Supplemental heating system

Most larger AC systems can be run in reverse. They are then referred to as heat-pumps. Heat pumps are theoretically the most efficient way to provide domestic heat, they're what you would want use for an all electric car if you lived in Maine. But we pay a lot for electricity in NYC so they are not as cost effective as gas or oil furnaces/boilers.

The biggest problem with them as supplemental heat is that a heat pump is tuned to a particular temperature differential between the heat source and sink. It will work very well when the temperature outside is up to about 30 Fahrenheit cooler outside than inside, but the efficiency will drop when the difference grows and it will provide almost no heat when you want the inside at 68 and the outside is at 0; which is when you need the heat the most.

When heat pumps are used instead of other means of heating in climates like ours, i.e. in areas where electricity is cheaper, they also include a supplemental resistive heating element. The resistive heating is inefficient, but it gets you through those cold days in comfort (a resistive heater is what a "space heater" and hair driers use). I don't know about the Space Pak AC, but since it is primarily intended as a cooling system I would doubt it includes a resistive heating element. Besides if you live in a the typical brownstone it would probably require you to upgrade your electrical service anyway if it did have a resistive heater.

A Space Pak system would also require tearing up your walls anyway, you might as well just get someone to add heating ducts in the front of the house. (If you do this, try to only put it the ducts in internal walls, the cavity in the external walls is probably only 1", which is insufficient even for small ducts, the interior walls in my house range in thickness from 2" to 3.5", the 3.5" thick ones are the ones containing the original ductwork.)

If you're trying to avoid tearing up the walls, then you can install a split AC system with the heat pump option and it will work as well as the Space Pak would without tearing up your walls. But again, in NYC, it will not work well on the coldest 15-30 days of the year; or 30-90 days if you like it toasty.

Posted by: danielk at October 18, 2007 3:25 PM