But he has no attic to blow insulation into.

Glazing is the second biggest heat gain/loss after infiltration losses....loss due to cracks letting air in or out.

Storm windows will help nearly as much as true insulated but will be hard to seal enough to prevent dirt building up in between the glass. Those big glass areas are lovely but big heat losers/gainers.

Depending on how much insulation is there now, adding good levels of insulation and going to storms or true insulated glass should cut your energy consumption in half.

If you have a couple inches of urethane between the decking and shingles you are pretty good there.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.