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October 12, 2009
New Double Glass in Old Windows?
Does anyone know if it's possible to replace an old single-paned glass window in a brownstone with new double-paned glass that would provide better insulation? These are floor-to-ceiling parlor floor windows, with four panes per window, but very thin glass. Is it possible to make them more energy-efficient, and if so, any recommendations for who can do this?
Thanks.
Comments
There are replicas made that are Landmarks-compliant
Posted by: Arkady at October 12, 2009 12:43 PM
Right. I know I can replace the window, but I was hoping it would be less expensive to just replace the glass, if possible, since the wood part of the window itself seems to be okay. Is it possible to just replace the glass but keep the old window?
Posted by: de95 at October 12, 2009 12:57 PM
I doubt it would be cost-effective. Double-glazed windows have to have a really airtight seal between the two pieces or else moisture collects in the space. I've never seen mass-produced units of those kinds of panes - tolerances would have to be so specific.
Posted by: Arkady at October 12, 2009 1:12 PM
Storm windows. Storms plus proper weather stripping and maintenance of your windows (glazing putty intact, cracks filled, etc) should be nearly as good as double-paned windows according to the research I've done.
Posted by: BHS at October 12, 2009 2:13 PM
Have a fine carpenter rout out the windows so they accept 3/8" old wavy glass which is available as salvage, or 1/4" store plate glass, or if you prefer, the double glazed.
Posted by: outerboro at October 12, 2009 2:20 PM
We did exactly that. When we renovated our brownstone, we decided not to replace the windows, but instead to restore them. Our windows were in pretty bad shape, but the cost to restore them was similar to replacing them with high end Marvins, and we much preferred to have beautifully restored original windows than to replace them with generic new Marvins.
Regarding the glass, we replaced the single pane glass with double pane glass. The double pane glass was purchased from a manufacturer of Insulated Glass Units (IGUs), so they came fully prepared - low E gas, UV protection, warranty, etc. We even had some of the IGUs made with laminated glass to make them impact resistant so we wouldn't have to put iron bars in front of our windows. My contractor “simply” installed the IGUs in the existing window frame. This involved custom woodwork for each sash.
It is important to note that double insulated glass is much heavier than single pane glass, so we had to change the counter-weights and weight pockets. That took some real calculations, but was straight forward. We also had to change all the hardware (chains, pulleys, latches, etc) to accommodate the heavier sashes and reduced space for the latches.
At the same time also we had the entire windows restored: all the moldings around the windows were removed, the sashes and frames were restored, the IGUs were installed, insulation was put in all around the windows, and we added interlocking bronze weather stripping on all sides of each sash.
We now have beautifully restored original windows that we adore, and which are wonderfully insulated.
Posted by: HappyDaddy at October 12, 2009 2:31 PM
I can vouch for HappyDaddy's windows, as I have seen them in person and they work well. I can't overemphasize the importance of weather stripping as he mentioned. In a brownstone window more heat loss occurs due to convection not conduction or radiation. An insulated glass unit will help more with preventing heat gain and reducing sound transmission. FWIW the further apart the two panes of glass are, the more efficient the unit becomes, that is why storm windows are good- basically it is a 4" thick insulated glass unit.
Posted by: southslope at October 12, 2009 4:34 PM
Happy Daddy and the last guy are right! Especially with the full height parlour floor windows, you want to keep the weights. Any good finish carpenter should be able to do this
Posted by: PAL at October 12, 2009 5:14 PM
Just curious HD - how much did one window cost? It sounds like a wonderful solution.
Posted by: Arkady at October 12, 2009 5:31 PM
Happy Daddy - Who did you use to restore? It seems like every place I call in Brooklyn wants me to replace rather than restore.
Posted by: keep at October 13, 2009 3:06 PM
Happy Daddy and everyone else who's done this -- please do tell us who did this for you, as most people have told me the same thing they told keep -- replace with new windows. I'd love to keep the old ones, though, if it's not more expensive to do that. But want to make sure I'm using someone who knows what they're doing.
Posted by: de95 at October 13, 2009 10:32 PM
The problem with double-paned glass is that the seal between the panes often fails after 5+ years and there's no simple way to fix this. Also, any window made to hold a single piece of glass is going to look different with two pieces in there. Storm windows essentially add a second pane of glass and are simple to maintain and repair and are historically accurate (or can be, certainly there are non-historically accurate ones). Why not have nice wood storm windows made and a little maintenance for your existing wood windows plus some weather stripping? Certainly this is a safer and likely much cheaper path. Old glass and single paned windows look different in a subtle way that's part of the charm of a historic house.
Posted by: BHS at October 14, 2009 1:14 PM
BHS -- I'm convinced. So where do you get the nice wood historically accurate storm windows? Most of the ones I've seen are metal and not very nice-looking.
Posted by: prospect heights renovator at October 17, 2009 10:07 PM
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