Air leakage is the rate of air movement around a window, door, or skylight in the presence of a specific pressure difference across it. 0000057926 00000 n 36" overhangs, 9' walls. 0000033432 00000 n Go . Winter design temperature (F), or coldest expected temperature.. 0000020266 00000 n 0000034703 00000 n In summary, there are many things to consider when choosing the best window replacement options. So if you have your heart set on high-solar-gain glazing, you should keep looking. 0000019351 00000 n Optimizing heat gain http://www.vitrowindowglass.com/lowe_glass/sungate_500.aspx. 0000008386 00000 n [3] The transmittance of each component is calculated in a similar manner to the shading coefficient. 0000052240 00000 n 0000059651 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. Other internet data sources may include somewhat different data, but the patterns of data would lead to similar conclusions. In Table 1, each city is listed with wintertime climate statistics. 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 . [4] Though the shading coefficient is still mentioned in manufacturer product literature and some industry computer software,[6] it is no longer mentioned as an option in industry-specific texts[2] or model building codes. 0000037304 00000 n West-facing windows are a bigger concern, needing shading of some sort during hot late afternoons. Map. 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_ That indirect light comes in all directions, including from south-facing windows, though the direct sunlight is much stronger. Kinda like today, 11 degrees, very sunny and pleasant indoors, with a high-pressure system in control. Table 2 shows the amount of solar heat gain per square foot of window glass for the cities listed previously. Seattle, Washington. 0000038796 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). /Parent 25 0 R 0000047854 00000 n North windows get almost no direct sunlight, so would be less of a problem. is thus the portion of absorbed and re-emitted energy across all assembly components beyond just the glass. This is quite significant in the design of roofs since dark roofing materials can often be as much as 50 C hotter than the surrounding air temperature, leading to large thermal stresses as well as heat transfer to interior space.[5]. . So the cost of electricity is used to compute the value of solar heat gains in the following analysis. Davor, All of the 22 northern U.S. locations examined previously exhibit the same pattern of superior winter energy performance for south-facing windows. Such devices can reduce the shading coefficient by blocking portions of the glazing with opaque or translucent material, thus reducing the overall transmissivity. 0000025308 00000 n Kansas City and cities along the northeast coast also look promising for wintertime daylighting, space heating, and PV. /GS2 4 0 R Table 2 lists solar gain data for the 22 northern U.S. cities. The data on solar heat gains is summarized in Figure 2, below. << U-factoris the rate at which a window, door, or skylight transmits non-solar heat flow. Glazing with lower U-factors (higher R-values) for north- and west-facing windows tend to have lower SHGC. 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. This information in an aid in choosing the best direction and size of windows facing different directions. (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. Long stretches of overcast days produce large heat losses through large windows, with minimal solar heat gains to compensate. southernwalls see about 6" of sun exposure at the bottom of each window. /Metadata 9 0 R 0000023459 00000 n Thanks for the kind words - and thanks for the explanation. Still, don't have AC. ( Thank you Bob for sharing this very thorough article! 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. You can maybe start to imagine how you might have different window needs if you are in Texas or Florida as compared with Rhode Island or Massachusetts. 0000011631 00000 n Does The New Glass In Windows Need Any Special Care? Is this correct? December 21st there is no shading from overhangs. 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. A U-factor of U-0.24 isn't bad, by the way. However I don't believe they sell sealed glass units retail, just to window manufacturers. My great aunt used to live with family in Oregon, but had to live elsewhere during the overcast winters there. The value of the shading coefficient ranges from 0 to 1. 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. So the solar heat gain analysis has focused on the coldest month (January) for the 22 northern U.S. locations. SHGC also decreases with the number of glass panes used in a window. cooling season. I'm old enough to remember the passive solar homes of the 1970s and 1980s. 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. 0000013076 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. /C2_0 15 0 R It is a safe bet to buy any material, so long as the overall replacement window is more energy efficient. / Motions of the Sun Simulator 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. comes through a product. d 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. 0000054052 00000 n 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. 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 An SHGC closer to 0 means that little solar heat is let in An SHGC closer to 1 means more solar heat is let in -- Seasonally, the coldest temps of winter, and the hottest temps of summer, lag the sun's seasonal changes in path and intensity. 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. 0000000016 00000 n 0000036017 00000 n One of the best I've read here. 0000042551 00000 n I found it both interesting and very useful. We want to keep our solar heat, not lose it back through the same window that brought it in. Great article! [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. The lower the U-factor, the more energy-efficient the window, door, or skylight. Even if it is not possible to build a classic passive solar home in other climates, solar gains can be used for substantial solar-tempered wintertime home heating. The ability of glazing in a window, door, or skylight to transmit sunlight into a home can be measured and rated according to the following energy performance characteristics: Review the state fact sheets or use the window selection tool for new construction or existing homes from the Efficient Windows Collaborative to determine the desired performance ratings for your climate. 0000050463 00000 n Map. Source: Text Bob Fegan 12/2008; Table on BTU per person heat gain from www.engineeringtoolbox.com 9/2005; diagram . 0000022215 00000 n 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. CCPA | Lack of sufficient thermal mass was likely a common problem too (resulting in large interior temperature fluctuations in winter, i.e., overheating). South-facing window glazing may optimize heat gains with higher SHGC, and west-facing windows with lower SHGC glazing. 0000037104 00000 n 0000058284 00000 n %3Qd Vw9k\1W7CL9tqM=~u5b&XfmFk!$"4c?9%fb|$N}0R16f]oqnDxo[hot;3Nq_fO-jldHA '*bIgdyfs[B[Z+^:E 9)Uii;/J PH( 6.u. w Overcast winter conditions are more likely for cities west of large bodies of water. He led a course in Sustainable Architecture for Lifelong Learning Collaborative, an adult ed organization in Providence, R.I. Bob has degrees in applied mathematics and in philosophy from Brown University, and psychology from UCLA. %PDF-1.6 % However, many northern U.S. locations can experience uncomfortably hot summers as well as cold winters. Solar, wind or other renewable energy source supplies not less than 80 percent of the energy for service water heating. 0000030287 00000 n n 0000044828 00000 n 0000049715 00000 n However, a few strategically placed deciduous trees and i have all but eliminated my summertime window solar exposure. [For those unfamiliar with the terminology Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. /TT1 22 0 R A 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. /Font Wall CLTD selection. The basement windows look out only on the east and south sides of the home where they barely see the light of day. 645 0 obj<>stream I see lots of examples where people try things without "doing the math" beforehand. However this tends to provide a good estimate over a wide range of angles, up to 30 degrees from normal in most cases.[3]. 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). endobj 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. (15) Consider less costly minisplit heat pumps or even simpler resistance or radiant heating in energy-efficient high performance homes, which have a much lower heating load. 0000059464 00000 n 0000056162 00000 n This label displays AL in U.S. units. 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). 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. In the context of passive solar building design, the aim of the designer is normally to maximize solar gain within the building in the winter (to reduce space heating demand), and to control it in summer (to minimize cooling requirements). The most important factors are budget and energy efficiency. include it on their labels. It is important to note that the standard SHGC is calculated only for an angle of incidence normal to the window. 0000021721 00000 n Personally, I think we should focus on better window shading methods than roof overhangs. 0000016860 00000 n 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. Currently, there's plenty of software and consultants to perform calculations, or do it yourself with spreadsheets. Used by solar PV installers for the most bang for the buck. I changed the color of walls from off-white to the same coffee color (from advice in an interior design class). 0000027723 00000 n 8 , fgMPW'J[2JM2~&e@l3-9wDWj2bXec&X.!X095 /MC0 0000060552 00000 n Traditional metal windows allow heat to transfer along the metal into the home, so if you live in a hot climate region, metal isn't a great choice for your replacement window frame. The following four cities are along the north central and western U.S. (Minneapolis; Salt Lake City; Bismarck, N.D.; and Billings, Montana) . Fortunately, Energy STAR pulled back a bit, which means windows could remain a bit more affordable. I know some others disagree with this perspective. The design was intended to reduce supplementary space heating substantially and minimize utility bills. Note (in the last two columns, #9 and #10) that Denver has better net solar heat gains than anywhere else in the list. {\displaystyle E(\lambda )} Subscribe to receive updates from Energy Saver, including new blogs, updated content, and seasonal energy saving tips for consumers and homeowners. 0000012014 00000 n In column 7, South Percentage of Total Gains, note that south-facing windows provide the majority of the total solar gains for every city in the list. 0000009857 00000 n [1] [5] The second factor is the CLF, or the cooling load factor. SHGC is expressed as a 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. Uncontrolled solar gain is undesirable in hot climates due to its potential for overheating a space. 0000032325 00000 n ( 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. 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. % m 0000010553 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). 0000042979 00000 n 0000032457 00000 n The advantages of south-facing windows become even greater when losses are incorporated. Most insulating glass units in windows sold in USA are closer to SGHC=0.3 for avoiding excess solar gains in summer. Yes the analysis assumed SHGC=0.5 for all windows, which wasn't stated earlier in the article. 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. /Rotate 0 0000039316 00000 n 0000019003 00000 n = 0000038526 00000 n 0000012792 00000 n In January, south-facing windows always account for more solar gain than east + west + north combined. 0000024129 00000 n 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. , 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. It is neat because you can pick a date, then move the hour from am to pm and watch the shadows dance across the house. 0000056381 00000 n "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- In colorado I found Milgard and Pella had high SHGC, low E options. Is there anything else other than minding where you put your furniture? Vertical fenestration that is located on the street side of the street-level story only, provided that. >> =J04pajo/7iv}F1&04 kkAVF/n0 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. This coefficient accounts for the time lag between the outdoor and indoor temperature peaks. 0000021486 00000 n = 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. /C2_1 14 0 R As such, the Energy Star Factors are as follows: When windows are rated for heat transference, the information may be for: In general, the values for the whole window will appear lower than for the center of the glass readings. 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. (2005 ASHRAE Handbook : Fundamentals at Amazon). Vinyl windows are generally made of one continuous piece. The NFRC label provides a reliable way to determine a window's energy properties and to compare products. 0000023071 00000 n On the flip side that means that cold air would normally go from outdoors to indoors with metal framed windows. 0000008689 00000 n 0000034107 00000 n Maybe we should not let the perfect be the enemy of the good. 0000010476 00000 n Table 1 lists 22 northern U.S. cities. Similar analysis could be performed by using web resources to compute solar gains for windows in other orientations. Some of the current research into this subject area is addressing the tradeoff between opaque thermal mass for storage and transparent glazing for collection through the use of transparent phase change materials that both admit light and store energy without the need for excessive weight.[14]. I used this website to analyze my site. ;"\ h;; nM"O*]\_n}s54xBb;L";`fJq=.s5?puuus9Eq=7wWT|# LhH{\=vf}+W8?fX'Xgp8=ZHQ-oGA2mN~~k. As you point out, it's a complex problem to design a good south-facing roof overhang for the windows below. [5], Apart from windows, walls and roofs also serve as pathways for solar gain. The SHGC measures how much of the sun's heat comes through the window. 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. Clear double (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. 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. 0000047632 00000 n - Jeff Pendl, Enervision, Cincinnati OH. Columns 1-3 lists the same city data, in the same order, as Table 1. Glass Color . ) (If interested, see interior photos in this GBA article: Turtle Code . 0000030116 00000 n Even during winter afternoons, additional space heating may not be needed by the afternoon. 0000053548 00000 n September 1st/March 1st modelling revealed modest exposure as the sun has dropped enough to negate most of the overhang benefit. 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). Average January temperature (F), the coldest month of the year. It can range in value 0000051339 00000 n In essence SC is an index of the effective solar rejection performance of a given glass type. 0000020469 00000 n 0000031213 00000 n The lower the SHGC, the less solar heat it transmits and the greater its shading ability. You must be a magazine subscriber to access this feature. 0000048853 00000 n Note that east- and west-facing glazing provide an equal amount of solar heat gain, but east gains mostly in the morning, and west mostly in the afternoon. A Contrarian View of Passive Solar Design, GBA Prime Sneak Peek: Reassessing Passive Solar Design Principles. 0000025712 00000 n The solar radiation amount depends on the orientation of the surface, solar altitude angle, and solar azimuth angle. 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. When too much heat is let in by an inappropriate SHGC and too much heat is trapped in by an incorrect u factor, you have what is commonly known as the greenhouse effect. 8 times table chart up to 1000 . While the U-Factor can take any value, in general for windows it ranges from 0.20 to 1.20. ( 0000060982 00000 n 0000054427 00000 n 0000038191 00000 n So for a traditional Cape style home, the small overhang doesn't shade the windows much in any season. Next, six cities in the Midwest and Great Lakes area (Chicago; Indianapolis; Detroit; Burlington, Vermont; Pittsburgh, Pennsylvania; and Buffalo, N.Y.). 0000041454 00000 n ) >> 0000030922 00000 n 0000009779 00000 n 0000051079 00000 n In Table 2, it was noted that north-facing windows are always a net BTU loss, since heat losses exceed the meager solar heat gains for all 22 cities. 0000036698 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. 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? If you live in a hotter climate zone, an SHGC closer to 0 to block the heat is more appropriate. The solar gain factor is a complicated series of factors multiplied together starting with the transmittance factor of the glass, and ending with all possible shading devices/methods and adjusted for local weather (cloud cover). While you may like having free heat in the winter, it might be too much of a good thing in the summer months if you live in a climate zone with extreme seasons. The larger the net solar gains, and the smaller the winter heating needed, the better the score on the index. 0000036867 00000 n NAAP Labs Motions of the Sun Simulator. 0000019489 00000 n Solar gain is most frequently addressed in the design and selection of windows and doors. I think that the key design criteria for passive solar involves locating and sizing windows, thermal mass, and doing sufficient insulating and air-sealing so that only solar heat gain can provide most of the home's wintertime space heating, yet avoid summertime overheating. 0000043411 00000 n 0000060652 00000 n 0000046325 00000 n hbbd```b``A$cXDDr@3N,IF@L@s&00Lg`` 0000050343 00000 n We don't seem to have an issue with glare. Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Labels on products sold in markets outside the United Many had problems with glare. The SHGC of the shaded vertical fenestration in the proposed building is permitted to then be reduced by using the multipliers in Table 5.5.4.4.1 for each fenestration product. SHGC ratings are used to help in quantifying the energy efficiency of windows and skylights. 0000035843 00000 n 0000053840 00000 n The NFRC (National Fenestration Council) describes Solar Heat Gain Coefficient (SHGC) as: Solar Heat Gain Coefficient(SHGC) measures how well a 0000041109 00000 n Is It Easier To Clean Replacement Windows? Which design principles from the 1970s are worth retaining, and which should be discarded? 0000048271 00000 n K{0VBAt[)#vx_iNhR qD4;-u'6RW ]`\OEh5V9` MRN&G4dYd*=/?1c,C\M@RU2 L/HkY2(*bRX'eQ9/[Z" g,j1Mu(n|u -L$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`