John, your a smart guy. That's exactly what I would do. You will not get much of a return at all by going triple pane. Go the route that offers the biggest return, and the plus is you can can the tax credit.

John. another thought is installing 'storm windows."

Because installation is often so easy, the bang for the buck may be better than replacing the originals. --really depends on the window type.

In your sutitation, double is the way to go. You do not need triple because it really doesn't do you any good. Save your money.

I like out swing windows because they can catch a draft during the hot months. they also do not take up space when they open outward,

Our house was built in 1926. House is brick exterior, plaster interior. Windows are a combination of doublehung and casement. I checked into the cost of replacement and it just wasn't going to be cost effective. Not to mention I love the look of the old windows. Instead I added insulation to the attic and sealed every gap I could find. The old double hung windows tend to leak a fair amount. You can get a weather stripping kit for the sashes that will seal the leaks. This Old House magazine has a great online how-to on doing this: Airtight Windows in 9 Steps | Windows | This Old House - 1

Frankly, I thought you were doing it for the appearance so that the windows matched the vinyl replacement windows you had done previously. If you are satisfied with the look and the windows are working well, I wouldn't replace them. If

i lived in a house that was in the flight path for seatac airport.
they port paid for the upgrade so they could add the third runway.
they put in @25k in sound insulation into the house
this included triple pane windows throughout.
sure the added insulation to the walls and roof we a big part in the sound and a byproduct was amazing heat savings.

but if the windows were closed you couldnt tell a plane was over head...with them open you couldnt hear yourseelf yelliing

Get the windows that are a close match the ones you have. Go over the rest of the house.

A do it yourselfer can blow in cellulose for a major increase in efficiency, for a minimal cost. Rent the biggest HP machine you can get, and use the largest nozzle. Pour in foam is notorious for leaving large voids, and is harder to install. Cellulose blown in properly can be packed quite tightly, and most has an adhesive element in it now as well.

Just be sure that you do any wiring upgrades in your outer walls before you insulate. I did cellulose with an installer when I was young, and the transformation of a house was really remarkable, especially if we did one in the winter.

If you already have a storm window on the outside, and the window can be made fairly air tight, you don't need to. Bare single pane is quite cold, even on a non-insulated house.

+1 on the storm windows
+1 on reducing air infiltration/leaks

If you decide to change the windows, I'd go with double paned factory sealed units that have the metal separators (not the caulking type) and casement style; imo.

Check your attick?
Properly vented and insulated.... biggest bang for your buck right there!
Cheers

John
Are you replacing the single pane windows because they are rotten? I'd only replace them in this case. Add a storm window that fits properly as others have said. If the existing original windows are solid and you have an old house with lath/plaster there is something to be said for that. Scrape and paint and keep all of your money and forget the grant unless the windows are truely shot.

Last time I checked, I would be dead before the upgraded windows would pay for themselves.

plastic sheets on the windows in winter ;) -- great ghetto look but does work a bit.

+1 insulation

double check around the window, leaks are nasty

Only one of the windows is not working, it is a double hung and I could repair the sash cord. The others are casements and working okay, not rotten. I was going to replace them for heat/cold reasons. But I am now reconsidering that. Maybe I will clean them up and repair what needs it, and call it good. I can't really put storm windows on them because we do need to open them sometimes during winter. I wonder if I can get double pane glass panels made to fit the existing window frames, I think I could make a thicker pane work.

When you get it all done and rub some paraffin wax on the edge of the sash and they will slide like if they are on rails. The old man I use to work for in college use to charge 40 bucks using this trick to make old windows work again. You can get a thin 1/4" or 5/16" thick dual pane glass insert made from a glass shop. check if your rabbet is deep enough.

One must remember glass panes are 1/8" or thicker and the usual airspace in an insulated unit is 1/4" or more so from my experience you would expect a unit to be 1/2" thick overall which is probably too thick unless your sash are 1 3/4" thick. Also, the 100 year old windows were not made to house the weight of double glass units (twice as much).

Reg

I'm surprised your local utility won't give you a freee energy audit and help with window costs as well - they do here, and all your & my area is under the same BPA parent program...

at any rate, I agree with your inclination - 2 panes, Argon fill, e-coating. This will do more than reduce your heating/cooling costs - it will make the house more comfortable. The reason why is complicated and somewhat distinct from the mere insulation value. But it deals with radiative losses from your body and the so-called 'radiative view factors." Anyway, I would particularly address any windows that you can see much of, when you are sitting on the couch, etc. - your normal places to be in the house (in front of computer, reading spot, dining areas, TV/video viewing or stereo listening areas).

you really need to get the walls insulated!

finally, the installation is very important - here, the utility certifies only ceretain contractors for their program

one thing is found out, is that some will cut off window fins and just push the repl. unit to make it quick and easy for them -- this will ruin the U-value of high $$ window unit, as air infiltration will be high.

you could ask; watch them; or even DIY - I did on some lower floor windows. Time consuming but it will keep you off the streets & out of trouble for a while.

Good Luck!