Unfortunately, she frequently turns it off to save on electricity, which exacerbates the issue.i have also sent her extra radiator heat so can just plug in , but she refuse to use because she has to pay high electric bill.She complained about the unit's insulation and requested that we install an additional baseboard heater( whats the use if she doesn't turn on the heat) .

These losses depend on the layout and geometry of the system (ductwork, piping, etc) and the insulation used, the ambient temperature that these ducts/pipes are traveling through, the temperature of the air or water/glycol mix etc...  

. - New windows, AC ducts, attic insulation, gutters, appliances, fans & lighting, paint, and tile.

We're seeing historically insulated submarkets to new construction get effected because of how much there has been as a percentage of existing stock.

Purchase price: $179,000 Cash invested: $15,000 Lived in the property for 1 year.Knocked down living room wall, replaced Hvac, floors and gutted and remodeled the kitchen, attic insulation, converted the living room and the dining area into rooms.

Typically these need now to be in a rated shaft and just not insulated. 

Just a side note.. houses in Cupertino that were built in the 50s and 60s many times had NO insulation they just put in two furnaces :) And as you noted they sold for 15 to 25k.. in those days I still remember late 60s when they were crawling up to the 50k mark..

Then insulation, then drywall, then paint primer.

(Tunnel holes in insulation and droppings).

I am not currently using a property manager, so any other extra insulating layer that I can get is useful to me.