Step 3: Assume standard air exchange for homes. What is the ventilation rate for your home?

Assuming standard air exchange for homes, we will calculate the ventilation rate for the home.  The density of air is about 0.075 lb_m/ft³ at 70 ⁰F.  By using the volume of the house of 8000 ft³ and neglecting the area taken up by the objects in the house and the walls separating the two rooms, we can see that 619.6 lb_m of air is in the house at all times. We will say that 40 percent of the air needs to be circulated to prevent stagnant air, which is a valid assumption. Also, this air change per hour is assumed to be 2 times, so 48 times over the course of a day. 


m_dot = (619.8 lbm)(0.40)(2 times per hour) = 495.7 lbm/hr = 8.26 lbm/min

Ventilation rate = Q = m­_dot/density of air = (8.26 lbm/min)/(.075 lbm/ft^3) = 110 CFM