The best and easiest way to retrofit an older home with wall insulation without removing the lathe and plaster is to drill from outside.

When carefully spackled and repainted, the holes created virtually disappear. Another option is to lift siding boards, drill through the sheathing, plug the holes and re-install the siding. However, when exterior brick veneer or other issues preclude an exterior drill, wall insulation can usually be installed from inside. Dust is a factor in this case, and care must be taken to protect furnishings and surfaces and clean up afterward. In a home with lath and plaster interior walls, drilling the holes is more challenging. It may take several expensive drill bits and therefore costs a bit more, but it can be done. Not every contractor is willing to install through plaster, however.

Insulating an attic as interior space can be complex and challenging to do correctly, and I would not want to give recommendations without looking at the attic. Challenges include getting sufficient insulation depth in the rafter/sloped ceiling area, blocking open joist cavities in the area between the existing ceiling and new floor above and properly ventilating the small roof and attic spaces created. An inspection would be needed to provide answers to these and other questions that may come up.

Some companies claim to have dimmable compact fluorescent light fixtures available. My impression is that these are able to dim only slightly. A truly dimmable and energy efficient option would be LED fixtures; however, these can be quite expensive.

Updated July 13, 2010