We have insulation thickness standards in the US, varying by weather "zone", but for residential construction they seem to be lightly enforced, and efficiency t

We have insulation thickness standards in the US, varying by weather "zone", but for residential construction they seem to be lightly enforced, and efficiency tests are rare to non-existant. (For an illustration of how we typically insulate, see [0].) It's only one data point, but I'm in New England and from my home office I've watched builders replace 3 1960's-era homes with large colonials. Each is insulated with fiberglass, no visible foam, and nothing outside the sheathing (exterior plywood) except vapor paper / tyvek. Sure, it meets code requirements for inches of insulation, but it's far from air tight or efficient. [0] https://www.energy.gov/energysaver/where-insulate-home https://www.energy.gov/energysaver/where-insulate-home