Manual J calculations
I have entered the exact same data on three “Free” manual J calculations sites.
coolcalc.com (by far more detailed than the others)
They all gave me completely different numbers.
coolcalc 90,000 btu’s per hour
servicetitan 18,000 btu’s per hour
pdhvac 48,000 btu’s per hour
This is totally inconsistent and thus useless. They also don’t let me enter specific data for double stud walls, triple paned windows, etc.
Can someone help me find an accurate way to determine what the Manual J will be on the house I have started to build? I want to size the HVAC system correctly and am willing to pay a reasonably priced professional. I also need to get the price/performance correct on insulating the hydronic slab under the whole house (no basement, single story). The walls and roof will be more than adequate, but the cost of the rigid foam under the house is painfully expensive and a general 4-6″ is a very large price difference for me also my foundation engineer is not green experienced and wants me to put in a 5″ slab with 1/2 rebar 6″ on center because “the concrete may break because of the insulation”. Any help is much appreciated. Mind you, we are on almost solid rock on a mountain in Colorado.
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