New Energy Modeling Guide Could Encourage Glazing to Optimize Energy Efficiency and Daylighting

October 5th, 2012 by DWM Magazine

As the design, specification and use of advanced glazing products continues to advance, so, too, will the need for performance modeling. In this respect, the American Institute of Architects (AIA) has released An Architect’s Guide to Integrating Energy Modeling in the Design Process. This new guide was created to provide a step-by-step map to predicting (and thus reducing) the energy usage of buildings.

The guide was written and assembled by a committee of architects, sustainability experts, and government building science officials, as well as AIA staff. It surveys members of the building design and construction industry to present baseline best practices for empirically evaluating the energy performance of buildings. Beyond defining and making a case for energy modeling, this primer walks readers through different types of energy modeling and the individual tools and software available for it. As a relatively new technical specialty, the guide also discusses how to bring energy modeling to other building team members, such as engineers, as well as the clients.

The guide explains that an energy model is “a calculation engine that accepts inputs such as building geometry, system characteristics, and operations schedules and produces outputs such as performance comparisons and compliance reports.”

Glazing and windows are also referenced in areas throughout the guide. For example, in a section on energy modeling for code compliance, the guide notes that the “new editions of both the International Energy Conservation Code and International Green Construction Code will require a greater understanding of the effects of a building’s energy consumption, in which code-compliant energy criteria have significant architectural implications, such as new daylighting requirements.” As an example, the guide says “the integration of windows into the building envelope is key to determining whether a building can be designed to meet prescriptive energy conservation requirements or will need to use performance requirements. Prescriptive requirements allow up to a certain ratio of glass to opaque wall area, above which the building will need an energy model to demonstrate code compliance.”

Helen Sanders, vice president of technical business development for Sage Electrochromics in Faribault, Minn., agrees that the increased use of energy modeling in building design will definitely be beneficial to the glass and glazing industry.

“From a code perspective, it is becoming more and more difficult to garner additional energy savings through changes to the prescriptive compliance path without becoming too prescriptive and limiting design freedom,” says Sanders. “Unfortunate trends such as reducing window-to-wall ratio and the current discussions around prescribing a minimum visible light transmission for fenestration are a negative consequence of this issue and could actually result in poorer buildings being constructed. The use of the performance approach to code compliance (which uses energy modeling to show overall energy performance) allows a great deal more flexibility in the building’s design. It allows trade-offs to be made between different parts of the building, providing a way to more holistically optimize the performance of the building. For the fenestration industry this means architects have more design freedom and product choice and with it they can design a building that is both energy efficient and creates a well daylight, comfortable, environment for the occupants.”

Tom Culp, industry consultant with Birch Point Consulting LLC in LaCrosse, Wis., says that while the guide only discusses fenestration in general terms, any efforts–especially from AIA–to further the use of energy performance modeling will be beneficial to the industry.

“Performance modeling encourages integrated design, which in turn promotes flexibility and the best uses of glazing to optimize energy efficiency and daylighting,” he says. “Performance modeling is also critical for advanced products such as dynamic glazing, BIPV, vacuum glazing and shading systems to receive full credit for their performance.”

“Energy modeling is fast becoming a more useful means to better inform major design decisions early and often throughout the building design process. It can provide a roadmap to help practitioners lead their clients toward energy efficiency goals, green code compliance and building certification programs,” said AIA President, Jeff Potter, FAIA. “It is imperative for the entire design and construction industry to be cognizant of the energy use implication buildings have, in terms of limited resources, climate change, and rising utility costs. This guide provides the energy modeling fundamentals that can serve the client’s high expectations and ultimately reduce energy costs and greenhouse gas emissions.”

Cities such as Washington, D.C, San Francisco and Philadelphia have passed legislation requiring nonresidential building owners to measure and report their buildings’ annual energy use.

Sanders adds, “Because of the difficulty in eking out increased energy savings in the baseline codes through the prescriptive path, there are a number of people calling for code compliance to happen through performance path alone. In fact this has already happened in a number of countries in Europe. The trend to compliance through whole building modeling is something that the glass and glazing industry should embrace. The move by AIA will definitely help encourage more building energy modeling can only help to promote the appropriate use of glass in buildings.”

Additional information about the guide is available through the AIA website.

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