I think a 100K BTU furnace and a 4 ton AC for a first floor consisting of 1300 sq. feet is very over sized. You need to find a contractor who will do a proper heating and cooling load calculation. Get an HVAC system that is too big is just as bad a getting one that is too small.

Did this contractor provide model numbers of the equipment? If not you don't have a valid quote. You also need to know what coil he is providing.

You have new duct work on the list. Is all the first floor duct work being replaced?

Did you want a direct vent hot water heater? You could still vent through the chimney if it is properly lined.

Agree with Mike especially about the oversizing. I would think a 60 K high eff two stage var speed furnace with a 2 1/2 ton AC condenser. Can't imagine what that dealer is thinking unless there is a missing piece in the size of area to be cooled/heated. Basements if below grade usually have low load requirements.

IMO

I'll ask the contractor for model numbers.

The contractor was saying that the 1st floor and partially finished basement need this capacity. And saying the ductwork in the basement is not appropriately sized. The current, old furnace is an 80%, 100k unit. The current, old water heat is chimney vented, I'd like to convert it to direct vent as well.

What else to ask the contractor? I have a 2nd contractor coming back with estimates today.

Your old furnace had an output of 80K BTU, the one being proposed will have an output of 95K BTU.

Do you know the size of the current AC? How well is it working so far?

I realize a house built in the 50s may not have insulation up to today's standards, but I would not expect to see the sizes being proposed.

Ask the contractor to show you how he calculated the required sizes. If he can't then continue getting more quotes from contractors.

The current looks like a 3 ton unit, it's 20 years old and working, but I'm thinking to replace if the price is right.

What is the rule of calculation for BTU vs square footage? I was told 40 BTU/sq ft. And 1st floor plus basement together is 2300 sq ft, which translates to 92000 BTU needs, is this the correct way to approach? How about the Aprilaire steam humidifier upgrade?

What you are describing is called the rule of thumb for HVAC sizing. It is the wrong way to do it and results in systems that are over sized. It is a form of guessing in my opinion. This is the way HVAC contractors who are lazy and can't be bothered to spend the time to calculate the requirements of your house.

Over sized systems cost more to install, are inefficient, noisy, uncomfortable, and die prematurely. The only positive is they are more profitable for the HVAC contractor.

I would not install a humidifier unless I really needed it. Are you currently having low humidity problems? Low humidity is usually a sign of leaking windows and doors. The steam humidifiers are supposed to be the best.

Thank you for the explanation. I'm learning all about HVAC as I go.

Estimate from 2nd contractor. What do you think about pricing and which can be improved upon?
- Install RUUD 92% hi-efficient furnace vent PVC flue outside home $3400
- Install RUUD 3 ton 13 seer A/C unit with matching coil replace copper lineset $3,600

Note - This contractor doesn't do hot water heater, due to plumbing license.

Don't accept a quote without model numbers!