Heating and ventilating a garden home office can be a problem. But do not neglect them; their importance is usually underestimated when building a garden office. Irritability when you are too warm, and lack of control when your hands are cold, will lead to bad working conditions and can be unproductive. Whatever type of electric heating you use, it will be cheaper in the long run if you insulate old buildings. You can opt for an electric radiator or electric underfloor heating.
A common mistake is to fit a free-standing electric fan, which just moves stale air around the room, instead of a proper extractor set in an outside wall. Ventilation ducts such as airbricks should also be fitted to let in fresh air to replace the extracted stale air.