solar heat gain factor table

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. It ranges from 0 to 1 and refers to the solar energy transmittance of a window or door as a whole, factoring in the glass, frame material, sash (if present), divided lite bars (if present) and screens (if present). Those panels closed during the 15 hour nights of winter make far more difference than thermal mass or solar gain. -- Seasonally, the coldest temps of winter, and the hottest temps of summer, lag the sun's seasonal changes in path and intensity. Hours earlier and later, the light could extend further but would be less intense. Cost of electricity varies over time as well. /ArtBox [0.0 0.0 612.0 792.0] Fortunately, these days, thermal breaks which are small pieces of plastic, are built into the window frame, to "break" the conductivity, and therefore do a better job of insulating by disrupting the heat transfer through the frame material. 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. 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). Blocking solar 0000053260 00000 n 0000008921 00000 n You might have to order windows, rather than just the sealed double or triple-pane IGUs. 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. 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). << 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 . I am having a hard time determining which specification to use when calculating solar heat gain through windows. 0000054894 00000 n What Is Solar Heat Gain Coefficient? December 21st there is no shading from overhangs. (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). 0000048271 00000 n Malcolm. = The solar heat gain coefficient of the skylights. 0000029773 00000 n 0000036472 00000 n High SHGC glazing 0000012014 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. >> 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. Table 4 only looks at solar heat gains without considering losses. 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. 0000055259 00000 n Martin I agree some passive solar homes did create window walls of south-facing glass, likely without quantifying solar heat gain beforehand. 0000049380 00000 n /BitsPerComponent 8 %%EOF NAAP Labs Motions of the Sun Simulator. how glass is used in the house design. 0000016860 00000 n (Of course you could use a light filtering curtain or shade to fix this.). SHGCs range from approximately 0.70 for single clear glass to 0.31 for low emissivity glass (toned or coated glass). Solar Heat Gain through Glass Internal Heat Gains from People, Lights, and Equipment ASHRAE Zones for Solar Cooling Load (SCL) Factors for Glass are based on: Floor Level and Room Location Single Story Building (Table 8.8-A) Top Floor (Table 8.8-B) First / Ground Floor (Table 8.8-C) Middle Floor (Table 8.8-D) Interior Rooms (Table 8.8-E) 0000024129 00000 n 0000030116 00000 n Passive solar heat gain through large south-facing windows provided most of the winter space heating energy. Response to Davor Radman For more information about SHGC and windows, see. U-Factor and the Solar Heat Gain Coefficient (SGHC). In Table 6, note that light from west or east facing windows in summer, is about the same as south-facing windows mid-winter. 0000045710 00000 n Vinyl replacement windows, those with a vinyl window frame, are a great economic choice and also provide great energy efficiency for your home, lowering bills. This simple computation provides a metric to rate locations for ease of using passive solar or solar tempered winter space heating. That would provide ideal sun shading for those dates at solar noon. 0000030489 00000 n 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. 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. A product with a higher VT transmits more visible light. 0000050463 00000 n 0000051730 00000 n 2225 0 obj <> endobj 0000060982 00000 n 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. The lower the SHGC, the better 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. If windows get direct sun in mid-winter, solar heat gain might provide the majority of needed space heating energy for a well-insulated, airtight building. So you could have a solar-tempered interior with tile or wood floors over wood frame construction, but not fully passive solar, unless you also have other significant thermal mass elsewhere. 0000039839 00000 n 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). 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. 0000021316 00000 n /XObject 0000053840 00000 n 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 You will not receive a notification when a response to your question has been posted. = 0000040713 00000 n For east- and west-facing windows, overhangs are not particularly effective in preventing unwanted heat gain. Yes the analysis assumed SHGC=0.5 for all windows, which wasn't stated earlier in the article. typically fall in a range between 0.1 and 0.3. 0000008765 00000 n First, thanks for sharing your many helpful comments and ideas on GBA articles on Q&A. ) 0000023982 00000 n 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. 0000040580 00000 n The solar heat gain coefficient (SHGC) is an index describing the proportion of light that is let through a window. In the early days, computer screens had hoods that blocked light from above and the sides. The cost-effectiveness of solar heating varies among regions as well. =J04pajo/7iv}F1&04 kkAVF/n0 0000009623 00000 n About | Being in a solar home definitely cures the winter blues and Seasonal Affective Disorder (SAD). Thank you for sharing your thoughts, Bob. Glazing with lower U-factors (higher R-values) for north- and west-facing windows tend to have lower SHGC. [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. qog7/f8S0f|+Ca(zS{ /IQW:8p=~cn7y 8,+!H6*"rd%oBT$DY^V7E aO/CZMI>*V2hxErMQX{fNFE DnAb 0000039534 00000 n . September 1st/March 1st modelling revealed modest exposure as the sun has dropped enough to negate most of the overhang benefit. Though transparent building materials such as glass allow visible light to pass through almost unimpeded, once that light is converted to long-wave infrared radiation by materials indoors, it is unable to escape back through the window since glass is opaque to those longer wavelengths. 0000036366 00000 n 0000024478 00000 n , 0000021224 00000 n Solar heat gain is calculated with the solar shading coefficient and the solar heat gain factor (not to be confused with the solar heat gain coefficient - see below). Some important factors for the amount of solar heat gain are the: Table 2 shows the amount of solar heat gain per square foot of window glass for the cities listed previously. So if you have your heart set on high-solar-gain glazing, you should keep looking. , Note (in the last two columns, #9 and #10) that Denver has better net solar heat gains than anywhere else in the list. A new, affordable but well-insulated window (with cellular blinds used at night) would attain values similar to those listed in the table. It is easier to maximize wintertime solar heating in some climates than others. Privacy | We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. 0000060552 00000 n Go . 0000035750 00000 n The value of the shading coefficient ranges from 0 to 1. Adjustable awnings, curtains, window shades, exterior shutters, or even deciduous trees, or other shading methods, can provide more flexible and more complete shading than a fixed roof overhang. hbbd```b``A$cXDDr@3N,IF@L@s&00Lg`` 0000039316 00000 n The sun is even lower before and after noon. -- "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. hb``` , b-0.X)![)?OXjL ~E-AzMVk+u9:MX@qKpDa%E={d C=H:]JxrWur{. Can I Get Replacements For Odd Size Windows? 154 0 obj <>/Filter/FlateDecode/ID[<7A4022D89D0845C14B1934A88527FBA7><3CC1F5B57CF1284BA9D476A461DF3FBB>]/Index[143 23]/Info 142 0 R/Length 76/Prev 918310/Root 144 0 R/Size 166/Type/XRef/W[1 3 1]>>stream /TT1 22 0 R 0000036216 00000 n It is important to note that the standard SHGC is calculated only for an angle of incidence normal to the window. Those won't work very well for passive solar homes. Since I built that passive solar house back in the 1980's, there were no low-e windows available. Currently, there's plenty of software and consultants to perform calculations, or do it yourself with spreadsheets. 0000011246 00000 n My wife has a small office at work with lots of south facing glass and pulls the shades on sunny days. The NFRC label can be found on all ENERGY STAR qualified window, door, and skylight products, but ENERGY STAR bases its qualification only on U-factor and solar heat gain coefficient ratings, which are described below. Solar heat gain coefficients are expressed as decimals from 0.00 to 1.00. 0000021721 00000 n 0000029557 00000 n In passive solar and solar-tempered homes, typically there are more or larger windows facing south, and fewer or smaller windows facing other directions. n So I don't think glare around the dining table on the opposite side of the room would be much of a problem. Solar Heat Gain Thru Glass Thermopane windows have no sash; therefore, sash area correction = 1/.85 (bottom Table 15). Its important to insulate thermal mass well, but Passivhaus insulation levels might be overkill in a passive solar home. 0000058589 00000 n 0000038191 00000 n /BleedBox [0.0 0.0 612.0 792.0] 0000034904 00000 n But hey nothing is perfect, so architects and builders could design roof overhangs to reduce summertime overheating. 0000053434 00000 n Kansas City and the seven northeastern seaboard cities do almost as well with average net solar heat gain in January. Solar heat gain factor btu/hr calculator. 0000046898 00000 n 0000033707 00000 n Roof overhangs can shade the top of a window yet allow solar gain at the bottom. 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. One shading method is to have roof overhangs stick out above the south-facing walls enough that they cast shade on south-facing windows in late August. 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]. (8) Unobstructed west-facing windows produce heat gains mostly in the afternoon. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun. You also may be able to increase the brightness of your screen, which some computer screens do automatically (depending upon ambient light levels). 643 0 obj <> endobj /TT2 21 0 R The U-Factor works in conjunction with the Solar Heat Gain Coefficient (SHGC). 0000031213 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.). /Length 2106 143 0 obj <> endobj 0000048946 00000 n 0000052240 00000 n This quantity includes both energy that is transmitted directly through the glass as well as energy that is absorbed by the glass and frame and re-radiated into the space, and is given by the following equation:[4], F 0000029142 00000 n South-facing windows produce the most natural daylighting and solar heat gain from the month of September through the month of April. Worth remembering that those early-'80's houses are one of the main reasons we are having such fruitful discussions today! East- and west- facing windows gain far more heat than south-facing windows during the summer months, until late August. 0000037104 00000 n 645 0 obj<>stream [5], Apart from windows, walls and roofs also serve as pathways for solar gain. 0000059464 00000 n 0000045617 00000 n Long stretches of overcast days produce large heat losses through large windows, with minimal solar heat gains to compensate. 0000011400 00000 n 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. SHGC is expressed as a 0000034811 00000 n I would hope that we learn to manage solar gain better, to reduce our dependence on auxiliary heating and air-conditioning, on fossil fuel usage, and to reduce utility costs for those who can't afford it. 0000048656 00000 n 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. , To model anything, you have to make some reasonable assumptions. 5. ( This is a huge house over 10,000 sq ft with 1300 sq ft of double glaze windows. % 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. 0000038387 00000 n They also recommended ceilings be white, to reflect light back to the floor. -Bob Opaluch designed and built a passive solar home in Colorado, renovated two homes in Massachusetts, and has many years of renovation, maintenance, repair, and furniture-building experience. It was an experiment, and I can now, after 5 years, say it exceeded my expectations. n 0000033121 00000 n Too much south-facing glazing can make a home very uncomfortable and unpleasant in February and March. Consequently, south-facing windows capture far more light, and thereby produce far more solar heat gain, than windows facing other directions. Our Comment Box is provided by Countable Web Productions countable.ca, Click to Show or Hide Citations & References, Heat Exchangers for Solar Water Heating Systems, Heat-Transfer Fluids for Solar Water Heating Systems, Solar Water Heating System Maintenance and Repair, Solar Water Heating System Freeze Protection, Scaling and Corrosion in Solar Water Heating Systems, Solar Heat Gain & Windows, the facts about, HOME INSPECTION EDUCATION COURSES (Canada), HOME INSPECTION EDUCATION: HOME STUDY COURSES, Ar-Lite Panelcraft, Inc., 13030 Wayne Rd., Livonia MI 48150, 2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707, 2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover). There is more total sunlight shining in summer (June to August in the northern hemisphere) than mid-winter (December to February). So overhangs tend to keep the house cooler in the Spring as well as late summer. We want to keep our solar heat, not lose it back through the same window that brought it in. I understand that some passivhaus builders pour 8 inch thick concrete slabs for heat distribution from solar gains. (10) Calculate solar heat gains when designing, and compare to heat losses. 0000050787 00000 n (3) Overall, unobstructed south-facing windows gain more heat than they lose during mid-winter in almost all U.S. climates. 0000041841 00000 n Energy Star Zone . It differs from active solar heating which uses exterior water tanks with pumps to absorb solar energy because passive solar systems do not require energy for pumping and store heat directly in structures and finishes of occupied space.[12]. 0000052109 00000 n 0000047632 00000 n ( We would agree heat loss and solar gain calculations should be done to optimize any home design. 0000047980 00000 n 0000014397 00000 n 0000045996 00000 n 0000044552 00000 n 0000009857 00000 n For windows, skylights, and glass doors, a U-factor may refer to just the glass or glazing alone. See Table 6 for details. [13] When designed properly, this can modulate temperature fluctuations. >> 0000032457 00000 n /Resources A g-value of 1.0 represents full transmittance of all solar radiation while 0.0 represents a window with no solar energy transmittance. Conversely, if your are trying to keep your home cool in a hot climate, adding the intensity of the sun's warmth could create a suffocating situation, particularly if the energy is trapped inside by an incorrect u factor. 0000036017 00000 n xref 0000041586 00000 n 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. ( 0000014495 00000 n I know some others disagree with this perspective. 0000011938 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. Annual heating degree days (HDD), an index of the amount of heating needed each winter season. Overcast winter conditions are more likely for cities west of large bodies of water. . 0000043512 00000 n 0000043781 00000 n 0000038067 00000 n 0000028760 00000 n North latitude location (degrees north of the Equator). /ColorSpace 27 0 R Varying window sizes and numbers can increase or decrease solar gains and heat losses to affect overall energy performance. 0000023071 00000 n Is It Easier To Clean Replacement Windows? 0000021621 00000 n Passive solar heating is a design strategy that attempts to maximize the amount of solar gain in a building when additional heating is desired. 0000026181 00000 n /Type /Page 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. Figure 1 depicts the grouping of northern U.S. cities by solar heating potential, as listed in Table 1. T The overall shading coefficient is thus given by the ratio: S 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. Appendix D, Degree Day and Design Temperatures. Rather than looking for a window with a high U-factor, you should be looking for a window with low U-factor. Still, don't have AC. 0000010013 00000 n Solar, wind or other renewable energy source supplies not less than 80 percent of the energy for service water heating. high SHGC options The solar transmittance of a window glazing or window is the percentage of visible and near-infrared light that passes directly through a window. Robert Solar gain is most frequently addressed in the design and selection of windows and doors. /TT7 16 0 R ) endstream endobj 701 0 obj<> endobj 702 0 obj<> endobj 703 0 obj<>stream 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. >> SHGC vg = The solar heat gain coefficient of the vertical fenestration. 0000058680 00000 n http://www.cardinalcorp.com/products/coated-glass/loe-180-glass/, PPG Industries manufactures two low-e/high SHGC products: Sungate 500 and Sungate 100 window glass with SHGC of about 0.7. I'm old enough to remember the passive solar homes of the 1970s and 1980s. 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. You want to shade your south-facing windows from the sun to avoid solar heat gain.