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
He added lead oxide to the glass to make it much easier to form and cut. This allowed glass blowers to make panes of glass much more quickly, making glass windows widely available.

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. Sunlit Glass QS = solar gain + conduction Fenestration
sun rays
reflected
energy
transmitted
glass
window
conduction
solar gain (radiation)
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
I. Calculating the Solar Gain
A. Q = SHGF x A x SC x CLF
where:
SHGF = Solar Heat Gain Factor
A = Area
SC = Shading Coefficient
CLF = Cooling Load Factor

9. Solar Heat Gain Factor (SHGF), Table 2-15A
Do you see the three variables?
I. Solar Heat Gain Factor, Table 2.8
A. A function of:
1. Latitude
2. Direction
3. Month
B. Based upon clear glass, 1/8” think
C. Based upon no shading
D. Based upon the 21st day of the month
E.. Units are BTU/hr-ft2

10. Shading Coefficients Table 2-16
I. Shading Coefficients, Table 2.8
A. Adjustment factor to take into account shading.
B. A lot of research has been done on shading
1. ASHRAE re: fabric styles

11. Shading Strategies Fins Overhangs I. Shading Types A. Fins
1. Popular in the 50’s and 60’s
2. Executive Office Building on 15th St.
is a good example.

12. Shading Strategies Adjacent Buildings I. Shading Types
A. Adjacent buildings
1. May completely shade the entire window
2. Our classroom is a good example of this.
3. Use Solar Heat Gain Factor (SHGF) for
North facing glass to account for this type
of shading. See Table 6.6

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. Effect of Glass on a South Wall
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

16. LEED EA Credit 1
Credit 1 – Optimize energy performance (1 to 10 points)
Building orientation
Harvest free energy
Sustainable strategies
Harvest free energy
Building orientation
Appropriate envelope design
Use of thermal mass to balance temperature variations
Natural ventilation
Use of appropriate glazing
Earth-coupled heat pumps
Turning off lights when daylight is available

17. Cooling Peak Load – Sum of All Cooling Loads at Peak Conditions
Sensible Latent 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