heat gains into a building solar gains shading. attendance what improvement did george ravenscroft...
TRANSCRIPT
Heat Gains into a Building
Solar GainsShading
Attendance
What improvement did George Ravenscroft (1618 – 1681) develop to make glass windows economically feasible?
A. Made it squareB. Added color to make it
more attractiveC. Added lead oxideD. Learned how to bevel
the glassE. Made it thinner
What You Need to Know
How solar radiation effects cooling loads
What You Need to be Able To Do
Be able to calculate solar loadsDevelop strategies to limit/postpone/utilize solar loads
Terms
FenestrationSolar Heat Gain Factor (SHGF)Shading Coefficient (SC)
sun rayssun rayssun rayssun rays
reflectedreflectedenergyenergy
reflectedreflectedenergyenergy
transmittedtransmittedenergyenergytransmittedtransmittedenergyenergy
glassglasswindowwindowglassglasswindowwindow
conductionconduction
solar gain solar gain (radiation)(radiation)
Sunlit Glass
QQSS = solar gain + conduction = solar gain + conduction
Fenestration
“Any opening in the external envelope of a building that allows light to pass.”
Glass - Conduction
•Calculated the same way as heating for conduction
Qconduction = U A TD
Calculating the Solar Gain
Q = SHGF x A x SCwhere:
SHGF = Solar Heat Gain FactorA = AreaSC = Shading Coefficient
Solar Heat Gain Factor (SHGF), Table 2-15A
Do you see the three variables?
Shading CoefficientsTable 2-16
Shading Strategies
Fins Overhangs
Shading Strategies
Adjacent Buildings
Shading Strategies
A completely shaded window is similar to a North facing window
Accounting for Shade
In the Northern hemisphere, use the North Column
Effect of Glass on a South WallGlass – ConductionQC = 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
LEED EA Credit 1
Credit 1 – Optimize energy performance (1 to 10 points) Building
orientation Harvest free
energy Sustainable
strategies
Cooling Peak Load – Sum of All Cooling Loads at Peak Conditions
Sensible LatentRoof = 14,253 Btu/HrWallS = 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/HrVentilation (372) = 8,184 Btu/Hr 7,083 Btu/HrInfiltration = 0 0
TOTAL 38,486 Btu/Hr 11,733 Btu/Hr