Solar Heat Gain Thru Glass Thermopane windows have no sash; therefore, sash area correction = 1/.85 (bottom Table 15). 0000059249 00000 n I found it both interesting and very useful. All you need to do is look for the ratings that indicate a good fit for your climate. 0000021997 00000 n Map. 0000033028 00000 n In summary, there are many things to consider when choosing the best window replacement options. Maybe some desiccant packets could help reduce fogging? 0000008921 00000 n 0000052866 00000 n Before choosing window locations, sizes and performance characteristics, we need to examine solar heat gains throughout the year, not just January. glazing 0000030489 00000 n Daylighting is good, and solar heat gain is good in winter and not good in the hot summer. What exactly does that give you? 0000035843 00000 n The highest percentages are highlighted in green, and the lowest red and pink. Solar transmittance is used to compare different types of glass. /Im0 10 0 R 0000031116 00000 n 0000056381 00000 n 0000055691 00000 n The higher the number, the more light transmitted without adding excessive amounts of heat. -- The lowest sun angle at noon is around Dec 21st,, when the sun is low on the southern horizon, even at noon. 0000042224 00000 n , Next seven cities are all located in the northeast, along the Atlantic coast (Providence; Hartford; Boston; Portland, Maine; New York City; Philadelphia; and Concord, N.H.). 0000038067 00000 n 0000010938 00000 n Unfortunately in the US, most windows sold are low SHGC. Remember when choosing the coefficient for each window: If you live in a warm climate, choose windows with an SHGC closer to 0, In colder climates choose a window with an SHGC closer to 1, When reading an Energy Star or NFRC tag, they report the SHGC on the WHOLE window, including the frame, not just the center point of the glass. Columns 1-3 lists the same city data, in the same order, as Table 1. Fortunately, Energy STAR pulled back a bit, which means windows could remain a bit more affordable. available solar energy falling on the window. Solar heat gain factors and heat loss coefficients for passive heating 0000023982 00000 n Sitemap | Remember, the solar heat gain coefficient ranges between 0 and 1, the lower the number the less heat (radiation) is let in, the higher the SHGC, the more heat is let in. It was an experiment, and I can now, after 5 years, say it exceeded my expectations. What about glare? 0000059851 00000 n Other cities in the list across the Midwest and northern central U.S. get about half the net solar heat gain of Denver. I am having a hard time determining which specification to use when calculating solar heat gain through windows. The lower the U-Factor, the better the window insulates. 0000032190 00000 n If you live in a climate where it is hot and sunny most of the year, then you may want to block more of the sun's heat with an SHGC closer to 1. Unfortunately, by late August, it is still hot summer weather, but the sun's path has changed to be lower on the horizon than June 21st. Finally, Anchorage, Alaska, along the far northern Pacific coast, with by far the lowest solar heat gain. You build a simple house, and then you can set your latitude, and then choose the date/hour. 0000055107 00000 n Malcolm. 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. E Table 1 shows wide variation in heating degree days, winter design temperatures, and Januarys average percentage of available sunlight. (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. That would provide ideal sun shading for those dates at solar noon. /Font The solar gain factor is a complicated series of factors multiplied together starting with the transmittance factor of the glass, and ending with all possible shading devices/methods and adjusted for local weather (cloud cover). Roof overhangs can shade the top of a window yet allow solar gain at the bottom. The Southern Climate Zone has hot summers and mild winters. 0000039733 00000 n South-facing window glazing may optimize heat gains with higher SHGC, and west-facing windows with lower SHGC glazing. I used double-pane windows, and four large double-pane IGUs (for site built fixed windows). 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. 0000029417 00000 n ( At home she is the first to pull them up on a sunny morning, maybe because we have more room at home. 0000024598 00000 n Not that I watch it much (or at all) during daytime), but still :) 0000013076 00000 n West-facing windows are a bigger concern, needing shading of some sort during hot late afternoons. What Is The Difference Between Convection And Drafts? 0000048946 00000 n He was a psychology professor for five years, and a software and web site usability and design engineer for 20 years. <]>> Still, don't have AC. A Designing south-facing roof overhangs Wyoming Climate Atlas: Solar Radiation - Wyoming State Climate Office HUrF}WoND{_2#J$v:>-%uE">Tw[~Aq}$,N.7n@0v]Av8`o Not just to design passive solar or solar-tempered buildings. Will Vinyl Replacement Windows Stop Condensation? Window Joe says to always keep it simple and follow NFRC and Energy STAR ratings that are suggested for your specific county. 0000021621 00000 n In contrast, the east, west, and north-facing windows lose more heat (column 8) than they gain in January (columns 4 or 5), except in Denver. 0000052778 00000 n 0000036017 00000 n Kansas City and cities along the northeast coast also look promising for wintertime daylighting, space heating, and PV. Currently, there's plenty of software and consultants to perform calculations, or do it yourself with spreadsheets. 0000034610 00000 n HEAT GAINS and LOSSES : ROOFS and WALLS | Energy-Models.com + 0000041454 00000 n Engineering-wise, this makes sense, but not for human perception. PDF ASHRAE STANDARD Energy Standard for Buildings Except Buildings The winter climates in these cities differ not just in temperature ranges, but also in the amount of winter sunlight. . Table 2 lists solar gain data for the 22 northern U.S. cities. Note from the cells highlighted in yellow: During the winter, from November through February, one south-facing window would produce more light and solar heat gain than the total gain of three windows facing north, east, and west, respectively. The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article. 0000030709 00000 n Worth remembering that those early-'80's houses are one of the main reasons we are having such fruitful discussions today! If your climate zone experiences many cold days, the sun's warmth, also referred to as the sun's radiation, is welcome because it allows the heat from the sun into your home. /Contents 24 0 R Will New Windows Save Money On Energy Bills? 0000027305 00000 n 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. Would seem 'Damn the torpedoes, full steam ahead' to catastrophic Global Warming. The solar heat gain coefficient (SHGC) is an index describing the proportion of light that is let through a window. North windows would be most desirable in cooling-dominated climates, or during hot summer periods anywhere in the U.S. but not during the cold and darker winters of northern U.S. locations. So overhangs tend to keep the house cooler in the Spring as well as late summer. >> product blocks heat from the sun. heat gain is particularly important during the summer Tables 4 and 5 show the re-ordered lists. ;"\ h;; nM"O*]\_n}s54xBb;L";`fJq=.s5?puuus9Eq=7wWT|# LhH{\=vf}+W8?fX'Xgp8=ZHQ-oGA2mN~~k. . 0000038900 00000 n /C2_2 13 0 R The lower the SHGC, the better 0000050787 00000 n It is a safe bet to buy any material, so long as the overall replacement window is more energy efficient. Thank you so much for sharing this with us. 0000047504 00000 n The question-and-answer article above, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. %3Qd Vw9k\1W7CL9tqM=~u5b&XfmFk!$"4c?9%fb|$N}0R16f]oqnDxo[hot;3Nq_fO-jldHA '*bIgdyfs[B[Z+^:E 9)Uii;/J PH( 6.u. w You want to shade your south-facing windows from the sun to avoid solar heat gain. 0000054427 00000 n I would also like to hear more about your/GBA community's thoughts on thermal mass and its relationship with solar heat gain. 0000044552 00000 n You bring up an important point. Contrast between the direct sunlight and the TV screen needs to be avoided. Shading analysis of the building site's landscaping and adjacent buildings is critically important. >> Alaska, the Pacific Northwest, and Midwestern cities would not be good candidates to rely on wintertime solar heating. 0000011631 00000 n 0000009545 00000 n 0000026274 00000 n Labels on products sold in markets outside the United But it might be a good compromise. This article explores the viability of passive solar and solar-tempered space heating in northern U.S. regions and metro areas. 0000039059 00000 n 0000032660 00000 n (The result also is multiplied by 100 so that numbers are transformed into a simple single digit range.). We want to keep our solar heat, not lose it back through the same window that brought it in. 0000012792 00000 n That's good for south-facing windows, because in the cold winter, you want the sun beating in your windows, warming your home's interior (and providing daylighting too). Though the SHGC is more realistic than the SC, both are only rough approximations when they include complex elements such as shading devices, which offer more precise control over when fenestration is shaded from solar gain than glass treatments. 0000041950 00000 n In buildings, excessive solar gain can lead to overheating within a space, but it can also be used as a passive heating strategy when heat is desired.[1]. Column 8 shows (with red negative numbers) the average January daily heat loss per square foot of glass (assuming glazing is rated R-5 or U=0.2, with window coverings adding some insulation during nighttime hours to attain U=0.15). 0000008689 00000 n 0000026777 00000 n The resources cited in the Appendix or other internet resources may provide climate data for your location or a similar climate nearby. Their net solar heat gain is only about a quarter of Denvers. The windows specifications used here might be typical for a Pretty Good House design, being relatively high-performance windows but in the affordable range. The warmer HDD numbers are highlighted in tan, and colder are highlighted in ice blue. /TT1 22 0 R The window projection factor shall be . 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 Be sure to educate yourself and to work with a professional installer for your project. 0000009311 00000 n 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 would hope this article would lead people to consider quantifying solar gains for any type of home, not just solar-oriented designs. Fortunately, retailers will tailor their stock to homes in your area. 0000030603 00000 n The North Central Climate Zone has more moderate seasons as such, the Energy Star Factors are as follows: The South Central Climate Zone has warmer summers and milder winters. Those panels closed during the 15 hour nights of winter make far more difference than thermal mass or solar gain. PDF Solar Heat Gain Factors (SHGFs) for selected latitudes of - Dartmouth on the climate, summer and winter fuels costs, and ) lL)Cg4xo` =[3lhb$qrCcUT?iFgqH10L9e:Q` 8 Solar Heat Gain Coefficient (SHGC) Worksheet -For Non-HERS Registered Projects (Page 3 of 3) TABLE 110.6-B DEFAULT SOLAR HEAT GAIN COEFFICIENT (SHGC) FRAME TYPE PRODUCT GLAZING FENESTRATION PRODUCT SHGC . Just that insulated door is shut at night and the porch is then isolated from the main heated building. I think that the key design criteria for passive solar involves locating and sizing windows, thermal mass, and doing sufficient insulating and air-sealing so that only solar heat gain can provide most of the home's wintertime space heating, yet avoid summertime overheating. Therefore, the sun is shining on your south-facing walls and windows during wintertime. 0000010707 00000 n , 0000057117 00000 n 0000041109 00000 n 0000020266 00000 n 0000025994 00000 n 0000008999 00000 n North windows get almost no direct sunlight, so would be less of a problem. 0000037011 00000 n To optimize the heat gain through windows heavily insulated shutters will change all the numbers. ASHRAEs table of solar heat gain factors[2] provides the expected solar heat gain for clear float glass at different latitudes, orientations, and times, which can be multiplied by the shading coefficient to correct for differences in radiation properties. into a home or building through a product. Personally, I think we should focus on better window shading methods than roof overhangs. Passivhaus is known for having lots of foam insulation below slab floors (8" to 10" thickness might be common) to keep within their limited heat loss budget. Note that air leakage also depends on proper installation of a window, which is assumed in all ratings. When integrated over the wavelengths of solar short-wave radiation, it yields the total fraction of transmitted solar energy across all solar wavelengths. Solar Heat Gain Coefficient, or SHGC, is the amount of solar radiation, or heat, that passes through windows into the home In other words, SHGC tells you how well the windows block the sun's heat from coming inside An SHGC closer to 0 means that little solar heat is let in An SHGC closer to 1 means more solar heat is let in 0000020026 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. We have no relationship with advertisers, products, or services discussed at this website. 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. The Energy STAR program provides window buying guidance on the most energy efficient windows for buyers based upon their regions: Some areas of the country are plagued with a hot, dripping summer as well as a long, cold, we winter. 0000050343 00000 n However this tends to provide a good estimate over a wide range of angles, up to 30 degrees from normal in most cases.[3]. 0000034462 00000 n /MC0 SHGC ratings are used to help in quantifying the energy efficiency of windows and skylights. endobj High-performance homes likely use these space heating appliances, since less space heating energy is required in well-insulated, airtight homes. 0000009155 00000 n 5. , 0000009389 00000 n Here are added factors defined by the NFRC as of 2005: Air Leakage(AL) measures how much outside air comes Column 8 computes an index of how cost-effective or how valuable solar heat gains can be for a location. hbbd```b``A$cXDDr@3N,IF@L@s&00Lg`` OR. Whatever IGUs you might find for sale retail, please share with us. Table 4 only looks at solar heat gains without considering losses. Only 22 cities are examined, and only in the northern U.S. It can't be a problem for north-facing windows, which receive almost no direct sunlight any time of year. 0000050182 00000 n We don't seem to have an issue with glare. (12) Consider different glazing for windows facing different directions. The lack of joints in vinyl windows increases their energy efficiency and reduces their solar heat gain coefficient because there are not any joints for heat to travel through. HUPTekzreUXT ey""E + efw# >XimcQLTs}w#HT^bo$kuYPU:)l {ewGJc'8qq`VHK'O]Hy&$z]=16FlN.S-$&uQ/:w 0000010861 00000 n 0000032325 00000 n 643 350 Like most things, you can have too much of a good thing. Maybe we should not let the perfect be the enemy of the good. 0000048563 00000 n It can range in value << endstream endobj startxref 0000056953 00000 n 0000033339 00000 n There is more total sunlight shining in summer (June to August in the northern hemisphere) than mid-winter (December to February). 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). This won't delete the articles you've saved, just the list. 0000028911 00000 n ( Passive solar designs typically employ large south facing windows with a high SHGC and overhangs that block sunlight in summer months and permit it to enter the window in the winter. We have about 2' overhangs on all south facing windows and doors which work well in this latitude. 0000029773 00000 n Having lots of sunlight entering the home in the winter is a way to elevate mood when many folks find it hard to be outside like when it's warm. 0000050037 00000 n 0000031310 00000 n Designing roof overhangs to avoid shading windows at noon on Dec 21st results in some shading at the top of the window at noon in January, February and November, when you still want that sunlight (though at 10AM or 2PM you won't be shading the top of the window since the sun is lower on the horizon at that time of day). endstream endobj startxref HEAT GAINS and LOSSES : WINDOWS and SKYLIGHTS (Glass) This feature has been temporarily disabled during the beta site preview. One of the best I've read here. The first five columns list each month of the year, and the daily solar heat gain per square foot of window glazing for windows facing south, north, and east, or west , and the average heat gain over the four window directions. As well, 3 years ago, having been so pleased with the shutter effect, I built a "low mass, super insulated south facing solar porch. When placed in the path of admitted sunlight, high thermal mass features such as concrete slabs or trombe walls store large amounts of solar radiation during the day and release it slowly into the space throughout the night. Too much south-facing glazing can make a home very uncomfortable and unpleasant in February and March. = Meanwhile, the solar heat gain through east- and west-facing windows is more intense due to the greater amount of solar radiation around June (for the northern hemisphere). The other climate zones underwent more stringent Energy Star qualifications that took effect on January 1, 2015. 0000019823 00000 n 0000040500 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 This is covered in the U-Factor article, but it is worth mentioning because it also impacted the solar heat gain coefficient for the Northern Zone. How do visible light transmittance, and shading coefficient relate to one another? Balcomb, J.Douglas, editor. September 1st/March 1st modelling revealed modest exposure as the sun has dropped enough to negate most of the overhang benefit. 0000053548 00000 n 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. You will not receive a notification when a response to your question has been posted. 0000010630 00000 n Solar gain (also known as solar heat gain or passive solar gain) is the increase in thermal energy of a space, object or structure as it absorbs incident solar radiation. We have a passive solar house we designed and built ourselves in SE Michigan in the late 80's. Like Cardinal, PPG only manufactures window glass, and I don't think sell glass units retail, just to window manufacturers. {\displaystyle T(\lambda )} Solar Heat Gain Factors (SHGF) for June/July at 4 p.m. h)u^Si!vr:(q;}xH)\@|&u$y?Cm_Sk5a4iiARd(q-tc:Ng^*,,eH%Gk(SX~w X%l0As6_L t 5i f5=P8E UUn vmSfoB`F(a\N`! w]T,&hX#XXJ Xo7Jj%I:hL$^B;4DC{=.! There is so little solar heat gain through all windows in Anchorage in January (and such large heat losses), that heat losses far exceed the gains, even for south-facing windows. /ArtBox [0.0 0.0 612.0 792.0] 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. 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. FIND A DEALER. A SHGC of 0.39 would be considered low-solar-gain glazing, not high-solar-gain glazing. 0000011400 00000 n Locations get lower scores if they cant generate much net solar gains, need less winter heating, or have cheap electric rates for minisplit heat pumps, electric radiant heating, or resistance electrical heating. I see lots of examples where people try things without "doing the math" beforehand. 0000055784 00000 n standard low-E and about .40 for spectrally selective low- 0.80 0.70 0.70 . Note that south-facing windows typically have solar heat gains (column 3) at least double the heat losses (column 8). Thirty-five years ago, I designed and built a classic passive solar home in Colorado. Only their (1) net south-facing glazing heat gains; (2) winter heating degree days; and (3) cost of electricity, would be needed to create a more comprehensive list. 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. Winter temperatures and cloudiness are major determinants of the potential and the cost-effectiveness of exploiting solar heat gain for space heating. Despite having minor differences in modeling standards compared to the SHGC, the two values are effectively the same. 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. When architects (yes I've done it for clients) draw diagrams showing the solar exposure of south-facing windows, they often decide on the depth of overhangs for shading based on the angle of the sun at noon in both summer and winter. 0000058060 00000 n 0000008432 00000 n As such, the Energy Star Factors are as follows:Factors for Energy STAR Ratings in the South Central Climate Zone. Denver, with the highest average solar heat gain in January. Hours earlier and later, the light could extend further but would be less intense. 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. Thank you for sharing your thoughts, Bob. Is this really necessary? 0000009701 00000 n There are lots of ways to provide that shading, or using low SHGC windows for west and east-facing windows to avoid interior overheating during the summer. How to Calculate Solar Heat Gain Coefficient for Windows Most manufacturers worked to retrofit products to meet the new and more stringent standards. 0000027723 00000 n << Be sure to read the article on u-factor as well, as it is closely related to energy efficiency in windows. Become a GBA Prime member and get full access to GBA articles, enyclopedia, videos, CAD library, and more. [4] Though the shading coefficient is still mentioned in manufacturer product literature and some industry computer software,[6] it is no longer mentioned as an option in industry-specific texts[2] or model building codes. (13) Design roof overhangs, patio or deck coverings, and landscaping to preserve unobstructed sunshine in winter, and shade west- and east-facing windows during summer months.