andrelplume...if the basement was not designed into the existing A/C and heating needs, you'll rob the rest of the house of the design temps. Heat Pumps are generally designed according to the cooling needs and then aux heat added as needed. Without knowing sq. footage of the entire house (including basement), heat loads, duct size and unit size, it would be impossible to say without a big guess, either way. If you can give us that info, there's several in this forum who can and will help you. I do know folks who had the same situation and opted to just add a pellet stove in the basement. It didn't do much in the way of dehumidification in summer (doesn't run)but was a huge help for the whole house in the winter.

When we had the basement finished years ago, they added some vents down there. It is still always cool/cold in the basement, so if you're looking for comfortable liveable conditions down there, I think you'll need to either A. zone it or B. add baseboard heat, or some independent source of heating. I wouldn't expect adding some vents down there to get a noticeable temperature change, judging by my own house. It also does take some air from the other floors which were designed for.

That was my fear too...how does adding the vents affect the rest of the home. We are in the process of replacing our hp so they could figure that into the size of the new unit. Right now we have a 2100 sq ft 20 year old colonial running a 20 year old trane 2.5T hp. The basement is about 750 sq feet. Maybe a 3T unit would allow some extra vents to get us to the point where the rest of the home is unaffected yet it adds enough heat to warm the basement OR gets it warm enough that some baseboard could be added and able to take the chill of relatively quickly if some one goes down there. Not sure if that is more economical than adding a zone...

"Maybe a 3T unit would allow some extra vents to get us to the point where the rest of the home is unaffected yet it adds enough heat to warm the basement OR gets it warm enough that some ba"seboard could be added and able to take the chill of relatively quickly if some one goes down there. Not sure if that is more economical than adding a zone..."

In all likelihood, your basement will add little/none heat load to your house (unless you're planning a media room).

As mentioned earlier, HPs should be sized for air conditioning with supplemental heat added as necessary. This would be especially important for your basement if it gets quite humid in summer time. Also, if you're looking for 'fast heat', a HP would might not be up to the job without aux heat operating. You need an accurate heat calc done to establish your exact needs.

If I were in your situation, I would install baseboard electric heat w/stats in each room. Easy (fast) on; easy (fast) off. Also, look into dehumidifier for summer use.

As an aside, I did not see any mention of installing returns in your options.

V

If your supply and return system are properly designed and you are replacing your existing heat pump with a 3 ton unit, you shouldn't have a problem. Make certain your new ducting to the basement includes properly sized supplys and a returns. In additon, have your technician do a load balance and you should be set to go for a year round area.

veesubotee,

I do not really think dropping a vent or two is going to add much heat either. (there would be a return) I think the benefit though might come in the summer, maybe the dehumidifier would not run as much; it might be good to have some conditioned air moving down there.

I figured the baseboards would heat and area fairly quick as needed. Over say 10 years; do you thing the added cost of running the baseboards would out cost the 2K to have the basement zoned and say, keeping the temp continuously at 67 or so over the winter?