Designing an Air Barrier for a Timbered Cathedral Ceiling

first_imgThe house that Dennis Miller plans on building next spring will include a cathedral ceiling with timber trusses exposed on the interior. The issue, as Miller explains in this Q&A post, is making sure the ceiling gets an effective air barrier that will prevent moisture problems in the roof. “In a regular ceiling I’d think a continuous plane of drywall would do the job,” Miller writes. “However, this is a cathedral ceiling built on timber kingpost trusses that are exposed to the interior. In this case, the ceiling drywall is not continuous but broken into sections by the exposed timbers.” As the drawing at the top of this column shows, the ceiling will be insulated with cellulose. Rafters in this Climate Zone 5 house will be supported by a ridge beam and the outer wall in this double-stud wall design.RELATED ARTICLESAir BarriersOne Air Barrier or Two?How to Hang Airtight DrywallRescuing a Problem Cathedral CeilingHow to Build an Insulated Cathedral Ceiling Miller wonders whether his only option is to do a “tedious caulking-gluing-sealing job” where the drywall meets the trusses. Or is there another way? “I think my question really applies to any situation where someone has a ceiling with exposed beams,” he says. “What are some good methods to ensure a good air barrier when the ceiling plane is segmented?” That’s the topic for this Q&A Spotlight. A continuous layer above would be best In general, Malcolm Taylor replies, the best approach is to include a continuous layer of material above the exposed trusses. “That’s in part why many timber-frame houses have tongue-and-groove or plywood roof decking, which can be fastened to the tops of the trusses,” he says. Taylor thinks that sheathing and taping the tops of the 2×4 strapping would be the safest and most effective approach. As an alternative, Miller could use rigid foam insulation for that layer, although it isn’t clear how he would go about sealing it, and then build the rest of the roof structure on top of it. Yes, adds Akos, use some kind of sheet material above the timber beams and tape the seams. If Miller tries to seal each seam between a truss and the drywall, failure is likely — even if he’s meticulous in his attention to detail. “Sealing drywall along long seams is a pain (speaking from personal experience),” Akos says. “If you want it to last, it has to be a very clean, even joint, and you need to put a backer rod into the gap, and then caulk. I did most of this work myself and even then had to redo a section where the joint failed after a couple of years. (No matter how careful, human nature is to take shortcuts and will bite you in the $%^). The probability of this being done properly by a contractor is near zero.” Adding a layer of foam above With those suggestions in mind, Miller considers adding a 1-inch-thick layer of extruded polystyrene (XPS) insulation above the drywall strapping, leaving a few small openings to blow in cellulose. Those openings could be sealed later. “This would make the XPS the primary air barrier rather than relying on the drywall layer,” Miller says. “Or,” he adds, “instead of XPS, just put down a 4- or 6-mil sheet of poly, with a few openings to blow cellulose and then seal them shut. I would think poly or XPS is OK if the [assembly] can dry to the exterior, and in this design there is a 2-inch ventilation space under the roof sheathing.” Zephyr7 suggests that Miller use polyisocyanurate insulation rather than the XPS (since the blowing agents in XPS have a high global warming potential). Reducing the thickness to 1/2 inch would produce the same air-sealing result. “Polyethylene sheeting would work, too,” Zephyr7 adds. “You’d still have to detail everything at the edges, which might be tricky if you have timber framing. You could caulk the poly to the timber pieces, that might be better than trying to tape it.” It’s the detailing that will count, points out GBA moderator Brian Pontolilo. “Airtight drywall is a legitimate approach to air-sealing,” he writes, “but it is much more involved than hanging and taping drywall panels.” Pontolilo said he initially wondered whether ZIP System sheathing might be an option for the continuous layer of material above the timbers. Whether Miller opted for that, or rigid foam, carefully taping the joints and detailing other potential trouble spots would be essential, and to that end Pontolilo points Miller toward an article and video series on the topic. Or, move the air barrier Trevor Chadwick has another idea: move the air barrier so it’s above the rafters, rather than in the area immediately above the trusses, as the drawing below illustrates. The air barrier also could be shifted upward, one GBA reader suggests. “Seems to me that the extra materials to do it this way would be less than all the labor trying to get a quality sealing job another way,” he says. The idea puzzles Miller, who has been planning on an interior air barrier that prevents moist interior air from getting into the wall and reaching an area where it might condense. “I assumed I would also have an exterior air barrier, basically what is shown in Trevor Chadwick’s drawing, to prevent external air from blowing into the insulation and undermining its R-value,” Miller adds. He also had imagined only drywall on the ceiling, rather than adding a layer of polyiso or XPS, so that the assembly could dry to the interior. “If you were doing the ceiling without the timbers breaking things up, wouldn’t you just make a giant drywall plane in an airtight manner, have an exterior air barrier (per the Chadwick drawing) and be done with it?” Miller asks. “But I’ve complicated things by allowing the timbers to be penetrations? And that’s the issue I’m trying to resolve.” Chadwick points to the ventilation channel between the insulation and the roof sheathing. He contends that given where Miller is building, and that he’s going to be using dense-packed cellulose, an air barrier on both sides of the insulation is probably unnecessary. “You’re right that I might not need so much air barrier,” Miller replies. “… So maybe the ventilation channel, uncaulked, is just fine. But one thing I was hoping to prevent was the moisture from humid summer air condensing in the insulation as it gets near the air conditioned ceiling. But again, maybe I’m over-thinking this — if it’s OK that the insulation in the attic doesn’t have air and vapor barriers over it, then why should my assembly need it?” Our expert’s opinion Here’s what GBA Technical Director Peter Yost has to add: The way in which Dennis Miller is thinking this through — and using the skilled advice of other GBA folks — is a testament to exactly how GBA does great work: collectively. Here are some additional recommendations to consider: Connecting exterior wall and roof air-control layers: So often with timber-frame structures, rafters and ridges extend from conditioned space to the outside. In my experience, these are never continuously sealed to start, nor maintained over time. There’s just too much wood movement for sealants to manage. So, healthy overlapping at the eaves (because rafter tails don’t extend to the exterior) eliminates a tough and losing battle. Mechanically supporting adhered overlaps: The other great performance feature of overlapping the roof and wall barriers happens at the eave, where you can reinforce your airtight seal with sticky stuff by mechanically supporting subsequent rigid materials. Relying on both chemistry and physics is a great “belt-and-suspenders” approach. Do you need two air control layers in this roof assembly? If your cavity insulation is air-permeable, then it must be confined on all six sides for the full insulating effect. Cellulose insulation is air-permeable — not nearly as air-permeable as, say, fiberglass batts, but cellulose insulation is 50 times too porous to qualify as an air barrier material. And if there is an air leak into the roof assembly, there will be moisture carried with that air, and moisture that will certainly reach dew point as it moves towards the first condensing surface. Using Huber Zip sheathing system on your roof: The thing about this sheathing system is that the material compatibility of the sheathing surface and the pressure-sensitive adhesive (PSA) tape has been worked out by the manufacturer. Zip tape sticks to the Zip sheathing very well (see my Sticky Business series of blogs). It’s at least worth considering. Polyethylene sheeting: I know that there are many Canadians who have successfully detailed polyethylene as an air control layer, but this remains a mystery to me personally. And I will take a rigid air control layer over a flexible one every time. The latter is simply more durable and easier to detail for sticky (chemistry) and mechanical trapping (physics). Test your air barrier: Since Miller will be doing most of the work himself, and also for the first time, I think it is essential that he test the continuous control layers with a blower door test supported by infrared imaging. This sort of performance testing is incredibly revealing, particularly at your first rodeo. Your ceiling interior vapor retarder: From what I can gather from reviewing your Pennsylvania code and the 2009 International Residential Code, there is no explicit guidance or requirement for an interior vapor retarder for your roof assembly. But if we apply the language of the code for exterior walls — and use the logic of vapor movement by diffusion during the winter in cold climates — I think you have three options: (a) Warm your air-permeable roof cavity insulation with topside rigid insulation according to R-value ratios that keep your first condensing surface temperature above the dew point for the three coldest months of the year; or, (b) replace enough of your cellulose with air-impermeable insulation, such as spray foam, to avoid first condensing surface temperature issues using the same R-value ratios as above; or (c) install a Class I or II interior vapor retarder in your roof assembly. For more on how much rigid foam to install, see “How to Install Rigid Foam On Top of Roof Sheathing.”last_img read more

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Get Those Wrists Ready: Samsung Reportedly Outing Smartwatch Sept 4

first_imgWhat it Takes to Build a Highly Secure FinTech … adriana lee The Rise and Rise of Mobile Payment Technology Bloomberg reports that Samsung will indeed announce its own smartwatch, the Galaxy Gear, at a press event on September 4.Not that smartwatches are anything new—see Pebble and Sony. And the rumor of a Samsung device has been going on for months. But if the wire service’s two anonymous sources are right, Samsung Galaxy Gear will be having its coming-out party next month—a week before Apple holds a similar launch event for its own new products.Apple has long been rumored to be working on its own wristworn smart device, unofficially dubbed the iWatch. Both patent filings and job listings strongly suggest Apple’s plans are real. See also: Arm Race: Samsung To Build A Smartwatch TooApple’s not the only company supposedly trying to make our wrists smarter. Others—including Google and Microsoft—are reportedly racing to bring their own smartwatches to market. The reason why is obvious: If any one of these companies can blaze this trail, it offers a substantial advantage. The market for smartwatches isn’t as saturated as tablets or phones, so the winner here has a better chance of standing out and locking even more users into its respective platforms.The wrist, in short, is viewed as virgin territory for gadgets. Though ReadWrite’s editor-in-chief may rail against wearable wrist-bound devices, he’s shouting at the waves. Smartwatches now officially seem to be the “It” thing in tech.According to this latest report, Galaxy Gear will be an Android device that makes calls, surfs the Web and manages email messages. It won’t, however, sport a flexible screen, at least not in the this version, though Samsung’s working on it for future devices.  Why IoT Apps are Eating Device Interfacescenter_img Role of Mobile App Analytics In-App Engagement Tags:#Arm Race#mobile#Samsung#smartwatch#Wearable Computing#wearables Related Posts last_img read more

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Create Unbelievable Cosmic Imagery With Everyday Ingredients

first_imgIt’s surprisingly simple and inexpensive to create jaw-dropping cosmic scenes with everyday ingredients. Put together a quick shopping list and get ready to blow some minds.I can only recount a dozen moments throughout the movies I’ve watched where I’ve been truly mesmerized — jaw on the floor, eyes wide open. A few moments that come to mind are the bear scene in The Revenant, a real 18-wheeler truck flipping in The Dark Knight, and the Big Bang sequence in The Tree of Life.The cosmic creation sequence in The Tree of Life completely blew me away. I had not seen anything like that before. One of the first things I did when I got home from the cinema was research how this scene was created.To my surprise and delight, a good portion of the scene was created with practical effects. Most incredibly, along with the use of liquid tanks, flashlights, glass paperweights, dry ice, pinhole flares and other tools, there was also the use of everyday items that you could buy from the grocery store — milk, dye, and paint.Visual effects supervisor Douglas Trumbull said:We were shooting with a combination of the Phantom Gold 2K camera at up to 1,000fps and sometimes with a Red One camera using it at 4K, sometimes at 24fps and sometimes even undercranked at 6 or 12fps. There were a lot of experiments in water tanks, different kinds of turbulence tanks that I would design. Lighting effects in tanks. Combinations of dyes and liquids, paint and a lot of milk and half and half. It’s the way I like to work. When we first spoke, Terry was frustrated that even some of the best supercomputers in the world that were doing galaxy and Black Hole simulations tended to look a little synthetic. So he wanted to explore the possibility of doing it in a more organic way. And I said that’s exactly what I would suggest. And so that’s what I was helping him with. The whole objective was to make shots that, even though we were using Nuke for compositing, were at least 80% organic.The thought of being able to create something spectacular from milk and dye was very appealing to me. I love organically creating effects. There’s a lot of satisfaction knowing that what is on screen was physically created by your hands. Not to mention that when you’re using liquid or elements that act randomly, it’s going to be unique. Even if I wasn’t going to be able to replicate The Tree of Life sequence, I was sure going to try and do something like it.One of the most important points taken away from Douglas Trumbull’s information was the use of water tanks. I imagine these tanks would be incredibly large, something well out of my reach. As this was a DIY task, my old fish tank would be sufficient.Here is the first attempt.It’s not The Tree of Life sequence by a far stretch, but it’s definitely something different that can be worked upon or used in a creative manner. This is where a lot of new ideas and techniques are born — by trying to imitate something else. Having a set of ready-to-use stock footage like this in your arsenal can be very useful.There are plenty of applications for effects like this. The gif below from Breaking Bad shows a chemical reaction. I’m sure something like this could be organically made through the use of water tanks and the ingredients.The SetupThe ingredients I bought were milk, red food coloring, blue food coloring, cooking oil, and flour. Then I set my unused fish tank upon a few books, with a gap in the center to place a small a Z-96 LED light underneath.I shot with a RED ONE M-X 2K at 120fps. Other than the camera, it was a very basic DIY setup for creating this sequence. Many DSLRs now offer that frame rate, and although it won’t be captured in RAW, with the right lighting setup, you could get something great.Nevertheless, it wasn’t The Tree of Life sequence replication I dreamt of, and I haven’t attempted to anything similar since this test three years ago. Thankfully, filmmaker and YouTuber Joey Shanks has been able to replicate the cosmos sequence with a more satisfactory result.Unlike The Tree of Life method, Shanks squirts liquid onto a transparent glass plate and films the reaction from above. There seem to be endless means of creating footage like this, all of which create unique pieces of media.Have you any practical effects techniques like this? Share them in the comments below.last_img read more

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3 more die in U.P. floods

first_imgThree more flood-related deaths have been reported in Uttar Pradesh on Monday, taking the toll to 72. The overall situation in the State is still grim, the Relief Commissioner’s office said.Over 20 lakh people have been hit by the current spell of floods in 24 districts and 2,688 villages are under water.A report said 43,602 people had taken shelter in relief camps in eastern U.P., whipped by the raging waters of the rivers emanating from Nepal.Army choppers, NDRF and PAC jawans continued relief and rescue operations.A Central Water Commission report said the Sharda river was flowing above the red mark at Palia Kalan and near the danger mark at Shardanagar while the Ghaghra was flowing above the red mark at Elgin Bridge, Ayodhya and Turtipar (Ballia).In Bihar, light to moderate rainfall occurred at one or two places in the past 24 hours.With the south west monsoon getting weak, major cities of Patna, Gaya, Bhagalpur and Purnea did not receive any rainfall during the day.last_img read more

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PH bid in Aimag goes in full swing

first_imgFor the 116 Filipino athletes lined up in 17 of the 21 sports, it will be all business until the closing rites on Sept. 27 of the biggest continental indoor games in history due to the inclusion of the Oceania region headed by Olympic powerhouse Australia and New Zealand.Prior to the opener, the Philippines already snatched a bronze medal courtesy of wrestler Alvin Lobreguito in the men’s freestyle -57kg category in traditional wrestling.“It was a good start for us and we’re looking forward to winning more medals as the tournament progresses,” said Philippine chef de mission and Makati City representative Monsour Del Rosario, who has Philippine Karatedo Federation secretary general Raymund Lee Reyes as deputy CDM.Philippine Olympic Committee president Peping Cojuangco is also monitoring the performances of the athletes together with POC 1st vice president Joey Romasanta, POC secretary general Steve Hontiveros and POC board member Robert Mananquil in this Central Asian nation known for its massive natural gas reserves.“We all know that competition here in the Aimag is tough. But I never doubt the ability of our athletes to come up with their best effort to get a medal,” said Cojuangco.ADVERTISEMENT Eric Cray of the Philippines competes in the men’s 400-meter hurdles event of the 29th Southeast Asian Games. Cray clocked 50.03 seconds to win the gold medal.INQUIRER/ MARIANNE BERMUDEZASHGABAT—The Philippine campaign in the 5th Asian Indoor and Martial Arts Games goes into full swing on Monday as Filipino fighters from ju-jitsu, taekwondo and wrestling together with the national tracksters figure in a tight and demanding contest for success.Southeast Asian Games 400m hurdles champion Eric Cray will test his forte in the men’s 60m hurdles against the fastest hurdlers in the continent while former Asian long-jump queen Marestella Torres is scheduled to compete in her pet event at the Indoor Athletics Arena here.ADVERTISEMENT Robredo: True leaders perform well despite having ‘uninspiring’ boss PLAY LIST 02:49Robredo: True leaders perform well despite having ‘uninspiring’ boss02:42PH underwater hockey team aims to make waves in SEA Games01:44Philippines marks anniversary of massacre with calls for justice01:19Fire erupts in Barangay Tatalon in Quezon City01:07Trump talks impeachment while meeting NCAA athletes02:49World-class track facilities installed at NCC for SEA Games A total of 41 gold medals are at stake on Monday with Filipino athletes entered in 19 events. The 12-day sportsfest is organized by the Olympic Council of Asia.Joining Cray and Torres in the gold-medal hunt in athletics are middle-distance runners Mervin Guarte and Marco Vilog in the men’s 800m and another long-jumper in Janry Ubas.Torres and Cray are going for a podium finish on the same day while Guarte, Vilog and Ubas should sparkle in their qualifying heats to reach the finals scheduled the following day.In the previous edition of the Aimag in 2013 Incheon, dancesport bets Cherry Clarice Parcon and Gerald Jamili won a gold and a bronze. Cue artist Rubilen Amit also brought home a bronze.“I don’t make predictions but I’m pretty optimistic that our athletes can make us proud,” said Del Rosario, also the secretary general of the Philippine Taekwondo Association. “They are relaxed and seemed to be confident.”Sports Related Videospowered by AdSparcRead Next Grapplers Michael Vijay Cater (men’s classic -57kg), Jonathan Maquilan (-62kg), Jhonny Morte (-68kg), Jefferson Manatad (-75kg), Cristof Hoffman Jr. (-90kg), Grace Loberanes (women’s classic -52kg) and Noemi Tener (-58kg) will also hunt for medals in today’s traditional wrestling.Taekwondo jin Ronna Levita Ilao faces Fatemeh Madahi of Iran in the round of 16 of the women’s -46kg category while Southeast Asian Games champion Samuel Morrison (men’s -75kg) and Jener Torillos (-54kg) are likewise expected to contend for a podium finish.FEATURED STORIESSPORTSSEA Games: Biñan football stadium stands out in preparedness, completionSPORTSPrivate companies step in to help SEA Games hostingSPORTSBoxers Pacquiao, Petecio torchbearers for SEA Games openingAn air of optimism surrounds the opening salvo of the country’s ju-jitsu specialists starring Alexander Lim (men’s ne-waza -69kg), Terrence Hansel Co (-77kg), Gilbert Ombao (-94kg), Asian champion Apryl Eppinger (women’s ne-waza -62kg) and Lou-Ann Jindani (-70kg).Host Turkmenistan welcomed more than 6,000 athletes from 62 countries in a grandiose opening ceremony amid a splashy display of sounds, lights, fireworks, amusing visualsand cultural presentations on Sunday night. Lacson: SEA Games fund put in foundation like ‘Napoles case’ LATEST STORIES NATO’s aging eye in the sky to get a last overhaul Trump signs bills in support of Hong Kong protesters Ethel Booba on hotel’s clarification that ‘kikiam’ is ‘chicken sausage’: ‘Kung di pa pansinin, baka isipin nila ok lang’center_img Desiderio sets career-high, UP pulls away in 2nd half to beat UE Don’t miss out on the latest news and information. Robredo should’ve resigned as drug czar after lack of trust issue – Panelo MOST READ Hotel says PH coach apologized for ‘kikiam for breakfast’ claim ‘A complete lie:’ Drilon refutes ‘blabbermouth’ Salo’s claims Celebrity chef Gary Rhodes dies at 59 with wife by his side View commentslast_img read more

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