The owner of the former Westinghouse building at 11 Stanwix Street is spending more than $4 million in a bid to make the structure greener.

Stanwix Lender Associates, L.P., an affiliate of Rugby Realty, is scrapping the building's old heating and cooling systems for new, more energy efficient ones, and upgrading the lighting in the 23-story structure.

Aaron Stauber, Rugby Realty president, said the company has installed new gas boilers to replace an all-electric heating system. The change is expected to cut heating costs in half.

It also will ditch a system that relies on Allegheny River water to cool the building in favor of on-site cooling towers that are expected to cut electric costs.

Mr. Stauber said one of the problems with the old system is that Zebra mussels are being pumped into it from the river and clogging pipes and screens, forcing maintenance crews to clean them frequently. The problem has become more pronounced in recent years as the river has become cleaner.

The building also has been equipped with new lighting with motion detectors to brighten spaces only when they are occupied. The energy-related improvements follow more than $2 million in investments at 11 Stanwix that included upgrading the lobby and common areas and adding a fitness center. Stanwix Lender acquired the building in 2008.

"We're not trying to win any awards here. We're doing these things because we think it makes sense. It makes sense for our tenants, it make sense for us as the owner, and it make sense for the environment," Mr. Stauber said.

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