(JBED) - Summer 2006 - The Whole Building Design Guide

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Studies define water and air leakage paths: • June 1980, Air Leakage in Newly Installed Residential Windows: Lawrence Berkeley Laboratory, University of California–Minnesota Energy Agency, John Weidt, Jenny Weidt, Prepared for the U.S. Department of Energy. Rate of Air Leakage through Installed Exterior Windows, Uninstalled, Windows and Jobsite. Conclusions: Manufacturers’ laboratorytested products always fell significantly short of the rating when in the field. Purchasers of products rely on ratings for product selection. Air Leakage is most severe in corners, interlocks, and sills. AAMA method of tabulating air leakage (by crack-foot length) was deemed misleading. Interface between window and wall: “The air leakage performance of the crack between the window unit and the wall has a significant effect on the air leakage performance of the entire window unit as installed.” • Durability by Design guideline published by the Partnership of Advancing Technology in Housing (PATH): “Most leakage problems are related to improper or insufficient flashing details or the absence of flashing.” • Water Penetration Resistance of Windows–Study of Manufacturing, Building Design, Installation and Maintenance Factors, By RDH Engineering Ltd., Vancouver 12/31/2002. “… the dominant leakage paths of concern are those associated with the window to wall interface, both through the window assembly to the adjacent wall assembly and through the window to wall interface with the adjacent wall assembly.” The study recommends redundant systems, sub-sill drainage for all windows. • Journal of Light Construction, November 2003, based on CMHC / HPO study: “35 per cent to 48 per cent of newly installed windows were found to leak through the window unit itself, through joints between the window and the rough opening, or both.” “100 per cent of installed residential windows examined after years in service were found to leak either through the window unit itself or at points of attachment to the building.” 42 Journal of Building Enclosure Design NATIONAL CONSENSUS INSTALLATION STANDARD: ASTM E 2112 Through 1995 there were no clear directions on how to install a window. In 1995 an ASTM committee was formed to write the first fenestration installation standard. The first edition was published in 2001 and covered four basic methods to integrate windows into the wall and membrane to form a system. This document, known as E 2112 Standard Practice for Installation of Exterior Windows, Doors and Skylights, was developed with energy in mind, as significant energy losses were occurring due to the window-wall interface. E 2112 is loaded with excellent information, however, its one major drawback is that it assumes that windows don’t leak in their joinery. Any leak in the joinery, unfortunately, would become trapped in the wall cavity and be forced to the interior. It is common knowledge today that windows will leak in their corners, if not immediately, then at some point after their installation, when the weather-stripping, vinyl, sealants and other components succumb to UV exposure, moisture and thermal expansion. That is not necessarily a bad thing; it is not uncommon for the complexity of this product. Therefore, window manufacturers are acknowledging that there is a distinct possibility of corner leakage on their products sometime in the life cycle of the product. In 2001, the ASTM E 2112 committee started working on the next iteration of the document, which is being published this year (E 2112-06). This document recognizes the reality that there will be joinery leakage and provides details and methods to install a variety of sill pan flashings under the window. Admittedly, this is still just a recommended feature but the majority of the committee hopes that someday it will be required under windows where known joinery leakage occurs. The new standard also recognizes self-adhered flashing. Why is that so revolutionary Well, up until eight months ago there was no credible standard for determining the serviceability or durability of self-adhered flashings. There was no in-service track record of continued performance during their service life. In reality, eight months ago, duct tape or even masking tape would have been allowed to be used as “flashing”, as there were no standards. In 2005 AAMA came to the rescue with AAMA 711 Self Adhering Flashing standard. While the standard is still far from complete, for the first time it establishes criteria to be able to compare one product against another for a particular application. INNOVATIVE BUILDING MATERIALS ADD TO COMPLEXITY OF INSTALLATION The struggle which began early in the twentieth century continues today, even though we have developed a national installation standard and have sealants, membranes, weather-stripping, gasketing, and the list goes on. The fact is, every innovation seems to have added more complexity to the installation. And the struggle continues. REALITY CHECK—REMOVAL AND REPLACEMENT What do roofs, water heaters and windows have in common They all leak eventually and have to be replaced. They all have a limited lifespan which is less than that of the building. More energy-efficient versions are made available continuously. It is reasonable to assume that you will have to change your water heater in ten years so it has been installed in a manner that makes it fairly simple to remove. The roof has a predictable life as well and so replacement is easily accomplished. Best of all, for both the roof and the water heater, the removal is non-destructive to the rest of the building. Now the window installation, by comparison, is bizarre. They are installed and embedded in the wall so deeply that only destructive technology can be used to remove their deeply ensconced roots. They are glued, screwed, nailed, covered with membranes and cladding on the outside and then embedded by gypsum, plaster, paint, finish, stools and aprons, just to mention a few, on the inside. Why in the world do we install windows so deeply among the layers of the wall, that you literally cannot get it out without destroying the wall CODES AND CHANGES In spite of the integration of all building code bodies into the International Code
Council (ICC), one might expect that code would require quality window installation. Factually, there is very little in the code that deals with installation of fenestration and its flashing. In the past several code cycles a little language is starting to creep in, which primarily requires manufacturers to supply installation instructions to the builder at the time of delivery of the product. Which manufacturers, you may ask— windows, membranes, sealants, flashings Who knows The codes have embraced membranes to be installed on the exterior of the building, which is starting to come into effect now. Strangely, codes do not define flashing. The new version of E 2112 clearly defines flashings and how they are used. MODULAR INSERT FENESTRATION SYSTEM: A NEW-OLD CONCEPT FOR INSTALLATION Consider a forward-looking concept where the builder is given a seamless, molded, robust receptor that is specially designed to marry with all standard windows and is based on standard sizes. Simplistically, this is a four-sided pan system which is molded and has no joints to leak. It integrates with the building’s water-resistive membranes and forces drainage to the outside of the cladding—just like the old master builders and architects knew, previous to the innovation of the preassembled window unit. This new system does not rely on the water being evacuated via the membranes in the wall cavity, but rather, diverts it immediately to the exterior of the cladding. Think of the benefit to the builder. He will be able to put the receptor in at any time when building the walls. This installation would then allow for a later window installation without penetration of claddings or membranes. The builder would then be able to finish the walls, add cladding, sheetrock, paint, clean the cladding—without the windows being in place. At a point when the builder felt it best to install the windows, he would come by and snap them into the receptors. Window manufacturers interviewed endorse the concept, as it will enhance the ability of the window to shed water to the outside, keep them clean and free of scratches during construction of the building and allow more flexibility for delivery. It will also keep them from being banged around on the job or stolen. The performance of the installed window would not be dependent on the skill and training, or lack thereof, of the installer. Current building practices have many different trades working around the fenestration openings, but the lack of coordination among them creates the difficulty with interface. PLANNED OBSOLESCENCE OF WINDOWS • Windows are the single largest contributor to energy loss in the exterior walls. • This loss translates to high energy bills and loss of comfort. • Cost of energy can be assumed to rise constantly and substantially over the lifetime of the building. • Allow for innovative technologies without prohibitive expenses and disruption. • The service life of a window is far less than the wall. It has to be replaced two to four times over the life of the building. • The labor cost to remove and replace windows and to repair the surrounding walls, interior and exterior, exceeds the cost of the window. Another important feature of the receptor system and methodology is that it will make for simple replacement of the window. Why is that important Because window technology is moving ahead in strides—self-cleaning glass, energy-efficient glass, photovoltaics, acoustical windows, impact-and blast-resistant glass and window systems. The list goes on. Without a doubt, manufacturers can agree that glass will continue to become more and more sophisticated, bringing more and more energy-saving concepts and comfort to the inhabitants of the building. The current destructive removal methods deter building owners from adopting innovative new window technologies sooner. RECENT TESTING OF PROTOTYPES Prototype receptor systems were installed in conjunction with two different EIFS systems. Specimen one used a liquidapplied water-resistive barrier (LWRB) over the substrate. Modular Insert Fenestration Systems (MIFS) product was installed on top of the LWRB. Additional LWRB was then applied over the MIFS installation flange with fiberglass netting. With specimen two, the MIFS frame was installed onto the substrate, then LWRB was applied over the substrate and over the MIFS attachment flange. Both specimens then had 1-1/2” Styrofoam installed, which was further coated with a 1.5 mm cementitious acrylic coating. • ASTM E 330 Test Method for Evaluation of Structural Performance— The combined wall and fenestration products achieved a 45 psf positive and negative using a fenestration product that was rated at 25 psf. • ASTM E 331 Test Method for Static Water Penetration—The combined wall and fenestration products achieved 12 psf for 15 minutes. • ASTM E 283 Air Infiltration—Both combined wall/fenestration products measured 0.03 cfm per square foot (54 sq. ft. samples) at1.57 lb/ft2. CONCLUSIONS There are manufacturers now developing this concept. Changes are expected in window installations that are based on traditional gravity-based water management principles. The receptor approach requires the receptor to be built into the wall, is designed in such a way that the window can be simply snapped into the receptor without piercing the receptor or the cladding or the membranes. Even if the joinery at the corners of the windows leaked, it would not make any difference, because that leakage would be diverted to the outside of the cladding. ■ Summer 2006 43
Page 1: JBED Summer 2006 Journal of Buildin
Page 6: Message from NIBS David A. Harris,
Page 10 and 11: Feature Dynamic, Integrated Façade
Page 12 and 13: 1. COMMERCIALLY AVAILABLE SOLUTIONS
Page 14 and 15: procure them for the final building
Page 16 and 17: obstruction and/or daylight reflect
Page 19 and 20: Feature All That Glass Is there an
Page 21 and 22: façade at the street corner. It is
Page 23 and 24: cess to the perimeter, concrete str
Page 26 and 27: Feature Architectural Glazing for S
Page 28 and 29: could consist of lites that have di
Page 30: esidents. Another concern from the
Page 33 and 34: from the California Central Valley
Page 37 and 38: Feature Window Comfort & Energy Cod
Page 39 and 40: By Valerie L. Block and Tammy Amos,
Page 41: Feature How Does Fenestration Fit I
Page 46 and 47: Industry Update By James C. Benney,
Page 48 and 49: BEC Corner HOUSTON-BEC By Andy MacP
Page 50: Buyer’s Guide AIR BARRIERS Dupont

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