solar heat gain factor table

n 0000053085 00000 n 0000042133 00000 n Avoiding south-facing windows because in rare cases people created window walls without considering the solar gain or glare impact would be a mistake. Low-emissivity coating is another more recently developed option that offers greater specificity in the wavelengths reflected and re-emitted. 0000040580 00000 n SOLAR RADIATION Solar radiation has important effects on both the heat gain and heat loss of a building. During the summer months, the path of the sun has changed. [I notice that after I wrote this response, you edited your comment, changing "high U-value" to "low U-value." My great aunt used to live with family in Oregon, but had to live elsewhere during the overcast winters there. To perform an approximate conversion from SC to SHGC, multiply the SC value by 0.87. 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. ) comes through a product. OR. How to calculate solar gain for a building: This article discusses the method for calculating solar heat gain through windows. 0000034107 00000 n Heat gains from windows can contribute to overheating. 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. So for a traditional Cape style home, the small overhang doesn't shade the windows much in any season. 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. (Plus the low utility bills and resilience in case of power outages.). 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]. 0000061092 00000 n 0000021134 00000 n It was an experiment, and I can now, after 5 years, say it exceeded my expectations. 0000051730 00000 n 0000055691 00000 n For some locations, the heat is more pronounced and longer in duration than the short months of frigid temperatures with little snow. %PDF-1.3 % I'm old enough to remember the passive solar homes of the 1970s and 1980s. 0000022215 00000 n Appendix D, Degree Day and Design Temperatures. We would agree heat loss and solar gain calculations should be done to optimize any home design. Thank you for sharing your thoughts, Bob. 0000050037 00000 n 0000036575 00000 n (12) Consider different glazing for windows facing different directions. Average percent of sunlight shining in January (opposite of cloudiness). 0000043195 00000 n *dPeU|A#rJ]dwiuEZDu-KIVc"*f}*%,?bAL& GH D. That makes more sense.]. Fortunately, Energy STAR pulled back a bit, which means windows could remain a bit more affordable. 0000027405 00000 n Alaska, the Pacific Northwest, and Midwestern cities would not be good candidates to rely on wintertime solar heating. /C2_0 15 0 R Motions of the Sun Simulator For double glazed windows SHGC is more often in the range of 0.42 - 0.55. On the flip side that means that cold air would normally go from outdoors to indoors with metal framed windows. 0000035843 00000 n [13] When designed properly, this can modulate temperature fluctuations. Figure 1 depicts the grouping of northern U.S. cities by solar heating potential, as listed in Table 1. /Type /Page 0000025994 00000 n 0000050604 00000 n Latitude: N: NE: E: SE: S: SW: W: NW: HORIZONTAL : 24 o N: 42: 37: 36: 26: 15: 95: 174: 134: 162: 25 o N: 41 . %YYgeG&1'd$`0l sLqk>0h&b{g.\)o>KC\#F[T(Al'd X Thank you Bob for sharing this very thorough article! (9) Design for the local climate, considering winter temperatures (heating degree days and winter design temperatures), cloudiness (or average percent of available sunlight in January), and costs of electricity (or fuel for heating). 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. >> 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]. 0000029882 00000 n See Table 6 for details. 0000041109 00000 n 0000036017 00000 n Light through windows isn't all direct sunlight. In Table 1, each city is listed with wintertime climate statistics. 143 0 obj <> endobj The lower the SHGC, the less solar heat it transmits and the greater its shading ability. Table 2 lists solar gain data for the 22 northern U.S. cities. "oRD"wB=k:p!TcSm]L [3] Since the quantities compared are functions of both wavelength and angle of incidence, the shading coefficient for a window assembly is typically reported for a single wavelength typical of solar radiation entering normal to the plane of glass. The lower the number, the less you'll spend on cooling. 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. 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. -- "Active solar" involves capturing solar heat gains, and moving the warmed air or liquid into some storage location via pumps or fans, to be used for heating when needed.]. In the early days, computer screens had hoods that blocked light from above and the sides. http://www.cardinalcorp.com/products/coated-glass/loe-180-glass/, PPG Industries manufactures two low-e/high SHGC products: Sungate 500 and Sungate 100 window glass with SHGC of about 0.7. Beyond climate region, there are some other factors in place that impact how SHGC will affect your life. /Height 99 0000011169 00000 n Providence, R.I., is not unique among northern U.S. cities. Kansas City and the seven northeastern seaboard cities do almost as well with average net solar heat gain in January. /MC0 The U-Factor works in conjunction with the Solar Heat Gain Coefficient (SHGC). 0000029773 00000 n Average daily solar heat gain per square foot of south-facing window glass in January. 0000044969 00000 n 0000011554 00000 n 0000019693 00000 n 0000037935 00000 n The Northern Energy STAR Climate Zone recently underwent changes it its criteria of what constitutes a window that insulates well. T There are a couple of ways that glass can maintain the indoor temperatures to keep you comfortable indoors. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun. We include definitions of solar input, shading coefficient, solar heat gain faactor, solar heat gain coefficient, and solar transmittance. Other internet data sources may include somewhat different data, but the patterns of data would lead to similar conclusions. 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. 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. Table 6 lists the BTUs per square foot of window glass per day for Providence, R.I. (the northeastern coastal city that looks most promising for solar heating). 0000009311 00000 n Glass Color . The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article. glazing has an SHGC of about .75 versus .60 to .70 for 0000055475 00000 n We designed it to be in east west direction, and on the south side we have a large 2.5m wide doors. 0000054427 00000 n To optimize the heat gain through windows heavily insulated shutters will change all the numbers. 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. Basically, any window frame material is going to insulate well whether it is wood, vinyl, aluminum clad wood, or fiberglass. In passive solar and solar-tempered homes, typically there are more or larger windows facing south, and fewer or smaller windows facing other directions. E. Which type of glazing is optimal for a given project depends /C2_1 14 0 R (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. Map. [For those unfamiliar with the terminology Ideally, the goal is to not block wintertime sunlight on south-facing windows. (8) Unobstructed west-facing windows produce heat gains mostly in the afternoon. 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. See ASHRAE Fundamentals, Chapter 27,for lists of solar heat gain factors. SHGC is expressed as a Very helpful. As indicated in the chart below, the EPA recommends . The higher the number, the more light transmitted without adding excessive amounts of heat. /Font The overall shading coefficient is thus given by the ratio: S 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. This home had sufficient, well-insulated thermal mass tiled slab floor, engineered quantitatively to offset wintertime heat losses with solar heat gains. At home she is the first to pull them up on a sunny morning, maybe because we have more room at home. 0000060982 00000 n As such, the Energy Star Factors are as follows:Factors for Energy STAR Ratings in the South Central Climate Zone. The lower the rating, the less solar heat is transmitted through the glass, and the greater its shading ability. All you need to do is look for the ratings that indicate a good fit for your climate. Currently, there's plenty of software and consultants to perform calculations, or do it yourself with spreadsheets. 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). 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. What about glare? , You want to shade your south-facing windows from the sun to avoid solar heat gain. 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` >> ( Windows orientation or direction (e.g., facing south, east, west or north); Solar Heat Gain Coefficient (SHGC), the solar gain potential, usually 0.35 to 0.7, or 35% to 70% for efficient new windows; and. Tile floors over wood doesn't provide much thermal mass (about 1/2" vs. 4" slab), but more than wood floors. The trapped heat thus causes solar gain via a phenomenon known as the greenhouse effect. Is this really necessary? Is it possible to determine an appropriate period of shading for summertime sun that also allows peak wintertime solar gain? It is important to note that the standard SHGC is calculated only for an angle of incidence normal to the window. 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. Column 7 shows the percentage of the total amount of solar gain that comes from the south-facing glazing. 0000022755 00000 n SOLAR GAIN CALCULATION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. 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. NFRC U-factor ratings, however, represent the entire window performance, including frame and spacer material. 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. 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. 0000056162 00000 n Fortunately, retailers will tailor their stock to homes in your area. 0000058284 00000 n endstream endobj 644 0 obj<> endobj 646 0 obj[647 0 R] endobj 647 0 obj<>>> endobj 648 0 obj<> endobj 649 0 obj<> endobj 650 0 obj<> endobj 651 0 obj<> endobj 652 0 obj<> endobj 653 0 obj<> endobj 654 0 obj<> endobj 655 0 obj<> endobj 656 0 obj<> endobj 657 0 obj<> endobj 658 0 obj<> endobj 659 0 obj<> endobj 660 0 obj<> endobj 661 0 obj<> endobj 662 0 obj<> endobj 663 0 obj<> endobj 664 0 obj<> endobj 665 0 obj<> endobj 666 0 obj<> endobj 667 0 obj<> endobj 668 0 obj<> endobj 669 0 obj<> endobj 670 0 obj<> endobj 671 0 obj<> endobj 672 0 obj<> endobj 673 0 obj<> endobj 674 0 obj<> endobj 675 0 obj<> endobj 676 0 obj<> endobj 677 0 obj<> endobj 678 0 obj<> endobj 679 0 obj<> endobj 680 0 obj<> endobj 681 0 obj<> endobj 682 0 obj<> endobj 683 0 obj<> endobj 684 0 obj<> endobj 685 0 obj<> endobj 686 0 obj<> endobj 687 0 obj<> endobj 688 0 obj<> endobj 689 0 obj<> endobj 690 0 obj<> endobj 691 0 obj<> endobj 692 0 obj<> endobj 693 0 obj<> endobj 694 0 obj<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 695 0 obj<> endobj 696 0 obj<> endobj 697 0 obj<> endobj 698 0 obj<> endobj 699 0 obj<> endobj 700 0 obj<>stream number between 0 and 1. 0000043952 00000 n Most manufacturers worked to retrofit products to meet the new and more stringent standards. Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat from the sun. What exactly does that give you? . In summary, there are many things to consider when choosing the best window replacement options. {\displaystyle N*A(\lambda ,\theta )} We don't have extensive open space, placing furniture near windows and glass doors. "Do the math!". 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 . 0000018593 00000 n Simple 2x6 with exterior 1" aluminium skinned polyiso foam, south facing rear with larger windows and doors, few windows on other walls. 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 lower the U-factor, the more energy-efficient the window, door, or skylight. 5.8.2.2 Labeling of Fenestration Products . 0000008765 00000 n 0000035512 00000 n 0000010399 00000 n 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 used double-pane windows, and four large double-pane IGUs (for site built fixed windows). 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. 0000054052 00000 n To minimize this and reduce cooling loads, several technologies exist for solar gain reduction. how glass is used in the house design. /Width 76 0000056000 00000 n These tables give the solar data needed for designing an air conditioning system by either the traditional hand- calculating procedures or digital computer techniques. Our Comment Box is provided by Countable Web Productions countable.ca, Click to Show or Hide Citations & References, Heat Exchangers for Solar Water Heating Systems, Heat-Transfer Fluids for Solar Water Heating Systems, Solar Water Heating System Maintenance and Repair, Solar Water Heating System Freeze Protection, Scaling and Corrosion in Solar Water Heating Systems, Solar Heat Gain & Windows, the facts about, HOME INSPECTION EDUCATION COURSES (Canada), HOME INSPECTION EDUCATION: HOME STUDY COURSES, Ar-Lite Panelcraft, Inc., 13030 Wayne Rd., Livonia MI 48150, 2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707, 2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover). First, thanks for sharing your many helpful comments and ideas on GBA articles on Q&A. Thanks for your comments. /Annots 26 0 R Winter design temperature (F), or coldest expected temperature.. 0000013076 00000 n The specific microclimate of any building location should be used in building design, rather than the rough approximation of solar potential shown in this map or Table 1. The value of the shading coefficient ranges from 0 to 1. The home show in the photo used ceramic floor tile which varied in color but overall was a coffee color. 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. If you live in a hotter climate zone, an SHGC closer to 0 to block the heat is more appropriate. David, Map. We have a passive solar house we designed and built ourselves in SE Michigan in the late 80's. 0000038260 00000 n In the hotter summer season, solar heat gain through windows is usually undesirable. Hours earlier and later, the light could extend further but would be less intense. How Do I Reduce Or Eliminate Condensation? A product with a low air leakage rating is tighter than one with a high air leakage rating. 0000051339 00000 n The larger the SHGC, the more light that can enter through the window. 0000009623 00000 n 0000032190 00000 n Davor, endstream endobj 701 0 obj<> endobj 702 0 obj<> endobj 703 0 obj<>stream 0000042317 00000 n 0000057378 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. In Vermont you'd probably have difficulty with fogging due to moisture between glass layers. IMHO the typical USA under-insulated home with oversized fossil fuel heating and AC is the failed design in need of our greatest attention. 0000028911 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. It is defined as the ratio of solar radiation at a given wavelength and angle of incidence passing through a glass unit to the radiation that would pass through a reference window of frameless 3 millimetres (0.12in) Clear Float Glass. 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. We have no relationship with advertisers, products, or services discussed at this website. The lower the U-factor, the better the performance. Locations get lower scores if they cant generate much net solar gains, need less winter heating, or have cheap electric rates for minisplit heat pumps, electric radiant heating, or resistance electrical heating. F Worth remembering that those early-'80's houses are one of the main reasons we are having such fruitful discussions today! 0000034462 00000 n It is a safe bet to buy any material, so long as the overall replacement window is more energy efficient. Your homes climate, orientation, and external shading will determine the optimal SHGC for a particular window, door, or skylight.

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