Gas and Oil Home Heating Furnaces - Finishing basement - options to heat/cool

I am finishing about 1/2 of my basement (725 sq ft). Currently have heat pump which is small for the size of the house, but we manage ok, excpet on coldest days. It is a 4 ton unit supplying about 2700 sq ft of living space in DC area. [The original heat exchanger in the basement was replaced last year. I took the opportunity to upgrade the unit to acommodate 5-ton capacity with 4-ton coil. This way, when the compressor goes (more than 10 years old now) I can add a 5-ton compressor and change out the coils ($250) and I will have 5-ton capacity in heat pump, heat exchanger, and blower.]

Back to the finishing question. Problem is that I would prefer not to tap into existing ducts for additional air flow as this would reduce supply to rest of house. Basement is routinely warmer in winter and cooler in summer than rest of house. So, I see no reason to add capacity to the basement except that we will be closing in the existing slab, foundation, and ceiling with insulation/vapor barrier/drywall/carpet.

The existing system returns air down the center of the house and supplies it through a main rectangular duct to both "wings" of the house up and out at the perimeters. 8" round ducts (I think) supply the first floor perimeter. I was thinking about tapping into those with perhaps 4" ducts just to be sure I had air flow in the basement. There is currently no return duct in the basement, but I planned to add on at the air handler.

Another option occurred to me as well. I could add heat-only to the basement in the form of baseboard electric or something like that. Since the temp in the basement is pretty constant year round, this heat would not be expected to run much if at all. I would not need separate cooling since the basement is mostly below grade and stays nice and cool in summer. There will be no bedrooms down there either. As an added bonus, I could seal up the ductwork better than it is now and add some insulation in the ceiling (which I am planning to do for sound proofing anyway) and hopefully improve flow/climate upstairs.

Other than complicating my electrical capacity plans in the second approach, I would appreciate any thoughts about these two approaches. Does the first approach make sense, and does the second approach have merit?

What would you do? Either of these or some other more sensible approach?

Thanks.

Im not sure what you have there. Did you put in a new 5 ton blower coil unit? A heat exchanger??? for a heat pump??? Dont know the home but 4 ton for 2700sq ft not bad.

Going to up grade to 5 ton. Yes but you still have the duct work for just 4 ton in the home . It dont work that way. Also you will find that the 5 ton will pull the temp down before it gets the humidity out of the home.;) ED

Sorry for confusing you. Let me try to explain. Please understand I am using generic terms, not necessarily terms of the trade. I have installed a 5-ton blower and air handler with coils matched to my 4-ton compressor. Actually, the installation was done professionally. I did not do it. I do not have the skills to handle refrigeration systems.

When the compressor goes, I will upgrade the coils and the compressor. The manufacturer was consulted and the licensed pros indicated that my ductwork was oversized for the compressor. Hope that helps. By heat exchanger I was referring to the coils in the air handler/blower box in my basement. If heat exchanger also refers to some other system, I did not mean to confuse you. I have a typical heat pump with compressor outside and air handler/coil inside.

Hopefully that can help you address my questions.

By the way, just the added blower capacity has helped significantly in the performance of the system overall. It may not be optimal, but it is much better and did not cost me very much to upgrade - couple of hundred dollars.

Thanks

When the compressor goes you will have to put a whole new unit out side to have a new 5 ton heat pump plus the lines and the coil inside. Id tap in to the duct for the basement You have to let more air out with that 5 ton on there.;) ED

Ok, thanks. That is the easiest thing to do anyway. Least cost, etc.

As for the compressor, I understand I would need a new unit outside to go to 5-ton and that is the plan. I would pretty much need a new unit when the 4-ton goes anyway judging by the condition of the parts out there. I'd be afraid to simply replace the compressor. The cost is really not much different, and I want to upgrade then anyway to a more efficient compressor.

Hopefully I have done minimal harm in any event.

As for tapping into the ducts, are there any problems with that. Seems pretty straightforward. What size would you suggest? Is there a minimum?

Man.. To me, 5 tons seems a bit over sized for home in the NE???

Use 6" take off and 6" pipe run to just off the outside walls.Use a 2 1/4"X 12 X 6" boot 90 o and blow down 2 1/4" X 12 " register. Dont forget a small cold air return.;) ED

Boy I have some 4k to 5ksq ft with just 6 ton AC up in MO. Down here 1800sq to 2000sq most of the time just 3 ton.

Thanks. Sounds like you are suggesting adding new 6" runs. Can't use the existing ones that feed the first floor registers, huh?

As for the size of the overall system, I have used several web tools that estimate the tonnage needed and all of them indicate over 6 tons for my situation. Also, a family friend who owns an HVAC business indicated he thought 4 tons was too small for our house (I have never spent a dime with him and he would not expect me to, I know it was truly a friendly estimate).

I have a bit under 4K ft^2 of finished space right now. Will be closing in on 5K with the basement finishing. On the second floor about 800 ft ^2 is vaulted ceilings, and the master bath (vaulted ceilings) has 2 skylights and several windows. I am sure a lot of wasted heat keeps the ceilings warm.

Anyway, we are still at 4 tons right now and I will be splitting some more wood for the fireplace to warm everyone up over the weekend.

If you go to your first post you said that you had 2700sq ft in the home. That is why we said it is to much. Yes add new runs for the basement dont cut into runs that go for upstairs.;) ED

Sorry about that, fellas. Typo - should have been 3700. My humble apologies.

Thanks for the help. Now if you could also advise me on what to do about these fat fingers of mine...