In this study, annual, monthly and hourly ambient temperature distributions are determined and analysed for Karabuk . For each month of the year, variance of outdoor air temperature, monthly and seasonal heating degree hour (HDH) values are calculated according to 11 different indoor reference temperature (18 degrees C to 28 degrees C), and the resulting coefficient of determination indicates high correlation as R-2 = 0.998. By considering HDH values, three kinds of fossil energy resources, (coal, natural gas, fuel-oil), annual unit area fuel needs, amount of carbon-dioxide and sulphur-dioxide. When indoor temperature is chosen 19 degrees C instead of 18 degrees C for coal, annual CO2 emission increases by 8.7%. On the other hand, 24 degrees C indoor temperature, rate of increase reaches to 53.2%. This study is first in the literature to investigate the effect of three kinds of fuel's energy impact on environment in the case of different indoor reference temperature for heating.