Insulating the walls of a sun-room

May second-floor sun-room was added without wall sheathing under the exterior clapboard. In other words, the clapboards were nailed directly to the studs. The interior is finished with paneling. Now I want to make the sun-room into a living room. What is the best way to insulate the walls without defacing the inside paneling? Could I do something to the exterior to compensate for the lack of wall sheathing, such as installing aluminum siding? Thelbert E. Sharpley Titusville, New Jersey

Wall and ceiling insulation may be blown into the walls by an insulation contractor. Minimum interior defacement may possibly be required in order to allow an insulation nozzle to enter the stud wall cavities. It is possible to pierce into the stud cavities through the exterior clapboard, but the second-story condition may be a deterrent to the contractor.

Have a couple of reputable insulation contractors visit the site and provide written bids for both ceiling and wall insulation method, material, and cost.

Whether or not the use of aluminum siding over the exterior clapboard is the thing to do is more a matter of aesthetics and economics than a substitute for the lack of wall sheathing.

Here's another point for you to consider: The sun-room very likely has more window area than is desirable for a living room. In these days of energy conservation, consider reducing the window area or else use window units with thermal-type panes.