Average human body temperature:

36.5°C (97.7°F)

1°C or more higher than this and medically this is considered to be a sign of a fever, resulting from an infection or another undesirable medical condition.

People over 65 tend to show temperatures around 0.5°C lower than average and with no ill effects.

See also:

Occupant Reaction to Air Movement
Air changes per hour (ACH) recommended