What is the cheapest option for adding insulation above a finished ceiling? There has never been any in the spot that I need it. Should I take the roof off or have it sprayed in? The space is 20 feet long and 9 feet 9 inches wide.
Depends on construction details. if it's merely "the contractor was too cheap to provide attic access" (a very typical issue of cheesy contractors), you cut a hole and put in access, then apply insulation as you like. If it's a cathedral ceiling sort of arrangement (roof deck on one side of rafters, ceiling on the other) then some sort of spray/blown insulation (might be foam, might be cellulose, might be fiberglass but I would not go there based on published research results) is the most likely option, though not the only option. If you are considering "taking off the roof" then it's usually more cost-effective (labor cost, mostly) to leave it in place & build on top of the current roof with a layer of insulation, for instance.