Decay rate of overpressure for a nuclear blast (shockwave) over an urban area?

I have come across a very new idea for me concerning nuclear weapons effects, check this please.

In brief, that person states that blast overpressure attenuates/decays by causing damage for each individual building it crosses in a radial line, which makes some sense. But, the numbers this guy gave were really shocking, for example, he stated (calculated from data given by W.Penney) that 1% of the blast energy is lost for each wood-frame house the blast crosses, and about 5% for each concrete or brick building. If that is true, then by correcting the blast overpressure rings driven from the usual scaling laws we find that for example : for a 1 MT, the ideal 20 psi ground range is about 2.6 km, then by applying the decay/attenuation rate over say 50 concrete buildings in a modern city (just a rough estimate for buildings in 2.6 km radial line), we get 0.95^50 = 7.5% of the value of the overpressure expected for an ideal surface at 2.6 km, which is about 1.5 psi, so that makes nuclear weapons much much weaker than we ever imagined.

So now my back to my question. Is there a way to calculate how the buildings will affect the attenuation of the blast wave in a common urban area ?

Also, do the numbers of 1% and 5% makes sense for you ?

I am sorry if I can't express what I want in a better way, English is not my first language so I did my best and I hope that was enough to explain what I want to know.

-