Finished basement. 400 sq ft area. Have gas furnace, forced air heat. Have no ducts in basement to speak of. Put in vented wall heater 30+ yrs ago. Heats basement fine but it died. Might put in new unit since basement is seldom used. Or would it be better to add more ducts? Don't want to heat basement 24/7 since it is used 10% of the time.