For an older house.What should you do first: insulate or replace the furnace?
Whether you should insulate or replace your furnace first depends on the situation in your house. Factors that influence this decision are the age and efficiency of your furnace, and the amount of insulation currently present in the house.
In general it is more cost-effective to upgrade insulation than it is to upgrade your furnace. However, if your furnace is old, and you are planning on replacing it anyway, you might want to upgrade the furnace if you have to choose between the two options. The average lifetime for a furnace is between 15 and 20 years. The efficiency of furnaces has increased over the years, so the older a furnace is, the more likely that furnace is to be inefficient. The average efficiency of new furnaces has increased from 63% in 1972 to 83% in 1995. Older furnaces, and furnaces which are used a lot are more cost-effective to replace than newer or infrequently used furnaces. Also, if you insulate your house at the time of furnace replacement, you might be able to buy a smaller capacity furnace and save money on the price. The same holds true for A/C and other heating and cooling equipment.
Typically older houses were built with poor levels of insulation. As insulation ages, it compresses, becoming less effective at preventing heat transfer. Dust and moisture also contribute to the aging process in insulation. In temperate areas, if the insulation level in your house is less than 6 inches, the most cost-effective action is to increase the insulation up to R-30. For areas with extreme hot or cold temperatures, it is cost-effective to increase the insulation up to R-42.
Here are approximate R-values of different insulation levels. The actual R-value of your insulation depends on the type and condition of the insulation, but these approximate values are helpful for judging whether adding insulation is the best plan for your house.
Insulation Level…….Approximate R-Value
3 inches………………….. R-9
6 inches………………….. R-19
10 inches…………………. R-30
13 inches…………………. R-42
Source:www.radiant-heat-floor-methods.com