No one will pay more for a house with a higher R-value. If this were a determining factor, it would be part of real estate listings. It's a secondary or even tertiary concern for most people.
If a home were priced as little at $200,000 then 20% would cover $40k in investments. Homes around here don't sell for the little.
Assuming your percentage is correct and home prices are much bigger it makes it seem like a spectacular investment. Actually too good to be true of an investment.
If the return were 2% or max 5% I could see it maybe not being worth it depending on home prices in your area.
If you're buying a house without asking for the trailing twelve month energy bills, you are an unsophisticated real estate market participant and will pay for the ignorance over time.
In the US, this is so true and sad. After building my first home with insulation way beyond code I learned the sad lesson that it won't get you a dime more when it is time to sell.
We keep in touch with the new owners who have since thanked us for building so well. Their bills are much lower than any in the neighborhood and they had no idea.
The same goes for heat pumps. I'm living in my third build and we had room to do a ground source heat pump. It is amazing and my bills are half of what my neighbor pays for a similar size house. Mine is also better insulated. When it comes time to sell it, nobody will care.
The US needs to up the codes on insulation. Hot climate, cold climate - who cares, it helps.
