New design simulation tool for window system energy performance to be released

Kerry Haglund, research fellow, Center for Sustainable Building Research, University of Minnesota, and Nils Petermann, project manager, Alliance to Save Energy, Washington D.C., made a presentation on Design and Simulation Tools for Window System Energy Performance on the last day of the Ecobuild & AEC-ST Fall conference. The conference started Dec. 8 at the Washington Convention Center, Washington, D.C., and ended today. The exhibit opened yesterday and ran through today.

“COMFEN is a design and simulation tool for the residential and commercial window markets designed by the Lawrence Berkeley National Laboratory,” Haglund said. We’ve added features to COMFEN version 2, and the upcoming version 3 has a whole new graphic user interface.”

Features added to COMFEN 2 include more cities, custom glazing systems and custom shading systems, Haglund said. COMFEN 1 and 2 were done on Excel spreadsheets, but version 3 is done on Flash and InDesign. COMFEN 3’s new graphic interface allows the designer to set up various scenarios in a project, drag and drop, and compare the performance of the different designs, she said. In façade design, the designer can drag and drop from a library selection that has a window, geometry of the window, glazing system and frame.

“It’s a zone modeling approach where you define a zone of a building, typical in commercial construction,” Haglund said. “So, you take the module information and bring it into your whole building system. It allows architects and designers to make a quick decision regarding window-wall ratio, glazing type, shading options and how all that is affected by the orientation.”

COMFEN 3 is expected to be released in summer of 2009 and COMFEN 2 in January 2009. “COMFEN 3's going to allow glaziers to build a customized library, and they could use it as a sales tool,” Haglund said. “It’s a tool that goes between full building simulation and product specification. Glaziers also could use this as a comparative tool between different manufacturers’ products. Eventually, all the information from COMFEN could be entered into a BIM modeler and hopefully, users of this tool will already have BIM libraries."

Architects and whoever makes early decisions on design will be the primary user of COMFEN.

EWC presentations

More speakers gave presentations at the Efficient Windows Collaborative Pavilion at the Ecobuild & AEC-ST Fall conference today.

Jim Nelson, sales manager, Mon-Ray Inc., Minneapolis, and Tom Patterson, president, The Window Man, Fairfax, Va., talked about Specifying and Installing Windows for Air Tightness and Water Resistance. “Windows lose energy through radiation, transmission and air infiltration/exfiltration,” Nelson said. “Air leaks through sash cracks and accounts for 60 percent of the energy loss through windows. Windows should be tested for positive and negative air pressure. Lab and field tests are different, and the real way to verify performance is through field testing.”

Water infiltration creates more problems than meet the eye, Nelson said. “It can damage wall cavity; create structural damage; wet insulation; cause mold and indoor air quality issues; and where water can get in, so can insects,” he said.

To avoid these issues, be aware of structural load requirements, Nelson said. “Keep in mind the local wind zones, building height, location of window, size of openings and local building codes. Look for materials that provide long product life and sustainability, and are compatible with each other; hardware that don’t corrode; and materials that can be recycled and won’t fill up the landfill.”

Proper installation is critical for an efficient window system, Patterson said. “The best window in the world is a piece of junk if not installed properly,” he said. “[Installers] need to tie the window system to the particular opening andinspect what they expect. Short-cuts won’t work. Install per shop drawings in manufacturer’s installation instructions. Don’t let buyers talk you into improper installation.” The American Architectural Manufacturers Association, Schaumburg, Ill., offers great installation standards for residential new construction. “What hasn’t been addressed yet is existing residential construction; it’s left up to the installers,” he said. “But there are so many variables that AAMA’s hard-pressed to come up with a solution. If manufacturers held more factory training sessions, that could help.”

AAMA installation masters is a good certification for installers, Patterson said, “but beware, there are bogus certificates out there. AAMA’s the only association from a national standpoint that offers certification."

References can be invaluable when installing a window, Nelson said. “Ask for similar project references. Select a product with proven performance. Ask for older project references, to see how a product’s performing, how the installation’s holding up,” he said. “Ask for successful, tested refurbishing references of products under consideration. Things like weather stripping are critical for sealing. Wood can be refurbished, there are great epoxies out there now. Seek experiences and trained installation contractors. Ask how long their good installation’s been around, that’s a good way to judge.”

Tim Finley, project manager, Sage ElectrochromicsInc., Faribault, Minn., talked about dynamic glazing from Sage. “Our electronically tintable glass, transitions to 62 percent visible transmittance and .48 solar heat gain coefficient, and in 3-5 minutes, transitions down to 3.5 VT and .09 SHGC,” he said. “Giving you best of both worlds, all the while keeping you in connection to the outdoors.” South facing sun-soaked facades in commercial buildings, atriums and skylights are the primary users of electrochromic glass, he said, as well as high-end residences.

Key benefits of Sage electrochromic tinted glass includes: 10 percent to 25 percent energy reduction during peak demand; 10 percent to 28 percent reduction in energy bills; 3 percent to 25 percent decrease in HVAC size; and 10 percent to 20 percent reduction in operating costs, Finley said. The glass is the only one of its kind that meets the ASTM standards for durability of switchable glass, E2141, which evaluates the combined degradative effects of elevated temperature, solar radiation and extended electrical cycling through 50,000 cycles of clear, tint, clear, he said. “Our glass has survived over a 100,000 cycles, equivalent of switching a window nine times per day for 30 years,” he said. “The product didn’t fail at that point, but they determined if you’ve doubled the cycles, it’s time to move on.”

Projects using Sage’s electronically tintable glass includes: a skylight in Greenwich, Conn., with 2,500 square feet glass; Century College, Science and Engineering Building, White Bear Lake, Minn.; and a upcoming project, Chabot College, Hayward, Calif., with 3,000 square feet of glass that will use a building integrated management system to allow the occupants automated control to zone the glass accordingly as the sun rises and sets, Finley said.

Sage has plans to open a high-volume manufacturing facility in Faribault by 2011, Finley said. Robin Roy, Serious Materials, Sunnyvale, Calif., also made a presentation at the EWC pavilion.