It's a bit esoteric and most people won't care or have an idea about the actual event, but there's a lesson here. The lesson is most people, even the "experts" are usually wrong.
I bought a house in the Zurich area. The heating system was old but rock solid. Switzerland adopted the EU emission standards for household heaters. My system was no longer allowed because it was only 92% efficient and it must be at least 93%! So to save 30 liters of heating oil (10 gallons) a year, I should invest 25K francs in a new heater.
Well, I just manged to pull off what most said would not work. I bought a used Brenner on Ricardo for 100 francs, and found a fellow in Affoltern am Albis to install it. He (and I) just finished (2 hours work) and it's running and more than meets the new standards! I am happy to say that I used a Laüchli Brenner-they don't sponsor any sports teams and don't drive around in snappy red trucks, but boy do they do the job!
In Kanton Zurich, systems are tested every two years. If your system fails, it must be corrected. Depending on the failure, you get less or more time to bring the system into compliance-I was given 5 years...my next door neighbor has gotten only two...both of us were looking at 2500 to 3000 in repairs that most said, "don't do it", better to spend the 25K with me.
Am not aware of any changes in ownership or tenancy as triggers.
As above, except here in SZ one's heating system is tested every year. My 15 year old system tested just fine when we first moved in, and again for the next two years. The testing has nothing to do with the house changing hands - and the tester is guy from the heating company who does your yearly service.
Funnily enough, the next year the heating company ran a big advertising campaign to sell new Brenners/ whole replacement systems. 'Special price, buy now!', you know the drill. When I told the gentleman who came to service the furnace that no, I was not interested in buying a new system, mine seems to be working fine thank you... suddenly my Brenner failed the test.
Connection? You may well think that, I couldn't possible comment.
Got a polite note from the canton, telling me I must replace the Brenner within five years. As I am selling the house, I haven't decided if it is better to sell with a nice discount for the cost of a new Brenner, letting the new owners choose the system they want, or to replace it before sale and include the cost in the sale price.
Changing the heating system might bring a tax break. On the other hand, a new heating system is one less thing for a buyer to have to worry about. Putting in a new heating system is something you should not lose money on as a seller. Perhaps you can get the tax break too.
Tax breaks are far more beneficial in AG than in SZ...
I personally would prefer to buy a house for a cheaper price and then can source the heating system I like - but I know that I am very un-Swiss in that perspective...
Here is Vaud they are required to check the emissions, clean the chimney, and do a few other checks every year. And this year, every 10 years, we have to have the fuel tank inspected and cleaned (the commune even reminded us of this inspection). Having replaced a 30+ year old heating system last year, which was quite rock solid, but not too efficient, it was well worth it for the savings in the fuel and a few other pluses. Depending on energy costs, it has already saved us quite a lot and the house is warmer and maintains constant temperature much better. Other pluses, better for the environment, uses less space, don't have to wait for the hot water, and is a lot quieter.
We had to replace ours because the emissions rules changed. But it was already nearly 20 years old, and was big enough to heat an entire apartment block, so we were glad to see the back of it.
Cost 15'000CHF, which was deductable against tax. We're saving about 500CHF per year on fuel now.