Oversized or Just Right
I have posted previous about comparing quotes and received some good advice. I have received 6 A/C quotes and am looking for a general sense that I am not being taken for a ride with sizing. Before we make a choice or narrow it down to two for a final comparison, I want to make sure nothing is outrageous.
Four of the quotes note a Manual J Calculation and I saw two of those calculations from the respective contractors. These four quotes all note a total central A/C (whether conventional or high velocity) capacity at 4.5 or 5 tons. The numbers were close to 4.5 or just over 4.5 for the ones I saw. The other two contractors did not discuss Manual J and sized me at 3.5 tons each.
I live in New Jersey in a 2 1/2 story, 1920 foursquare, stucco exterior that has radiator heat (water) with a natural gas triangle tube prestige excellence combi boiler for heat and hot water. There is a third floor family room (450 sq. feet), 4 bedroom second floor (950 sq. feet) and a three room first floor (1100 sq. feet). There is no insulation in the outside or interior plaster & lathe walls. I do have rigid foam insulation and air sealing in the basement, with blown insulation and air sealing in the third floor knee wall. I have 31 original, double hung, single pane windows with new storm windows. The back of the house has a southwest exposure with no shade so the suns beats down in it in afternoon.
I think that four contractors that used a Manual J all stating 4.5 ton or 5 ton means I need a 4.5 or 5 ton system. I just want to make sure that it not outrageous sizing for the description above.
As an aside, the two contractors with 3.5 ton quotes are the cheapest by far, so a quick review had me excited. However, I noted no Manual J discussion and the sizing discrepancy.
Thanks in advance,