.mudandwood.com">www.mudandwood.com</A></FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=derek@unm.edu href="mailto:derek@unm.edu">Derek Stearns Roff</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=GSBN@sustainablesources.com
href="mailto:GSBN@sustainablesources.com">Global Straw Building Network</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, November 20, 2014 2:28
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [GSBN] Ceiling Air
Barrier</DIV>
<DIV><BR></DIV>It’s wonderful to have your input, John. I wonder what
your opinion is of airtight drywall under (closer to the outside world) the
tongue and groove wood ceiling. The advantages would be greater fire
resistance and greater thickness and stiffness that might suffer less damage
to the airtightness during the subsequent steps in the construction process,
than would an unsupported layer of Intello (unsupported until the T & G is
installed). There are disadvantages as well. Would drywall plus
Intello ever make sense?
<DIV>
<DIV><BR></DIV>
<DIV>Thanks,</DIV>
<DIV>Derek</DIV>
<DIV><BR>
<DIV>
<DIV>On Nov 20, 2014, at 6:45 AM, John Straube <<A
href="mailto:jfstraube@uwaterloo.ca">jfstraube@uwaterloo.ca</A>>
wrote:</DIV><BR class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">I am going to disagree with Ian here. What he
has described, we would describe as a roof underlayment, not an air barrier.
It is installed in line with the slope of the pitch and is therefore not
able to be used as an air barrier if the attic is ventilated like normal
wood frame pitched roofs. The asphalt impregnated paper material
is very difficult to seal at laps and joints to make it an air barrier.
when the wind blows, the laps open up and air rushes through. It
is almost impossible to seal tight around pipe penetrations and other
joints. Even if it could be sealed, most materials like this will rip
if they are airtight when a big wind gut comes along. Thankfully they
are not airtight, and work great as a temporary water protection, as stated,
and continue to catch all the rain leak from holes and laps in the roofing
and direct these leaks harmlessly to the outside. But an air barrier
they are not.<BR>An air barrier at the ceiling plane level should be under
the insulation and rafter, and ideally there should be some experience with
testing the system in real buildings. The Intello solution is
definitely one such solution— tested with blower doors and IR cameras all
the time.<BR><BR>On Nov 20, 2014, at 2:33 AM, Ian Redfern <<A
href="mailto:ian@adobesouth.co.nz">ian@adobesouth.co.nz</A>>
wrote:<BR><BR>
<BLOCKQUOTE type="cite">Good evening Enga,<BR><BR>First a question :
are you installing a fluffy blanket type insulation above and
against the tongue and groove sarking i.e. between the
purlins, or if the sarking is under the rafters the insulation the
insulation will be between the rafters ?<BR><BR>Assuming this
scenario, we have for decades used a heavy weight black bituminous
kraft breather paper building wrap across the slope with generous laps
fish scale like to shed moisture during construction - one advantage
is that these mask out any splits or loose small knots in the sarking
as well as providing the essential weather resistance at a critical
stage of the build (who wants water stains on their sarking) <BR>Another
advantage is that it is non reflective so no glare for the building team
- the roof underlay is over the purlins and usually installed by the
roofing gang = this is another story<BR><BR><BR>From: Enga
Lokey<BR>Sent: Wednesday, November 19, 2014 20:46<BR>To: Global Straw
Building Network<BR>Reply To: Global Straw Building Network<BR>Subject:
[GSBN] air barrier<BR><BR>G'day all,<BR><BR>I have been getting
conflicting info on a ceiling air barrier, so I would love it if some of
you that have experience in this realm would like to weigh in on the
confusion.... or solution. I realise that a tongue and groove
cathedral ceiling is a potential nightmare for air exchange. I realise
that drywall can be installed airtight. It is claimed that air barrier
wrap such as Intello can be used between the rafters and the ceiling
lining boards to create an air barrier, thus the lining boards leak like a
sieve and the roof cavity does not get air from inside. Can anyone confirm
if an air barrier used in this position would be effective? With usual
detailing of air-sealing at penetrations and wall/ceiling interface of
course.<BR><BR>Thanks for any bits of wisdom.<BR><BR></BLOCKQUOTE><BR>John F
Straube<BR><A
href="mailto:jfstraube@uwaterloo.ca">jfstraube@uwaterloo.ca</A><BR>www.JohnStraube.com<BR><BR><BR><BR>_______________________________________________<BR>GSBN
mailing
list<BR>GSBN@sustainablesources.com<BR>http://sustainablesources.com/mailman/listinfo.cgi/GSBN<BR></BLOCKQUOTE></DIV><BR>
<DIV apple-content-edited="true"><SPAN
style="LINE-HEIGHT: normal; WIDOWS: 2; TEXT-TRANSFORM: none; FONT-VARIANT: normal; FONT-STYLE: normal; TEXT-INDENT: 0px; LETTER-SPACING: normal; BORDER-COLLAPSE: separate; FONT-FAMILY: Helvetica; WHITE-SPACE: normal; ORPHANS: 2; COLOR: rgb(0,0,0); FONT-WEIGHT: normal; WORD-SPACING: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px"
class=Apple-style-span>Derek Roff<BR><A
href="mailto:derek@unm.edu">derek@unm.edu</A><BR><BR></SPAN></DIV><BR></DIV></DIV>
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