The BREATH (Building Retrofit for Efficiency, Air quality, Thermal comfort and Health) project was a research pilot led by the City of Melbourne in partnership with Cbus Property, the University of Melbourne, AG Coombs, SEED engineering, AURECON and Westaflex. It was a rapid retrofit project that tested various air conditioning and ventilation retrofit options with the express purpose of reducing airborne particulates and infection transmission, but also considering the energy and cost consequences. The work was undertaken within an existing building. Open windows, conventional air conditioning, ceiling-mounted HEPA filters, and displacement ventilation were included in this initial pilot. Personal air was also showcased but not integrated into the overall research. Results indicate that some recommendations to reduce transmission may have impacts on power demand. Leaving the windows open on a floor of the 10-story test building led to an estimated 12% increase in air conditioning energy consumption. The best option for reducing transmission risk and improving energy consumption appeared to be a low-level displacement supply air system; provided the workers exercised social distancing and the stratified room temperature profile was maintained. The lower energy consumption of displacement ventilation was estimated to increase the NABERS rating of the building by 0.5 stars. The most cost effective and simplest approach to improvement was in-ceiling fan filtration units, these reduced transmission risk with minor increases in energy consumption if appropriately dimensioned. This paper looks at what these possible interventions mean for office buildings retrofit improvement.