To solve this problem, we can use the concept of permutations. Since the order in which the building inspector visits the construction sites matters, we can use the formula for permutations:
nPr = \frac{n!}{(n-r)!}
where n is the total number of new construction sites (10 in this case) and r is the number of construction sites the building inspector visits (7 in this case).
Plugging in the values:
10P7 = \frac{10!}{(10-7)!} = \frac{10!}{3!} = \frac{10*9*8*7*6*5*4*3*2*1}{3*2*1} = 604800
So, there are \boxed{604800} different ways the building inspector can visit 7 new construction sites out of a total of 10 construction sites.
\boxed{Answer: 604800}