Need more precise climate information. Some of what some people call "Northeast" is not humid. Some of what some people call "Northeast" is not that cold.

If you want duct, they will go in the basement? Do we assume that nat gas is not available to you?

Hi, thanks for replying. We are in eastern PA. There is no gas available, we are in a small town.

Do they always go in the basement? The attic has easy access too.

The attic is outdoors. You want the ducts indoors if you can do it. They leak and it is better to have them leaking to the living space than to the outside. Loss of conditioned air is one thing, but if the supply ducts leak to the outdoors, you have to remember that you are also sucking air in somewhere rather random. If the return is sucking air in, you are blowing it back out in random places. It is like having an unintended vent fan going.

Since you mentioned humidity, I am guessing SE PA in the costal plain. NE is pretty different, cooler and drier. With current incentives, you might be a candidate for ground-source heat pump. Another thing to consider are mini split heat pumps. No ducts is nice in some ways. Don't forget that you have to provide a return in each room, install jump ducts or undercut the doors.

Prefer basement/crawl space before attic for ductwork. But either way would be fine. Get a high eff heat pump with var speed air handler. Preferred that heat pump have electronic demand defrost that reduces/eliminates nuisance, unnecessary, and expensive defrost calls.

I can make some recommendations if you like.

Keep the oil boiler for extreme lows and redundancy for heating.

IMO

Here is my general spec sheet for new system.

both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset
10 yr warranty on parts and compressor

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

My personal recommendation is Trane/AmStd, Rudd/Rheem, and Carrier/Bryant.

Depending on your location, I would not purchase a new system that did not have electronic demand defrost.

IMO

You guys are great, thanks for your time. Ionized, yes, we are in SE PA, and the humidity is unbearable at times. I hadnt thought about a ground source heat pump, maybe we will inquire about that. In regards to duct work in the basement, how intrusive is that. The house is small, under 1500 sf, but it has a full basement which I will be renovating, low ceiling though. 7.5 feet. So id rather not have bulkheads all over the place.

Tiger, great info. I would love any recommendations. Another question. Do they usually replace your boiler with a new one, matching the brand to work with your new AC? Ours isnt that old, installed in 2007, a Bryant I believe.

Thanks again. You guys have a great wealth of information.

There is no need to replace your boiler. If you get a heat pump you will only be using it on cold nights. It is going to last a long time.

Be aware that Carrier and Bryant are the same equipment. You should be able to compare the costs of the same equipment.

Contractors who are factory authorized usually have better training with the equipment than those who are not. It increases your chances of getting a better installation.

What type of hot water heater do you have? How much do you spend on fuel oil each year?

How intrusive ducts in the basement depend on where the central unit will be located and the layout of the rooms. If you can put most of it at the perimeter....

If you are going to remove your hydronic radiators and heat with hot air in the new duct system, they might be able to use the boiler and a big hot water coil to heat the air. I don't know how that would break down in long term and short term cost compared to an entirely new furnace. I would find it a tough decision to keep or remove the radiators when adding ducts. I like the hydronic heat. OTOH, if the heat pump is going to be shouldering the load for the most part, why not?

Tigerdunes, he would not need heat strips if keeping the oil, right? One question associated with that arrangement, if oil and electric fuel costs are similar, electric would be better due to much lower maint. costs, right?

Given that you probably have a central support beam in the basement, ducts next to that probably won't be a big deal either.

Mike, we don't have a separate water heater, everything is heated thought the furnace. I'd have to check, but just a quick estimate would be roughly $1200-1400 cost of oil throughout the year. Of course, 95% of that is from November through April. Very little is used between may through October, even though the hot water is from the furnace. I don't think we had any delivery of oil through that period last year

I don't think removing the radiators was in the plan. I love the heat, grew up with that sort of heat, so would like to keep them. I would just like to use them less often.

One of the other reasons we are interested in a central air system is we seem to have high humidity in the house. New double pane windows were put in, and we usually have moisture on the inside of them in the mornings and at nite. The R.H. Is usually in the 55-62% range

Thanks again

I lived in Philly for a few years. That was my introduction to humid Summers. When I got out into the countryside, it was my introduction to chiggers, ticks and poison ivy too. Great and livable city though.

I think that the pros are going to want to take a close look at your boiler and its operation. If heating load is shifted away from the boiler, it becomes a less efficient way to heat DHW.

"I don't think removing the radiators was in the plan. I love the heat, grew up with that sort of heat, so would like to keep them."

I can't agree more.

"One of the other reasons we are interested in a central air system is we seem to have high humidity in the house. New double pane windows were put in, and we usually have moisture on the inside of them in the mornings and at nite. The R.H. Is usually in the 55-62% range"

This condensation is happening in the winter? You must have a pretty tightly-sealed house or be engaged in a lot of humidity-generating activities:

Big family with lots of long showers and no exhaust fan?
Lots of cooking with bad or no exhaust vent?
Growing lots of plants (legal, I hope)?
Damp basement?
Line dry laundry indoors or bad dryer vent?

What does having a "tightly sealed house" mean? Wouldn't that be a benefit? We've replaced all the windows and doors in the house since most of the stuff was dated and inefficient.

There is a exhaust fan in the bathroom, its old so that might not be helping. I do think the kitchen exhaust vent is not very helpful. Growing plants? lol. Not me, but I'll check with my wife.

We've had a couple companies come out for estimates, so when we get some info back I'll post it for comments and recommendations.

Would a system without an electric demand defrost be a deal breaker in my area? I'm pretty sure Carrier & Bryant dont have that, but they do have something like a timed defrost? Is that essentially the same thing?

Thanks

For your location, I would not have a new HP system that did not have electronic demand defrost. As said before, EDD eliminates/reduces unnecessary, nuisance, and expensive defrost calls. Yes, it would be a deal breaker for me. You will have to decide that. A pet peeve of mine that Carrier and Bryant have not moved in that direction. Timed defrost is like having hand crank windows in one's auto. Another factor to consider is also the unnecessary wear and tear to condenser moving into and out of defrost mode.

IMO

Yup a well-sealed house is a good thing, but there are sometimes unintended consequences. Leaky houses in heating conditions tend to be dry because the outdoor air has lower absolute humidity when it is cold. In leaky houses it is constantly washing out the humidity generated by living activities. At some point the water generated by living can outpace the leak rate. At that point you have to start paying attention to controlling the humidity you generate with spot ventilation (fans in baths and kitchen).

Make sure that your bath and kitchen ventilation is sized correctly, and working properly. Is that kitchen hood actually vented to the outside or does it recirculate? You might consider installing a timer switch in the bath.

If the home is really tight, you need to think about controlled ventilation. That can be done with controlled outdoor air introduction and maybe an HRV or ERV.