If glare is an issue, you could manage lighting levels with sheer curtains or partially drawn "buttom up, top down" cellular shades. 0000025618 00000 n 0000010938 00000 n endobj Much of the population of northern U.S. live in or near these metropolitan areas. , hbbd```b``A$cXDDr@3N,IF@L@s&00Lg`` ) Solar, wind or other renewable energy source supplies not less than 80 percent of the energy for service water heating. 0000023071 00000 n Adjustable awnings, curtains, window shades, exterior shutters, or even deciduous trees, or other shading methods, can provide more flexible and more complete shading than a fixed roof overhang. 0.80 0.70 0.70 . 0000028135 00000 n So I'd recommend designing overhangs for minimal shading mid-winter, and not worry so much about summer (for winter-dominated northern climates). 0000048108 00000 n Buffalo, Pittsburgh, and cities in the Pacific Northwest do not do as well as most other cities. Is it, say, the angle of the sun at 11:00am and 1:00 pm? In the summer, that afternoon heat gain typically is undesirable. In this article, Window Joe guides you to thefactors to consider then determining the best SHGC for your window replacement project. Glare Does one use visible light transmission or some other figure? Those panels closed during the 15 hour nights of winter make far more difference than thermal mass or solar gain. If the TV were on the same wall, next to a south window around noontime mid-winter, the light from the window would be likely be much brighter than your TV or computer screen. 0000023337 00000 n 0000041841 00000 n 0000035147 00000 n 0000049884 00000 n 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. 0000020469 00000 n Column 7 computes an index of how easily solar heat gains from window glazing can be used to heat a building for each of the cities. Heat gains from windows can contribute to overheating. Generally she, me and the cat sit in the sun if we can. 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). glazing Key issues to be learned: a. 0000060083 00000 n 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. They can work well in late summer hot weather, yet not block the sun on cooler days in the Spring. The first six columns list the same 22 U.S. cities and other previously displayed data, which are helpful in determining the value and ease of using solar heat gains for space heating. 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. South-facing windows gain about 3.5 times as much light and solar heat gain per square foot than either east- or west-facing windows in December and in January. Those screens weren't very bright. 0000039175 00000 n 0000050694 00000 n North windows are a great example, since with the exception of dawn and sunset around June, there's no direct light through north-facing windows. 0000045710 00000 n Additionally, the homeowner may choose to augment solar heat coming in the windows with exterior awnings or interior window blinds or curtains. Personally, I think we should focus on better window shading methods than roof overhangs. The window projection factor shall be . 0000048656 00000 n N 5. 0000030489 00000 n 0000040295 00000 n 0000036216 00000 n Many had problems with glare. I found it both interesting and very useful. Thanks for your comments. 0000026777 00000 n The warmer HDD numbers are highlighted in tan, and colder are highlighted in ice blue. [8], A conversion from SC to SHGC is not necessarily straightforward, as they each take into account different heat transfer mechanisms and paths (window assembly vs. glass-only). southernwalls see about 6" of sun exposure at the bottom of each window. Is It Easier To Clean Replacement Windows? Currently, there's plenty of software and consultants to perform calculations, or do it yourself with spreadsheets. 0000052109 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. For all other areas, solar heat gain through south-facing windows exceeds the heat lost through the glass. 0000046325 00000 n /GS2 4 0 R Winter design temperature (F), or coldest expected temperature.. 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. Response to Davor Radman The following web resources were useful for gathering climate and solar gain data. 0000035512 00000 n 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. This article explores the viability of passive solar and solar-tempered space heating in northern U.S. regions and metro areas. Source: Text Bob Fegan 12/2008; Table on BTU per person heat gain from www.engineeringtoolbox.com 9/2005; diagram . Whatever IGUs you might find for sale retail, please share with us. 0000022755 00000 n "oRD"wB=k:p!TcSm]L U-Factor * SHGC (Solar Heat Gain Coefficient) * Product Type * Frame Material * Air Fill Type * Impact Resistance * Series . NFRC U-factor ratings, however, represent the entire window performance, including frame and spacer material. (12) Consider different glazing for windows facing different directions. 0000047854 00000 n I enjoyed the bright sunlight and warm interior temps mid-winter too. 0000054894 00000 n Overcast winter conditions are more likely for cities west of large bodies of water. 0000020608 00000 n 0000018449 00000 n , E a9` zY ZOy 7!K?e. 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. From what I've read, slab depth beyond 4" thick doesn't get you much additional heat storage or dampening of temperature fluctuations in direct gain passive solar designs. 0000029142 00000 n %%EOF Designing south-facing roof overhangs If not, how can I find a better alternative at a reasonable price? So if you have your heart set on high-solar-gain glazing, you should keep looking. This raises the question: Could a passive solar home be built successfully and cost-effectively in other cold, northern climates climates more challenging than the sunny but cold climate of the Rocky Mountain Front Range? 0000055691 00000 n - Jeff Pendl, Enervision, Cincinnati OH. A og = The skylight area. What Is The Difference Between Convection And Drafts? 0000051214 00000 n Range: 0-1 Look for: Low numbers Air Leakage measures how much air will enter a room through a product. 0000059373 00000 n /BitsPerComponent 8 0000008611 00000 n Elevates mood in winter 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. 0000060877 00000 n 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. 8 times table chart up to 1000 . The higher its solar transmittance or solar heat gain coefficient, the better a glazing is for solar heating use. xSmHSQ~f:MLQBBQ20 XJ Solar gain is most frequently addressed in the design and selection of windows and doors. We have a passive solar house we designed and built ourselves in SE Michigan in the late 80's. Solar Pathfinder The other climate zones underwent more stringent Energy Star qualifications that took effect on January 1, 2015. Taking account of heat losses from the windows produces much more extreme results favoring south-facing glazing. For east- and west-facing windows, overhangs are not particularly effective in preventing unwanted heat gain. 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. >> The lower the SHGC, the better Finally, Anchorage, Alaska, along the far northern Pacific coast, with by far the lowest solar heat gain. Great article! Air leakage is the rate of air movement around a window, door, or skylight in the presence of a specific pressure difference across it. 0.83 0.73 0.73 . The SHGC measures how much of the sun's heat comes through the window. The lower the SHGC, the less solar heat it transmits and the greater its shading ability. 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. (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. 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. 0000048946 00000 n 0000043952 00000 n But hey nothing is perfect, so architects and builders could design roof overhangs to reduce summertime overheating. Grid Type . Column 7 shows the percentage of the total amount of solar gain that comes from the south-facing glazing. =J04pajo/7iv}F1&04 kkAVF/n0 In both cases, NFRC standards outline the procedure for the test procedure and calculation of the SHGC. 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. Like Cardinal, PPG only manufactures window glass, and I don't think sell glass units retail, just to window manufacturers. 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). In January, south-facing windows always account for more solar gain than east + west + north combined. 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. 0000047632 00000 n The intense summer sun on the east side of the building in the morning, and the west in the hot afternoon, is greater than the sunlight striking the south side. (4) South-facing windows can provide about fifteen times as much light and solar heat gain in winter as north-facing windows. 0000032810 00000 n (6) South-facing windows have less undesirable solar gain during summer than west- or east-facing windows. 0000038260 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. Should homes with floor joist/subfloors opt for tile over wood? [11] Materials with high SRI will reflect and emit a majority of heat energy, keeping them cooler than other exterior finishes. (14) Exploit sustainable solar heating to lower the buildings heat load, utility bills, and supplementary space heating systems. Used by solar PV installers for the most bang for the buck. 0000029981 00000 n The home is a three story house, with a basement comprising the bottom floor. /Contents 24 0 R /TT6 17 0 R 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. Calculating solar gains by hand is a laborious, imperfect process. 0000054052 00000 n 0000049162 00000 n Maybe we should not let the perfect be the enemy of the good. I would hope this article would lead people to consider quantifying solar gains for any type of home, not just solar-oriented designs. But maybe that's because of my partly cloudy location of zone 5 Iowa City Iowa? Other cities in the list across the Midwest and northern central U.S. get about half the net solar heat gain of Denver. 0000009467 00000 n (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. U-factor (inverse of R-value), which measures the rate of heat losses through that window to the cold outdoors. Note that air leakage also depends on proper installation of a window, which is assumed in all ratings. A product with a low air leakage rating is tighter than one with a high air leakage rating. 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. You bring up an important point. 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). You build a simple house, and then you can set your latitude, and then choose the date/hour. December 21st there is no shading from overhangs. (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. We have white walls and flat white ceilings in the main living spaces. 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. 0000037750 00000 n Column 8 computes an index of how cost-effective or how valuable solar heat gains can be for a location. Overall, it is best to take your time, build your knowledge, and scrutinize each portion of the process and product when choosing new replacement windows. /TT3 20 0 R 143 0 obj <> endobj {\displaystyle F(\lambda ,\theta )=T(\lambda ,\theta )+N*A(\lambda ,\theta )}. 0000030603 00000 n 0000019489 00000 n Despite having minor differences in modeling standards compared to the SHGC, the two values are effectively the same. "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- This label displays AL in U.S. units. . 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. 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. Rather than looking for a window with a high U-factor, you should be looking for a window with low U-factor. T 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. 0000060552 00000 n Solar heat gain coefficients are expressed as decimals from 0.00 to 1.00. (If interested, see interior photos in this GBA article: The reason Energy STAR, from the U.S. Department of Energy, designates four climate zones is to help make it easier for homeowners to know which new house windows will work in their climate. 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. 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]. 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. 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. /ColorSpace 27 0 R 0000009779 00000 n Ideally, the goal is to not block wintertime sunlight on south-facing windows. I used Google Sketchup, the free version, to roughly model shadows on my soon to be built house. In essence SC is an index of the effective solar rejection performance of a given glass type. 0000048853 00000 n 0000040918 00000 n /CS0 8 0 R The solar heat gain coefficient (SHGC) is an index describing the proportion of light that is let through a window. >> Intro to roof overhangs and shading To minimize this and reduce cooling loads, several technologies exist for solar gain reduction. 0000027861 00000 n 0000036575 00000 n 0000023459 00000 n n To perform an approximate conversion from SC to SHGC, multiply the SC value by 0.87. number between 0 and 1. 0000050037 00000 n Thank you for sharing your thoughts, Bob. In summary, there are many things to consider when choosing the best window replacement options. 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. = I bet under-insulating was also a common problem, especially for that thermal mass that serves as an overnight heating system. << Here are added factors defined by the NFRC as of 2005: Air Leakage(AL) measures how much outside air comes %%EOF /TT0 23 0 R Is this really necessary? 0000034610 00000 n 36" overhangs, 9' walls. Modeling thermal mass performance seems difficult or approximate. 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. Blocking solar The following four cities are along the north central and western U.S. (Minneapolis; Salt Lake City; Bismarck, N.D.; and Billings, Montana) . 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. 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. 0000040032 00000 n 0000008386 00000 n Roof overhangs can shade the top of a window yet allow solar gain at the bottom. /Resources F The home show in the photo used ceramic floor tile which varied in color but overall was a coffee color. Note that south-facing windows typically have solar heat gains (column 3) at least double the heat losses (column 8). As indicated in the chart below, the EPA recommends . While it isn't absolutely necessary to be so exacting when choosing new replacement windows, every little bit of energy efficiency helps when planning your window replacement project. 0000008921 00000 n So for a traditional Cape style home, the small overhang doesn't shade the windows much in any season. 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 0000050946 00000 n You might be able to find or make untreated triple pane glass units, or even try to use three layers of glass for your own site-built fixed window if you are looking for the ultimate cheap solution. , Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly. Blocking solar heat gain is particularly important during the summer cooling season. 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. 1 0 obj Being in a solar home definitely cures the winter blues and Seasonal Affective Disorder (SAD). We do have medium dark wood floors, linoleum and tile. /Length 2106 The maximum U-factor and solar heat gain coefficient (SHGC) for fenestration shall be as specified in Table C402.4. /TT7 16 0 R Terms | I changed the color of walls from off-white to the same coffee color (from advice in an interior design class). The advantages of south-facing windows become even greater when losses are incorporated. 0000051599 00000 n 0000021134 00000 n Similar analysis could be performed by using web resources to compute solar gains for windows in other orientations. << 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 . The amount of solar gain a space experiences is a function of the total incident solar irradianceand of the ability of any intervening material to transmitor resist the radiation. Kansas City and cities along the northeast coast also look promising for wintertime daylighting, space heating, and PV. U-factor = 0.5, or R-2, very poor by today's standards. As you point out, it's a complex problem to design a good south-facing roof overhang for the windows below. ( 0000045185 00000 n Map. 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. Map. 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). 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. AL rates Same for east or west-facing windows, early or late in the day, respectively. 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 . << Solar gain can have both positive or negative effects depending on the climate. 0000053637 00000 n States may display AL in metric units. My house is orientated 45* off south, with a large wall (38') with 4 large-ish windows orientated south-west, and 2 largish windows orientated south-east. MIT Press, 1992. Providence, R.I., is not unique among northern U.S. cities. /ColorSpace /GS0 3 0 R 0000033707 00000 n 0000009701 00000 n Its important to insulate thermal mass well, but Passivhaus insulation levels might be overkill in a passive solar home. You must be a magazine subscriber to access this feature. stream . We would agree heat loss and solar gain calculations should be done to optimize any home design. /ArtBox [0.0 0.0 612.0 792.0] 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{=.! Note that the photo at the top of the page shows a passive solar house from 1982. Vinyl windows are generally made of one continuous piece. 0000012727 00000 n Contrast between the direct sunlight and the TV screen needs to be avoided. 0000033028 00000 n 0000021012 00000 n It can't be a problem for north-facing windows, which receive almost no direct sunlight any time of year. 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. 0000014397 00000 n Cities in the table are listed in descending order of their mid-winter solar heat gain. Watch out: other very important factors need to be considered in arriving at an accurate picture of solar heat gain through windows. North latitude location (degrees north of the Equator). Passive solar heat gain through large south-facing windows provided most of the winter space heating energy. Passive solar heat gain almost eliminated the need for space heating on the main floor. standard low-E and about .40 for spectrally selective low- 0000041109 00000 n %PDF-1.3 % 0000038900 00000 n Be sure to read the article on u-factor as well, as it is closely related to energy efficiency in windows. (3) Overall, unobstructed south-facing windows gain more heat than they lose during mid-winter in almost all U.S. climates. 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). However, I did have problems with too much solar heat gain from west-facing windows during hot summer days. is the spectral transmittance at a given wavelength in nanometers and /Height 99 0000018593 00000 n 0000010322 00000 n First, thanks for sharing your many helpful comments and ideas on GBA articles on Q&A. To model anything, you have to make some reasonable assumptions. 0000009311 00000 n ) The cost of electricity, natural gas, or other heating fuels can impact the use of passive solar heat gains for wintertime space heating. 0000044828 00000 n Thank you so much for sharing this with us. Before choosing window locations, sizes and performance characteristics, we need to examine solar heat gains throughout the year, not just January. At What Point Is It Worth Replacing Windows? The overall solar energy gain is expressed by the solar gain factor g and is given by [Fig. Average percent of sunlight shining in January (opposite of cloudiness). The complete source for building, designing, and remodeling green homes. ) 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. The solar radiation amount depends on the orientation of the surface, solar altitude angle, and solar azimuth angle. I will quantify solar heating potential by looking at climate data for 22 large cities across the northern U.S. 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_ 1 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. /GS1 5 0 R So the cost of electricity is used to compute the value of solar heat gains in the following analysis. 0000041586 00000 n 0000041950 00000 n SHGC is expressed as a number between 0 and 1. 0000042040 00000 n 0000022599 00000 n *dPeU|A#rJ]dwiuEZDu-KIVc"*f}*%,?bAL& GH D. 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. 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.