No not the Robert A. Heinlein classic sci-fi survival novel, we’re talking earth bound technology to bring light into the interior of your home. Why? Economics. If you can reduce your dependency on artificial light you can save energy. You may even be able to recoup your investment in as early as two years. So, what are we talking about specifically? That would be skylights and light tunnels. Say what? Heard of a sky light but never heard of a light tunnel.
Energy Efficient Skylight Design
They’ve been around for some time, though modern design and technology have made them superior to those that haunted the 1960’s through the 80’s. Fully insulated modern skylights not only admit light but can be opened to provide ventilation. Ventilation is merely a push of a button. These can be fitted with solar blinds which can be used to improve energy efficiency. Blinds can diffuse or block light if necessary and can be manually or electrically operated. Skylights admit light directly into the room.
What are Sun Light Tunnels?
Sun tunnels are 10-14 inch diameter metal tubes. Polished on the inside and galvanized on the outside, sun tunnels direct light where there are not windows such as in hallways. They are installed with what appears to be a recessed lighting fixture. Diffused natural light is brought to the laundry room, closets and hallways. Less expensive than a skylight to install and they are very energy efficient.
Benefits of Natural Light in Your Home, Classroom, Office & More
Natural light inside your living space has added psychological and health benefits. SAD is Seasonal Affective Disorder and is a direct result of insufficient natural sunlight. In schools, the use of skylights has seen a correlation to better student performance, and in business improved productivity and reduced absenteeism has been noted with the introduction of natural light. With the increase in those working from home the introduction of diffused natural sunlight would have direct and effective benefits in health and productivity.
Energy Ratings of Skylights & Sun Light Tunnels
How are skylights, light tunnels and windows in general rated? There is an organization that rates these products and a corresponding label to pass this information to the consumer. It is the National Fenestration Rating Council (NFRC) and is a third-party non-profit that tests these products compliance with standards.
• U-Factor measures the insulation provided by window and rates heat flow. It ranges generally from 0.25 to 1.25 and are rated in Btu/h∙ft2 or British Thermal Units per hour times the area in square feet. This rating is required by the EPA. A Btu is the amount of heat needed to raise one pound of water one-degree Fahrenheit and the SI (metric) unit is the calorie, and one Btu is equal to about 252.164 calories.
• Solar Heat Gain Coefficient (SHGC) measures the amount of solar energy transmitted and indicates the products ability to block heat caused by sunlight. It is rated on a scale of 0-1, typically 0.25 to 0.80 the lower the SHGC the less the heat transmission. Another EPA labelling standard.
• Air Leakage (AL) measures the rate of the flow of air that passes through the window joints. AL is measured in cubic feet of air passing through 1 square foot of window area per minute. The lower the value, less the leakage. Industry standards require an AL of 0.3 ft3 times minute/ft2. Wind standard is 25 mph and ratings can go between 0.1 to 0.3 with 0.1 being the best.
• Visible Transmittance (VT) is a measure of how much light gets through versus how much is absorbed by the window media. Measured on a scale of 0-1, generally expected range is 0.20 to 0.80 and the higher the rating the better meaning more light is being transmitted.
• Condensation Resistance is measure of how well the window resists water condensation build-up. This rating runs from a low of 0 to 100, the higher the rating the more the window resists condensation.