[GSBN] Ceiling Air Barrier
Frank Tettemer
frank at livingsol.com
Fri Nov 21 02:36:11 UTC 2014
I'd advocate for drywall AND the membrane. The membrane, when installed
with great care to seal all seams, is a good attempt at a perfect air
barrier. I've used a product by CertainTeed called Membrain, which is a
variably permeable sheet material, similar to your product, (in
intention, at least).
I have used this material would good results, in double-stud,
dense-packed cellulose wall construction.
To the ceiling, I would add drywall and a rough taping of the seams, to
seal them, with a drywall 'mud'. This layer acts as a bit of a
fire-stop. Or, at least a fire slow-down.
On top of the drywall, (towards the inside of the ceiling), I would add
the wood layer, for aesthetic purposes.
Some building codes require a layer of drywall, under any other ceiling
covering materials, such as wood, bamboo, rattan, etc., for fire
resistance. II imagine that it could mean the difference between a
fire-ruined interior, or a total fire-loss of the roof.
My Canadian back-woods two-cents.
Frank Tettemer
Living Sol ~ Building and Design
www.livingsol.com
613 756 3884
On 20/11/2014 5:14 PM, Min Hall wrote:
>
> Hi Enga - And now another two cents worth. Cathedral ceilings are not
> that great for the acoustics in a room and adding the dry wall(gib as
> we call it in NZ) certainly helps with this. It helps muffles external
> noise – rain, hail, etc. and it can also be part of an absorptive
> acoustic treatment – having drywall, then some more battens with 2
> inches(50mm) of acoustic insulation and then your timber ceiling
> lining with ¼ to 3/8 inch (6-10mm)gaps between each board.
>
> Just designing a house for a music buff and we are striking all these
> issues.
>
> Cheers
>
> Min
>
> *From:*GSBN-bounces at sustainablesources.com
> [mailto:GSBN-bounces at sustainablesources.com] *On Behalf Of *Derek
> Stearns Roff
> *Sent:* Friday, 21 November 2014 10:55 a.m.
> *To:* Global Straw Building Network
> *Subject:* Re: [GSBN] Ceiling Air Barrier
>
> Enga, I was not advocating drywall plus Intello, but rather asking the
> man who knows, John Straube, if he could see any reason to use both. I
> was also asking his views on drywall instead of Intello. Intello is a
> great product, from what I read. I’m not arguing that you should
> change your plan, rather I hope to hear more about comparing the options.
>
> I think the increased fire protection is the strongest reason to
> consider drywall. The roof/ceiling is the most vulnerable part of the
> building envelope, from a fire perspective. A secondary factor would
> be greater reliability/success rate in air-sealing penetrations. These
> considerations may also seem like belt and suspenders to some. My
> guess is that around here, the cost of installing airtight drywall,
> with all materials and labor, would be a bit less than installing
> Intello, materials and labor. Your situation could be different.
>
> I’d like to understand your comment about needing to calculate the
> mass in the original engineering. Please say more.
>
> Thanks,
>
> Derek
>
> On Nov 20, 2014, at 1:57 PM, Enga Lokey <enga at thelokeys.net
> <mailto:enga at thelokeys.net>> wrote:
>
>
>
> Thanks all of you for the discussion. Yes and no answers are so
> useless. They are very unhelpful in fleshing out the subtleties
> and "why's" of an issue and mostly used by those that don't really
> know what they are taking about but are strongly opinionated.
> Feile, your info about multiple blower door tests is something I
> need to be aware of when design some future studies. Do you have
> any links to that info? Derek, you are not the first to suggest
> the drywall idea. To me it sounds like belt and suspenders. Yes
> your pants are doubly certain not to fall down, but when it comes
> to drywall and air barrier, the extra drywall is alot of extra
> materials, time and labour (plus mass that would need to be
> calculated in the engineering originally). I personally am too
> lazy for that. But, maybe I just don't understand something
> important there. Would the Intello not be a redundant and a waste
> of money at that point?
>
> You guys rock! Thanks,
>
> E
>
> Natimuk, Australia
> enga at thelokeys.net <mailto:enga at thelokeys.net>
>
>
>
> On 21/11/2014, at 4:05 AM, Feile Butler wrote:
>
>
>
> 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.
>
> 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.
>
> 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.
>
> 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.
>
> 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.
>
> 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.
>
> Regards
>
> Feile
>
> feile at mudandwood.com <mailto:feile at mudandwood.com>
>
> www.mudandwood.com <http://www.mudandwood.com/>
>
> ----- Original Message -----
>
> *From:*Derek Stearns Roff <mailto:derek at unm.edu>
>
> *To:*Global Straw Building Network
> <mailto:GSBN at sustainablesources.com>
>
> *Sent:*Thursday, November 20, 2014 2:28 PM
>
> *Subject:*Re: [GSBN] Ceiling Air Barrier
>
> 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?
>
> Thanks,
>
> Derek
>
> On Nov 20, 2014, at 6:45 AM, John Straube
> <jfstraube at uwaterloo.ca <mailto:jfstraube at uwaterloo.ca>> wrote:
>
>
>
> 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.
> 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.
>
> On Nov 20, 2014, at 2:33 AM, Ian Redfern
> <ian at adobesouth.co.nz <mailto:ian at adobesouth.co.nz>> wrote:
>
>
> Good evening Enga,
>
> 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 ?
>
> 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)
> 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
>
>
> From: Enga Lokey
> Sent: Wednesday, November 19, 2014 20:46
> To: Global Straw Building Network
> Reply To: Global Straw Building Network
> Subject: [GSBN] air barrier
>
> G'day all,
>
> 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.
>
> Thanks for any bits of wisdom.
>
>
> John F Straube
> jfstraube at uwaterloo.ca <mailto:jfstraube at uwaterloo.ca>
> www.JohnStraube.com <http://www.johnstraube.com/>
>
>
>
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>
> Derek Roff
> derek at unm.edu <mailto:derek at unm.edu>
>
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> Derek Roff
> derek at unm.edu <mailto:derek at unm.edu>
>
>
>
>
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