Here is a link to the pbs interview where Larry Silverstein said it:
https://www.youtube.com/watch?v=Wq-0JIR38V0
I know everyone has seen the building go down. That is never a building's response to a fire, according to what I have seen. The 911 report kind of skimmed over it and went into no detail. I don't put any stock in quasi scientific explanations of why, in this one special case, a fire led to a pancaking collapse. When you have a foregone conclusion and look to find reasons why the conclusion is true you are not engaging in science. I wouldn't even read the popular mechanics article supposedly debunking the conspiracy theories. I talked to 4 or 5 grad and undergrad students in civil engineering back when this happened just because they were around and I wanted to pick their brains. None of them thought it was a controlled demolition but they all had distinct theories of why the building collapsed. Obviously they cannot all be correct. But that doesn't make them conspiratards. They are simply using their education and judgement to make a guess, although they were far more adamant than I am. I know that there is a decent chance that it wasn't a controlled demolition. But I think more likely than not it was.
If someone were to show that this type of collapse happens sometimes resulting from a fire that would go a long way towards me reconsidering. But from what I have been told this type of collapse resulting from fire is practically unheard of.
Maybe I should read more about it. But like I said, when smart people decide on a conclusion and
then start looking for supporting evidence they can sound very convincing while being way wrong. You can be assured that the people who write the official reports did not ever consider the possibility that there was controlled demolition. Look at all the "evidence" of WMD's in Iraq. Look at all the smart people who had us believing ice cream trucks were mobile weapons factories (well not me but most people). They believed it too because they started with a conclusion and went from there. That is not how to do science.
There are several physicists and engineers at accredited universities who believe the twin towers were a controlled demolition. In that case I suspend judgement because that event was such a novel experiment that you kind of have to take it at face value. You can see the planes impacting the buildings and who knows what kind of effect that has- it has never been studied experimentally or longitudinally. But with building 7 we see just a fire and some apparently minor structural damage. We have plenty of comparisons for that in the past and, though I could be misinformed, we haven't ever seen that outcome resulting from similar scenarios in the past.