[jiofih]

Looks like you did not understand that comment. Concrete will not let a draft through no matter where the wind hits. For fiberglass and others, one bad fitting means a current can form through the material. This is why you need tyvek to begin with.

[CapitalistCartr]

You are misunderstanding the American building system. We don't use fiberglass insulation by itself. You're picking a small part of a greater system and complaining it doesn't work in isolation. There are multiple layers to our construction and it's effective.

As for the wall material stopping drafts in a window frame, that makes no sense at all.

[jiofih]

Exactly, the critique is that you need multiple layers, and if one fails, the R values you thought you had go out of the window. Whereas a concrete, wattle and daub etc wall will tolerate less-than-perfect fitting and maintenance. Of course if you assume construction is flawless, there will be no issues, and that’s the usual case.

[rootusrootus]

How does concrete stop a draft that is going between a window frame and the wall itself?

I've never had a draft through a fibercement/wood/fiberglass/drywall wall, in any case.

[zdragnar]

A poor fit, minor damage, or any defect allows convection within the fiberglass. R-value assumes zero air movement, which is why it is far less useful comparing fiberglass to foam or aerated cement. In real world settings, aerated cement will outperform fiberglass.

[Retric]

The same thing can happen when concrete cracks, which is quite common. All of this a question of basic building maintenance rather than the building materials chosen.

Cracking is why single family homes generally avoid concrete walls in the permafrost.