solar heat gain factor table solar heat gain factor table

Reflectivity can be modified through the application of reflective metal oxides to the surface of the glass. If you started shopping prior to January 1, 2016, then you might notice some of the windows you were considering buying no longer carry the Energy STAR sticker. Grid Type . 0000052473 00000 n We would agree heat loss and solar gain calculations should be done to optimize any home design. %PDF-1.6 % 0000049162 00000 n SHGC is expressed as a number between 0 and 1. Malcolm. Response to Davor Radman 0000029882 00000 n 0000060982 00000 n 0000030709 00000 n 0000011631 00000 n Unfortunately, whatever shading is caused by these roof overhangs also causes just as much shading on April 21st (two months before June 21st) as two months after (August 21st). (10) Calculate solar heat gains when designing, and compare to heat losses. 0000034200 00000 n ( 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 Heat-Gain Coefficient Ratings for Windows by Nick Gromicko, CMI The amount of solar radiation that can pass through a window or skylight can be measured in terms of its solar heat-gain coefficient, or SHGC. Column 9 shows the net heat gain per day for south-facing windows (which is the solar heat gain minus the heat loss). 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. Thank you for sharing your thoughts, Bob. high SHGC options 0000037104 00000 n 0000010553 00000 n Should homes with floor joist/subfloors opt for tile over wood? Is this really necessary? Other internet data sources may include somewhat different data, but the patterns of data would lead to similar conclusions. 0000053548 00000 n /BleedBox [0.0 0.0 612.0 792.0] 0000057926 00000 n Solar Heat Gain Coefficient measures how well a product can resist unwanted heat gain, which is especially important during summer cooling season. 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. 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. We designed it to be in east west direction, and on the south side we have a large 2.5m wide doors. I found it both interesting and very useful. = The solar heat gain coefficient of the skylights. http://www.vitrowindowglass.com/lowe_glass/sungate_500.aspx. 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). 0000054052 00000 n This is a huge house over 10,000 sq ft with 1300 sq ft of double glaze windows. *dPeU|A#rJ]dwiuEZDu-KIVc"*f}*%,?bAL& GH D. 0000023071 00000 n 0000032457 00000 n In colorado I found Milgard and Pella had high SHGC, low E options. 0000030815 00000 n Which design principles from the 1970s are worth retaining, and which should be discarded? 5. % Table 2 lists solar gain data for the 22 northern U.S. cities. As well, 3 years ago, having been so pleased with the shutter effect, I built a "low mass, super insulated south facing solar porch. /TT6 17 0 R I enjoyed the bright sunlight and warm interior temps mid-winter too. 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? 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. n In June, the sun is closer to overhead at noon, so south windows have far less solar heat gain. But hey nothing is perfect, so architects and builders could design roof overhangs to reduce summertime overheating. 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. 0000045401 00000 n /GS1 5 0 R 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 . 0000031652 00000 n /TT0 23 0 R A new, affordable but well-insulated window (with cellular blinds used at night) would attain values similar to those listed in the table. Daylighting is good, and solar heat gain is good in winter and not good in the hot summer. ( xref In this example, of the window is covered with the venetian blind and is not; therefore, the solar heat gain factor equals of the overall factor + of the glass factor. 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. 0000056639 00000 n In Table 6, note that light from west or east facing windows in summer, is about the same as south-facing windows mid-winter. 0000011862 00000 n << on the climate, summer and winter fuels costs, and I will quantify solar heating potential by looking at climate data for 22 large cities across the northern U.S. 0000023641 00000 n 0000034610 00000 n 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. trailer 0000060426 00000 n between 0 and 1. Blocking solar Taking account of heat losses from the windows produces much more extreme results favoring south-facing glazing. 0000028760 00000 n 0000014163 00000 n /ColorSpace 27 0 R If you were to draw a Dec 21st shading line for the top of the window, then draw a shading line for June 21st from the bottom of the window, the point of intersection could be used to set the lowest, farthest out point of the roof overhang. 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). East- or west-facing windows produce the most heat gain from May through August. Again, it would reflect off the floor and other surfaces to diffuse the light. Additionally, the homeowner may choose to augment solar heat coming in the windows with exterior awnings or interior window blinds or curtains. Many computer programs make the job easier by calculating solar heat gain for you. Thanks for your comments. Will there be sun in the eyes of people sitting on the north side of the table during winter? The lower the number, the less you'll spend on cooling. The U-Factor works in conjunction with the Solar Heat Gain Coefficient (SHGC). The cost-effectiveness of solar heating varies among regions as well. Get building science and energy efficiency advice, plus special offers, in your inbox. Tile floors over wood doesn't provide much thermal mass (about 1/2" vs. 4" slab), but more than wood floors. Winter temperatures and cloudiness are major determinants of the potential and the cost-effectiveness of exploiting solar heat gain for space heating. This may help break up the glare. If your TV screen is in direct sunlight, it would be difficult to see the screen. Extending them would have an effect on the top of the window but not extend very far down the window. 0000051467 00000 n 0000052997 00000 n (3) Overall, unobstructed south-facing windows gain more heat than they lose during mid-winter in almost all U.S. climates. 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. 0000050037 00000 n 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. At the bottom of the table, the yearly gains are totaled for south-, north-, east-, and west-facing windows. Only one image can be added per comment but you can post as many comments, and therefore images, as you like. Turtle Code . But it might be a good compromise. Long stretches of overcast days produce large heat losses through large windows, with minimal solar heat gains to compensate. The sun rises in the east, goes overhead, then sets in the west, with little sunlight directly striking a south-facing wall or window. <]>> 0000053260 00000 n Seattle, Washington. b +{roFw@Qv.Pb=Z"3>!06&rhS8EnVw\/bw +rt|bSL6),W=^O *cAL^u'MH} ^D;p.'*{6OQYbS2tAD2)T=z 0!"Tl,|Am5q/Up+XwNM7}!/;yy6Q@=vjI~}krN>+e_CC-ccB: p7B . This article notes the importance of using south-facing windows to capture warmth (and natural lighting) in winter, yet not suffer as much heat gain in summer (vs. west and east-facing windows). qog7/f8S0f|+Ca(zS{ /IQW:8p=~cn7y 8,+!H6*"rd%oBT$DY^V7E aO/CZMI>*V2hxErMQX{fNFE DnAb Thank you Bob for sharing this very thorough article! 0000032190 00000 n Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Here, is the wavelength of radiation and is the angle of incidence. At What Point Is It Worth Replacing Windows? The larger the net solar gains, and the smaller the winter heating needed, the better the score on the index. This is a particular concern in hot, tropical climates such as southern Florida, Georgia, Texas and other states in that experience extreme heat. This is a very basic question I confess not knowing the answer to. AL, the better a product is at keeping air out. We have about 2' overhangs on all south facing windows and doors which work well in this latitude. 0000029142 00000 n 0000019823 00000 n For more information, see All About Glazing Options. South-facing windows produce the most natural daylighting and solar heat gain from the month of September through the month of April. 0000008999 00000 n The higher the number, the more light transmitted without adding excessive amounts of heat. Thirty-five years ago, I designed and built a classic passive solar home in Colorado. 0000043411 00000 n (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. /XObject Generally she, me and the cat sit in the sun if we can. Columns 3-6 lists the daily amount of solar heat gain in January, per square foot of glass, for windows facing south, east, west, and north (and the total of all four), respectively. 0000054151 00000 n [For those unfamiliar with the terminology The solar radiation amount depends on the orientation of the surface, solar altitude angle, and solar azimuth angle. A og = The skylight area. Key issues to be learned: a. Range: 0-1 Look for: Low numbers Air Leakage measures how much air will enter a room through a product. 0000035147 00000 n The solar transmittance of a window glazing or window is the percentage of visible and near-infrared light that passes directly through a window. 0000012329 00000 n 0000009779 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. 0000054894 00000 n The SHGC measures how much of the sun's heat comes through the window. /Metadata 9 0 R 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 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. Kansas City and cities along the northeast coast also look promising for wintertime daylighting, space heating, and PV. We don't have extensive open space, placing furniture near windows and glass doors. ( The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article. 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. Low-E Type . 0000057764 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. My great aunt used to live with family in Oregon, but had to live elsewhere during the overcast winters there. sketchup (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. 0000011785 00000 n 0000009467 00000 n The data on solar heat gains is summarized in Figure 2, below. 0000046682 00000 n In both cases, NFRC standards outline the procedure for the test procedure and calculation of the SHGC. 0000052649 00000 n The overall shading coefficient is thus given by the ratio: S Locations that lack significant net solar heat gain, or that require a lot of wintertime heating, score lower on this index. 0000018332 00000 n The NFRC label provides a reliable way to determine a window's energy properties and to compare products. 0000053434 00000 n 0000020608 00000 n The primary metric in opaque components is the Solar Reflectance Index which accounts for both solar reflectance (albedo) and emittance of a surface. {\displaystyle E(\lambda )} Wall CLTD selection. For those trying to figure out directions and overhang sizes and angles, the best tool is the Solar Pathfinder and many new apps like that which show all angles and azimuths of the sun for any location throughout every day of the year. 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. Depending on how many changes a manufacturer had to make, it could have greatly impacted the retail price of your window replacement installation. N CCPA | 0000008360 00000 n U-Factor and the Solar Heat Gain Coefficient (SGHC). Go . 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. In this article, Window Joe guides you to thefactors to consider then determining the best SHGC for your window replacement project. For January solar heat gain from south-facing windows, the highest numbers are triple the lowest. {\displaystyle T=\int \limits _{350\ nm}^{3500\ nm}T(\lambda )E(\lambda )d\lambda }, Here Different types of glass can be used to increase or to decrease solar heat gain through fenestration, but can also be more finely tuned by the proper orientation of windows and by the addition of shading devices such as overhangs, louvers, fins, porches, and other architectural shading elements. Florida Energy Code . Column 7 shows the percentage of the total amount of solar gain that comes from the south-facing glazing. One quick note: It appears that you are assuming a SHGC of 0.5 for the heat gain calculations. /TrimBox [0.0 0.0 612.0 792.0] Gases are added between the layers of glazing to further increase insulation, the gases are heavier than air, making it less likely air will penetrate the glazing. optional rating, and manufacturers can choose not to ) ( 0000010784 00000 n 0000040162 00000 n 0000033229 00000 n This shows that a good percentage of the gains from south windows are retained, despite losses, except in Anchorage, Alaska. The heat gain through a wall or roof in summer is: . 0000036698 00000 n 3500 0000009623 00000 n For a classic direct-gain passive solar design with a south-facing window wall paired with thermal mass, the answer seems to be no or not easily. Five cloudy days in a row is not unusual for New England, for example. North latitude location (degrees north of the Equator). 0000050946 00000 n Designers and builders can use higher solar heat gain windows on south-facing windows and higher R-value (lower U-factor) windows on north, west, and east-facing windows to further increase solar gains and reduce heat losses overall. 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 lowest numbers are about double the highest. Many more cities in the U.S., Canada, Europe, and elsewhere could be added to this list to compute comparative solar heating ease and value. 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. 0000042551 00000 n 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. As such, the Energy Star Factors are as follows: When windows are rated for heat transference, the information may be for: In general, the values for the whole window will appear lower than for the center of the glass readings. At solar noon on Dec 21st, light from a south-facing window at typical height would cast direct sunlight about 13' into the home's interior. And if you design for best wintertime performance, you will get undesirable solar heat gain in the late summer. 0000008432 00000 n Despite having minor differences in modeling standards compared to the SHGC, the two values are effectively the same. 0000054427 00000 n Some important factors for the amount of solar heat gain are the: Table 2 shows the amount of solar heat gain per square foot of window glass for the cities listed previously. SHGC & U-Factor Tool. 4. In direct solar gain systems, the composition and coating of the building glazing can also be manipulated to increase the greenhouse effect by optimizing their radiation properties, while their size, position, and shading can be used to optimize solar gain. -- "Passive solar" requires sunlight to shine on thermal mass (e.g., concrete slab floors, masonry walls, large containers of water) so that most of the solar heat gain is stored in the thermal mass, to avoid overheating the interior air during the day. . I used this website to analyze my site. https://www.greenbuildingadvisor.com/homes/passive-solar-home-1980s 0000010938 00000 n /TT1 22 0 R 0000047854 00000 n 0000055259 00000 n /GS0 3 0 R 0000029050 00000 n 0000037935 00000 n My wife has a small office at work with lots of south facing glass and pulls the shades on sunny days. Its no accident that Cape style homes appeared in winter-dominated climate up north; and southern plantation style homes with big windows, big overhangs and wide porches in the cooling dominated climate of the southern US. I think glare would be a bigger problem if you were sitting in direct sunlight, not at the other end of the room. Map. 0000052561 00000 n U-factor = 0.5, or R-2, very poor by today's standards. 0000041718 00000 n 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. AL is an . 0000037504 00000 n 0000059851 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. 0000060317 00000 n 0000057378 00000 n 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. 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. 0000038526 00000 n 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. 0000030116 00000 n 0000025308 00000 n Very helpful 0000060771 00000 n 0000029981 00000 n 0000021486 00000 n Solar gain can also be transferred to the building by indirect or isolated solar gain systems. Terms | 0000010168 00000 n There is more total sunlight shining in summer (June to August in the northern hemisphere) than mid-winter (December to February). But if you really don't want to move your TV and have glare issues, besides curtains or shades, you could use other ways to block light from reflecting off your TV screen or creating too much glare competing with the TV in your viewing direction. 0000038900 00000 n Is it possible to determine an appropriate period of shading for summertime sun that also allows peak wintertime solar gain? 0000026274 00000 n 0000036575 00000 n 0000044168 00000 n In essence SC is an index of the effective solar rejection performance of a given glass type. 0000034904 00000 n 0000037304 00000 n Solar Pathfinder To maximize wintertime interior daylighting and solar heat gains, south windows should be larger in size or in number than windows facing other directions. %%EOF 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. The windows specifications used here might be typical for a Pretty Good House design, being relatively high-performance windows but in the affordable range. 0000008843 00000 n What Is Solar Heat Gain Coefficient? 0000040713 00000 n Simple 2x6 with exterior 1" aluminium skinned polyiso foam, south facing rear with larger windows and doors, few windows on other walls. The highest percentages are highlighted in green, and the lowest red and pink. potential for daylighting. 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. SHGC can either be estimated through simulation models or measured by recording the total heat flow through a window with a calorimeter chamber. 0000048656 00000 n I have 35 year old home-made fixed glass windows on the south side of my house that need to be replaced. Unlike the upstairs, the first floor has a tiled, concrete floor (with large amounts of thermal mass) to absorb heat to radiate later, stabilizing interior temperature fluctuations. /TT2 21 0 R 0000024129 00000 n Table 2 lists solar gain data for the 22 northern U.S. cities. Its important to insulate thermal mass well, but Passivhaus insulation levels might be overkill in a passive solar home. 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. 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).