I honestly don't see a link to low interest rates being the reason construction costs have increased. Rather that their is a labour shortage in North America with proposed projects in infrastructure and buildings outstripping supply of said labour.Low interest rates.
If in previous years, you could borrow 1Billion at 8% interest; that means 80 Million per year in interest costs alone to service that debt.
If today, you can borrow that same sum at 3% its 50M per year cheaper.
That's the essence of 'cheap money'.
In a direct sense, this can lower the cost of a debt-financed project.
But it also causes many more people to enter the real estate market (and stock market) than otherwise would, using 'the banks' money, rather than their own.
In so doing, the cost of real estate is driven up.
In so far as it fuels high levels of construction; that puts ever greater demand on a relatively fixed labour pool in the skilled trades; which tends to drive up wages at rates faster than inflation.
Cheap money is not, by any means a fulsome explanation of why construction costs have risen inordinately in Canada, and in cities like Toronto and Vancouver in particular.
High levels of immigration, creating a real need for additional housing and infrastructure factor in to this as well; amongst other things.
But 'cheap money' is a part of the story for sure.