Will Vinyl Replacement Windows Stop Condensation? The trapped heat thus causes solar gain via a phenomenon known as the greenhouse effect. 0000046541 00000 n 0000059957 00000 n >> 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, A window with a climate correct SHGC can be like a free heat source in cold climates and it can also lower AC costs in hot climates, Pay up to 50% LESS for energy costs by purchasing replacement windows that meet stringent Energy STAR ratings, The direction the windows face in relation to the sun, The amount of shade your home gets each day, The basement windows got a higher SHGC to allow in warmth, The living room got a middle of the road SHGC, The sunroom got a higher SHGC because of the sheer number of windows it has, The westward facing bedroom windows got an SHGC closer to 1 to prevent it from heating up in the afternoon hours, Blocking out cold temperatures in winter months, Allowing in more of the sun's thermal radiation (heat), U Factor of 0.28 and SHGC of greater than or equal to 0.32, U Factor of 0.29 and SHGC of greater than or equal to 0.37, U Factor of 0.30 and SHGC of greater than or equal to 0.42, Keeping homes comfortable in more moderate weather, Finding balance in letting heat in and keeping cold air out, U Factor of less than or equal to 0.30 and an SHGC or less than 0.40, Keeping more heat out in the summer to lower air conditioning costs, Letting some heat in during winter months, U Factor of less than or equal to 0.30 and an SHGC of 0.25, Keeping heat out in the spring and summer to lower air conditioning costs, Lowering energy bills by keeping heat out most of the year, U Factor of less than or equal to 0.40 and an SHGC less than or equal to 0.25. The other climate zones underwent more stringent Energy Star qualifications that took effect on January 1, 2015. Fortunately, retailers will tailor their stock to homes in your area. At home she is the first to pull them up on a sunny morning, maybe because we have more room at home. 0000041454 00000 n My wife has a small office at work with lots of south facing glass and pulls the shades on sunny days. 0000018740 00000 n [3], The g-value (sometimes also called a Solar Factor or Total Solar Energy Transmittance) is the coefficient commonly used in Europe to measure the solar energy transmittance of windows. 0000038191 00000 n U-factor (inverse of R-value), which measures the rate of heat losses through that window to the cold outdoors. In addition to glass properties, shading devices integrated into the window assembly are also included in the SC calculation. 350 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. So I'd recommend designing overhangs for minimal shading mid-winter, and not worry so much about summer (for winter-dominated northern climates). 0000008169 00000 n /MediaBox [0.0 0.0 612.0 792.0] 0000048853 00000 n Thank you Bob for sharing this very thorough article! 0000042317 00000 n 0000026684 00000 n 0000053434 00000 n 0000048656 00000 n Solar gain can also be transferred to the building by indirect or isolated solar gain systems. potential for daylighting. 0000011631 00000 n 0000049380 00000 n Sitemap | In January, one south-facing window produces more solar heat gain than the solar gains from three windows facing north, east, and west for all 22 cities. 0000009467 00000 n In the United States, The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)[2] and The National Fenestration Rating Council (NFRC)[3] maintain standards for the calculation and measurement of these values. For more information, see All About Glazing Options. But overall, if values are changed to reflect other information sources, a similar overall pattern will emerge, unlikely changing any of the main conclusions of this modeling effort. 0000026181 00000 n /TT7 16 0 R I would hope this article would lead people to consider quantifying solar gains for any type of home, not just solar-oriented designs. is the incident solar spectral irradiance. We designed it to be in east west direction, and on the south side we have a large 2.5m wide doors. , ;"\ h;; nM"O*]\_n}s54xBb;L";`fJq=.s5?puuus9Eq=7wWT|# LhH{\=vf}+W8?fX'Xgp8=ZHQ-oGA2mN~~k. 0000012329 00000 n The maximum U-factor and solar heat gain coefficient (SHGC) for fenestration shall be as specified in Table C402.4. 0000047288 00000 n /Im0 10 0 R Locations in the northern U.S. are winter-heating-dominated (meaning that more energy is needed for winter heating and much less for summer cooling). I think glare would be a bigger problem if you were sitting in direct sunlight, not at the other end of the room. The amount of solar heat gain from windows varies tremendously. 3Lg !+P&U|,8| >kIoszd\p 5:X[KE]MmxHYnpmxq {BW5y.%LY^z#YeSl|]MO_-hl{b~S6y}-/O)@tHT;qZGw~Ny4{}ihda):Gu")17EXZ}s_S: ZFa|gGU=r 2$$4!&xL'`ewL ($2BLrP+Q(Iq(zj%I)%Y0T4"\2%r(D%;X%KnG;]YB#mc*AwQ}~%J@`c*KbQem&ek.ck)5F^nV_ The whole window; meaning the window frame and glazing (glass) or: Center of the glass; meaning it only includes the SHGC for the the glass, Coatings bounce heat and light out or inside the home to increase or decrease light and heat that enters the house, Glazing comes in single or multiple layers to keep mother nature outdoors. 0000044828 00000 n Its important to insulate thermal mass well, but Passivhaus insulation levels might be overkill in a passive solar home. Uncontrolled solar gain is undesirable in hot climates due to its potential for overheating a space. {\displaystyle S.C.=F(\lambda ,\theta )_{1}/F(\lambda ,\theta )_{o}}. First, thanks for sharing your many helpful comments and ideas on GBA articles on Q&A. 0000012014 00000 n hb```g`` ,@Q ?>K kwlsEGyGG#h`@ %X 0000019351 00000 n 0000025712 00000 n It is easier to maximize wintertime solar heating in some climates than others. Visible transmittance (VT)is a fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through the glazing of a window, door, or skylight. , 0000037104 00000 n [9], SHGC is the successor to the shading coefficient used in the United States and it is the ratio of transmitted solar radiation to incident solar radiation of an entire window assembly. 0000031405 00000 n Next, six cities in the Midwest and Great Lakes area (Chicago; Indianapolis; Detroit; Burlington, Vermont; Pittsburgh, Pennsylvania; and Buffalo, N.Y.). {\displaystyle T(\lambda )} This is a different figure from visible transmittance (VT) of light, also defined by the NFRC as follows: Visible Transmittance(VT) measures how much light 0000040162 00000 n 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. What Is The Difference Between Convection And Drafts? I found it both interesting and very useful. << The VT you need for a window, door, or skylight should be determined by your home's daylighting requirements and/or whether you need to reduce interior glare in a space. Light-to-solar gain (LSG)is the ratio between the VT and SHGC. Solar heat gain factors and heat loss coefficients for passive heating 0000018860 00000 n 0000031934 00000 n Use ASHRAE table 8.5, page 8.26 (page 26 note) to . We have about 2' overhangs on all south facing windows and doors which work well in this latitude. 0000039316 00000 n 0000011862 00000 n {\displaystyle N*A(\lambda ,\theta )} When too much heat is let in by an inappropriate SHGC and too much heat is trapped in by an incorrect u factor, you have what is commonly known as the greenhouse effect. between 0 and 1. ( 0000031018 00000 n They have been prepared in exactly the same way as the tables in the ASHRAE Handbook of Fundamentals (1967), but are for the latitudes of particular relevance in Canada and for . PDF SOLAR RADIATION - Michigan Technological University Which design principles from the 1970s are worth retaining, and which should be discarded? 0000051079 00000 n The window projection factor shall be . 0000059464 00000 n 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. 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. The following web resources were useful for gathering climate and solar gain data. 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. I have 35 year old home-made fixed glass windows on the south side of my house that need to be replaced. While the U-Factor can take any value, in general for windows it ranges from 0.20 to 1.20. To optimize the heat gain through windows heavily insulated shutters will change all the numbers. E. Which type of glazing is optimal for a given project depends [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. When the sun's rays hit an object, such as a window, some of the sun's energy is absorbed, warming that object, and allowed to pass through. NAAP Labs Motions of the Sun Simulator. Finally, Anchorage, Alaska, along the far northern Pacific coast, with by far the lowest solar heat gain. So overhangs tend to keep the house cooler in the Spring as well as late summer. The SHGC is the measurement of how much radiant heat, or heat produced by the sun, comes in through a window. Even though south-facing windows have much higher solar gain during December and January than other orientations, the situation in summer has changed significantly due to changes in the position of the sun at midday. /GS0 3 0 R 0000031213 00000 n You bring up an important point. The U-Factor measures how well the window in-sulates. Ideally, the goal is to not block wintertime sunlight on south-facing windows. In Vermont you'd probably have difficulty with fogging due to moisture between glass layers. It was an experiment, and I can now, after 5 years, say it exceeded my expectations. 0000052240 00000 n 0000043195 00000 n SHGC & U-Factor Tool | PGT Industries - Custom Aluminum, Vinyl and 0000049884 00000 n 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). Thanks for all the great details and comments, and your work on this type of efficient home design. 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. 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. MIT Press, 1992. HEAT GAINS and LOSSES : ROOFS and WALLS | Energy-Models.com Objects struck by sunlight absorb its visible and short-wave infrared components, increase in temperature, and then re-radiate that heat at longer infrared wavelengths. 0000038260 00000 n (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. This home had sufficient, well-insulated thermal mass tiled slab floor, engineered quantitatively to offset wintertime heat losses with solar heat gains. Whatever IGUs you might find for sale retail, please share with us. 0000030603 00000 n 0000032457 00000 n They also recommended ceilings be white, to reflect light back to the floor. They can work well in late summer hot weather, yet not block the sun on cooler days in the Spring. 0000055784 00000 n 0000048271 00000 n Glare would not be the reason shades were drawn at that hour for south-facing windows in any home, unless someone needs a dark interior, like trying to sleep late. , 0000011323 00000 n In essence SC is an index of the effective solar rejection performance of a given glass type. 0000045185 00000 n 0000053840 00000 n In June, the sun is closer to overhead at noon, so south windows have far less solar heat gain. Technical Report: Solar Heat Gain Through Fenestration Systems Containing Shading: Procedures for Estimating Performance from Minimal Data Title: Solar Heat Gain Through Fenestration Systems Containing Shading: Procedures for Estimating Performance from Minimal Data Full Record Other RelatedResearch Abstract Locations needing a lot of heating, that have high electricity prices, and that have good net solar gains, get higher scores. Here are added factors defined by the NFRC as of 2005: Air Leakage(AL) measures how much outside air comes 0000042410 00000 n Seattle, Washington. 0000008999 00000 n FIND A DEALER. 5.8.2.2 Labeling of Fenestration Products . As such, the Energy Star Factors are as follows:Factors for Energy STAR Ratings in the South Central Climate Zone. be adjusted for thermal lag and time delay. Note that this article doesn't promote classic passive solar design, even though a well-designed passive solar home works great in dry cold winter climates (but not in climates with overcast winters). 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. 0000050182 00000 n is the spectral transmittance at a given wavelength in nanometers and 0000020608 00000 n /ProcSet [/PDF /Text /ImageC] SHGC is expressed as a 0000011092 00000 n 0000039733 00000 n Some of the current research into this subject area is addressing the tradeoff between opaque thermal mass for storage and transparent glazing for collection through the use of transparent phase change materials that both admit light and store energy without the need for excessive weight.[14]. Therefore, the sun is shining on your south-facing walls and windows during wintertime. 0000032325 00000 n Such devices can reduce the shading coefficient by blocking portions of the glazing with opaque or translucent material, thus reducing the overall transmissivity. (3) Overall, unobstructed south-facing windows gain more heat than they lose during mid-winter in almost all U.S. climates. Solar transmittance is used to compare different types of glass. The challenge in selecting the appropriate SHGC is balancing out the ideal amount of incoming solar radiation in cold months (to heat your home from the sun's warmth and to lower heating bills), versus keeping solar heat out in hotter months of the year in order to save on air conditioning costs. Solar Heat Gain Factors (SHGFs) for selected latitudes of the Northern Hemisphere Source: Handbook of Fundamentals American Society of Heating, Refrigeration and Air-Conditioning (ASHRAE) Use: Select latitude (16o-64oN) month of year (January-December) and orientation of exposure (North, East, South, West or intermediate orientation). (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. Vertical fenestration that is located on the street side of the street-level story only, provided that. And it would shade some of the top of the window during January, February and November, when you'd prefer full sun. 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. 0000018332 00000 n , ( 0000055107 00000 n Passive Solar Buildings. 0000021721 00000 n standard low-E and about .40 for spectrally selective low- 0000052649 00000 n Is It Easier To Clean Replacement Windows? 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. The larger the SHGC, the more light that can enter through the window. Last edited on 13 February 2023, at 00:16, Learn how and when to remove this template message, https://en.wikipedia.org/w/index.php?title=Solar_gain&oldid=1139027242, This page was last edited on 13 February 2023, at 00:16. Fortunately, Energy STAR pulled back a bit, which means windows could remain a bit more affordable. 0000036472 00000 n This feature has been temporarily disabled during the beta site preview. [3] Since the quantities compared are functions of both wavelength and angle of incidence, the shading coefficient for a window assembly is typically reported for a single wavelength typical of solar radiation entering normal to the plane of glass. A product with a high SHGC rating is more effective at collecting solar heat during the winter. optional rating, and manufacturers can choose not to Again, it would reflect off the floor and other surfaces to diffuse the light. About | Since heat gain is desirable during January for homes in northern latitudes, locating windows on the south side is far more beneficial than other orientations, assuming that that south window is not blocked from getting sunlight from obstructions during midday. 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 Other cities in the list across the Midwest and northern central U.S. get about half the net solar heat gain of Denver. Higher SGHC=0.7 could be used on south-facing glazing to increase solar gains, but still get decent heat loss performance (e.g., Cardinal LoE-180 glass with SHGC=.69, U=26). High SHGC glazing 36" overhangs, 9' walls. how glass is used in the house design. "T" is the transmissivity of the glass, "A" is its absorptivity, and "N" is the fraction of absorbed energy that is re-emitted into the space. 0000057117 00000 n Other factors like style, finish, hardware, and function can also play a big part in the curb appeal and aesthetics of your home. Thank you so much for sharing this with us. If not, how can I find a better alternative at a reasonable price? 0000059651 00000 n You must be a magazine subscriber to access this feature. 0000011708 00000 n The sun rises in the east, goes overhead, then sets in the west, with little sunlight directly striking a south-facing wall or window. 0000032660 00000 n For south-facing windows, designing overhangs to maximize mid-winter solar gains yet reduce summertime solar gains is useful, but more of a detail than a major contribution to passive solar heat gain management. "Rjk=6}TIF }l,MHU{j>k(g_VqL14VToD_fvCF O=^&~]D;_"?/4M$gi3c'fL12#PK6eSvIP9@CLG[4fmRKn#Ga'kenD1pM8|b,yZMwtxxvr;PI})1Z8ruT^a{ZANQ XHXM!zwR`OqQzq/y[moWk&jaR6vl_3=OM sK}GJNU 7vd+`y`,Sk- Daylighting is good, and solar heat gain is good in winter and not good in the hot summer. I would also like to hear more about your/GBA community's thoughts on thermal mass and its relationship with solar heat gain. I changed the color of walls from off-white to the same coffee color (from advice in an interior design class). ( /CS0 8 0 R 0000042133 00000 n The more you learn about energy efficiency in windows, the more you will be able to evaluate a quality window replacement installer. SHGC also decreases with the number of glass panes used in a window. Solar Heat Gain Calculation - InspectAPedia Window manufacturers use Solar Heat Gain Coefficient (SHGC) to describe how much energy passes through a window and . For example, in triple glazed windows, SHGC tends to be in the range of 0.33 - 0.47. 0000021997 00000 n 0000020469 00000 n 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. Elevates mood in winter To what extent does this help? /Rotate 0 Argon filled would be affordable and add about R-1. 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. The U-factor, Solar Heat Gain Coefficient (SHGC), Visible Light Transmit-tance (VT), and air leakage rate for all manufactured fenestra-tion products shall be determined by a laboratory accredited by a nationally recognized accreditation organization, such as the National Fenestration Rating Council. 0000023176 00000 n lL)Cg4xo` =[3lhb$qrCcUT?iFgqH10L9e:Q` 8 0000034904 00000 n ) A SHGC of 0.39 would be considered low-solar-gain glazing, not high-solar-gain glazing. -- Seasonally, the coldest temps of winter, and the hottest temps of summer, lag the sun's seasonal changes in path and intensity. The solar gain factor is a complicated series of factors multiplied together starting with the transmittance factor of the glass, and ending with all possible shading devices/methods and adjusted for local weather (cloud cover). 0000056254 00000 n Designing roof overhangs to avoid shading windows at noon on Dec 21st results in some shading at the top of the window at noon in January, February and November, when you still want that sunlight (though at 10AM or 2PM you won't be shading the top of the window since the sun is lower on the horizon at that time of day). 0000033574 00000 n hb``` , b-0.X)![)?OXjL ~E-AzMVk+u9:MX@qKpDa%E={d C=H:]JxrWur{. 2252 0 obj <>/Filter/FlateDecode/ID[<83C04542AF040F4C833A7DC507AC7EE9><9975C82B1E27C340964B5370330FFFE6>]/Index[2225 55]/Info 2224 0 R/Length 124/Prev 708226/Root 2226 0 R/Size 2280/Type/XRef/W[1 3 1]>>stream Passive solar designs typically employ large south facing windows with a high SHGC and overhangs that block sunlight in summer months and permit it to enter the window in the winter. 0000058589 00000 n North windows get almost no direct sunlight, so would be less of a problem. Our energy use for the area is almost off the chart lower than other homes mainly due to passive solar design at not much/or no higher cost than conventional. Your home and the Colorado passive solar house I designed and built seem quite similar in construction. (10) Calculate solar heat gains when designing, and compare to heat losses. F HUrF}WoND{_2#J$v:>-%uE">Tw[~Aq}$,N.7n@0v]Av8`o 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. 0000055475 00000 n 0000011400 00000 n 0000058060 00000 n At the bottom, Anchorage is the only city that has average net heat losses through south-facing windows. Wall CLTD selection. (2) To exploit solar heat gains from windows in mid-winter (and minimize heat gain in summer), we can, as much as practical, locate more and larger windows facing within 15 degrees of south, and try to reduce the glazing on walls facing north and west (and perhaps east). hbbd```b``v ;+) D,`RD&`!=D)`sJAdLdtDD2MU'I%R0H2Nd32p]4u~>0 ) 0000010091 00000 n (14) Exploit sustainable solar heating to lower the buildings heat load, utility bills, and supplementary space heating systems. For more information about SHGC and windows, see. [1] [5] The second factor is the CLF, or the cooling load factor. South-facing windows produce the most natural daylighting and solar heat gain from the month of September through the month of April. - Jeff Pendl, Enervision, Cincinnati OH. /Font The amount of solar gain a space experiences is a function of the total incident solar irradiance and of the ability of any intervening material to transmit or resist the radiation. by A Bhatia Cited by 44 - Thermal Transmittance or Heat Transfer Coefficient (U-factor) - is the rate In determining the heating load, credit for solar heat gain or internal heat . Providence, R.I., is not unique among northern U.S. cities. The windows specifications used here might be typical for a Pretty Good House design, being relatively high-performance windows but in the affordable range. 0000022215 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). Labels on products sold in markets outside the United This information in an aid in choosing the best direction and size of windows facing different directions. Two cities along the Pacific northwest coast (Portland, Oregon; and Seattle). /Annots 26 0 R %%EOF 0000022887 00000 n In the context of passive solar building design, the aim of the designer is normally to maximize solar gain within the building in the winter (to reduce space heating demand), and to control it in summer (to minimize cooling requirements). A U-factor of U-0.24 isn't bad, by the way. >> 0000008843 00000 n Will be adding solar panels on our large south facing roof when our city, state and utility stop punishing those with a solar tax who have. 0000041841 00000 n 0000047743 00000 n https://www.greenbuildingadvisor.com/homes/passive-solar-home-1980s transmitted portion of the solar heat gain coefficient is given by:[4], T 0000049715 00000 n For some locations, the heat is more pronounced and longer in duration than the short months of frigid temperatures with little snow. 0000041586 00000 n 0000025308 00000 n The Climate Zone 5 site has 5,600 heating degree days. 0000009311 00000 n Solar heat gain factor btu/hr calculator. 0000023071 00000 n 0000026274 00000 n SHGC vg = The solar heat gain coefficient of the vertical fenestration. Table 3 shows the net solar gain and value of solar gains in northern U.S. cities. CCPA | (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. Our property has some young-ish maples that are already 30' tall and are perfect for transplanting into the exact spot that we need to maximise winter gains and reduce summer gains. (7) East-facing windows provide sunlight early in the morning when a house interior is the coolest, so they are more useful than west-facing windows. /C2_2 13 0 R Be sure to educate yourself and to work with a professional installer for your project. 0000051730 00000 n The data on solar heat gains is summarized in Figure 2, below. 0000027405 00000 n 0000043781 00000 n What about glare? d This label displays AL in U.S. units. Most manufacturers worked to retrofit products to meet the new and more stringent standards. 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. This Solar Value Index uses south window glazing net BTUs of heat per day per square foot of glazing, and multiplies by the Heating Degree Days and by the price of electricity. 0000012792 00000 n Even for east- and west-facing windows, losses exceeded solar heat gains except for Denver. 0000040713 00000 n Vinyl windows are generally made of one continuous piece. 0000036216 00000 n /Parent 25 0 R 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. endstream endobj 701 0 obj<> endobj 702 0 obj<> endobj 703 0 obj<>stream ( Solar heat gain coefficient or SHGC primarily reflects the percentage of solar radiation or sunlight admitted through a door, skylight, or a window, either directly or absorbed, only to release a fraction of heat inside the house to keep it warm. /Contents 24 0 R Column 7 shows the percentage of the total amount of solar gain that comes from the south-facing glazing. We don't seem to have an issue with glare. Robert 0000053548 00000 n Very helpful Windows, doors, skylights can gain and lose heat through: These properties can be measured and rated according to the following energy performance characteristics: NFRC labels on window units give ratings for U-factor, SHGC, visible light transmittance (VT), and (optionally) air leakage (AL) and condensation resistance (CR) ratings. Solar Pathfinder 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.