I plan to say more about designing passive solar homes effectively in a future blog. 0000019003 00000 n Similar analysis could be performed by using web resources to compute solar gains for windows in other orientations. 0000033229 00000 n In passive solar and solar-tempered homes, typically there are more or larger windows facing south, and fewer or smaller windows facing other directions. This home had sufficient, well-insulated thermal mass tiled slab floor, engineered quantitatively to offset wintertime heat losses with solar heat gains. SOLAR RADIATION Solar radiation has important effects on both the heat gain and heat loss of a building. 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. 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. 0000059744 00000 n -- Buildings are considered "solar tempered" if they provide enough wintertime solar heat gain to keep the building's interior warm during sunny days. , 0 Other cities in the list across the Midwest and northern central U.S. get about half the net solar heat gain of Denver. Designers and builders can use higher solar heat gain windows on south-facing windows and higher R-value (lower U-factor) windows on north, west, and east-facing windows to further increase solar gains and reduce heat losses overall. But maybe that's because of my partly cloudy location of zone 5 Iowa City Iowa? a product is at blocking unwanted heat gain. As well, 3 years ago, having been so pleased with the shutter effect, I built a "low mass, super insulated south facing solar porch. Be sure to educate yourself and to work with a professional installer for your project. So the cost of electricity is used to compute the value of solar heat gains in the following analysis. 0000027861 00000 n 0000023641 00000 n This article notes the importance of using south-facing windows to capture warmth (and natural lighting) in winter, yet not suffer as much heat gain in summer (vs. west and east-facing windows). 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. -- Seasonally, the coldest temps of winter, and the hottest temps of summer, lag the sun's seasonal changes in path and intensity. 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]. Solar, wind or other renewable energy source supplies not less than 80 percent of the energy for service water heating. 0000038693 00000 n (13) Design roof overhangs, patio or deck coverings, and landscaping to preserve unobstructed sunshine in winter, and shade west- and east-facing windows during summer months. When designing a building, the solar heating potential can be computed. 0000050694 00000 n {\displaystyle F(\lambda ,\theta )=T(\lambda ,\theta )+N*A(\lambda ,\theta )}. 0000051079 00000 n 0000060877 00000 n We pull tight insulating shades over the windows in the evening to reduce heat loss. Unfortunately, by late August, it is still hot summer weather, but the sun's path has changed to be lower on the horizon than June 21st. Such devices can reduce the shading coefficient by blocking portions of the glazing with opaque or translucent material, thus reducing the overall transmissivity. 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_ The design was intended to reduce supplementary space heating substantially and minimize utility bills. , 0000034107 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. 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. 0000018030 00000 n 0000043411 00000 n The reason Energy STAR, from the U.S. Department of Energy, designates four climate zones is to help make it easier for homeowners to know which new house windows will work in their climate. /CS0 8 0 R Seattle, Washington. It's free and doesn't require a download. The lower the 0000009701 00000 n I don't ever remember using shades to reduce glare or overheating during the winter. Maybe some desiccant packets could help reduce fogging? (4) South-facing windows can provide about fifteen times as much light and solar heat gain in winter as north-facing windows. Privacy | 0000018276 00000 n Is there anything else other than minding where you put your furniture? Just that insulated door is shut at night and the porch is then isolated from the main heated building. Intro to roof overhangs and shading 0000044828 00000 n -- 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. /Type /Page 0000023337 00000 n 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. 0000018449 00000 n The shading coefficient (SC) is a measure of the radiative thermal performance of a glass unit (panel or window) in a building. 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. The Climate Zone 5 site has 5,600 heating degree days. . 0000041586 00000 n 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. 350 You can use the energy performance ratings of windows, doors, and skylights to understand their potential for gaining and losing heat, as well as bringing sunlight into your home. Thank you Bob for sharing this very thorough article! Maybe we should not let the perfect be the enemy of the good. It is easier to maximize wintertime solar heating in some climates than others. The lower the rating, the less solar heat is transmitted through the glass, and the greater its shading ability. endstream endobj startxref (2005 ASHRAE Handbook : Fundamentals at Amazon). I see lots of examples where people try things without "doing the math" beforehand. 0000014397 00000 n lL)Cg4xo` =[3lhb$qrCcUT?iFgqH10L9e:Q` 8 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. be adjusted for thermal lag and time delay. 3M's Sungain Film brochure mentions "Solar Input," which represents the shading coefficient times 0.87. Here's some information not included in the article that provides background to those unfamiliar with the topic raised by Malcolm. The first six columns list the same 22 U.S. cities and other previously displayed data, which are helpful in determining the value and ease of using solar heat gains for space heating. E The lower the U-Factor, the better the window insulates. 0000037750 00000 n But it would not shade the window as much as you'd like by late August, or earlier or later during the day on June 21st, as you point out. 0000031802 00000 n 0000025618 00000 n 0000021224 00000 n 0000021316 00000 n Low-E Type . 0000026777 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. South-facing windows provide between 59% and 77% of the total solar gains, despite making up only 25% of the glazing of the four windows of equal size. Passive solar heat gain through large south-facing windows provided most of the winter space heating energy. For double glazed windows SHGC is more often in the range of 0.42 - 0.55. qog7/f8S0f|+Ca(zS{ /IQW:8p=~cn7y 8,+!H6*"rd%oBT$DY^V7E aO/CZMI>*V2hxErMQX{fNFE DnAb Thank you for sharing your thoughts, Bob. 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 . You want to shade your south-facing windows from the sun to avoid solar heat gain. 0000030709 00000 n 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. This quantity includes both energy that is transmitted directly through the glass as well as energy that is absorbed by the glass and frame and re-radiated into the space, and is given by the following equation:[4], F trailer % 0000047056 00000 n If your TV screen is in direct sunlight, it would be difficult to see the screen. ( Long stretches of overcast days produce large heat losses through large windows, with minimal solar heat gains to compensate. How do you optimize this shading in a more so sophisticated way that the common arc diagram? They have been prepared in exactly the same way as the tables in the ASHRAE Handbook of Fundamentals (1967), but are for the latitudes of particular relevance in Canada and for . For the months of December and January, the sun is low on the horizon during midday. Also for example, if I am to have brunch/lunch during daytime, where do I put dining table? In the early days, computer screens had hoods that blocked light from above and the sides. I found it both interesting and very useful. Solar heat gain coefficients are expressed as decimals from 0.00 to 1.00. You bring up an important point. 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). I look forward to reading your future articles. 0000025511 00000 n 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. >> Modify the landscape of the property to optimize wintertime solar heat gain (and reduce summertime solar heat gain from the west). Glare 0000043195 00000 n 0000027129 00000 n 0000033339 00000 n 0000010476 00000 n 0000052109 00000 n SHGC & U-Factor Tool. 0000059957 00000 n However, a few strategically placed deciduous trees and i have all but eliminated my summertime window solar exposure. 0000029050 00000 n 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. 0000010091 00000 n Glass Color . 0000008467 00000 n At solar noon on Dec 21st, light from a south-facing window at typical height would cast direct sunlight about 13' into the home's interior. {\displaystyle N*A(\lambda ,\theta )} 0000011708 00000 n /Height 99 The lower the SHGC, the less solar heat it transmits and the greater its shading ability. [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. To perform an approximate conversion from SC to SHGC, multiply the SC value by 0.87. Locations needing a lot of heating, that have high electricity prices, and that have good net solar gains, get higher scores. This article explores the viability of passive solar and solar-tempered space heating in northern U.S. regions and metro areas. 0000058284 00000 n
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