To get the most out of green construction or renovation, developers need to think about a project as an integrated whole whose value can far exceed the sum of its parts. That’s 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. LEED is quite effective at delivering energy-saving performance within budgets comparable to those for traditional construction.
Here’s what developers need to know when planning a green project.
• Energy efficiency is a function of many building components, design elements, and equipment working together as an integrated system. The many choices among these components that need to be made will impact the project’s final incarnation as a green facility.
• Use LEED to guide you through the process. LEED simplifies decision-making for achieving green objectives.
• The point is not to earn a particular LEED rating (Silver, Gold or Platinum signifying increasing levels of energy efficiency). Use LEED to achieve the level of efficiency that the budget will allow.
The integrated approach inherent in the LEED process is best demonstrated by evaluating the role of window glass as a component in determining the energy efficiency of an entire project. In an era of R-19 walls and ceilings (R being a measure of insulating performance), glass has been the weak link in conservation. From 25% to 35% of the energy used in buildings is wasted due to inefficient windows and glass, which account for 10% of all CO2 emissions.
Glass has a disproportionate impact on efficiency compared to other building components. Here’s why.
• Single pane glass does not adequately prevent heat transfer and is no longer acceptable for buildings in most of the US.
• Insulating glass, providing an insulating performance of R-2 as compared to an R-19 wall, is unacceptable although still code-compliant in many locations. Selection of insulating glass will necessitate the use of larger HVAC systems than would otherwise be the case.
• Insulating glass with low-e coatings, providing twice the performance of standard insulating glass, is the de facto energy efficient standard for buildings in which both cooling and warming are important. The “e” in low-e, which stands for “emissivity”, is the ability of a surface to radiate energy.
However this level of performance is not enough to achieve what green building promises in energy savings and CO2 reduction. Higher performing glass provides alternatives to low-e glass and in relationship to LEED accreditation (see sidebar below) will help achieve desired green results.
A superior alternative to low-e glass consists of suspending a very thin, low emissivity and solar reflective coated film inside of an insulating glass unit. Without the weight disadvantages of a third pane of glass, suspended film can create two, three or even four insulating cavities that provide conservation performance ranging from R-6 to R-20. Such internally-mounted films do not replace low-e glass. Rather, they leverage the benefits of film-based and glass-based technologies to create a lightweight, multi-cavity insulating glass that enables developers to downsize or eliminate other building components (AC systems, perimeter heating, etc) to cost-effectively achieve maximum energy savings.
Understanding the potential of film-based, multi-cavity insulating glass to reduce costs while achieving desired efficiencies will make the choices of property developers that much more effective in the greening of facilities.
Rich Wipfler is Applications Engineering Manager at Southwall Technologies Inc. in Palo Alto, Calif.
LEEDing the Way
Multi-cavity suspended film insulating glass offers an opportunity for a project to flexibly achieve certification under the LEED program.
Suspended film insulating glass as part of an integrated construction or renovation strategy can help developers earn up to 21 LEED credits, or 54 percent and 40 percent of the total required credits for Gold and Platinum certification, respectively. Superior glass performance can help achieve LEED credits in the following categories:
• Sustainable Sites (SS) Credit 1, Site Selection;
• Energy and Atmosphere (EA) Credit 1, Optimize Energy Performance;
• Materials and Resources (MR) Credit 1, Building Reuse;
• MR Credit 5, Regional Materials;
• Indoor Environmental Quality (EQ) Credit 2, Increased Ventilation;
• EQ Credit 7, Thermal Comfort; and
• EQ Credit 8, Daylight & Views.