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Design Guidance

Overall Strategies

Maximizing the thermal performance of the windows in an office space can drastically reduce the energy spent on heating and cooling. Window upgrades play a key part in a sustainable workplace. A window's energy efficiency criteria is based on the entire window assembly including the frame and the glass. Factors such as heat loss, solar gain, and visible light can be optimized by carefully selecting window coatings and frames. Solar-powered shades can be used to limit solar gain in the summer months or vice versa in the winter months. There are several important factors to consider regarding glazing. The first factor relates to the efficiency of the glass which contributes to the window's U-Factor and Solar Heat Gain Coefficient (SHGC). Typically, a lower U-Factor and SHGC is desired. Additionally, Visible Light Transmittance (Tvis) must be considered. An optimal window system achieves desired efficiency while allowing light penetration.

Fiberglass

Fiberglass glazing is typically only used for skylights and other specialty applications. Fiberglass glazing has excellent thermal properties and is extremely durable. Fiberglass may cost more than standard glass and may turn yellow over time.

Interior Light Shelves

Interior light shelves direct daylight deep into a space by bouncing natural light from the light-colored shelves up to the ceiling, where it is reflected down to occupied areas. Blinds and other daylight control devices should be installed as part of a good daylight design strategy because uncontrolled natural light can cause glare.

Clerestory Window

Clerestory windows allow daylight to penetrate into a space. They are designed to allow daylight to penetrate a space, and therefore are located above eye level.

Skylights / Solar Tubes

Skylights/light tubes allow daylight to penetrate into a space. They are typically located in the roof/ceiling and can vary in size. Certain solar tracking skylights have mirrors in them that track the sun in order to maximize the amount of daylight brought into the space. Installation of either exterior baffles or interior shades on skylights provide control of natural light flow allowing for the minimization of heat gain and glare.

Green Tips

  • Install double or triple paned glass to increase efficiency and reduce energy consumption.
  • Use interior light shelves to effectively distribute the natural light throughout a space.
  • Consider installing solar powered window shades or blinds to reduce glare and allow control of the daylight entering a space.
  • Use light color schemes such as white or tan painted walls to reflect natural light throughout the space.
  • Select durable, efficient window frames that can withstand exposure to exterior elements and reduce thermal bridging.
  • Consider windows with low-emissivity coatings to prevent heat and ultra-violet (UV) rays from passing through the glass.
  • Consider installing frosted or fritted glass or window blinds to allow daylight to enter the office space while still maintaining privacy.

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EB = Existing BuildingsNC = New Construction and Major Renovation

Legal Requirements

Guiding Principles

  • Recycled Content ( Guiding Principles, Executive Order 13514 & 13423 [EB, NC])
    Section: V. Reduce Environmental Impact of Materials

    Per Section 6002 of the Resource Conservation and Recovery Act (RCRA) (PDF), for EPA-designated products, specify products meeting or exceeding EPA's recycled content recommendations. For other products, specify materials with recycled content when practicable. If EPA-designated products meet performance requirements and are available at a reasonable cost, a preference for purchasing them shall be included in all solicitations relevant to construction, operation, maintenance of or use in the building. EPA's recycled content product designations and [recycled content] recommendations are available on EPA's Comprehensive Procurement Guideline website.

  • Environmentally Preferable Product ( Guiding Principles, Executive Order 13514 & 13423 [EB, NC])
    Section: V. Reduce Environmental Impact of Materials

    Use products that have a lesser or reduced effect on human health and the environment over their lifecycle when compared with competing products or services that serve the same purpose. A number of standards and ecolabels are available in the marketplace to assist specifiers in making environmentally preferable decisions. For recommendations, consult the Federal Green Construction Guide for Specifiers.

  • Energy Efficiency ( Guiding Principles, Executive Order 13514 & 13423 [NC])
    Section: II. Optimize Energy Performance

    Establish a whole building performance target that takes into account the intended use, occupancy, operations, plug loads, other energy demands, and design to earn the ENERGY STAR - targets for new construction and major renovation where applicable. For new construction, reduce the energy use by 30 percent compared to the baseline building performance rating per the American National Standards Institute (ANSI)/American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., (ASHRAE)/Illuminating Engineering Society of North America (IESNA) Standard 90.1-2007, Energy Standard for Buildings Except Low-Rise Residential. For major renovations, reduce the energy use by 20 percent below pre-renovations 2003 baseline. Laboratory spaces may use the Labs21 Laboratory Modeling Guidelines. Use ENERGY STAR and FEMP-designated Energy Efficient Products, where available.

  • Daylighting and Lighting Controls ( Guiding Principles, Executive Order 13514 & 13423 [EB])
    Section: IV. Enhance Environmental Quality

    Automated lighting controls (occupancy/vacancy sensors with manual-off capability) are provided for appropriate spaces including restrooms, conference and meeting rooms, employee lunch and break rooms, training classrooms, and offices. Two options can be used to meet additional daylighting and lighting controls performance expectations: ? Option 1: Achieve a minimum daylight factor of 2 percent (excluding all direct sunlight penetration) in 50 percent of all space occupied for critical visual tasks, or? Option 2: Provide occupant controlled lighting, allowing adjustments to suit individual task needs, for 50% of regularly occupied spaces.

SFO

  • ENVIRONMENTALLY PREFERABLE BUILDING PRODUCTS AND MATERIALS (DEC 2007) ( SFO)
    Section:

    A. The Lessor shall use environmentally preferable products and materials. The Lessor is encouraged to consider the lifecycle analysis of the product in addition to the initial cost. B. Refer to EPA's environmentally preferable purchasing web site, www.epa.gov/epp and USDA BioPreferred products web site biobased.oce.usda.gov/fb4p/. In general, environmentally preferable products and materials do one or more of the following: 1. Contain recycled material, are biobased, are rapidly renewable (10-year or shorter growth cycle), or have other positive environmental attributes; 2. Minimize the consumption of resources, energy, and water; 3. Prevent the creation of solid waste, air pollution, or water pollution; or 4. Promote the use of nontoxic substances and avoid toxic materials or processes. C. The Lessor is encouraged to use products that are extracted and manufactured regionally.

  • WOOD PRODUCTS (AUG 2008) ( SFO)
    Section:

    A. For all new installations of wood products, the Lessor is encouraged to use independently certified forest products. For information on certification and certified wood products, refer to the Forest Certification Resource Center (www.certifiedwood.org), the Forest Stewardship Council United States (www.fscus.org), or the Sustainable Forestry Initiative (www.aboutsfi.org). B. New installations of wood products used under this contract shall not contain wood from endangered wood species, as listed by the Convention on International Trade in Endangered Species. The list of species can be found at the following web site: www.certifiedwood.orglResources/CITES/CITESContent, html. C. Particle board, strawboard, and plywood materials shall comply with Department of Housing and Urban Development (HUD) standards for formaldehyde emission controls. Plywood materials shall not emit formaldehyde in excess of 0.2 parts per million (ppm), and particleboard materials shall not emit formaldehyde in excess of 0.3 ppm.

  • QUALITY AND APPEARANCE OF BUILDING (AUG 2008) ( SFO)
    Section:

    The building shall have energy efficient windows or glass areas consistent with the structural integrity of the building, unless not appropriate for intended use.

  • WINDOWS (SEP 2009) ( SFO)
    Section:

    B. All windows shall be weather tight. Operable windows that open shall be equipped with locks. Off street, ground level windows and those accessible from fire escapes, adjacent roofs, and other structures that can be opened must be fitted with a sturdy locking device. Windows accessible from fire escapes must be readily operable from the inside of the building.