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.
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