Real time side-by-side experimental validation of energy and comfort performance of a zero net energy retrofit package for small commercial buildings

•Ownership structure of small commercial buildings makes energy retrofits challenging.•Retrofit package for Zero Net Energy small offices in Mediterranean climate.•Energy use and occupant comfort evaluated experimentally, side-by-side, in real time.•65%-68% energy savings for cooling season; 22%-25% for heating season.•Energy savings are achieved while maintaining visual and thermal comfort.