None of my contractors will admit that you can have savings with storms but even without low e glass I had great energy savings with storms and the old double hungs and they really protect your windows. My bills were lower than anyone! the problem I encountered was that there is only one style of storms still available which have the plastic things to hold them up. Before my fire we had 6 fixed and replaced and it cost almost $400 for the ones that were broken and that seemed expensive.
the thing I don't like about the low e galss is the tint.

i don't believe you will find any storms with low e glass as this requires insulated units and the weight would be too heavy for a thin aluminum framed storm unit. Really they are not very energy efficient they just provide another barrier for the weather to have to permeate.

afsa: I meant getting new storms with low e-glass. Larson has low e as an options. Anyway, I've decided to stay with the single panes. I am having someone to reglaze where needed, paint the outside including the storms and recaulk around the storms.

Storm windows generally have zero R value, but are effective at limiting infiltration losses (a large issue with older double hung windows).

A 71 x 32 double hung window with as small a crack width around the sash and the meeting rail of 1/32 inch has an open area of ~7.4 square inches.

This is equivalent to a completely sealed window of the same size left open almost 1/4 inch.

Metal storm windows cannot have a temperature difference from the outside to between the storm and interior window.
Metal conducts heat way to well, as does the large glass area of the storm.

Wood storms have a little value, but often are not as tight as metal unless gasketed, and still have the large glass area.

Caulk and close up gaps and keep the storms you have.

Thanks brickeyee, I like your analogies. I am staying with my storms and double hungs. I am having the windows repainted, reglazed where necessary and storms taken out, painted white on the outside to blend with the primary windows and reinstalled with new caulking.

I do have a question if you could answer. If someone is considering replacing double hung windows purely for the R value improvement, is it usually worth it. I assume they have storm windows. Thanks

Cost can be an issue relative to the value of your home. With heating bills increasing in recent years, the energy savings can justify the cost of new windows. However, putting 25,000 worth of new windows in a $75,000 house just doesn't make sense unless you plan to live there forever and the rest of the house is sound.

With a 25 yr old house, I doubt you have the very old lead weight counterbalances. One option that can save you money is what they call a "sash pack". Several manufacturers offer this. If the frame of you window is square and level, it could be an option.

Basically, you take the existing sashes out. This generally requires a wooden stop to be removed. The sash liners maybe be vinyl or aluminum that is flexible on both sides. There also maybe a cord to hold for counterbalance with a spring. The sash liners, cord and spring must all be removed.

Several manurfactures offer this product. Kolbe, Eagle, Semco, Marvin come to mind. There are probably more. Get the measureing instructions and follow them closely. What you get is a pair of sash liners that install on both sides. The new sashes can have insulated, lowe glass. Installation will also include some kind of adjustable head or foot too.

Keep in mind with sash paks you are not replacing the entire window unit and I don't think it qualifies for tax credit.

Ironically, if you go to a vinyl window company, they have replacement windows which is really a window that fits inside you existing window after you remove the sash and liners. There are dozens of companies selling this kind of installation. They have it down to a science and can yank your sashes out, stick the replacements in and caulk them in a very short time.

Even though many of these replacement windows qualify for tax credit, they are generally very cheaply made. What that means is they meet tax credit performance in a factory test but after a few years in the sun, vinyl can sag, letting in wind and cold.

That doesn't mean all replacements are made cheaply but you do have to do your homework. If you have Tom, Dick, Harry or Jack come out and do you windows as a package deal, be careful. Ask to see a cross section of the window and go to a long term window dealer or lumber yard and compare what you are getting.