The formula for volume of a cone is V=(1/3)*h*π*(r^2)
our height is 7.5 feet, and since the length of the base of the cone (diameter) is 22 feet long, the radius is 11 feet long. 
(1/3)*7.5*π*(11^2)=302.5*π=950.3 
so the volume of the house is about 950 feet cubed.