We live in an older house that isn’t well insulated. The furnace is old, too. Which problem do we deal with first?

It’s usually better NOT to replace the furnace before upgrading insulation levels. Recommended insulation levels for different parts of the house can be found at the ENERGY STAR® website. If you are able to upgrade your home’s insulation according to these recommendations, there’s a good chance that you’ll be able to replace your old furnace with a smaller unit, since your HVAC system won’t have to work as hard to maintain comfortable indoor temperatures.