Advice for Insulating a Greenhouse or Solarium Against Night Time Heat Loss
The accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Our page top photos shows a sunspace constructed by the website editor (DF) and an example of indirect solar glare (to the right of the plant in our photograph).
Beating Sunspace or Greenhouse Glare in buildings
Usual sources of complaints of solar glare: long term exposure
How to reduce or control solar glare in greenhouses and sunspaces
Seasonal vs. year-round control of solar light glare in buildings
Rearranging room contents to eliminate solar or sunlight glare
Use of supplemental lighting to reduce indoor glare effects
Use of solar shades or blinds to control or reduce sunlight glare indoors
Question: what strategies are most promising for controlling indoor glare from sunlight or other sources?
A building we own and occupy has a three-story atrium/sunspace with over 30 2x5-foot windows. Our computer room faces the atrium and users complain about the glare.
We are considering installing shades or films to control the glare from sunlight. What solar glare strategies are most promising? - Lou Nemesec, Illinois Industrial Commission, Chicago IL
Answer: Solutions to Sunlight and Indoor Light Glare
Glare can interfere with vision and cause discomfort, eye fatigue, and over time, eye damage, even contributing to cataract formation where UV wavelength light is also present.
Types of Light Glare: Indirect & Direct
There are two kinds of glare: direct glare and indirect glare.
Direct glare is caused by light coming directly into the eye from the light source.
Indirect glare is caused by reflected light (see our photo at page top).
Strategies for Controlling Glare in buildings
As we elaborate below, you can control glare and reduce glaring light complaints in buildings by one or more of the following six methods:
Reducing the brightness or size of the light source
Changing the position of the light source
Making the area around the light source brighter
Rearranging furniture and seating positions to change the relationship between the light source, work surface, and worker
Reducing the contrast between incoming light and surrounding surfaces
Adapting glaring light control to seasonal changes in sunlight
You can control glare by reducing the brightness or size of the light source, changing the position of the light source, or making the area around the light source brighter.
We assume that the complaints about glare come from long exposure, since short term exposure to glare can usually be tolerated. We also assume that you can't rearrange the building or room to change the relationship between the light source, work surface, and the workers themselves in order to change the angles of light and light reflection to simply eliminate the problem.
The size of the light source in your building too is fixed, unless you block out some of the entering sunlight with an opaque material.
So what measures are left to reduce indoor glaring light problems?
You could reduce the contrast between the incoming light and the surrounding surfaces by increasing the lighting level on the interior surfaces with electric lighting.
But it seems that your best bet is limiting the brightness of the light source.
If you need year-round help, use window films. Window films can cut out anywhere from 45 to 86 percent of the incoming light. If view is not important, permanent louvers may do.
If you want seasonal control over glaring light, use movable or removable shades or blinds. Interior choices for glaring light source control include vertical or horizontal blinds(discussed in more detail at SOLAR SHADES & SUNSCREENS).
External choices for glaring light control include woven fiberglass shades or aluminum mini-louvers.
The question-and-answer article on this pate paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
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Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
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Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: email@example.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
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Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v1.pdf
Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v2.pdf [This is a large PDF file that can take a while to load]
Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v3.pdf
"Passive Solar Home Design", U.S. Department of Energy, describes using a home's windows, walls, and floors to collect and store solar energy for winter heating and also rejecting solar heat in warm weather.
"Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
"Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.
"Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.
"Solar Air Heating" U.S. DOE also referred to as "Ventilation Preheating" in which solar systems use air for absorbing and transferring solar energy or heat to a building
"Solar Liquid Heating" U.S. DOE, systems using liquid (typically water) in flat plate solar collectors to collect solar energy in the form of heat for transfer into a building for space heating or hot water heating. The term "solar liquid" is used for accuracy, rather than "solar water" because the water may contain an antifreeze or other chemicals.
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