BPI: BUILDING SCIENCE FUNDAMENTALS QUESTIONS
AND ANSWERS A+ GRADED
CFM
cubic feet per minute
CFM50
cubic feet per minute at 50 pascals of pressure
ACHn
natural air changes per hour
ACH50
air changes per hour at 50 pascals of pressure
How to calculate ACH50
CFM50 x 60 / volume of home
AFUE
Annual Fuel Utilization Efficiency. The efficiency of a boiler or furnace. It is the ratio of
annual heat output of the furnace or boiler compared to the total annual fossil fuel
energy consumed by a furnace or boiler
SSE
Steady State Efficiency. This is the heat extracted from the fuel and delivered to the
heat exchanger. The ratio of Btu input to useful or recoverable heat.
SEER
Seasonal Energy Efficiency Ratio. The efficiency measurement for a central air
conditioner or heat pump (during cooling season). The ratio of cooling capacity (BTUH
or BTUs per hour of heat removed) to watts.
EER
Energy Efficiency Ratio. The efficiency measurement for a central air conditioner, heat
pump AND room air conditioners (during cooling season). It is the ratio of cooling
capacity (BTUH) to watts of power.
HSPF
Heating Seasonal Performance Factor. A rating for heat pumps Ratio of BTUs of energy
used to watt-hr of electricity consumed.
Testing for SSE
High CO2 = good High O2 = bad
Watt
Unit of power (j/s)
Ton of Refrigeration
a measure of the amount of heat removed. 1 ton of refrigeration = 12,000 BTU/hr =
3,517 watts
BTU
unit of energy. 1 BTU is equal to the energy needed to raise 1 lb of water 1 degree F.
Therm
, 6.Therm - a unit of heat equal to 100,000 BTUs
Decatherm
one million BTU's or 10 therms
Energy
What is delivered
Power
rate at which it is delivered, Power = work/time
Effective Leakage Area
is a measurement of the air tightness of a home that is expressed as an area (in2) to
help the homeowner better visualize and quantify leakage in a home.
ELA example
take your measured CFM50 and divide it by 10. Your answer is the equivalent size hole
in square inches. So a CFM50 measured at 1,440, would have an ELA equal to 144 sq
inches or, 1 sq ft.
R-Value
the measure of a materials thermal resistance in units of ft²·°F·h/Btu. Insulation
properties are described in terms of R-values. The higher the R-value, the greater the
thermal resistance.
U-Value
the overall heat transfer coefficient. U-values are a measure of conductance a material.
It tell us how much heat conducts through a 1 sq ft area in 1 hr when there is a 1 degree
F temperature difference.
Understanding U-value
It tells us how much heat conducts through a 1 sq ft area in 1 hr when there is a 1
degree F temperature difference. The smaller the U-value, the better the object is at
reducing heat transfer.
Relationship between U and R values
1 / R-value = U-value
1 / U-value = R-value
Difference between U and R values
R-values can be added together, U-values cannot
Assumptions for weighted R value calculations
•16-IOC (inch-on-center) studs account for 20-25% of the wall area OR 75% of the wall
area is an open cavity
•24-IOC studs account for 15-20% of the wall area
Everything rolls down hill
High temp to low, high pressure to low, high moisture to low
Radiation
Radiant energy flies through space through electromagnetic waves from one object to
another.
What happens to radiant heat?
All radiant heat is either absorbed, reflected or transmitted.
Emissivity
AND ANSWERS A+ GRADED
CFM
cubic feet per minute
CFM50
cubic feet per minute at 50 pascals of pressure
ACHn
natural air changes per hour
ACH50
air changes per hour at 50 pascals of pressure
How to calculate ACH50
CFM50 x 60 / volume of home
AFUE
Annual Fuel Utilization Efficiency. The efficiency of a boiler or furnace. It is the ratio of
annual heat output of the furnace or boiler compared to the total annual fossil fuel
energy consumed by a furnace or boiler
SSE
Steady State Efficiency. This is the heat extracted from the fuel and delivered to the
heat exchanger. The ratio of Btu input to useful or recoverable heat.
SEER
Seasonal Energy Efficiency Ratio. The efficiency measurement for a central air
conditioner or heat pump (during cooling season). The ratio of cooling capacity (BTUH
or BTUs per hour of heat removed) to watts.
EER
Energy Efficiency Ratio. The efficiency measurement for a central air conditioner, heat
pump AND room air conditioners (during cooling season). It is the ratio of cooling
capacity (BTUH) to watts of power.
HSPF
Heating Seasonal Performance Factor. A rating for heat pumps Ratio of BTUs of energy
used to watt-hr of electricity consumed.
Testing for SSE
High CO2 = good High O2 = bad
Watt
Unit of power (j/s)
Ton of Refrigeration
a measure of the amount of heat removed. 1 ton of refrigeration = 12,000 BTU/hr =
3,517 watts
BTU
unit of energy. 1 BTU is equal to the energy needed to raise 1 lb of water 1 degree F.
Therm
, 6.Therm - a unit of heat equal to 100,000 BTUs
Decatherm
one million BTU's or 10 therms
Energy
What is delivered
Power
rate at which it is delivered, Power = work/time
Effective Leakage Area
is a measurement of the air tightness of a home that is expressed as an area (in2) to
help the homeowner better visualize and quantify leakage in a home.
ELA example
take your measured CFM50 and divide it by 10. Your answer is the equivalent size hole
in square inches. So a CFM50 measured at 1,440, would have an ELA equal to 144 sq
inches or, 1 sq ft.
R-Value
the measure of a materials thermal resistance in units of ft²·°F·h/Btu. Insulation
properties are described in terms of R-values. The higher the R-value, the greater the
thermal resistance.
U-Value
the overall heat transfer coefficient. U-values are a measure of conductance a material.
It tell us how much heat conducts through a 1 sq ft area in 1 hr when there is a 1 degree
F temperature difference.
Understanding U-value
It tells us how much heat conducts through a 1 sq ft area in 1 hr when there is a 1
degree F temperature difference. The smaller the U-value, the better the object is at
reducing heat transfer.
Relationship between U and R values
1 / R-value = U-value
1 / U-value = R-value
Difference between U and R values
R-values can be added together, U-values cannot
Assumptions for weighted R value calculations
•16-IOC (inch-on-center) studs account for 20-25% of the wall area OR 75% of the wall
area is an open cavity
•24-IOC studs account for 15-20% of the wall area
Everything rolls down hill
High temp to low, high pressure to low, high moisture to low
Radiation
Radiant energy flies through space through electromagnetic waves from one object to
another.
What happens to radiant heat?
All radiant heat is either absorbed, reflected or transmitted.
Emissivity
