No, solar gains should not be taken as a credit in heating load calculations unless the building is specifically designed for solar heating. Solar gain is not a reliable source of heat, as it is only available during the day and is affected by factors such as cloud cover and shading. Moreover, solar gain is not a factor at night when design temperatures generally reach their lowest point. Therefore, it’s recommended to ignore solar gains when calculating the heating load to ensure that the heating system is sized to meet the maximum heating demand.