If you have a wall assembly that is 25% R-2 glass and 75% R-20 insulated wall -- the total R-Value of that assembly is only R-6.15.
Say you doubled the wall insulation and superinsulated 75% of the assembly to R-40, that would surely make a big impact, right? Nope, total R-value of the assembly only increases to R-6.95, an improvement of only 13%.
If on the other hand, you merely increased the R-2 glass to R-3, the total wall assembly would improve to R-8.3. An improvement of nearly 35%.
So as you rightly hypothesize, the "first" bit of insulation is more important than the next bit. Going from R-1 to R-2 decreases energy loss by 50%, going from R-2 to R-3 decreases it by a further 30%, R-3 to R-4 by a further 20%, etc.
So for my example with a 40ºF difference between inside and outside, if that wall assembly were 120sq ft, the original wall with R-6.15 would be losing 780btu/hr. The 13% improvement in R-Value from the first example would reduce energy costs by 10% (700btu/hr of energy loss), the 35% improvement would reduce costs by 25% (578btu/hr). It's strictly better to increase r-value but the highest leverage impacts come from the bottom.
https://www.greenbuildingadvisor.com/article/all-about-u-fac...
One nice trick I have seen is windows offset so that the light penetrates deep into rooms during winter but does not penetrate in at all during summer. And then the floors acting as thermal mass and made to distribute the heat throughout the house. And so on.
I wish I could find this youtube video again. The house was built probably a hundred years ago or so by an American architect for himself.
There is a lot that can be done with mundane materials with a little bit of thoughtful design.
https://greenpassivesolar.com/passive-solar/building-charact...
But for commercial buildings where they're trying to squeeze out every square foot of rentable space, and probably are not allowed to overhang their property lines, it's likely not an option.
I am looking to buy a property right now and I have resigned myself that if I want a nicely designed house I will probably have to do it myself.
A well designed house does not have to be more expensive, it is just engineering -- and engineering is about knowledge, experience and ability to use both to make tradeoffs for a better result.
The knowledge is there but very few seem to be making use of it. Everybody tries to squeeze a lot of new tech but forget about old lessons -- just like in software development...
