I wrestled with the idea of window replacement for quite a while. I am not certain if the existing windows are original, but they are probably close to it. They are the classic, six-over-six, double-hung wood-sash windows that are in many buildings of the late 1800s vintage. The glass doesn’t look particularly old, but it is likely the panes didn’t survive the 1917 Halifax Explosion that occurred only 3 km away.
You might think that window replacement is a no-brainer, but I have found quite a bit of information that argues otherwise. A pane of glass has an R-value of 1. A pocket of still air also has an R-value of 1. So a plain-jane double-glazed window will have, at most, an R-value of 3. Compared to a wall of R-12 or R-20, it’s not that great. Even a really awesome, fibreglass, triple-paned, gas-filled, low-e, technical wonder window will get you up to R-6 or so. While it is 100% better than the plain-jane version, it’s still a lot lower than a solid insulated wall. Nerd alert: There is a lot more to picking windows and if you are really interested check the National Fenestration Rating Council website. They speak in terms of U-values rather than R-values. For practical puposes, R = 1/U. Nerd out.
A window is a building envelope liability in terms of unwanted energy losses (and gains), air leakage and moisture intrusion. That is why I always get a little clenched up when I see “sustainable” building designs with huge expanses of glass such as the plans for the Halifax Central Library and the NS Power headquarters renovation. If your definition of sustainable includes excessive energy use, then yeah, go ahead and make a building clad entirely in glass. Truly energy-efficient designs aim for a total window area of 10-40% of total wall area while optimizing for passive solar gains, daylighting and views.
At my place, I am restricted by the Heritage Property Program from making any substantial exterior changes. It is really not that onerous, they want it to look original but it doesn’t have to use original materials. Some residents of the the Twelve Apostles have replaced their windows with convincing looking wood or vinyl double-hung windows coloured the same dark green of the originals. Other residents don’t pay any attention at all to the heritage provisions and slap in whatever cheap white vinyl junk they can get at their local home centre. I did some homework and decided to get the original windows restored.
Slightly crazy perhaps, but cost-effective and with proper weather-stripping and a decent storm window, I think it will be a great compromise. I asked Natalie, the local Passivehouse guru and Accurate Dorwin rep, to come by and give me a quote for some awesome techno wonders that pressed every one of my must-have window buttons. AD is out of Winnipeg, home of Damn Cold. They know their windows out there. Another former Winnipeg company, Willmar, built a quintuple-paned window (!) for the Alberta Sustainable House where I abided for one long month back in the 90s. It is the window looking onto the front porch, not terribly large, but if I recall correctly it was around R-7 and cost $5000. For one window and that was 15 years ago. I am not building to passivehouse standards or even R2000 standards, and I have a soft spot for authentic! original! historic! so I jumped off the fence and onto the Restoration path. And if I discover they will not do, then I can always upgrade later.
The Heritage folks turned me on to the city’s window restoration guy, Sefton Squires. He lives over in Annapolis Royal, one of the oldest settlements in North America, and they have some old windows. If you think I am crazy, here is the story of a 300-year old window restoration. It’s not his project, but he does specialize in heritage restoration and I have seen his work around town and that was enough for me. So he and his crew stopped by last week to pop out the windows and bring them back to Annapolis Royal for a going over. The place looks a little forlorn with the windows boarded up but it definitely looks officially Under Construction.