solar heat gain factor table

0000053952 00000 n ( As indicated in the chart below, the EPA recommends . However, a few strategically placed deciduous trees and i have all but eliminated my summertime window solar exposure. Please bookmark this page to make it easy for you to check back for our response. My goal was to build an energy-efficient home using materials that cost no more in total than typical home construction. Kids in school and adults at work have been shown to have better moods and do complex work better with sunlight entering the room. 0000036017 00000 n Those principles work in all types of buildings, and unfortunately can be ignored in subdivision design, building design, and building orientation. For more information, see All About Glazing Options. South-facing windows provide between 59% and 77% of the total solar gains, despite making up only 25% of the glazing of the four windows of equal size. Thanks for the kind words - and thanks for the explanation. %%EOF As well, 3 years ago, having been so pleased with the shutter effect, I built a "low mass, super insulated south facing solar porch. 0000053434 00000 n The specific microclimate of any building location should be used in building design, rather than the rough approximation of solar potential shown in this map or Table 1. 0000048656 00000 n 0000023760 00000 n 0000020026 00000 n Table 1 lists 22 northern U.S. cities. If the TV itself is not in or adjacent to direct sunlight, and at a 90 degree angle to the window receiving direct sunlight, it should be okay. Therefore, the sun is shining on your south-facing walls and windows during wintertime. /TT2 21 0 R (17) Cities and towns can promote energy efficiency and public health by incorporating zoning laws and incentives that provide building lots with south-facing solar access, and protect solar access for existing buildings. It's free and doesn't require a download. On a traditional southern plantation style home with porches and monster roof overhangs, you could design a south-facing overhang that would completely shade south-facing windows in June, yet not shade much of the top of the window during winter. NFRC U-factor ratings, however, represent the entire window performance, including frame and spacer material. Climate zone temperatures are important, as are available solar heat gains and utility prices. 0000054427 00000 n For example, If my living/dining/kitchen open space is taking up the whole south facing side of the house, where do I put the TV? Getting free heat and sunlight to raise mood is great. What about glare? 0000010553 00000 n /XObject product blocks heat from the sun. 0000034610 00000 n 0000024598 00000 n Note that northeastern coastal cities now rate highly along with Denver and Kansas City, for the value of solar heat gain (due to high electricity rates in the Northeast). 0000045617 00000 n Choosing a window frame material that does a fine job of insulating against thermal (heat) transference is one way to reduce the solar heat gain coefficient. But solar transmittance does not include the solar heat that the glass absorbs and re-radiates into the building, so alone it is not accurate enough for calculating total solar gains through windows. 0000052997 00000 n /ColorSpace Solar Heat Gain Thru Glass Thermopane windows have no sash; therefore, sash area correction = 1/.85 (bottom Table 15). Response to Davor Radman The lower the SHGC, the better But this angle represents a brief moment and most of the arch of the sun's path, while still influencing the solar gain, is much lower during the periods of time on both sides of noon. In Model 1, the top three most sensitive factors were the solar heat gain coefficient, the window-to-wall area ratio and infiltration; in model 2, they were the heating setpoint temperature . NFRC is so well-trusted that its testing results inform Energy STAR ratings. (15) Consider less costly minisplit heat pumps or even simpler resistance or radiant heating in energy-efficient high performance homes, which have a much lower heating load. 0000034200 00000 n 0000040500 00000 n A Contrarian View of Passive Solar Design, GBA Prime Sneak Peek: Reassessing Passive Solar Design Principles. 0000039433 00000 n If not, how can I find a better alternative at a reasonable price? heat gain is particularly important during the summer You bring up an important point. hbbd```b``A$cXDDr@3N,IF@L@s&00Lg`` Basically, any window frame material is going to insulate well whether it is wood, vinyl, aluminum clad wood, or fiberglass. %PDF-1.6 Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat from the sun. 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. 0000029773 00000 n 0000013076 00000 n For the months of December and January, the sun is low on the horizon during midday. This allows glass to block mainly short-wave infrared radiation without greatly reducing visible transmittance.[3]. be adjusted for thermal lag and time delay. We find the coldest days are very clear and let in a lot of light and heat contrary to what some say about passive solar in this area. I'll address passive solar and other home design issues in the next article. 0000052473 00000 n Alaska, the Pacific Northwest, and Midwestern cities would not be good candidates to rely on wintertime solar heating. ( Though the original proposed changes to U-Factor and SHGC to Energy STAR would have cut the market share by 50% due to vastly increased costs of manufacturing that would have been passed on to the consumer. stream December 21st there is no shading from overhangs. (16) Reduce the amount spent on larger and more complex supplementary space heating systems to allocate funds for more insulation, air-sealing measures, and more energy-efficient windows and doors. Other cities in the list across the Midwest and northern central U.S. get about half the net solar heat gain of Denver. The standard method for calculating the SHGC also uses a more realistic wavelength-by-wavelength method, rather than just providing a coefficient for a single wavelength like the shading coefficient does. glazing has an SHGC of about .75 versus .60 to .70 for Its important to insulate thermal mass well, but Passivhaus insulation levels might be overkill in a passive solar home. Solar Heat Gain Coefficient measures how well a product can resist unwanted heat gain, which is especially important during summer cooling season. 0000025308 00000 n For windows, skylights, and glass doors, a U-factor may refer to just the glass or glazing alone. (11) Make adjustments to window locations, sizes, and glazing options (SHGC and U-factor) to optimize natural lighting and solar heat gain in winter and summer seasons. 0000008921 00000 n /Parent 25 0 R This factor is used to represent the temperature difference between indoor and outdoor air with the inclusion of the heating effects of solar radiation. In climate-responsive design for cold and mixed climates, windows are typically sized and positioned in order to provide solar heat gains during the heating season. 0000009545 00000 n In column 7, South Percentage of Total Gains, note that south-facing windows provide the majority of the total solar gains for every city in the list. Cost of electricity varies over time as well. You might find a double or triple pane sealed insulated glass unit (IGU) with no "heat mirror" low-e treatment on any of the panes, or rare low-e treatments that don't reduce solar gain as much. on the climate, summer and winter fuels costs, and . Table 2 shows the amount of solar heat gain per square foot of window glass for the cities listed previously. 0000043952 00000 n That's good for south-facing windows, because during the hot summer, you don't want the sun beating in your windows, causing solar heat gain in your home's interior. 0000009701 00000 n 0000022435 00000 n Simply choose your state and then your county below and we will display the combinations of u factor and SHGC as recommended by Energy STAR and the National Fenestration Rating Council. ) This may help break up the glare. It can't be a problem for north-facing windows, which receive almost no direct sunlight any time of year. 0000051944 00000 n Adjustable awnings, curtains, window shades, exterior shutters, or even deciduous trees, or other shading methods, can provide more flexible and more complete shading than a fixed roof overhang. Used by solar PV installers for the most bang for the buck. ( However, I did have problems with too much solar heat gain from west-facing windows during hot summer days. For some locations, the heat is more pronounced and longer in duration than the short months of frigid temperatures with little snow. Solar heat gain coefficient (SHGC) is the fraction of solar radiation admitted through a window, door, or skylight -- either transmitted directly and/or absorbed, and subsequently released as heat inside a home. 0000044828 00000 n 0000011708 00000 n The manufacturers may have improved the materials that made up the frames or the coatings to the glass to meet demands. 0000050343 00000 n /Height 99 A g-value of 1.0 represents full transmittance of all solar radiation while 0.0 represents a window with no solar energy transmittance. 0000029417 00000 n In this article, Window Joe guides you to thefactors to consider then determining the best SHGC for your window replacement project. However, many northern U.S. locations can experience uncomfortably hot summers as well as cold winters. 0000008999 00000 n Thirty-five years ago, I designed and built a classic passive solar home in Colorado. But it might be a good compromise. The glass on the TV or computer screen can also be highly reflective smooth glass for best visual screen performance, or can be less reflective glass for less interference with reflections on the screen. This information in an aid in choosing the best direction and size of windows facing different directions. The following web resources were useful for gathering climate and solar gain data. Passive solar heat gain almost eliminated the need for space heating on the main floor. 0000011862 00000 n Average daily solar heat gain per square foot of south-facing window glass in January. 0000011785 00000 n 0000000016 00000 n 0000021134 00000 n 0000023071 00000 n = There is more total sunlight shining in summer (June to August in the northern hemisphere) than mid-winter (December to February). ) SHGC also decreases with the number of glass panes used in a window. I saw that a lot: first, the designer included too much south-facing glazing; then the homeowners installed interior shades to cut down on the glare. 0000019693 00000 n 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. ) 0000042317 00000 n To maximize wintertime interior daylighting and solar heat gains, south windows should be larger in size or in number than windows facing other directions. 0000054676 00000 n The following four cities are along the north central and western U.S. (Minneapolis; Salt Lake City; Bismarck, N.D.; and Billings, Montana) . This Solar Gain Index uses south window glazing net BTUs of heat per day per square foot of glazing, and divides by the Heating Degree Days for that location. Calculating solar gains by hand is a laborious, imperfect process. 0000058978 00000 n The lower the U-factor, the better the performance. (5) During mid-winter, south-facing windows can provide more than triple the amount of light and solar heat gain in winter than east- and west-facing windows. endstream endobj startxref %PDF-1.6 % You also may be able to increase the brightness of your screen, which some computer screens do automatically (depending upon ambient light levels). 0000009389 00000 n In a room, its likely you have light coming from multiple windows on different sides of the home. Generally she, me and the cat sit in the sun if we can. 0000039633 00000 n The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article. 0000010707 00000 n The lower those numbers are, the more suitable a glazing is for cooling. Ideally, the goal is to not block wintertime sunlight on south-facing windows. Other internet data sources may include somewhat different data, but the patterns of data would lead to similar conclusions. Even if there's only one south-facing window in the room at mid-day in winter, light will bounce off the window sill and floor and diffuse the light, especially at the other end of the room. 0000011938 00000 n 0000057117 00000 n You can maybe start to imagine how you might have different window needs if you are in Texas or Florida as compared with Rhode Island or Massachusetts. /TT3 20 0 R /C2_2 13 0 R << /ExtGState The U-Factor works in conjunction with the Solar Heat Gain Coefficient (SHGC). The value of the shading coefficient ranges from 0 to 1. While it isn't absolutely necessary to be so exacting when choosing new replacement windows, every little bit of energy efficiency helps when planning your window replacement project. The window area is 400 sq ft and the secret is low mass. 0000018030 00000 n 0000023459 00000 n h[koG+`z?qN5A9 Y2dffIQMb?oE2+bXYkW6Dl-uJG%M}I2lF 9{lbbcJ*MZ&`S~PmQ9cU:VV)L+o/,7Z._}o.)?/o/\=|'7/>\?G{gN-`W>>llY9[Gyhenzvs=~zbW^z.67O_n2a}~s*y~ugg>g^=u|zrvqzbt 0000028911 00000 n Single Pane SHGC Double Pane SHGC Glass Block SHGC Metal Operable Clear . For January solar heat gain from south-facing windows, the highest numbers are triple the lowest. Heat gain during the summer months is usually undesirable, especially in cooling-dominated climates of the southeastern U.S. North-facing windows produce the least natural daylighting and solar heat gain for every month of the year. The solar gain is not stored near the windows to be lost at night but is captured through an open door into the main building. Is this correct? Light through windows isn't all direct sunlight. For double glazed windows SHGC is more often in the range of 0.42 - 0.55. Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. , Even for east- and west-facing windows, losses exceeded solar heat gains except for Denver. << In colorado I found Milgard and Pella had high SHGC, low E options. 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. Malcolm. Kansas City (east of Denver), second highest. As you point out, it's a complex problem to design a good south-facing roof overhang for the windows below. 0000060317 00000 n The maximum U-factor and solar heat gain coefficient (SHGC) for fenestration shall be as specified in Table C402.4. The "solar input" in the 3M Sungain film brochure, also known as the solar heat gain coefficient, is the solar transmittance modified to account for re-radiated heat. 0000054516 00000 n /Metadata 9 0 R 0000028760 00000 n 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. I built and installed R20-30 closing shutters both internally and externally more than 5 years ago in Western Canada at 51 latitude north. E 0000059464 00000 n Thanks for your comments. 0000033574 00000 n trailer 0000042979 00000 n The list of 22 northern U.S. cities can be re-ordered by the two indices for the ease of heating by solar gains and the value of solar heating. /TT5 18 0 R 0000026777 00000 n [4] Factors such as color, tint, and reflective coatings affect these properties, which is what prompted the development of the shading coefficient as a correction factor to account for this. The shading coefficient (SC) is a measure of the radiative thermal performance of a glass unit (panel or window) in a building. 0000039839 00000 n What Are The Top Factors To Consider In New Windows? Glazing with lower U-factors (higher R-values) for north- and west-facing windows tend to have lower SHGC. Solar Heat Gain Factors (SHGF) for June/July at 4 p.m. /ArtBox [0.0 0.0 612.0 792.0] I see lots of examples where people try things without "doing the math" beforehand. /TT6 17 0 R SHGC is expressed as a number between 0 and 1. 0000022979 00000 n Most insulating glass units in windows sold in USA are closer to SGHC=0.3 for avoiding excess solar gains in summer. {\displaystyle N*A(\lambda ,\theta )} 0000041718 00000 n North windows are a great example, since with the exception of dawn and sunset around June, there's no direct light through north-facing windows. The NFRC label provides a reliable way to determine a window's energy properties and to compare products. The overall shading coefficient is thus given by the ratio: S 0000045710 00000 n Argon filled would be affordable and add about R-1. Wall CLTD selection. 0000051467 00000 n 0000008386 00000 n 0000045996 00000 n The rightmost column 6 of the table shows the percentage of gains for one south-facing window compared to the combined total of three windows facing north, east, and west. Window specifications and climate data for your specific construction project are more important than the generalizations made here. 0.83 0.73 0.73 . 0000027129 00000 n Low-E Type . Terms | Your homes climate, orientation, and external shading will determine the optimal SHGC for a particular window, door, or skylight. 350 0000010168 00000 n Providence, R.I., is not unique among northern U.S. cities. (Of course you could use a light filtering curtain or shade to fix this.). One quick note: It appears that you are assuming a SHGC of 0.5 for the heat gain calculations. 0000029557 00000 n n We designed it to be in east west direction, and on the south side we have a large 2.5m wide doors. The amount of solar heat gain from windows varies tremendously. Two cities along the Pacific northwest coast (Portland, Oregon; and Seattle). Fixed Clear . << 0000052561 00000 n 0000058680 00000 n "Do the math!". I am having a hard time determining which specification to use when calculating solar heat gain through windows. OR. n Re-allocating costs would reduce the cost and complexity of the space heating system, and can enable solar heating to provide a greater portion of space heating. F endstream endobj 644 0 obj<> endobj 646 0 obj[647 0 R] endobj 647 0 obj<>>> endobj 648 0 obj<> endobj 649 0 obj<> endobj 650 0 obj<> endobj 651 0 obj<> endobj 652 0 obj<> endobj 653 0 obj<> endobj 654 0 obj<> endobj 655 0 obj<> endobj 656 0 obj<> endobj 657 0 obj<> endobj 658 0 obj<> endobj 659 0 obj<> endobj 660 0 obj<> endobj 661 0 obj<> endobj 662 0 obj<> endobj 663 0 obj<> endobj 664 0 obj<> endobj 665 0 obj<> endobj 666 0 obj<> endobj 667 0 obj<> endobj 668 0 obj<> endobj 669 0 obj<> endobj 670 0 obj<> endobj 671 0 obj<> endobj 672 0 obj<> endobj 673 0 obj<> endobj 674 0 obj<> endobj 675 0 obj<> endobj 676 0 obj<> endobj 677 0 obj<> endobj 678 0 obj<> endobj 679 0 obj<> endobj 680 0 obj<> endobj 681 0 obj<> endobj 682 0 obj<> endobj 683 0 obj<> endobj 684 0 obj<> endobj 685 0 obj<> endobj 686 0 obj<> endobj 687 0 obj<> endobj 688 0 obj<> endobj 689 0 obj<> endobj 690 0 obj<> endobj 691 0 obj<> endobj 692 0 obj<> endobj 693 0 obj<> endobj 694 0 obj<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 695 0 obj<> endobj 696 0 obj<> endobj 697 0 obj<> endobj 698 0 obj<> endobj 699 0 obj<> endobj 700 0 obj<>stream Despite having minor differences in modeling standards compared to the SHGC, the two values are effectively the same. East-facing windows can be more useful on winter mornings to warm up a cold house, but are quickly overtaken by warming from south-facing windows. 0000021486 00000 n /TrimBox [0.0 0.0 612.0 792.0] In Table 1, each city is listed with wintertime climate statistics. Solar gain can have both positive or negative effects depending on the climate. But hey nothing is perfect, so architects and builders could design roof overhangs to reduce summertime overheating. What Is The Difference Between Convection And Drafts? Remember, Window Joe and the staff at WindowReplacement.net are always here to answer any questions. 0000059651 00000 n Seattle, Washington. Industry technical experts recognized the limitations of SC and pushed towards SHGC in the United States (and the analogous g-value in Europe) before the early 1990s. 0000028440 00000 n 0000059957 00000 n Finally, Anchorage, Alaska, along the far northern Pacific coast, with by far the lowest solar heat gain. 0000032325 00000 n 0000048563 00000 n 0000049715 00000 n Solar heat gain coefficients are expressed as decimals from 0.00 to 1.00. 1 0 obj 0000032190 00000 n 643 350 0000010938 00000 n I bet under-insulating was also a common problem, especially for that thermal mass that serves as an overnight heating system. Does one use visible light transmission or some other figure? Heating Degree Days vary year-to-year, so other HDD numbers may be found. Locations that lack significant net solar heat gain, or that require a lot of wintertime heating, score lower on this index. Passive Solar Buildings. Same for east or west-facing windows, early or late in the day, respectively. 0000049162 00000 n 0000057247 00000 n xSmHSQ~f:MLQBBQ20 XJ Source: Text Bob Fegan 12/2008; Table on BTU per person heat gain from www.engineeringtoolbox.com 9/2005; diagram . The lower the SHGC, the better a product is at blocking unwanted heat gain. We have a passive solar house we designed and built ourselves in SE Michigan in the late 80's. How do you optimize this shading in a more so sophisticated way that the common arc diagram? -- Seasonally, the coldest temps of winter, and the hottest temps of summer, lag the sun's seasonal changes in path and intensity. -- The highest sun angle (for the northern hemisphere) is around June 21st, when the sun is nearly overhead at noon, just a little toward the southern horizon. The larger the roof overhang, the more important it is to do shading analysis, as it makes a big difference in the size of the shadow. 0000025712 00000 n Balcomb, J.Douglas, editor. 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. Use our Energy Star climate zone tool to look up the specific combinations of u factor and solar heat gain coefficient for the county you live in. 4. (If interested, see interior photos in this GBA article: The lower the SHGC, the less solar heat it transmits and the greater its shading ability. Solar Heat Gain through Fenestration Systems Containing Shading: Summary of Procedures for Estimating Performance from Minimal Data Publication Type Conference Paper Authors Joseph H Klems LBNL Report Number LBNL-48672 Abstract Solar heat gain factors and heat loss coefficients for passive heating concepts Full Record Research Abstract The concept of solar heat gain factor has been introduced for calculating the net energy gain of passive heating elements and other components of a building as a result of incident solar radiation. {\displaystyle T(\lambda )} 0000029882 00000 n At What Point Is It Worth Replacing Windows? Yet, the living room and the sun room, get a little bit more but welcome heat, while the bedrooms on the top floor facing west get a wallop in the afternoon. 0000051079 00000 n HW=oFX72X?A(l5 $?ASN* 0000049380 00000 n 0000028620 00000 n 0000020469 00000 n Table 1 shows wide variation in heating degree days, winter design temperatures, and Januarys average percentage of available sunlight. To that end, glazing with a relatively high solar heat gain coefficient is often used so as not to block solar heat gains, especially in the sunny side of the house. The larger the net solar gains, and the smaller the winter heating needed, the better the score on the index. Kansas City and cities along the northeast coast also look promising for wintertime daylighting, space heating, and PV. I think these recommendations are a mistake, as that high contrast of dark floor and white ceiling and walls adds to the perception of glare. High-performance homes likely use these space heating appliances, since less space heating energy is required in well-insulated, airtight homes. Taking account of heat losses from the windows produces much more extreme results favoring south-facing glazing. 2 (b)] /a; + a~ ` g=r+URI h +Ra;I (5) where T is the total transmittivity; UR is the overall heat loss coefficient of the window; aj, aare, respectively, the absorptivities of the inner and outer glasses; R is the heat resistance of the glazing; and ho is We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. 0000008360 00000 n The resources cited in the Appendix or other internet resources may provide climate data for your location or a similar climate nearby. /BleedBox [0.0 0.0 612.0 792.0] 0000043781 00000 n Shading Coefficient (SC) SHADING COEFFICIENT (SC) is the ratio of the solar heat gain through a fenestration product to the solar heat gain through an unshaded 1/8-inch-thick clear double strength glass under the same set of conditions. 0000018332 00000 n Their net solar heat gain is only about a quarter of Denvers. 0000059851 00000 n 0000022215 00000 n All you need to do is look for the ratings that indicate a good fit for your climate. At home she is the first to pull them up on a sunny morning, maybe because we have more room at home. This simple computation provides a metric to rate locations for the value or cost-effectiveness of passive solar or solar tempered winter space heating. The basement windows look out only on the east and south sides of the home where they barely see the light of day. Otherwise, the ordering remains similar to the previous ordering by amount of solar heat gain from south windows (Tables 1 through 3). Martin I agree some passive solar homes did create window walls of south-facing glass, likely without quantifying solar heat gain beforehand. The window orientations were limited to true south, east, west, and north. Glass Color . Here's some information not included in the article that provides background to those unfamiliar with the topic raised by Malcolm. /MediaBox [0.0 0.0 612.0 792.0] /ColorSpace 27 0 R The other two factors related toSolar Heat Gain Coefficient when choosing replacement windows are: Window Joe went to look at a home recently that required different solar heat gain coefficients based on the two factors above. I would hope this article would lead people to consider quantifying solar gains for any type of home, not just solar-oriented designs. SHGC is expressed as a The warmer HDD numbers are highlighted in tan, and colder are highlighted in ice blue. Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

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