Retrotec Residential Pressure & Air Leakage - Manual (Page 62)

Page 62 of 75
©Retrotec Inc. 2014
Table 20: Resulting natural ventilation and potential savings in energy for various ACH50 values
ACH50
Natural
Air
Change
Rating
% of
Energy
bill
% savings
potential
Ventilation requirements
1.5 0.075
Super 2% none Requires constant energy recovery ventilation
3.5 0.18
Excellent 6% 1 to 3% Will require occasional forced ventilation
5 0.25
Better 10% 2 to 4% May require occasional forced ventilation
7 0.35
Good 14% 2 to 5% Does not require additional ventilation
10 0.50
Fair 20% 3 to 10% Start of excessive energy loss and over -ventilation
20 1.0
Bad 40% 5 to 20% Excessive energy loss and over –ventilation.
With reference to the Table 20 above:
ACH50 is the air flow at 50 Pa in CFM divided by the conditioned volume of the house.
Natural Air Change is the number of times per hour that all the air in the house will be changed, based on the
value for ACH50. It is generally considered that 0.35 is sufficient but the amount is dependent upon occupancy,
building dimensions, indoor pollution sources, and weather. Most homes will be under and over ventilated at
different times.
% of energy bill is the amount of the total energy bill that can be attributed to air leakage.
% savings potential is attributed to the fact that leakage can be reduced by 12 to 50 % with the average being
25%. Duct leakages can double these losses.