0000009701 00000 n Here are added factors defined by the NFRC as of 2005: Air Leakage(AL) measures how much outside air comes o Thank you Bob for sharing this very thorough article! Even if it is not possible to build a classic passive solar home in other climates, solar gains can be used for substantial solar-tempered wintertime home heating. 0000010938 00000 n 0000014397 00000 n [I notice that after I wrote this response, you edited your comment, changing "high U-value" to "low U-value." Locations that lack significant net solar heat gain, or that require a lot of wintertime heating, score lower on this index. 1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 , Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 AShrae Handbook - Fundamentals (Hardcover), Harry J., Jr. Sauer (Author), Ronald H. Howell, ISBN-10: 1931862923 or ISBN-13: 978-1931862929, 1993 ASHRAE Handbook Fundamentals (Hardcover), ISBN-10: 0910110964 or ISBN-13: 978-0910110969, Colloidal Materials, Inc., PO Box 696, Andover MA 01810, Pennwalt Corp., King of Prussia, PA 19406, The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083, www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850 is the base U.S. DOE website for these articles, Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the. (Of course you could use a light filtering curtain or shade to fix this.). It ranges from 0 to 1 and refers to the solar energy transmittance of a window or door as a whole, factoring in the glass, frame material, sash (if present), divided lite bars (if present) and screens (if present). Is It Easier To Clean Replacement Windows? m 0000031018 00000 n 0000011400 00000 n The lower the That's where your observation about winter sun angles before and after solar noon is most critical. Contact | 0000053637 00000 n Winter design temperature (F), or coldest expected temperature.. The cost of electricity, natural gas, or other heating fuels can impact the use of passive solar heat gains for wintertime space heating. The first six columns list the same 22 U.S. cities and other previously displayed data, which are helpful in determining the value and ease of using solar heat gains for space heating. The maximum allowable fenestration U-factors in Table R402.1.2 (for the prescriptive compliance path) for climates zones 3 through 8 have been reduced from the values in the 2015 edition. Table 6 lists the BTUs per square foot of window glass per day for Providence, R.I. (the northeastern coastal city that looks most promising for solar heating). Solar gain(also known as solar heat gainor passive solar gain) is the increase in thermal energy of a space, object or structure as it absorbs incident solar radiation. 0000060198 00000 n http://www.cardinalcorp.com/products/coated-glass/loe-180-glass/, PPG Industries manufactures two low-e/high SHGC products: Sungate 500 and Sungate 100 window glass with SHGC of about 0.7. They also recommended ceilings be white, to reflect light back to the floor. number between 0 and 1. Passive solar heat gains are more valuable in areas with higher costs for electricity or other heating fuels, or with occupants who are less affluent, or architects, owners, or builders more concerned with sustainable building. 0000050694 00000 n ;"\ h;; nM"O*]\_n}s54xBb;L";`fJq=.s5?puuus9Eq=7wWT|# LhH{\=vf}+W8?fX'Xgp8=ZHQ-oGA2mN~~k. Daylighting and heat gain are desirable especially in cold winter-heating-dominated climates of the northern U.S. Incredibly, south-facing windows gain about fifteen times as much light and solar heat gain as north-facing windows in December and in January. 0000009857 00000 n Comparable data was not readily available for Canada or Europe, and limits on the length of the article and readable table size limited the cities listed. 0000025618 00000 n ( South-facing windows produce the most natural daylighting and solar heat gain from the month of September through the month of April. For more information, see All About Glazing Options. Table 1 shows wide variation in heating degree days, winter design temperatures, and Januarys average percentage of available sunlight. I'm not so sure about small windows of a dark passive house that is currently expensive to build, even if you can find someone who can do the work right, but the very low energy use is great. Although glare hadn't been much of a problem, that uniform interior color reduced color contrast, and did seem to reduce the perception of glare. Kansas City and cities along the northeast coast also look promising for wintertime daylighting, space heating, and PV. Apologies for the delay. ) Great Article! 2 0 obj 0000008467 00000 n Latitude: N: NE: E: SE: S: SW: W: NW: HORIZONTAL : 24 o N: 42: 37: 36: 26: 15: 95: 174: 134: 162: 25 o N: 41 . 0000020026 00000 n 0000050037 00000 n (10) Calculate solar heat gains when designing, and compare to heat losses. >> If you divide by 0.87 (the coefficient for 1/8-inch clear glass), you get the shading coefficient you need to calculate solar heat gain. Rather than looking for a window with a high U-factor, you should be looking for a window with low U-factor. Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. A product with a higher VT transmits more visible light. 0000054676 00000 n 0000031213 00000 n In practice though, most g-values will range between 0.2 and 0.7, with solar control glazing having a g-value of less than 0.5. It comes down to three ways windows are improved with the use of glass technology, coatings and gases: Review in-depth information on energy efficient glass for your window replacements. Clear double The National Fenestration Rating Council (NFRC) operates a voluntary program that tests, certifies, and labels windows, doors, and skylights based on their energy performance ratings. 1 Since I built that passive solar house back in the 1980's, there were no low-e windows available. 0000053548 00000 n ) Table 2 lists solar gain data for the 22 northern U.S. cities. Daylighting is good, and solar heat gain is good in winter and not good in the hot summer. 0000000016 00000 n But it would not shade the window as much as you'd like by late August, or earlier or later during the day on June 21st, as you point out. 0000031116 00000 n In passive solar and solar-tempered homes, typically there are more or larger windows facing south, and fewer or smaller windows facing other directions. However, if shades are needed to reduce overheating mid-winter, likely there's a design error of over-glazing with west or south-facing windows. For more information about SHGC and windows, see. /GS1 5 0 R Wall CLTD selection. Annual heating degree days (HDD), an index of the amount of heating needed each winter season. I bet under-insulating was also a common problem, especially for that thermal mass that serves as an overnight heating system. My goal was to build an energy-efficient home using materials that cost no more in total than typical home construction. Shading analysis of the building site's landscaping and adjacent buildings is critically important. The basement windows look out only on the east and south sides of the home where they barely see the light of day. So the solar heat gain analysis has focused on the coldest month (January) for the 22 northern U.S. locations. For example, in triple glazed windows, SHGC tends to be in the range of 0.33 - 0.47. (1) To exploit solar heat gains from windows in mid-winter (and minimize heat gain in summer), we can build on a building lot that has good south-facing solar access during mid-winter, when the sun appears lower on the horizon mid-day. Hours earlier and later, the light could extend further but would be less intense. 0000037304 00000 n To minimize this and reduce cooling loads, several technologies exist for solar gain reduction. 0000019489 00000 n /CropBox [0.0 0.0 612.0 792.0] Would seem 'Damn the torpedoes, full steam ahead' to catastrophic Global Warming. . We do have medium dark wood floors, linoleum and tile. The larger the net solar gains, the larger the amount of winter heating needed, and the higher the price of electricity, the better the score on the index. SHGC is expressed as a number between 0 and 1. 0000020750 00000 n 0000010168 00000 n 0000058978 00000 n A U-factor of U-0.24 isn't bad, by the way. So I'd recommend designing overhangs for minimal shading mid-winter, and not worry so much about summer (for winter-dominated northern climates). AL is an The manufacturers may have improved the materials that made up the frames or the coatings to the glass to meet demands. . This site is protected by reCAPTCHA and the Google, What's Really Behind the Gas Stove Debate, Common Method of Sewer Repair Poses Health Risks, Appendix D, Degree Day and Design Temperatures, https://www.greenbuildingadvisor.com/homes/passive-solar-home-1980s, http://www.cardinalcorp.com/products/coated-glass/loe-180-glass/, http://www.vitrowindowglass.com/lowe_glass/sungate_500.aspx, Reassessing Passive Solar Design Principles, A Proposed Solution to the Embodied Carbon Problem, A Look at State Premiers New Heat Pump Water Heater, Indoor Air Quality and Building Diagnostics. Note that east- and west-facing glazing provide an equal amount of solar heat gain, but east gains mostly in the morning, and west mostly in the afternoon. 36" overhangs, 9' walls. South-facing window glazing may optimize heat gains with higher SHGC, and west-facing windows with lower SHGC glazing. << In essence SC is an index of the effective solar rejection performance of a given glass type. Glazing in conditioned spaces has a solar heat gain coefficient of less than or equal to 0.40, or has an overhang with a projection factor equal to or greater than 0.30. You wouldn't be able to see the TV well, and would experience glare from the window. 0000024716 00000 n East- and west- facing windows gain far more heat than south-facing windows during the summer months, until late August. xref The sun rises in the east, goes overhead, then sets in the west, with little sunlight directly striking a south-facing wall or window. 2252 0 obj <>/Filter/FlateDecode/ID[<83C04542AF040F4C833A7DC507AC7EE9><9975C82B1E27C340964B5370330FFFE6>]/Index[2225 55]/Info 2224 0 R/Length 124/Prev 708226/Root 2226 0 R/Size 2280/Type/XRef/W[1 3 1]>>stream The NFRC (National Fenestration Council) describes Solar Heat Gain Coefficient (SHGC) as: Solar Heat Gain Coefficient(SHGC) measures how well a 0000023071 00000 n Varying window sizes and numbers can increase or decrease solar gains and heat losses to affect overall energy performance.