My house is a single story of 1700 sf of inside living space.
Due to constant high gas montly bill of $ 240.00 and considering that that I keep the internal temperature from to 62 F to 64F , I found out that all the ducts do not provide an adeguate flow of war air in all rooms . So this is the reason why my house never is getting warm or if I increase the temperature set up on the thermostate , it take forever.
The furnace is a 80,000 BTU ,three year old , maintained clean properly .
A friend told me that probably the returning duct is too small in size and need to be replaced with a larger one . A contractor told also that , in order to increase the air flow out of the furnace , I need to replace the actual oulet duct , from a 90 degree type with at elbow one . Any other professional suggestions ?
Thank for your time

Stef

Since we cannot see the layout of your duct from here I suggest you follow at site professional opinions. Get 3 estimates and have them fix it.