Of course there's the problem of being unable to improve a rental- the landlord doesn't reap any reward and the renter doesn't have a stake to be willing to invest- so rental stock tends to be uninsulated, uncomfortable, poorly designed, rarely renovated, etc.
Last summer I spent $900 in materials to build a pergola that I carefully planned as passive solar management. It made a huge difference in comfort and slashed cooling loads. In rentals, I just suffered.
Landlords improve rentals when they think it will allow them to raise the rent enough to make back more than the renovation cost in the long term.
Or when they think it will allow them to attract a “better” type of tenant who’s more likely to pay rent on time and take care of the space instead of damaging it.
Or because the real estate is their nest egg and they want to maintain and increase its value. Or because they live in the building and the improvements will improve their own quality of life.
Every apartment I’ve rented in NYC has been in a building over 75 years old. Even at fairly low rents (by NYC standards), every one had been gut renovated less than 10 years before I moved in.
I know there are scenarios where rentals do get improved. But insulation, efficiency & comfort is really hard to value, and so I've not really seen it happen. This is specifically called out by government & eco groups as a major challenge going forward to improving energy efficiency of the housing stock.
Last summer I spent $900 in materials to build a pergola that I carefully planned as passive solar management. It made a huge difference in comfort and slashed cooling loads. In rentals, I just suffered.