How old is your home?
Do you have good windows and siding on the outside?Leak proof?
Do you have any push button switchs in your home? This could mean knob and tube wiring.A no-no with insulation.
Is it ballon framed, meaning if you go into the basement you can see the floor joists and wall studs and up into the walls.
You may have blocking in the walls, then you only insulate half the wall.
Square Eye said it best... removing the plaster (I know this because you dont have insulation) is the Way to go. This is the only way you will do the job correctly.To many people are worried about insulating their homes without understanding how the dynamics change that they end up with more damage to structure down the road.
I wish it was as easy as those big box stores selling all that good stuff made it out to be.
My second home was a post and beam saltbox colonial built in 1742. I rebuilt most of the house to original.The only part I insulated was the attic R-40. I fixed all the windows and doors, installed insulated electrical boxs and insulated my perimeter floor joists.Behind your plaster is a type of gypsum board that helps to hold the heat, just like your plaster absorbs some heat. The trick is to stop all those door, window and electrical box drafts.Then insulate the attic and make sure you have good ventilation up there.
These should help you to feel more comfortable.
Take your extra money to Vegas!! The odds are better.
(Hope your not a recovering addict!!)
Looking for the perfect home. (or mabey just warmer)