Another insulation question

[rad41]

My daughters house which they just purchased is a bunglow built in the 1920s. while performing the electrical and other construction work I noted that there is no insulation in the walls of the house. The attic has real 2x4s as joisted as is insulated with celouis (spelling).

There are heaters all over the house so I don't think the they will be cold in the winter. But the house is hot during the summer days.

One local construction guy suggested the the windows should be replaced first, and not even bother with insulation.

So I guess I am asking for some advice

Thanks
rad41

[suemarkp]

Empty walls and single pane windows have about the same R value (about R 1). Since you usually have much more wall area than window area, you'll have less heat loss by insulating the walls. Note that you'll quickly reach diminishing returns though if you superinsulate the walls, there will be so much heat loss through the windows to make the superinsulation worthless.

The other factor to consider for windows is are you getting a bunch of sun through them which overheats the house in summer? If so, then putting in low-e glass will block a lot of the solar radiation, and that is a bigger factor than insulation or R values.

So if you don't have sun beating in (or can block it with shades or trees), then insulate the walls with R-11 or R-13. I'd also investigate your attic venting to make sure its letting out enough heat. If you have less than 6" of insulation in the attic, you may want to consider adding more or laying some R-11 or R-19 fiberglass across the attic floor. Consider a radiant barrier in the attic if you're in the sunny south.