The Counterflow model is specifically designed for use in concrete slab buildings or those with crawl space areas using perimeter or radial type systems. Non-combustable base available for installation on wood floors. Available from 90,000 to 1,000,000 BTU/Hr. Standard models are equipped with front flues; rear flues available on special order. Two stage firing is available on 700,000 and 1,000,000 BTU models.