Formulas Flashcards
Illuminance / footcandle
E=I/d^2
I or intensity
d or distance
Luminance
L=E(R)
E or illuminance
R or reflectance
Conduction or Heat Gain
U x A x Delta T
Power
P= V x I x PF x sqrt(3) P or Power in Watts V or voltage in volts I or current in amps PF or power factor
U - value
1/R value or
(Ux area of window + U x Area of wall)/total area
Q - Ventilation / convection
Q= 1.08 x CFM x Delta T
Foot Candles
Foot candles = Lumens/ Area in Ft2
or
(Lamp Lumens) x Lumens per Fixture x number of fixtures x CU x LLF / Area
Building Loss Coefficient
BLC = UAenvelope + UAinfiltration
1 ACH/ HR
63.2% new air in room
1 PSI
2.31 feet of water ( 1 PSI will raise water 2.31 feet vertically)
Thermal Expansion
Length x Coefficient of Expansion x Delta T
1 Watt
3.41 BTU/hour
1 ton of AC
12,000 BTU/hr
1kwh
3,400 BTU/hr
Cross section area of a duct
144x(the flow rate in CFM)/ velocity measured in feet per min (V)
Ohms Law
I=V/R
I or current in amps
V or voltage in volts
R or Resistance
Number of Luminaires
footcandles x floor area/ lumens x CU x LLF
Coefficient of Clear Glass
85%
Coefficient of Frosted Glass
70-85%
Contrast ratio of task to adjacent surface
1:1/3
Contrast ratio to dark surfaces
1:1/5
Contrast to lighter surfaces
1:10
Daylight factor
0.2 x window area/floor area
Wavelength
velocity of sound/frequency of sound
Sabins
Surface area of room x absorptivity of surfaces
NRC
Total sabins or A/ Total surface area in the room or S
Elevator Speed
1.6 x building height + 350
1 therm = ___________ Btu
10,000 btu
