Data and Details
With recent energy code changes and new developments in engineered glass, how is anyone to make sense of all the options and ratings? We break it down for real people so you can select the best glass options for your windows.
When purchasing windows today, you’ll find four basic ratings listed on the glass sticker:
1) U-FACTOR: similar to wall insulation, this measures the insulating quality of glass on a scale from 0 (greatest insulation) to 1 (least insulation). The smaller the number the better the glass is at insulating. Insulation acts like a coat for your house in the winter to hold warm air in, and like a cooler to hold cold air in during summer. Argon gas between two panes of glass will greatly increase the insulated quality. This all equates to savings on your utility bill no matter your climate.
2) SOLAR HEAT GAIN COEFFICIENT (SHGC): measures how well the glass blocks heat from the sun on a scale from 0 (greatest heat blocked) to 1 (least heat blocked). This has the greatest affect on the south side of your home where the sun shines directly year-round.
3) VISIBLE TRANSMITTANCE (VT): similar to sunglasses, this measures how much light passes through the glass affecting the brightness of a room. It’s measured on a scale from 0 (least light / brightness) to 1 (greatest light / brightness).
4) LOW-E COATINGS: Invisible metallic coatings on glass that reflect heat but still allow light through. This affects all the above ratings, but has the largest affect on the Solar Heat Gain Coefficient. There are several levels of Low-E: 180, 240, and 366 (and a few in between); the lower the number (180), the less heat blocked from the sun, the higher the number (366) the greater the heat blocked from the sun.
For example, if you have south facing windows that are not shaded from the summer sun, Low-E 366 will greatly reduce the summer heat gain and reduce your utility bill. However, if your home is sited for passive solar – large windows facing south to allow winter time heating from the sun but are shaded during the summer – Low-E 180 would allow the greatest heat gain in the winter, 240 would allow a mid-range heat gain in the winter, and 366 would block most of the heat gain and negate most of the benefits of passive solar heating.
The majority of residential glass in the U.S. is manufactured by Cardinal glass (their website has additional useful info) and used by most window manufacturers. Some window manufacturers have changed the nomenclature, i.e. Low-E 180 may be called “advanced” or the like. Ask your dealer for the Low-E level equivalent.
If nothing else, remember you always want a low U-Factor number, and the Solar Heat Gain Coefficient may vary depending on how much heat gain you desire from the sun on a given side of your home.
Great lighting advice for home owners and design professionals. fb.me/2rufbEoYz
Recently I attended a great seminar produced by energy consultant Sean Tobin, Optima Engineering, and Southern Energy Management. I’ve attempted to summarize some of what I learned below coupled with my past experiences and posts. I left an even bigger fan of solar and geothermal and with greater knowledge of the pros and cons of the many green rating systems out there. The issues are complex and the numbers vary, but these are the big ideas.
THE BUILDING ENERGY ISSUE
BUILDING ENERGY, FUEL, EMISSIONS
Worldwide buildings contribute more than 45% of all man-made CO2 (carbon) emissions which in mass has detrimental effects on the earths atmosphere ozone layer that helps protect us from the radiation of the sun (leading to global warming). The remaining carbon emissions is divided between 35% transportation (cars) and 20% manufacturing.
Buildings consume 72% of the electricity produced (from power plants) in the U.S. Manufacturing primarily consumes the remaining electricity produced.
Most energy in the U.S. is fueled with non-renewable resources (eventually we’ll use them all up). Our fuels breakdown like this: 22% Coal, 25% Natural Gas, and 38% Petroleum. The U.S. uses about 10% Nuclear energy and 6% Renewable energy (solar, wind, and hydro).
U.S. buildings consume about 13.6% of potable water annually. The average american uses about 64 gallons of water per day (check your water bill).
About 0.37% (less than half a percent) of the water on earth is available for human consumption and sanitation (90% of this is in underground aquifers). The rest: 97.5% is salt water, 1.6% is locked in glaciers, and the remaining 0.53% in plants, animals, and atmosphere water vapor.
HOW MUCH ENERGY DOES MY BUILDING CONSUME?
Recently we took a hard look at residential water heaters. We tried to make real sense of the many sustainable claims and options available on the market in search of the best investment for our clients. We scoured many sources, including Consumer Reports, the U.S. Department of Energy, manufacturer’s testing data, consumer blogs and reviews, industry professional experiences and many more. What we found was surprising.
1) Plan with the Local Climate:
Planning your home with the local climate in mind will reduce the time and energy required of your heating and cooling system in addition to providing a more pleasant living experience. Be sure the layout of your home, the placement of windows, and the size of overhangs are designed to take advantage of prevailing breezes and changing sun conditions throughout the year. When the weather is nice you can turn your air conditioner off, open the windows, and enjoy the day.
2) Insulation, Insulation, Insulation:
Insulation slows the time it takes for heat to transfer through walls and roofs. The more you have, the longer your house Read More…
1) Temperature is Free Money:
Set your water heater thermostat to 120 degrees year-round to save energy. For winter, set your heating & cooling system thermostat to 68 degrees or below; for summer, 74 degrees or higher. Keep your system off and windows open when it’s nice outside. Contrary to popular belief, the thermostat is not reflective of the temperature coming out of the air vents. The thermostat is the target temperature for the air inside the home, and setting it higher or lower will not speed it up. Find your comfort zone and leave it be for maximum efficiency.
2) Watts Matter (But So Does Color and Brightness):
Some fluorescent lights can make your living room look like a hospital room. But Compact Fluorescent Lights (CFLs) have come a long way in recent years; they use half the energy and can even match the warm light of incandescent bulbs. To save even more energy Read More…