I had a Manual J calculation, equipment sizing and duct design done by an energy mechanical engineer for my single family new construction. I have energy efficient windows and 2×6 exterior framing. The family room is a 2 story open concept. My energy consultant came up with a 1.5 ton heat pump ducted system upstairs and 3 ton heat pump ducted system downstairs (conditioned basement and unconditioned attic). Now I am trying to get quotes from HVAC contractors and I am getting all kinds of crazy tonnage quotes. Some is calling for two 5 ton system and some are saying my designer is wrong and some wants to oversize by 10%. This has caused me to question my designer but I had him recheck his numbers and he stood by his calculation. I am kinda stuck and afraid which contractor to use. Any suggestions or help would be greatly appreciated. Thank you.
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