> What is the R-value of a Norwegian wall?

That varies greatly I think. There are a lot of old houses here; built to a very different standard than a modern house. Double glazed windows has been the norm for a long time though, through the invention of the easy to clean husmorvinduet or h-vinduet:

https://www.h-vinduet.com/

Husmor translates to housewife, vindu to window (housewife window). Easy to clean, since they can flip around, i.e. you can wash the outside from the inside. So for most older homes, I guess it's a mix.

For new buildings; what you say holds true I think.

Speaking for myself here, my house was built around 1850-1861 (no one really knows when it was made exactly). Timber construction covered with boards on both sides; but with minimal insulation (until we started renovating the house).

There are stricter rules for building new homes now, then what they had in the 1850's of course :-). A new house built now should follow the TEK17 standard made into law in 2017 (prior versions are the TEK10 standard from 2010, TEK07 from 2007, TEK97 from 1997 etc.). They regulate everything, from how much area you should have outside to how big a shed you can set up I think. Eco friendliness is an important category though; and these are the minimum requirements that came up with a google search (in Norwegian) for your question:

https://dibk.no/regelverk/byggteknisk-forskrift-tek17/14/14-...

Unfortunately in Norwegian as well, but they do state how much a wall/roof etc is allowed to leak; i.e. U value. As you can see (with Goole translate at least), walls should have better insulation than windows at minimum at least.

Norwegians build fairly typical Nordic homes. 198mm (8") studs with insulation between is pretty typical. Then another 48mm (2") insulated layer on the inside for services, and optionally a 50mm (2") insulation board on the outside before the cladding is applied. So 300mm (12") insulated thickness + whatever inner/outer cladding you use would be common, but up to 400mm will happen (300mm framing + 50 either side). Thicker than that is uncommon. U would be I think ~0.18 for the worst constructions but usually better. And yes, even the best windows have higher U than this. U=0.5 is fantastic for a window, and U=1.0 to 1.2 is common even in Nordic new construction (Standard 3-glass).