efficient furnace vs insulating

[zen_tantos]

Can't afford to do both at the same time, so am hoping for advice on which to do first.
I have a newly purchased 100+ year old house with no insulation and a 50 year old furnace.
What would reduce home heating costs more: a new, efficient furnace or insulating?

[Thatguy]

A 100% efficient furnace will still lose heat through too little insulation.
You'd be paying to heat the air outside and around your house.

With perfect insulation, the heat given off by your appliances and the people in your house (about 100w per person) could heat your house, if you never opened windows or doors and had no infiltration losses.

Here's how much insulation you should have
http://www1.eere.energy.gov/consumer...nsulation.html (http://www1.eere.energy.gov/consumer...nsulation.html)
The law of diminishing returns says don't add more than this.

[leejosepho]

I would definitely do the insulation first, and depending upon the type of furnace you have, certain efficiency adjustments might be possible. Also, there might be a way to extract some of the heat from your exhaust before it goes out the chimney:
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200331508_200331508

[nhmaster]

Inasulation is always the first step. As old as the heating system is changing it now will not have near as much effect as insulating would. I had a similar situation a few years back with a 200 year old house. I did the really smart thing and sold it. :D