Air sealing and pressure differencesReaders who live in Southern states will particularly appreciate Bailes’ Georgia perspective. A few samples of Bailes’ writing give a flavor of the range of his blog topics.On thermal bypasses: “In such houses, the problem results from the top of the walls being open to the attic. You can go into the attic and look down into the interior walls and see the drywall. That means that cold attic air gets down into those cavities.”On sealing air leaks: “So, before you go around caulking your windows and weatherstripping your doors, get up in your attic and seal the real leaks!”On aligning air barriers with insulation: “We’ve got 2×8 floor joists, with a depth of 7.25 in. The R-7 fiberglass batts are only about 2 in. thick. (R-7? Really?! Why bother!) You can see in the photo below that these batts don’t come anywhere close to touching the subfloor, and that’s how they’re installed in just about every cavity in this floor.”On the quality of spray foam jobs: “I’ve seen a number of houses with problems even though they’re insulated with spray foam. In order of prevalence, here are the problems I’ve seen, with explanations following the list:Spray foam isn’t thick enough.Spray foam installers missed some of the air leakage sites.Spray foam installers didn’t understand the building envelope and sprayed either too little or too much.Spray foam contracts and pulls away from framing.”On the value of measuring air changes per hour: “Infiltration occurs at the surface, not in the volume. … We need to stop talking about infiltration rates in terms of air changes per hour because there are too many problems with it. … Normalizing to volume also builds in a bias toward larger homes. Since surface area is proportional to the square of the radius and volume is proportional to the cube of the radius, the volume increases faster than the surface area as a house grows in size. So, large houses benefit when dividing by volume instead of surface area. …. It’s time to quit using ACH to talk about infiltration.”On the difficulties of measuring “natural” air changes per hour: “Pressure differences created by mechanical systems can eclipse those created by wind and the stack effect. The disconnected supply duct, the panned return, the 1,200-cfm commercial range hood with no makeup air — all these things can dwarf the effects we’re trying to capture in ACHnat.”On carpet stains: “Do you have light colored carpet in your home that has dark edges where it meets the baseboard? If so, don’t beat yourself up so much for not being a good enough house cleaner. The problem is probably in your building envelope, not your vacuum cleaner. The reason the dirt is accumulating there in the first place, you see, is that a lot of air is moving through the carpet at that point. For air to move from one place to another, two conditions must be met:A pressure difference drives air from the high pressure side to the low pressure side.A pathway allows the air to move.”On the fact that particulates piggybacking on air leaks often stain fiberglass batts: “It was really nice of the insulation manufacturers to make their products in colors that show dirt really well — white, yellow, and pink. If they made grey insulation, finding air leaks would be more difficult.”On dehumidifiers in vented crawl spaces: “No dehumidifier can dehumidify all the air in Atlanta, which is what they’re asking this little one to do because the crawl space is vented to the outside.” by Martin HolladayGBA is launching a new feature: periodic reviews of interesting blogs. To get the ball rolling, I’m recommending the Energy Vanguard blog.The author of the Energy Vanguard blog, Allison Bailes of Decatur, Georgia, is a RESNET-accredited energy consultant and trainer. He performs heat loss calculations, provides HERS rating services, and provides rater training and Energy Star training, among other services.Allison has a PhD in physics, a fact that is reflected in his approach to building science. He’s worked at a variety of jobs; at one point he worked as a contractor offering air sealing, duct sealing, insulation installation, and crawl space encapsulation services. For a few years, Bailes worked at the Southface Energy Institute as the regional manager for the EarthCraft House program. Photos illustrating leaks and problemsLike many home performance contractors, Bailes always keeps a camera handy. He has an excellent collection of photos illustrating a variety of home-performance problems, and he effectively uses those photos to clarify points made in his blogs.A tiny quibble: Bailes’ blog (like portions of the GBA Web site, it must be admitted) is a little confusing to navigate. That said, it’s well worth clicking a few links until you figure out how to find all of Bailes’ blogs.GBA highly recommends Bailes’ blog. So go visit the Energy Vanguard.To read a sample of Bailes’ writing, check out his guest blog here at GBA: Is There a Downside to Lumpy Attic Insulation?.
Horizontal tape is problematicThe installation procedure for housewrap, regardless of the manufacturer, is fairly standard across the board. Because the cap fastener prevents the tape from making a complete seal, debris has been carried by the water that penetrated behind the tape. You can see that the water has run horizontally along the seam, taking the path of least resistance.Many of the problems related to the seam seal tape start with the wrap installation, particularly the fastener placement. Oftentimes cap fasteners installed at the tape edge prevent a complete seal. Wrinkles in the wrap can leave voids at the tape contact surface.All of these conditions can allow water to migrate behind the tape, follow the horizontal seam to the nearest vertical seam, and ultimately into the structure. Since most areas of housewrap are over wood-based sheathing, leaks at the seams may go undiscovered for years. The debris from the water intrusion can be seen at the wrinkle in the wrap. Note that the housewrap has been wrapped into the rough opening of the door, so water can migrate horizontally past the door frame and into the interior.While this reverse lap might not result in leakage in laboratory conditions, in the field the installation of the tape is not always done properly. At times the wrap is not clean when the tape is applied. Other times the surface is damp, preventing the tape from adhering properly. Every year we inspect thousands of homes with one brand or another of housewrap installed as the water-resistive barrier (WRB).As energy costs increase and energy code requirements become more stringent, we are seeing housewrap installations where the seams are sealed with tape. Many housewrap manufacturers have proprietary seam seal tapes that they sell for exclusive use with their housewrap system.As implied by the name, the tape is used for sealing the seams of the housewrap. The purpose of sealing the seams is to create a continuous air barrier. Some of the manufacturers imply that the use of their tape will also reduce moisture intrusion. If the seams are going to be taped, the work generally occurs after the entire house is wrapped or after several courses of wrap are installed. Note the dark line of debris at this horizontal seam — debris which continues to the vertical seam.The horizontal seam tape is installed by lapping the tape over both layers of wrap. This means that the seam tape installation creates a reverse lap at the top of the tape, creating an opportunity for water to get behind the tape at the upper edge of any horizontal tape. Installation begins with a course at the base of the wall and that course is overlapped horizontally with the next course. The amount of the horizontal overlap varies by manufacturer. Additionally, vertical seams must also be overlapped. Why not use double-sided tape?We have contacted one of the larger housewrap manufacturers about these problems and asked about the possibility of a double-sided tape for use on horizontal seams. We were informed that they make such a tape, but it is not for sale in the U.S.We will be contacting all of the manufacturers to attempt to encourage them to provide a double-sided tape or other method to eliminate reverse laps.Until such tape is available, when you are sealing the horizontal seams make sure to follow all of the manufacturer’s instructions and recommendations, including making sure the wrap is clean and dry and that you are installing the tape within the effective temperature range of the tape as stated by the product manufacturer.Additionally, make certain that fasteners and other objects are not installed in a location that will prevent or compromise the complete seal of the tape. Always use a roller to bond the tape and never rely on smoothing it out with your hand. Care must be taken and attention to detail is critical when installing the seam tape at transitions to avoid gaps between the tape and the wrap.For any additional information or details always consult your housewrap system manufacturer’s details and specifications. Water entry leads to litigationThere have been litigation cases where the major contributing factor was improper sealing of the housewrap causing major structural damage to the wood sheathing and other building components.Except under rare circumstances where the reverse lap is part of a small repair, our company would never recommend a reverse lap installation. Manufacturer’s window installation details no longer recommend wrapping housewrap into the rough opening and then taping the window head nailing flange to the wrap as an effective means of sealing the window. They now indicate a weatherboard installation. This article is © Quality Built and is reprinted with permission.Jeff Hoch is an architect and field consultant at Quality Built in San Diego, California. Jeff has been involved in the inspection industry and related fields for over 23 years.
Posted: October 7, 2018 KUSI Newsroom Pedestrian hospitalized with gunshot wound after fight with motorist in Del Cerro October 7, 2018 SAN DIEGO (KUSI) – A 57-year-old man suffered a gunshot to his right forearm while fighting a motorist who almost struck him Sunday morning in the Del Cerro community of San Diego, a police sergeant said.The victim told police he was walking southbound across the street in the 5200 block of Adobe Falls Road when he was almost struck about 1 a.m. by a white, four-door sedan, said San Diego police Sgt. Michael Tansey.“He exchanged words with the driver of the vehicle. The vehicle stopped and a Pacific Islander male exited the driver’s seat,” Tansey said. “The two became involved in a fight, and the victim was knocked unconscious.”The 57-year-old man regained consciousness and was taken to the hospital by an unknown citizen.He realized that he had been shot in the forearm while at an area hospital and was transferred to the hospital’s trauma unit, where he was treated for his injuries, he said.The suspect in connection with the shooting was described as a 6-foot, 2-inch tall Pacific Islander weighing 220 pounds with long hair. KUSI Newsroom, Categories: Local San Diego News FacebookTwitter