solar heat gain factor table

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. I see lots of examples where people try things without "doing the math" beforehand. Will Vinyl Replacement Windows Stop Condensation? 0000021134 00000 n 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 ($2BLrP+Q(Iq(zj%I)%Y0T4"\2%r(D%;X%KnG;]YB#mc*AwQ}~%J@`c*KbQem&ek.ck)5F^nV_ optional rating, and manufacturers can choose not to lL)Cg4xo` =[3lhb$qrCcUT?iFgqH10L9e:Q` 8 What about glare? The lower the SHGC, the less solar heat it transmits and the greater its shading ability. 0000029882 00000 n 0000026490 00000 n To maximize wintertime interior daylighting and solar heat gains, south windows should be larger in size or in number than windows facing other directions. Solar transmittance is used to compare different types of glass. U-Factor * SHGC (Solar Heat Gain Coefficient) * Product Type * Frame Material * Air Fill Type * Impact Resistance * Series . 0000059089 00000 n West-facing windows gain that heat in the afternoon, usually during the hottest time of the day, making west-facing windows particularly undesirable unless well shaded. 0000030116 00000 n The U-Factor measures how well the window in-sulates. /GS2 4 0 R - Jeff Pendl, Enervision, Cincinnati OH. (Of course you could use a light filtering curtain or shade to fix this.). Which design principles from the 1970s are worth retaining, and which should be discarded? There are a couple of ways that glass can maintain the indoor temperatures to keep you comfortable indoors. The Climate Zone 5 site has 5,600 heating degree days. I built and installed R20-30 closing shutters both internally and externally more than 5 years ago in Western Canada at 51 latitude north. September 1st/March 1st modelling revealed modest exposure as the sun has dropped enough to negate most of the overhang benefit. I changed the color of walls from off-white to the same coffee color (from advice in an interior design class). 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. 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. We don't seem to have an issue with glare. I would hope this article would lead people to consider quantifying solar gains for any type of home, not just solar-oriented designs. This is also hugely effective. In the hotter summer season, solar heat gain through windows is usually undesirable. 0000010322 00000 n 0000057247 00000 n Glare I'm less familiar with these lighting issues, so hope someone else can chime in. Uncontrolled solar gain is undesirable in hot climates due to its potential for overheating a space. Other cities in the list across the Midwest and northern central U.S. get about half the net solar heat gain of Denver. Great article! Should homes with floor joist/subfloors opt for tile over wood? 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. IMHO the typical USA under-insulated home with oversized fossil fuel heating and AC is the failed design in need of our greatest attention. The product Explained differently, the lower the SHGC ratio, the better the new window is at blocking the sun's heat from coming inside your home, the higher the SHGC ratio, the more heat is let in to your home. (14) Exploit sustainable solar heating to lower the buildings heat load, utility bills, and supplementary space heating systems. 0000060552 00000 n 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. [13] When designed properly, this can modulate temperature fluctuations. 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. 0000012239 00000 n The SHGC measures how much of the sun's heat comes through the window. Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. Since I built that passive solar house back in the 1980's, there were no low-e windows available. 0000041109 00000 n Those panels closed during the 15 hour nights of winter make far more difference than thermal mass or solar gain. Column 8 computes an index of how cost-effective or how valuable solar heat gains can be for a location. 0000021316 00000 n 0000054427 00000 n 0000038067 00000 n 0000021012 00000 n /TT6 17 0 R 0000037750 00000 n 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. (If interested, see interior photos in this GBA article: 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. That makes more sense.]. Solar gain can have both positive or negative effects depending on the climate. As well, 3 years ago, having been so pleased with the shutter effect, I built a "low mass, super insulated south facing solar porch. This may help break up the glare. E It is a safe bet to buy any material, so long as the overall replacement window is more energy efficient. See Table 6 for details. East- or west-facing windows produce the most heat gain from May through August. 0000054052 00000 n 0000018449 00000 n 0000018332 00000 n Table 3 shows the net solar gain and value of solar gains in northern U.S. cities. 2023 The Taunton Press, Inc. All rights reserved. To remain as Energy Star products, manufacturers had to either make changes to their effected products or lose the rating altogether. 0000050946 00000 n 643 0 obj <> endobj The advantages of south-facing windows become even greater when losses are incorporated. 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. 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. 0000030287 00000 n 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 enjoyed the bright sunlight and warm interior temps mid-winter too. Those principles work in all types of buildings, and unfortunately can be ignored in subdivision design, building design, and building orientation. 0000040918 00000 n 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). The higher the VT, the higher the 0000011400 00000 n /Resources T December 21st there is no shading from overhangs. Lack of sufficient thermal mass was likely a common problem too (resulting in large interior temperature fluctuations in winter, i.e., overheating). 0000058589 00000 n /ColorSpace is the spectral transmittance at a given wavelength in nanometers and 0000027305 00000 n "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. 0000056795 00000 n 0000055107 00000 n Even during winter afternoons, additional space heating may not be needed by the afternoon. 0000058680 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. 0000037504 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. AL rates 0000031652 00000 n >> Annual heating degree days (HDD), an index of the amount of heating needed each winter season. The lower those numbers are, the more suitable a glazing is for cooling. I'll address passive solar and other home design issues in the next article. 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. Apologies for the delay. 0000041454 00000 n Overcast winter conditions are more likely for cities west of large bodies of water. 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. Map. Thank you so much for sharing this with us. That's good for south-facing windows, because during the hot summer, you don't want the sun beating in your windows, causing solar heat gain in your home's interior. 0000010091 00000 n In buildings, excessive solar gain can lead to overheating within a space, but it can also be used as a passive heating strategy when heat is desired.[1]. 645 0 obj<>stream F Industry technical experts recognized the limitations of SC and pushed towards SHGC in the United States (and the analogous g-value in Europe) before the early 1990s. Currently, there's plenty of software and consultants to perform calculations, or do it yourself with spreadsheets. 0000025712 00000 n 0000040162 00000 n The question-and-answer article above, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. At the bottom of the table, the yearly gains are totaled for south-, north-, east-, and west-facing windows. /TT3 20 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. 0000024598 00000 n {\displaystyle T(\lambda )} The solar heat gain coefficient (SHGC) is an index describing the proportion of light that is let through a window. Denver, with the highest average solar heat gain in January. HUrF}WoND{_2#J$v:>-%uE">Tw[~Aq}$,N.7n@0v]Av8`o The smaller amount of heating needed for space heating in high-performance homes makes more costly or elaborate heating systems no longer cost-effective or necessary. The lower the rating, the less solar heat is transmitted through the glass, and the greater its shading ability. glazing My wife has a small office at work with lots of south facing glass and pulls the shades on sunny days. The primary metric in opaque components is the Solar Reflectance Index which accounts for both solar reflectance (albedo) and emittance of a surface. 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. This article also explores the difference in solar gain between south-facing windows and windows facing other directions. 0000045401 00000 n And it would shade some of the top of the window during January, February and November, when you'd prefer full sun. 0000029773 00000 n 0000018740 00000 n Glazing with lower U-factors (higher R-values) for north- and west-facing windows tend to have lower SHGC. 0000040295 00000 n This is a particular concern in hot, tropical climates such as southern Florida, Georgia, Texas and other states in that experience extreme heat. -- The lowest sun angle at noon is around Dec 21st,, when the sun is low on the southern horizon, even at noon. 0000055784 00000 n A new, affordable but well-insulated window (with cellular blinds used at night) would attain values similar to those listed in the table. . The manufacturers may have improved the materials that made up the frames or the coatings to the glass to meet demands. 0000022979 00000 n As we discuss in detail at Choosing Window Glazing Based on Climate, (a chapter in Best Practices Guide for Windows & Doors): A window with an SHGC of .70 captures about 70% of the 0000040713 00000 n 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. Table 2 shows the amount of solar heat gain per square foot of window glass for the cities listed previously. The NFRC (National Fenestration Council) describes Solar Heat Gain Coefficient (SHGC) as: Solar Heat Gain Coefficient(SHGC) measures how well a I look forward to reading your future articles. Map. Yes the analysis assumed SHGC=0.5 for all windows, which wasn't stated earlier in the article. HW=oFX72X?A(l5 $?ASN* If not, how can I find a better alternative at a reasonable price? (My apologies if these assumptions are printed and I overlooked them.). 8 , fgMPW'J[2JM2~&e@l3-9wDWj2bXec&X.!X095 0000036216 00000 n 0000023176 00000 n Excellent Resource! High-performance homes likely use these space heating appliances, since less space heating energy is required in well-insulated, airtight homes. /Fm0 11 0 R 0000053085 00000 n Cardinal glass makes LoE-180 for passive solar applications. << 0000051599 00000 n Be sure to read the article on u-factor as well, as it is closely related to energy efficiency in windows. 0000008611 00000 n Solar gain compared to Denver, the city with the highest solar heat gain in the list. South-facing windows also have increased solar heat gain in late August to consider. 0000050694 00000 n 0000024359 00000 n 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. 0000042551 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). 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. 0000031802 00000 n SHGCs range from approximately 0.70 for single clear glass to 0.31 for low emissivity glass (toned or coated glass). For more information about SHGC and windows, see. /TT4 19 0 R What Are The Top Factors To Consider In New Windows? 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. Can I Get Replacements For Odd Size Windows? [1] [5] The second factor is the CLF, or the cooling load factor. The maximum U-factor and solar heat gain coefficient (SHGC) for fenestration shall be as specified in Table C402.4. 0000012792 00000 n Column 9 shows the net heat gain per day for south-facing windows (which is the solar heat gain minus the heat loss). We would agree heat loss and solar gain calculations should be done to optimize any home design. I did heat loss, air infiltration, solar gain, and hourly interior temperature calculations for the home pictured (using pencil and paper, before the days when home computers were available). 0000010630 00000 n 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. The maximum allowable fenestration U-factors in Table R402.1.2 (for the prescriptive compliance path) for climates zones 3 through 8 have been reduced from the values in the 2015 edition. /CropBox [0.0 0.0 612.0 792.0] Again, it would reflect off the floor and other surfaces to diffuse the light. 0000024129 00000 n Most insulating glass units in windows sold in USA are closer to SGHC=0.3 for avoiding excess solar gains in summer. 0000052649 00000 n 0000025050 00000 n Wall CLTD selection. 2225 0 obj <> endobj As can be seen from the table, the top three rural family model types are Model 1, Model 2 and Model 3, accounting for 49%, 8% and 8%, respectively. 0000028135 00000 n The home is a three story house, with a basement comprising the bottom floor. The warmer HDD numbers are highlighted in tan, and colder are highlighted in ice blue. The "solar input" in the 3M Sungain film brochure, also known as the solar heat gain coefficient, is the solar transmittance modified to account for re-radiated heat. 0000041950 00000 n Only 22 cities are examined, and only in the northern U.S. 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. OR. This article explores the viability of passive solar and solar-tempered space heating in northern U.S. regions and metro areas. For all other areas, solar heat gain through south-facing windows exceeds the heat lost through the glass. 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]. 0000013076 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). 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. 0000049884 00000 n 0000052778 00000 n 0000023071 00000 n Being in a solar home definitely cures the winter blues and Seasonal Affective Disorder (SAD). Is this really necessary? = 0000009935 00000 n . high SHGC options Providence, R.I., is not unique among northern U.S. cities. 0000057378 00000 n Two cities along the Pacific northwest coast (Portland, Oregon; and Seattle). Because of this, the most common metrics for quantifying solar gain are used as a standard way of reporting the thermal properties of window assemblies. 0000011246 00000 n /Properties 0000034107 00000 n 0000039733 00000 n Passive solar heat gain through large south-facing windows provided most of the winter space heating energy. The basement windows look out only on the east and south sides of the home where they barely see the light of day. In these components heat transfer is entirely due to absorptance, conduction, and re-radiation since all transmittance is blocked in opaque materials. << That indirect light comes in all directions, including from south-facing windows, though the direct sunlight is much stronger. + But, how to deal with glare? 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. stream Ideally, the goal is to not block wintertime sunlight on south-facing windows. 0000028760 00000 n To perform an approximate conversion from SC to SHGC, multiply the SC value by 0.87. It can range in value And if you design for best wintertime performance, you will get undesirable solar heat gain in the late summer. K{0VBAt[)#vx_iNhR qD4;-u'6RW ]`\OEh5V9` MRN&G4dYd*=/?1c,C\M@RU2 L/HkY2(*bRX'eQ9/[Z" g,j1Mu(n|u -L$y(T*gR*x!~Uf* 5xPxU)gxF#\$@aX%IXV:RJ9 (C*[!/SUH;_) "~SQgbbL5*8GN%H*J_mI,sQ~d2L,#66H{k ^%Kd}%\XwME\)|MLVRu*{EoRAFxg";k*CNd oR6l1?]14} 5 {{h@LX!izyR<42:+p`XKml6s0 lwMn:%e7;L1sGw66Pp&X lXv[3;gk9`w` It is important to note that the standard SHGC is calculated only for an angle of incidence normal to the window. ) -- The highest sun angle (for the northern hemisphere) is around June 21st, when the sun is nearly overhead at noon, just a little toward the southern horizon. /TT2 21 0 R This shows that a good percentage of the gains from south windows are retained, despite losses, except in Anchorage, Alaska. 3M's Sungain Film brochure mentions "Solar Input," which represents the shading coefficient times 0.87. ( SHGC also decreases with the number of glass panes used in a window. 0000060982 00000 n (8) Unobstructed west-facing windows produce heat gains mostly in the afternoon. 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. 0000042317 00000 n 0000010399 00000 n 0000014397 00000 n is thus the portion of absorbed and re-emitted energy across all assembly components beyond just the glass. 10;I#l3*O@`0wo : 0000032810 00000 n The lower the SHGC, the less solar heat it transmits and the greater its shading ability. When integrated over the wavelengths of solar short-wave radiation, it yields the total fraction of transmitted solar energy across all solar wavelengths. (4) South-facing windows can provide about fifteen times as much light and solar heat gain in winter as north-facing windows. 0000059464 00000 n 0000031405 00000 n The Energy STAR program provides window buying guidance on the most energy efficient windows for buyers based upon their regions: Some areas of the country are plagued with a hot, dripping summer as well as a long, cold, we winter. Next, six cities in the Midwest and Great Lakes area (Chicago; Indianapolis; Detroit; Burlington, Vermont; Pittsburgh, Pennsylvania; and Buffalo, N.Y.). 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 . (16) Reduce the amount spent on larger and more complex supplementary space heating systems to allocate funds for more insulation, air-sealing measures, and more energy-efficient windows and doors. ) ) /Im0 10 0 R T ( ASHRAEs table of solar heat gain factors[2] provides the expected solar heat gain for clear float glass at different latitudes, orientations, and times, which can be multiplied by the shading coefficient to correct for differences in radiation properties. At the bottom, Anchorage is the only city that has average net heat losses through south-facing windows. 0000011631 00000 n transmitted portion of the solar heat gain coefficient is given by:[4], T . Other internet data sources may include somewhat different data, but the patterns of data would lead to similar conclusions. Kansas City and the seven northeastern seaboard cities do almost as well with average net solar heat gain in January. 0000048108 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. 0000025511 00000 n Buffalo, Pittsburgh, and cities in the Pacific Northwest do not do as well as most other cities. 0000039433 00000 n We find the coldest days are very clear and let in a lot of light and heat contrary to what some say about passive solar in this area. how glass is used in the house design. 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. This simple computation provides a metric to rate locations for the value or cost-effectiveness of passive solar or solar tempered winter space heating.

solar heat gain factor table 2023