I live in Auburn GA., which is about 40 miles northeast of Atlanta. My home is a four sided brick 2 story on an unfinished basement. It was built 13 years ago. HVAC system needs replacing due to continued mechanical problems.

I’ve had several contractors in my home to provide me a proposal for a new HVAC system, and they all have provided proposals with the same size system I have now or larger . Not one of the contractors has performed a Manual J calculation for my home. They have all used the general rule of thumb and a very low square footage per ton to propose the size my new system needs to be.

How should I go about trying to ensure that my new system will be sized correctly. Pricing changes greatly past 2 tons. Should I hire an independent company to perform a proper Manual J calculation or is there something I can do my self to determine the correct size AC and furnace?

Thank you to any and all advice, recommendation, and/or suggestions. Also, any contact info for a reliable and reputable company that can perform a proper and complete Manual J for my home is appreciated….