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Windows and Daylighting

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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.

Storefront / Curtainwall Assemblies

Storefront or curtainwall assemblies are "built-up" systems of glazing and metal frames that can span full or multiple floors. These systems require careful study of both the quality of glazing and the recycled content of the metal frame.

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.

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.

Best Practices

  • 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.
  • Skylights can provide copious ambient light, minimizing the reliance on electric lighting for portions of the day.
  • Shading devices can be employed to minimize glare and heat gain.
  • Focusing window glazing in a specific direction can assist in either harnessing more direct light (to the south) or providing more diffuse, constant ambient light (to the north).
  • Install daylighting control systems (e.g. photosensors) with zones for electric lights that are dimmed or switched off when there is adequate sunlight.
  • Commission the lighting controls system to make sure it works as designed.
  • Add interior or exterior light shelves to extend the daylighting zone into the laboratory space, while reducing glare. These are most effective on south facades.
  • Specify light-colored interior spaces to help distribute natural light more effectively.
  • Design work space options to reduce levels of job stress by providing access to daylight, views of nature, flexible areas, and workspace amenities.
  • Design work space options to include access to daylight to synchronize circadian rhythms.
  • Design work space options to reduce levels of job stress by providing access to daylight, views of nature, flexible areas, and workspace amenities.
  • Design work space options to reduce levels of job stress by providing access to daylight, views of nature, flexible areas, and workspace amenities.

Compare Windows and Daylighting Options

EB = Existing BuildingsNC = New Construction and Major Renovation

Federal Requirements

Guiding Principles

  • Materials - Recycled Content (D) ( <span>Guiding Principles criteria 5.1</span>)
    Section: <span>Guiding Principles 5:&nbsp; Reduce the Environmental Impact of Materials</span>

    “Use products that meet or exceed the Environmental Protection Agency’s (EPA’s) recycled content recommendations for building construction, modifications, operations, and maintenance, where applicable and as required by statute.”

  • Products ( Guiding Principles criteria 5.3)
    Section: <span>Guiding Principle 5:&nbsp; Reduce Environmental Impact of Materials</span>

    “Procure and utilize construction materials and building supplies that have a lesser or reduced effect on human health and the environment over their life cycle when compared with competing products that serve the same purpose.”

  • Energy Efficiency ( Guiding Principles criteria 2.1)
    Section: <span>Guiding Principle 2:&nbsp; Optimize Energy Performance</span>

    “Comply with all relevant statutory and regulatory requirements that establish Federal building energy efficiency standards and require the purchase, installation, and use of energy efficient products. Employ strategies that continue to optimize energy performance and minimize energy use throughout the operation and life of the building.”

  • Daylighting and Lighting Controls ( <span>Guiding Principles criteria 4.2</span>)
    Section: <span>Guiding Principle 4: Enhance the Indoor Environment</span>

    “Maximize opportunities for and benefits of daylighting in regularly occupied space to introduce daylight and views into the spaces, reinforce circadian rhythms, and reduce the use of electrical lighting. Ensure appropriate lighting controls and task lighting.”

  • Energy Efficiency (B) ( <span>Guiding Principles criteria 2.1</span>)
    Section: Guiding Principle 2:&nbsp; Optimize Energy Performance

    “Comply with all relevant statutory and regulatory requirements that establish Federal building energy efficiency standards and require the purchase, installation, and use of energy efficient products. Employ strategies that continue to optimize energy performance and minimize energy use throughout the operation and life of the building.”

  • Indoor Air Quality during Construction and Operations ( <span id="docs-internal-guid-f1e45d2e-bf74-2656-0c1b-777092dd54a0"><span>Guiding Principles criteria 4.6</span></span>)
    Section: Guiding Principle 4:&nbsp; Enhance Indoor Environmental Quality

    “Implement necessary policies and protocols to prevent moisture damage to building materials and protect indoor air quality during renovations, repairs, and construction. Ensure indoor air quality procedures are in place that protect the air quality for occupants of the building during operations”

  • Occupant Health and Wellness ( <span id="docs-internal-guid-f1e45d2e-bfa3-fe9d-96f4-ff81811a5b68"><span>Guiding Principles criteria 4.9</span></span>)
    Section: Guiding Principles 4:&nbsp; Enhance Indoor Environmental Quality

    “Design building features and integrate programs and initiatives that promote voluntary physical health and wellness opportunities for the building occupants.”

  • Material Content and Performance ( Guiding Principles&nbsp;[EB])
    Section: V. Reduce the Environmental Impact of Materials

    From the Guiding Principles for EB: Procure construction materials, products, and supplies that have a “lesser or reduced effect on human health and the environment over their life cycle when compared with competing products or services that serve the same purpose”, including:
    (i) “Use Resource Conservation and Recovery Act (RCRA) section 6002 compliant products that meet or exceed EPA’s recycled content recommendations for building construction, modifications, operations, and maintenance.”
    (ii) “Per section 9002 of the Farm Security and Rural Investment Act (FSRIA), for USDA-designated products, use products with the highest content level per USDA’s biobased content recommendations.”
    (iii) “Purchase products that meet Federally Recommended Specifications, Standards and Ecolabels or are on the Federal Green Procurement Compilation.”
    (iv) Eliminate, to the maximum extent practicable, “ozone depleting compounds and high global warming potential (GWP) chemicals where EPA’s SNAP has identified acceptable substitutes or where other environmentally preferable products are available” during construction, repair, or replacement at the end of life.
    Determining Compliance: “Procure products that meet the following requirements where applicable: (A) RCRA section 6002, and (B) FSRIA section 9002, and (C) Federally Recommended Specifications, Standards and Ecolabels or are on the Federal Green Procurement Compilation for other green products, as appropriate, and (D) Avoid ozone depleting compounds and high GWP chemicals.”