Intertherm Cmf Series Base Packages Cb 200A Cottage Base. In some special cases a direct vent system is required for this type of installation (2) A direct vent residential single-story dwelling type installation for which ductwork can be attached to the cottage base. Please Note: Ducted applications require a Direct Vent System. Non-ducted applications do not require a Direct Vent System. Both ducted and non-ducted Installations require flue products to be exhausted by an Intertherm SRJ Roof Jack or existing chimney. Residential is only defined herein as a non-manufactured housing single-story dwelling type application. Features of Intertherm 901696 Cmf Series Base Packages Cb 200A Cottage Base Designed for use with all CMF furnaces Use in a residential single-story dwelling type installation for which no ductwork can be used. In some special cases a direct vent system is required for this type of installation Use in a direct vent residential single-story dwelling type installation for which ductwork can be attached to the cottage base Residential is only defined herein as a non-manufactured housing single-story dwelling type application Both ducted and non-ducted Installations require flue products to be exhausted by an Intertherm SRJ Roof Jack or existing chimney Package Contents: Intertherm 901696 Cmf Series Base Packages Cb 200A Cottage Base Intertherm 901696: Cmf Series Base Packages Cb 200A Cottage Base