Creation of buildings with very low energy consumption is the main target of the European Union in the coming years. The possibility of creating buildings with zero CO₂ emissions due to energy use is currently a challenge which could contribute in the mitigation of climate change. An investigation using various reliable and cost-effective renewable energy sources for providing all the heat and electricity required in an office building located in Crete, Greece has been implemented. It has been indicated that locally produced solid biomass and solar electricity could cover all the energy requirements of an office building. The same result could be obtained with the use of low enthalpy geothermal energy with a heat pump and solar electricity. Preliminary cost analysis indicates that the required investments in the abovementioned renewable energies in Crete, Greece are not high and they could result in a zero CO₂ emissions office building.