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