i work in nuclear power... my plant has been online for over 30 years and we have yet to emit any greenhouse gases. The coal plant on the south side... not so much.
The trouble with solar and wind is that they do not produce near as much power for the amount of space they take up, as a nuclear power plant does. Nuclear is actually the most power for the least land usage.
how much power the building needs, will determine how big of a solar panel the building needs. What type of a wind generator? Wind turbines are complex to engineer and expensive to produce and put online.