CBC:
How 24 Sussex Drive can become the greenest official residence it can beThis includes an interview with Bryan Baeumler. Both the CTV and CBC interviews he talks about gutting it. He actually claims trying to save any existing structure costs more than gutting and starting over. That's backwards. One of the points of replacing as little as possible is to reduce the cost. And he claims the $10 million price is low, it would cost a lot more. I think he smells a gravy train.

Bryan said the house is set on stone rubble foundation. But the house has a full basement. That doesn't add up.
Bryan also talks about rebuilding 24 Sussex to be some kind of demo of new environmental tech, completely abandoning any heritage. The website of the National Capital Commission laments the modernization of 1950, they certainly wouldn't approve doing it again. Ok, Bryan's out.
Lemmy and Robair think Holmes is just as bad. This is getting disheartening.
Another point: a 2x4 was called that because it was 2 inches by 4 inches. Lumber companies got cheap, started to sell 1-3/4" x 3-3/4" but called them 2x4. That was some time in the 1920s. Since 1961 they sell 1-1/2" x 3-1/2" and call them 2x4. Similar with 2x6, they used to be 2"x6", now 1.5"x5.5". That house was originally built between 1866 and 1868, right at the time of confederation. It was massively overhauled in 1950. However, that means its structure is still real 2x4. I doubt they changed to 1.75"x3.75". Today you would have difficulty finding matching lumber. In 1997 I found one lumber mill in Virginia that did; don't remember who or how to contact them.
My house was built in 1907, has 9 foot ceilings on the ground floor, and real plaster/lathe walls. When I installed a security system, I found the plaster is 2" thick. That's solid! 24 Sussex would be just as solid. And you don't want polyurethane putty, real plaster is composed of slaked lime and fine sand. When water is added, it combines with carbon dioxide from the air to form calcium carbonate. That's limestone. That's why real plaster is so much harder and stronger. And it's non-flammable. Try finding someone today able to apply real plaster.