I am building a home that has "historic" windows specified. These windows are specific enough that I will have to build them myself and there is no way to have double pane glass. I am wondering about the thermal performance of interior storm windows. Can I make a window with an interior storm window as efficient as a standard double pane window? Are there any known issues with interior storm windows?

You mean that historic commission will not allow double pane windows or that you can't build them?
You can buy double pane insulated glass panels from most glass companies that could be installed in your handmade sashes.

There is not a historic commission. The windows will have leaded glass similar to a stained glass window. Part of the window will use rondels or spun glass. Kind of hard to double insulate that sort of thing. Exterior storm windows would ruin the outside.

Any way to use insulated panels, and then mount your 'historic' glass as the interior 'storm' panel?
This would keep the handmade sashes out of the weather, and significantly increase their life expectancy.

According to the heat loss calculations provided to us by our geothermal installer, storm windows are more efficient than new double-paned glass.  In addition, double paned glass had a very high failure rate and often needs to be replaced in 10-15 years.  In addition, keeping your original windows means there are less items filling up a landfill.

It is for these reasons that I think it is much better to restore original windows than replace. 

Make sure all holes are sealed and weather stripping is used in all possible areas.  Use internal storms as necessary.  We decided to keep and restore our historic, original steel casement windows and I we are very happy that we did.  If you love old homes, in the long run, you will be happy that you did too. 

I agree with Art Moderne, the old windows with a storm can be efficient.  And will not leak gas and become useless.  I have seen far too many double panes fail early in life. 

I have an old house with old windows I plan to repair and add storms.  Notsureif I am going to use interior or exterior.  There are "historic" wood frame storms available for the exterior, or you could even build them yourself.  That maintains a historic look and protects the window. 

I agree that the interior storm windows should work to reduce heat transfer, although not as well as a sealed double-pane, low-e window, perhaps R-2 rather than R-3 for the sealed windows.  The single panes would be around R-1.  Adding insulated cellular shades on the inside might add another R-0.5 to R-1 at night, or insulated shades with the side seals R-1.2 to R-2.0.  I don't know if what you use at night might violate historic standards, but it could cut your energy bills.   

Lee Dodge
www.residentialenergylaboratory
in a net-zero energy house

Hunter Dougls Duette Architella Architella 3/4 " semi opaque without tracks add R 2.6. Duette Architella 3/4 " opaque shade without tracks add R 3.68. My interior double sided interior storm panel with shrink wrap adds R 2.3. and seal out the drafts effectively stopping air infiltration in either direction, significantly reducing the possibility of condensation. Over single glazed historic windows which probable will only test at about R.9 This combination could yield R 6.88 Adding tracks would be a cosmetic compromise inside and are not user friendly but they would add to the insulating value.

Rod-

Do you have a technical reference for the R-values that you quoted?  I have done a fair amount of testing on both light-filtering and room-darkening shades, both with and without the side seals, and found the measured R-values to be much lower than those given in advertisements.  (Is this surprising?!)  I will be working on writing up the results and posting them on my website in the near future.  I would like to reference other technical papers if you know of them.  I have found one write-up by Steven Winter Associates, but it has some errors in it that I will be documenting.  If you are quoting only the advertised values, I would be suspicious of them. 

Lee Dodge
www.residentialenergylaboratory.com
in a net-zero energy house

hmmmmmmm
suspicious indeed anxiously await more info.

Rod Ladman

I find home made double insulated interior storm panels to be the best that ever happened to this old house. rod l.

Posted By Rsipgeo on 10 Jan 2010 08:23 PM
There is not a historic commission. The windows will have leaded glass similar to a stained glass window. Part of the window will use rondels or spun glass. Kind of hard to double insulate that sort of thing. Exterior storm windows would ruin the outside.

Depending on size and 101 other variables, many glass companies can seal "stained glass" inside double or triple pane glazings.