Furnace Decision

The first step would be to let us know where you live so we can base our decision on climate. Another possibility would be celing height and age of the structure.

Without all the parameters we can get, we can't offer trustworthy advice.

You need to tell us where you live, what direction your unit faces, if you are a end unit, if you have a basement/ crawl space etc.

And are you looking a adding insulation in the attic or floors/walls, new windows, also did your existing unit heat/cool the unit as it should ?

Who "sized" your system? Either max output size looks way too big for any level of recent construction.

My home is 1460 SF, was built in 1969 and only has an 80,000 input furnace (old style) that is actually too big.

If you are only heating a 800 sqft townhouse, I would not use a furnace at all. Do you have access to Natural Gas? If so, go out an buy a gas log, they do not need to be vented and can run about 500$ from a plumbing supply company Installed if you have gas in the house can run another 300 depending. (I heat my 1300 sqft ranch with this in Massachusetts winters and it is pleantly hot)

If you do not have NG I would recommend a pellet stove (wood pellets) they can heat anywhere up to 1500 sqft and cost double and it needs to be vented (clearance from opening min 3-ft).

With both of these options you are elligable for a green tax credit (check you state) and it is much less work then installing baseboard units if you do not have them now. Anyway I can never recommend a diesel furnace (big heating $$$) unless you are makeing Biodiesel and do all the work necessary to burn it in your furnace at 100% concentration (injectors need to be pulled back to get propper dispursion).

To correctly size your heating needs you need to do a heat loss calculation that takes into account where you live, orientation of the building and other factors. If you have a unit to large it will short cycle and you will be unhappy with it, if it is too small it will not keep up during the coldest winter days. A two-stage unit is always a good way to go because of the lower BTU output that will be used most of the time and having the higher BTU available when needed. This will allow the furnace to run for longer periods of time keeping the air moving within your home, creating a more comfortable environment. If heating with too large of unit the heat coming from the registers satisfies the heat requirements too quickly and will leave cool zones in your home so it is normally better to run the furnace for longer periods of time.

How good are:

• the building's insulation level
• the building's draught exclusion level
• the quality of the glazing - single, double, triple
• the thickness of the walls
• etc.

The better these are, the smaller the heating unit can be, in relative terms.