State-of-the-art upgrades are costly and may soon be obsolete. "Technological advances mean that modifications, such as LED lighting or HVAC controls, now meet return on investment expectations," Jain told The Investor. "However, for glazing and façade modification, these projects are still considerably expensive and tricky to implement, making it harder for investors to justify."

That's why Jani likes building management systems.

"Submetering and close control of BMS, for example, is one way to manage energy use in more detail," he told The Investor. "That may require more management and personnel – but could ultimately prove beneficial."

When installing sustainability upgrades, resident disruption is another concern. Some installations, such as common area lighting, aren't disruptive to residents. But some in-unit updates can be a nuisance. That's why green upgrades can require a bit of strategy. Making them when residents leave their unit isn't always possible. "If you wait to add features as an apartment unit turns, you don't have that quick return, and it's obviously very slow," Hatcher says.

Another thing landlords need to consider is purchasing green products. For owners with large portfolios of green buildings, such as AMLI, can find efficiencies.

Hatcher says AMLI is evaluating its internal purchasing system and reviewing the products that are in there. "We are working to align everything that we are purchasing with the same green standards that we are building to," Hatcher says. "Since all of our new buildings get LEED certified, it aligns with our sustainability goals."