The value of the shading coefficient ranges from 0 to 1. To optimize the heat gain through windows heavily insulated shutters will change all the numbers. It quantifies how some US climates (and not others) can use solar heat gain for space heating, or reduce utility bills cost-effectively, by designing to manage solar heat gain. 0000057599 00000 n
number between 0 and 1. . Note that this article doesn't promote classic passive solar design, even though a well-designed passive solar home works great in dry cold winter climates (but not in climates with overcast winters). 36" overhangs, 9' walls. Locations in the northern U.S. are winter-heating-dominated (meaning that more energy is needed for winter heating and much less for summer cooling). I used this website to analyze my site. (For Denver, east- and west-facing windows do have a net solar heat gain of 25%, which is positive, but only one-third as much as south-facing windows 75% net gain.). 0000045996 00000 n
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C-bJD[F;#lTM5Xn"[. The last column (#10) shows the percent of net heat gain compared to the heat gain for window glass. 0000025712 00000 n
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(4) South-facing windows can provide about fifteen times as much light and solar heat gain in winter as north-facing windows. Solar gain compared to Denver, the city with the highest solar heat gain in the list. /TT6 17 0 R 0000011169 00000 n
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). Reflections of the window or objects in direct sunlight (that are behind you) could be visible on your TV or computer screen as reflections on the screen. -- The lowest sun angle at noon is around Dec 21st,, when the sun is low on the southern horizon, even at noon. South-facing windows also have increased solar heat gain in late August to consider. << 0000045401 00000 n
The following four cities are along the north central and western U.S. (Minneapolis; Salt Lake City; Bismarck, N.D.; and Billings, Montana) . Columns 1-3 lists the same city data, in the same order, as Table 1. Response to David Martin standard low-E and about .40 for spectrally selective low- 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. 0000021486 00000 n
Here are added factors defined by the NFRC as of 2005: Air Leakage(AL) measures how much outside air comes Tile floors over wood doesn't provide much thermal mass (about 1/2" vs. 4" slab), but more than wood floors. /GS2 4 0 R (7) East-facing windows provide sunlight early in the morning when a house interior is the coolest, so they are more useful than west-facing windows. Simply choose your state and then your county below and we will display the combinations of u factor and SHGC as recommended by Energy STAR and the National Fenestration Rating Council. Unfortunately in the US, most windows sold are low SHGC. For more information, see All About Glazing Options. 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. 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. I'm less familiar with these lighting issues, so hope someone else can chime in. During the summer months, the path of the sun has changed. 0000024716 00000 n
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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. 0000044552 00000 n
Excellent Resource! Passivhaus is known for having lots of foam insulation below slab floors (8" to 10" thickness might be common) to keep within their limited heat loss budget. 0000009623 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. 0000029981 00000 n
5.8.2.2 Labeling of Fenestration Products . ) However this tends to provide a good estimate over a wide range of angles, up to 30 degrees from normal in most cases.[3]. 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. And if you design for best wintertime performance, you will get undesirable solar heat gain in the late summer. 0000022435 00000 n
But it might be a good compromise. 0000020469 00000 n
Thanks for all the great details and comments, and your work on this type of efficient home design. /Rotate 0 0000053637 00000 n
We have about 2' overhangs on all south facing windows and doors which work well in this latitude. From this ordering of cities by average mid-winter solar heat gain potential, we may begin to conclude: Next, we need to explore solar heat gains and losses in more detail for each metro area. Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Modify the landscape of the property to optimize wintertime solar heat gain (and reduce summertime solar heat gain from the west). 0000027028 00000 n
The resources cited in the Appendix or other internet resources may provide climate data for your location or a similar climate nearby. In June, the sun is closer to overhead at noon, so south windows have far less solar heat gain. Engineering; Chemical Engineering; Chemical Engineering questions and answers; 400 TABLE 15 SOLAR HEAT GAIN THRU ORDINARY GLASS (Contd) Btu/(hr) (sq ft sash area) 400 East 110 102 47 90 40 NORTH LATITUDE . The lower the SHGC, the less solar heat it transmits and the greater its shading ability. 0000046682 00000 n
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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. 1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 , Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 AShrae Handbook - Fundamentals (Hardcover), Harry J., Jr. Sauer (Author), Ronald H. Howell, ISBN-10: 1931862923 or ISBN-13: 978-1931862929, 1993 ASHRAE Handbook Fundamentals (Hardcover), ISBN-10: 0910110964 or ISBN-13: 978-0910110969, Colloidal Materials, Inc., PO Box 696, Andover MA 01810, Pennwalt Corp., King of Prussia, PA 19406, The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083, www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850 is the base U.S. DOE website for these articles, Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the. 0000042133 00000 n
, 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. 0000022887 00000 n
A product with a high SHGC rating is more effective at collecting solar heat during the winter. This article explores the viability of passive solar and solar-tempered space heating in northern U.S. regions and metro areas. How do visible light transmittance, and shading coefficient relate to one another? To perform an approximate conversion from SC to SHGC, multiply the SC value by 0.87. 2252 0 obj
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This is a particular concern in hot, tropical climates such as southern Florida, Georgia, Texas and other states in that experience extreme heat. 0000008689 00000 n
(Of course you could use a light filtering curtain or shade to fix this.). Air leakage is the rate of air movement around a window, door, or skylight in the presence of a specific pressure difference across it. startxref
A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun. 0000052561 00000 n
AL rates The solar transmittance of a window glazing or window is the percentage of visible and near-infrared light that passes directly through a window. 0000053840 00000 n
) This article also explores the difference in solar gain between south-facing windows and windows facing other directions. 0000036216 00000 n
/TT7 16 0 R Locations that lack significant net solar heat gain, or that require a lot of wintertime heating, score lower on this index. 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. 0000033574 00000 n
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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. 0000030709 00000 n
Watch out: other very important factors need to be considered in arriving at an accurate picture of solar heat gain through windows. We do have medium dark wood floors, linoleum and tile. include it on their labels. [10] For dynamic fenestration or operable shading, each possible state can be described by a different SHGC. So thermal mass dampens daily temperature swings from solar gains, keeping interiors within about a ten degree Fahrenheit range (5 degrees C), if designed reasonably well. 0000032457 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. Yet, the living room and the sun room, get a little bit more but welcome heat, while the bedrooms on the top floor facing west get a wallop in the afternoon. 0000057378 00000 n
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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. Kansas City and cities along the northeast coast also look promising for wintertime daylighting, space heating, and PV. 0000014163 00000 n
Most manufacturers worked to retrofit products to meet the new and more stringent standards. 0000052109 00000 n
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East- and west- facing windows gain far more heat than south-facing windows during the summer months, until late August. I used double-pane windows, and four large double-pane IGUs (for site built fixed windows). 0000027405 00000 n
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/C2_1 14 0 R Still, don't have AC. North windows get almost no direct sunlight, so would be less of a problem. The cost of electricity, natural gas, or other heating fuels can impact the use of passive solar heat gains for wintertime space heating. Light-to-solar gain (LSG)is the ratio between the VT and SHGC. Table 4 only looks at solar heat gains without considering losses. 0000037104 00000 n
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Shades, overhangs, or many other alternatives can be used to cut down on solar heat gain during hot days in any type of home, to reduce AC or uncomfortable interior temps. 0000009077 00000 n
Maybe some desiccant packets could help reduce fogging? The cost-effectiveness of solar heating varies among regions as well. The warmer HDD numbers are highlighted in tan, and colder are highlighted in ice blue. {\displaystyle S.C.=F(\lambda ,\theta )_{1}/F(\lambda ,\theta )_{o}}. 0000032190 00000 n
{\displaystyle E(\lambda )} June 21st, only sees direct sun in the early hours of the morning, and the window son the north-west side of the house in the late evening. HUPTekzreUXT ey""E + efw# >XimcQLTs}w#HT^bo$kuYPU:)l {ewGJc'8qq`VHK'O]Hy&$z]=16FlN.S-$&uQ/:w Long stretches of overcast days produce large heat losses through large windows, with minimal solar heat gains to compensate. You want to shade your south-facing windows from the sun to avoid solar heat gain. 0000056381 00000 n
Consequently, south-facing windows capture far more light, and thereby produce far more solar heat gain, than windows facing other directions. 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. 0000050604 00000 n
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= The solar heat gain coefficient of the skylights. The thermal mass also will radiate stored heat when the sun isn't shining to keep interior temperatures from getting too cool.) The standard method for calculating the SHGC also uses a more realistic wavelength-by-wavelength method, rather than just providing a coefficient for a single wavelength like the shading coefficient does. Passive solar heat gain through large south-facing windows provided most of the winter space heating energy. That indirect light comes in all directions, including from south-facing windows, though the direct sunlight is much stronger. The Southern Climate Zone has hot summers and mild winters. 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. 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. /TT1 22 0 R Table 3 shows the net solar gain and value of solar gains in northern U.S. cities. The NFRC label provides a reliable way to determine a window's energy properties and to compare products. 0000028760 00000 n
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U-Factor * SHGC (Solar Heat Gain Coefficient) * Product Type * Frame Material * Air Fill Type * Impact Resistance * Series . Visible transmittance (VT)is a fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through the glazing of a window, door, or skylight. How to calculate solar gain for a building: This article discusses the method for calculating solar heat gain through windows. Finally, Anchorage, Alaska, along the far northern Pacific coast, with by far the lowest solar heat gain. >> For any home design, heat loss, solar gain and other analysis needs to be done for best results, especially considering the high cost of building a home. A product with a higher VT transmits more visible light. C 350 The North Central Climate Zone has more moderate seasons as such, the Energy Star Factors are as follows: The South Central Climate Zone has warmer summers and milder winters. 0000051467 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. /XObject Daylighting is good, and solar heat gain is good in winter and not good in the hot summer. 0000034369 00000 n
glazing has an SHGC of about .75 versus .60 to .70 for He was a psychology professor for five years, and a software and web site usability and design engineer for 20 years. Thank you so much for sharing 0000020750 00000 n
Not sure when I took the photo, other than it shows AM shadows, and not during winter, as the deciduous plants had their leaves. 0000033707 00000 n
/MediaBox [0.0 0.0 612.0 792.0] [11] Materials with high SRI will reflect and emit a majority of heat energy, keeping them cooler than other exterior finishes. {\displaystyle T(\lambda )} glazing 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. 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. 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. So I'd recommend designing overhangs for minimal shading mid-winter, and not worry so much about summer (for winter-dominated northern climates). [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. 0000039433 00000 n
Solar heat gain factors and heat loss coefficients for passive heating concepts Full Record Research Abstract The concept of solar heat gain factor has been introduced for calculating the net energy gain of passive heating elements and other components of a building as a result of incident solar radiation. These properties are the transmissivity "T" , absorptivity "A", emissivity (which is equal to the absorptivity for any given wavelength), and reflectivity all of which are dimensionless quantities that together sum to 1. 0000009311 00000 n
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In the early days, computer screens had hoods that blocked light from above and the sides. 0000023176 00000 n
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The glass on the TV or computer screen can also be highly reflective smooth glass for best visual screen performance, or can be less reflective glass for less interference with reflections on the screen. SHGCs range from approximately 0.70 for single clear glass to 0.31 for low emissivity glass (toned or coated glass). It can't be a problem for north-facing windows, which receive almost no direct sunlight any time of year. This allows glass to block mainly short-wave infrared radiation without greatly reducing visible transmittance.[3]. -- Seasonally, the coldest temps of winter, and the hottest temps of summer, lag the sun's seasonal changes in path and intensity. 0000050037 00000 n
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First, thanks for sharing your many helpful comments and ideas on GBA articles on Q&A. endstream
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I would hope this article would lead people to consider quantifying solar gains for any type of home, not just solar-oriented designs.
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. 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. To model anything, you have to make some reasonable assumptions. 10;I#l3*O@`0wo :
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Note that the values in Table 6 highlighted in light blue show that south-facing windows gain less heat in June and July compared to east- or west-facing windows. Q(summer) = U*A*(CLTD) using the CLTD method. 0000049380 00000 n
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/Width 76 You build a simple house, and then you can set your latitude, and then choose the date/hour. ;"\ h;; nM"O*]\_n}s54xBb;L";`fJq=.s5?puuus9Eq=7wWT|#
LhH{\=vf}+W8?fX'Xgp8=ZHQ-oGA2mN~~k. The lower the SHGC, the better a product is at blocking unwanted heat gain. 0000048853 00000 n
Terms | As such, the Energy Star Factors are as follows:Factors for Energy STAR Ratings in the South Central Climate Zone. Passive solar design is a key element of creating resilient homes, Cold-climate glazing is surprisingly hard to find. The first five columns list each month of the year, and the daily solar heat gain per square foot of window glazing for windows facing south, north, and east, or west , and the average heat gain over the four window directions. Table 1 shows wide variation in heating degree days, winter design temperatures, and Januarys average percentage of available sunlight. VT is expressed as a number The south-facing window advantage ranges from at least 140% (Indianapolis) and 144% (Denver), to the most extreme 179% (Seattle) and 338% (far-north Anchorage, Alaska). 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. 0000030384 00000 n
Worth remembering that those early-'80's houses are one of the main reasons we are having such fruitful discussions today! 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. ) 0000023071 00000 n
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As well, 3 years ago, having been so pleased with the shutter effect, I built a "low mass, super insulated south facing solar porch. Optimizing heat gain 0000011631 00000 n
T 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? 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. 645 0 obj<>stream
Should I be satisfied with a U of 0.24 and SHGC of 0.39? is the incident solar spectral irradiance. (The result also is multiplied by 100 so that numbers are transformed into a simple single digit range.). Cardinal glass makes LoE-180 for passive solar applications. Grid Type . In both cases, NFRC standards outline the procedure for the test procedure and calculation of the SHGC. 0000057247 00000 n
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When designing a building, the solar heating potential can be computed. h[koG+`z?qN5A9 Y2dffIQMb?oE2+bXYkW6Dl-uJG%M}I2lF 9{lbbcJ*MZ&`S~PmQ9cU:VV)L+o/,7Z._}o.)?/o/\=|'7/>\?G{gN-`W>>llY9[Gyhenzvs=~zbW^z.67O_n2a}~s*y~ugg>g^=u|zrvqzbt These cold sunny days the furnace rarely comes on all day long. Canadian companies might be your best bet (e.g., Thermotech, Accurate Dorwin, Inline). b +{roFw@Qv.Pb=Z"3>!06&rhS8EnVw\/bw +rt|bSL6),W=^O *cAL^u'MH}
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p7B . The window orientations were limited to true south, east, west, and north. E >> Currently, there's plenty of software and consultants to perform calculations, or do it yourself with spreadsheets. (If interested, see interior photos in this GBA article: 0000012014 00000 n
Fortunately, Energy STAR pulled back a bit, which means windows could remain a bit more affordable. All of the 22 northern U.S. locations examined previously exhibit the same pattern of superior winter energy performance for south-facing windows. SOLAR RADIATION Solar radiation has important effects on both the heat gain and heat loss of a building. Calculating solar gains by hand is a laborious, imperfect process. 0000033229 00000 n
SHGC can either be estimated through simulation models or measured by recording the total heat flow through a window with a calorimeter chamber. Which design principles from the 1970s are worth retaining, and which should be discarded? Winter temperatures and cloudiness are major determinants of the potential and the cost-effectiveness of exploiting solar heat gain for space heating. The Climate Zone 5 site has 5,600 heating degree days. Two cities along the Pacific northwest coast (Portland, Oregon; and Seattle). When integrated over the wavelengths of solar short-wave radiation, it yields the total fraction of transmitted solar energy across all solar wavelengths. 0000030922 00000 n
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One quick note: It appears that you are assuming a SHGC of 0.5 for the heat gain calculations. We have a passive solar house we designed and built ourselves in SE Michigan in the late 80's. Thermal mass may be used to even out the fluctuations during the day, and to some extent between days. 0000040500 00000 n
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) The sun is even lower before and after noon. 0000052866 00000 n
In January, south-facing windows always account for more solar gain than east + west + north combined. 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. 0000038796 00000 n
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/C2_2 13 0 R ( Solar Heat Gain through Fenestration Systems Containing Shading: Summary of Procedures for Estimating Performance from Minimal Data Publication Type Conference Paper Authors Joseph H Klems LBNL Report Number LBNL-48672 Abstract These cities are geographically dispersed, with more cities located in the northeast and Great Lakes regions. potential for daylighting. 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 However, a few strategically placed deciduous trees and i have all but eliminated my summertime window solar exposure.