I own a two story, 1500-1600 SF townhome in Shoreline, North of Seattle. The original furnace is a downflow electric Wesco installed in a main (bottom) floor closet. I've been told that the Wesco used to be installed in mobile homes. The townhome has been remodeled and fronts a 30 x 30 garden that is a focal point for the house. I would like to replace the Wesco with a heat pump system, however the spouse has nixed putting a large "box" in the garden.
I've researched the following three options and am interested in professional (or educated) opinions about each. Or, alternatively, more options.
Option 1: Put a small heat pump on the roof of the building, which is flat. Is this feasible? If so what are the typical limitations (weight, type, etc...) for installing a heat pump on a flat roof? I'm not exactly sure of the roof material - a tar of some type, I suppose.
Option 2: Install a vertical packaged air source heat pump, such a GE Zoneline. I have an area very near the existing furnace which fronts an exterior wall that could accommodate the unit (cutouts, etc). Trouble is nobody that I have researched (Friedrich, Skymark, Adirondack, etc...) makes a downflow packaged unit. Knowing that, would it be possible or prudent to field adapt an upflow version of one of these units to function in a downflow system. Before you laugh your xxx off, understand that I'm trying to find a balance between cost and performance, not achieve engineering or design greatness.
Option 3: Install a through-the-wall heat pump (I've only found two, made by First Company and National Comfort Products) in an upstairs closet and route it to a new downdraft air handler where the existing furnace resides. My concern about the through-the-wall unit is that it appears to be old, replacement technology. What are your opinions of this option?
I can't imagine I would need anything bigger than a 2 ton system. There are a total of 8 registers in the house.
Thanks in advance for your help.