Transcript Formulas - Washington State University

Design
 What is the first step in designing a high-performance
building?
 Would it be:

Identify synergies

Select the correct HVAC system

Design around human comfort

Reduce the load
Heat Loss due to Infiltration &
Ventilation
Infiltration
1.1 x [(ACH x vol.) /60] x (Ti -To)
-or.018 x ACH x Vol. x (Ti- To)
Note: CFM = (ACH x volume) / 60 min per hour
Ventilation
1.1 x [( Ra x SF) + (No. of people x Rp)] x
(Ti –To)
Heat Loss Due to Infiltration
Infiltration
Please Note:
For tight construction use 0.5 for ACH.
For medium construction use .85 for ACH.
For loose construction use 1.3 for ACH.
For really bad construction use 2.0 for ACH
For the summer months (cooling) use 70% of the winter
values.
Heat Loss Due to Infiltration
 Infiltration through a wall is not an intended. We do
try and reduce and / or control amount of air leakage.
Heat Gains from Occupant Loads
Sensible
per occupant X number of occupants = Btu h
Latent
per occupant X number of occupants = Btu h
Heat Gains from Infiltration Loads
Sensible
Btu h = 1.1 x CFM x TD
Latent
Btu h = 4,500 x CFM x (Wroom – Woa)
Heat Gains from Outside Air for
Ventilation Loads
Sensible
Btu h = 1.1 x CFM x TD
Latent
Btu h = 4,500 x CFM x (Wroom – Woa)
-orBtu h = .68 x CFM x (W2 – W1)
Degree Days
 Temperatures between 600 and 800 Fahrenheit are
comfortable.
 Temperatures between 600 and 800 are nicknamed the
Goldilocks Zone.
 Degree days HDD heating is based on each degree
below the base of 650 U.S. 60o in Great Britain
 Degree days CDD cooling is based on each degree
above the base of 800 U.S. 60o in Great Britain
Degree Days
for Pullman
 HDD = 6655
 CDD = 1154
Degree Day = 65°F ((high temp. – low
temp])/2)
Formula
Operating Hours = [Degree Days x 24] /
[ Temperature Difference]
Heating Degree Days for Pullman = HDD =
6655
Temperature Difference =ΔT (for project)
Formula
Operating Hours = [Degree Days x 24] /
[ Temperature Difference]
Heating Degree Days
Example: The Kirk Building
Operating Hours = (6655 x 24)/87
Operating Hours = 1,836
Formula
Operating Hours = [Degree Days x 24] /
[ Temperature Difference]
Cooling Degree Days for Pullman = CDD = 1154
Temperature Difference =ΔT (for project)
Formula
Operating Hours = [Degree Days x 24] /
[ Temperature Difference]
Cooling Degree Days
Example: The Kirk Building
Operating Hours = (1154 x 24)/25
Operating Hours = 1,108
Estimating Annual Energy
Heating $/Yr
Electric
(BTU/Hr) * (hours of operation) * $/energy unit
BTU/energy Unit * Efficiency
Electric conversion = 3,400 BTU h/Kilowatt
Efficiency = 1.0
Note: Does not include fan energy. Add 10% for
residential and 20% for commercial fan energy
Estimating Annual Energy
Heating $/Yr
Gas
(BTU/Hr) * (hours of operation) * $/energy unit
BTU/energy Unit * Efficiency
Electric conversion = 100,000 BTU h/Therm
Efficiency = 80% - 96%
Note: Does not include fan energy. Add 10% for
residential and 20% for commercial fan energy
Estimating Annual Energy
Cooling $/Yr
(Btu/Hr) * (hours of operation) * $/energy unit
SEER * 1000
Note: Does not include fan energy. Add 10% for
residential and 20% for commercial fan energy
Estimating Annual Energy
SEER Seasonal Energy Efficiency Ratio
The U.S. Department of Energy claims energy we use in
an average house is responsible for twice as many
greenhouse gas emissions as an average car.
Estimating Annual Energy
Estimating Annual Energy
SEER Seasonal Energy Efficiency Ratio
The efficiency of central air conditioning regulated by the
U.S. Department of Energy (DOE).
The SEER is defined as the total cooling output (in British
thermal units or Btu) provided by the
The change from SEER 10 to SEER 13 represented a 30 percent
improvement in energy efficiency.
SEER = (seasonal Btu of cooling) / (seasonal watt-hours of
electricity used)
Estimating Annual Energy
SEER Seasonal Energy Efficiency Ratio
Great strides have been made in the last 10 in efficiency
of air conditioners and heat pumps.
SEER ratings for air conditioning and air-source heat
pump systems manufactured today range from 13
SEER to 24.
Central air conditioners that are in the top 25 percent of
efficient may carry the ENERGY STAR® label. To
qualify, they must have a minimum SEER efficiency
level of 14
Estimating Annual Energy
Example: The Kirk Building
Heating $/Yr
(2,324,056) * (hours of operation) * $/energy unit
BTU/energy Unit * Efficiency
Note: Does not include fan energy. Add 10% for
residential and 20% for commercial fan energy
Electrical Cost to Heat
[(BTU/Hr) * (hours of operation) * $/energy unit]/
BTU/energy Unit * Efficiency
.08 electrical cost per kilowatt hours
[(2,310,240) * (1,836) * .08]/ (3,400 * 1 .00) = $99,802.37