Warm Air Systems
A warm air system does exactly what is says; it warms the air within the building and not the fabric. Warm air systems can come in many forms and guises; they can be oil fired or they can be direct or indirect gas fired; they can be fully re-circulatory or partially re-circulatory.
Warm air systems are usually better suited to modern churches as modern construction techniques allow for larger temperature differentials. They can also be integrated into new-build projects.