Infiltration rates in unoccupied houses in Melbourne and found that background infiltration rates were 0.33 air exchanges per hour (ACH).
Figure 1. Tracer Gas Infiltration Rates in 91 Homes with the Air Handler Off and On. The return leak fraction (RLF) was measured in each home with the AH operating (Figure 2). Sixty percent were found to have return leaks equal to or greater than 5% of the AH total air flow. Thirty percent have greater than 10% RLF.  The overall tightness of the PVRES home was 1587 CFM50 or 4.9 ACH50 with a house ELA of 69.0 square inches. For Central Florida's climate, a useful rule of thumb to determine the house natural air infiltration rate is to divide the house ACH at 50 pascals by 30. This would estimate a typical natural air change rate of about 0.16 ACH in the PVRES home and 0.21 ACH in the Control.  This Home Energy classic, originally printed in 1986, explains a simple way to take one air infiltration measurement and determine a home's average air infiltration rate. Many researchers have sought to develop a correlation between a one-time pressurization test and an annual infiltration rate. average infiltration rate (ACH) = ACH50(1) ----- 20. A person conducting pressurization tests on a particular house can collect considerable information about these details. Studies show that this leakageamounts to only 1% to 4% of a typical home’s total infiltration. Since infiltration accounts for up to 40% of ahome’s total heat loss, electrical outlet infiltration isresponsible for 4% of 40%, or 1.6% of a home’s total heatloss.  Thus, for a house with 15 ACH at 50 Pascals (ACH50 = 15), one would predict an average air change rate of (15/20 =) 0.75 ACH. This simple formula yields surprisingly reasonable average infiltration estimates, even though it ignores many details of the infiltration process. Many researchers have sought to develop a correlation between a one-time pressurization test and an annual infiltration rate. average infiltration rate (ACH) = ACH50(1) ----- 20. A person conducting pressurization tests on a particular house can collect considerable information about these details. Infiltration measures [edit]. The infiltration rate is the volumetric flow rate of outside air into a building, typically in cubic feet per minute (CFM) or liters per second (LPS). The air exchange rate, (I), is the number of interior volume air changes that occur per hour, and has units of 1/h.  12 Whole House Ventilation Strategies attempted to quantify the average natural infiltration rate for typical manufactured homes. These studies established an approximate average rate of 0.25 air changes per hour (ACH) under natural conditions (3, 13, 14, 35). Natural infiltration rates were measured in two mobile homes in Indiana for 16 months. The. researchers developed a correlation for the rate of infiltration as a function of inside-outside. temperature difference and wind speed.
http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-217-96/index.htm http://www.fsec.ucf.edu/en/research/buildings/zero_energy/lakeland/bldg_envelope.htm http://homeenergy.org/show/article/nav/blowerdoor/id/1015 http://www.certainteed.com/resources/30-21-1225.pdf http://homeenergy.org/show/article/nav/blowerdoor/id/1015 https://en.wikipedia.org/wiki/Infiltration_(HVAC) http://www.huduser.gov/publications/pdf/house_ventilation.pdf
typical infiltration rates for houses