I know a number of people in a similar situation that want to add insulation to older, poorly insulated homes. Homes are similar. Poorly insulated attics (6" of fiberglass batts), no insulation in exterior walls. The attic square footage is relatively small compared to the roof area because of high pitched roofs and kneewalls.
Doing this as a DIY project that would be completed in stages maybe one weekend every couple of months or so.
What order would you tackle each project the following insulation/air sealing projects to get the most cost savings early?
A) Add R-30 unfaced fiberglass batts over existing attic insulation. Attic floor sq footage is I'd say roughly 75% or less of the 2nd floor sq footage due to kneewalls on most of the exterior walls on the 2nd floor.
B) Get access to back of kneewalls on 2nd floor and add insulation to back of interior wall and over interior ceiling. Studs are only 2x4 but since there's plenty of space may use R19 or greater kraft faced insulation for walls, R30 for over ceiling. About 60% or so of the 2nd floor exterior walls are kneewalls with conditioned living space underneath.
C) Add fiberglass batt insulation and those foam insulation vent boards to allow airflow to the sloped ceiling space over the kneewall. This would be done at the same time as either A or B.
D) Blow in fiberglass insulation to exterior 2x4 framed walls from interior that are not knee walls. All the exterior walls on the 1st floor and about 40% of the 2nd floor exterior walls.