A post-occupancy evaluation (POE) was carried out on the identified optimum task performance zone (OTPZ) in an office space (Dodo 2015). The OTPZ is a zone that daylighting can be used most times except when the sky conditions are not favourable to provide up to 300lux. The amount of carbon dioxide (CO2) saving when no artificial light is used this zone was calculated and tabulated. This can directly reduce building cooling energy usage The findings denotes that the OTPZ of 3m x 1m required lumens is 969 lm and 2 bulbs would be required to produce the desired power which will give a required illumination of about 323 lux. The study identified that OPTZ would reduce the amount of energy required to lit of the space and since the zone requires little or no artificial lighting, the amount of CO2 emission will reduce. The result shows that about 304.82Kg of CO2 will be saved from polluting the atmosphere if an Incandescent (60 Watts) lighting technology (800 Lumens) on a daily kilowatt bases is used. An equivalent of 69.86kg of CO2 would be saved from polluting the atmosphere if 14what compact fluorescent lamp (CFL) lighting technology were to be employed. If the OPTZ is adapted and used in an office then, there the probability that a 90% to 95% saving of CO2 emission to the environment is possible. Future research is recommended towards comparing the results with different office buildings, regions and a longer duration period and probably using different energy savings lighting bulbs. Likewise, calculating the actual amount that can be achieved from the OTPZ zone.