Sustainable Land Development Today - February 2009 - (Page 20)

SLDT FINANCE INNOVATION Pane Relief High-performance, multi-layer glass can maximize green-building potential. By Bruce Lang acility managers understand that by making buildings more energy efficient and environmentally friendly they can reduce operational costs and increase building occupant productivity and health. That’s the good news. The bad news is that it isn’t obvious how to produce an all-green facility. As stakeholders desire to save energy and make facilities more environmentally benign, property managers need not become versed in the often confusing language of sustainability to define realistic, green-construction and renovationproject objectives and management requirements. Fortunately, there is plenty of help available. Surprisingly, the promise of green design, as exemplified in the Leadership in Energy and Environmental Design (LEED®) certification process of the United States Green Building Council, is very straightforward. It is quite powerful and effective at delivering desired energy-saving performance within budgets often comparable to those for traditional construction. F The Role of Glass This integrated systems approach to green design inherent in the LEED process is demonstrated by evaluating the role of high-performance window glass as a key component in determining the energy efficiency of an entire facility. Why is that so? The building envelope — foundation, roof, walls and windows — is the interface between the building and its environment and a structure’s first line of defense against 20 February 2009 Sustainable Land Development Today the elements. Design choices regarding building envelope components affect a project’s ultimate energy efficiency more than the internal systems and components (lighting, heating and cooling, etc.). In an era of R-19 walls and ceilings, window glass has been the weak link in conservation performance. From 25-35 percent of the energy used in American buildings is wasted due to inefficient windows and glass, which themselves account for 10 percent of all CO2 emissions. Improving the performance of windows represents a significant savings opportunity both for the nation and for individual green-building and renovation projects. Glass options alone will have a disproportionate impact on overall building energy efficiency compared to other building components. In that regard let us evaluate those glass options in terms of their impact on energy efficiency and achieving a project’s green objectives. • Single pane glass does not adequately prevent heat transfer and is no longer acceptable for buildings in most of the US. • Standard insulating glass, providing an insulating performance of R-2 as compared to an R-19 wall, is obviously unacceptable although still codecompliant in many locations. Selection of Infrared photography illustrates warmer indoor surface temperature of Heat Mirror (very red) compared to cooler temperature of both standard insulating glass (blue green) and generic low-e glass (orange) as shown in these two windows. standard insulating glass will necessitate the use of much larger and expensive HVAC systems than would otherwise be the case. • Insulating glass with low-e coatings, providing twice the insulating performance of standard insulating glass, simultaneously reflects radiant solar and ambient heat and is the de facto, energy efficient-standard for buildings in which both summer cooling and winter warming are important. The “e” in low-e, which stands for “emissivity,” is the ability of a surface to radiate energy. Efficiency Comes in Layers Many might think that this is where the story ends, because generic low-e insulating glass, consisting of two pieces of coated glass separated by a sealed, gasfilled air space (or cavity), achieves a maximum R value of 4. However, this level of performance is not nearly enough to achieve what green building promises in terms of energy savings and CO2 reduction. Fortunately, much of the success of green construction is due to higher-performing glass technology that

Table of Contents Feed for the Digital Edition of Sustainable Land Development Today - February 2009

Sustainable Land Development Today - February 2009 Contents Our Voice Modern Flood Disasters Origin of the Sustainability Movement SLDI in Focus Calendar Build Smart Product Innovation Takeoff and Cost Management Industry News Products & Services Advertiser Index Editorial Board SLDT Resources Last Word

Sustainable Land Development Today - February 2009

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