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Heat Gains into a Building

This document explores the impact of solar radiation on cooling loads in buildings and offers insights into efficient shading strategies. It highlights historic improvements in glass window production that made it economically feasible, focusing on innovations by George Ravenscroft. Key terms such as Solar Heat Gain Factor (SHGF), Shading Coefficient (SC), and fenestration are defined to enhance understanding. Additionally, practical calculations for solar gains and strategies to limit or utilize these loads are provided, making it a valuable resource for sustainable building design.

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Heat Gains into a Building

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  1. Heat Gains into a Building Solar Gains Shading

  2. Attendance • What improvement did George Ravenscroft (1618 – 1681) develop to make glass windows economically feasible? • Made it square • Added color to make it more attractive • Added lead oxide • Learned how to bevel the glass • Made it thinner

  3. What You Need to Know • How solar radiation effects cooling loads

  4. What You Need to be Able To Do • Be able to calculate solar loads • Develop strategies to limit/postpone/utilize solar loads

  5. Terms • Fenestration • Solar Heat Gain Factor (SHGF) • Shading Coefficient (SC)

  6. sun rays solar gain (radiation) transmitted energy conduction reflected energy glass window Sunlit Glass Fenestration “Any opening in the external envelope of a building that allows light to pass.” QS = solar gain + conduction

  7. Glass - Conduction • Calculated the same way as heating for conduction Qconduction = U  A TD

  8. Calculating the Solar Gain Q = SHGF x A x SC where: SHGF = Solar Heat Gain Factor A = Area SC = Shading Coefficient

  9. Solar Heat Gain Factor (SHGF), Table 2-15A Do you see the three variables?

  10. Shading CoefficientsTable 2-16

  11. Fins Overhangs Shading Strategies

  12. Shading Strategies • Adjacent Buildings

  13. Shading Strategies • A completely shaded window is similar to a North facing window

  14. Accounting for Shade • In the Northern hemisphere, use the North Column

  15. Glass – Conduction QC = U x A x (T2 – T1) QC = .47 x (24 x 4) x 17 QC = 767 Btu/Hr Glass – Solar QS = SC x A x SHGF QS = .90 x (24 x 4) x 29 QS = 2,505 Btu/Hr QT = 2278 Btu/Hr Wall – Conduction QC = U x A x TETD QC = .26 x 377 x 19 QC = 1,875 Btu/Hr Effect of Glass on a South Wall

  16. LEED EA Credit 1 • Credit 1 – Optimize energy performance (1 to 10 points) • Building orientation • Harvest free energy • Sustainable strategies

  17. Cooling Peak Load – Sum of All Cooling Loads at Peak Conditions SensibleLatent Roof = 14,253 Btu/Hr WallS = 1,875 Btu/Hr WallN = 593 Btu/Hr WallE = 2,162 Btu/Hr GlassS = 3,272 Btu/Hr GlassN = 797 Btu/Hr People (30) = 7,350 Btu/Hr 4,650 Btu/Hr Ventilation (372) = 8,184 Btu/Hr 7,083 Btu/Hr Infiltration = 0 0 TOTAL 38,486 Btu/Hr 11,733 Btu/Hr

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