If there are heating units inside the attic will the attic ventilation system interfere?

Heating units or any gas-fired appliance in the attic should not be affected by an attic ventilation system.

Heating units or any gas-fired appliance in the attic should not be affected by an attic ventilation system. There is the potential for problems when a system is installed without enough intake ventilation. Without appropriate amounts of intake ventilation an attic may become negatively pressurized. A negatively pressurized attic could cause combustion appliances to back draft, thus bringing combustion gases back into the attic. Heating ducts in an attic can contribute to ice dams, but as long as the ducts are well insulated the heat loss to the attic should not be substantial.