Hill House, Scotland, Charles Rennie Mackintosh. Can you imagine this in vinyl?
John recently wrote that "Rising fuel costs and environmental concerns have forced councillors to consider lifting a ban on double glazed windows in Edinburgh's most historic buildings. Hundreds of residents in and around the New Town are currently prevented from replacing their draughty old windows, because of fears that double glazing would change the appearance of their properties."
Don't do it, Edinburgh! Donovan Rypkema lists a couple of reasons:
- The vast majority of heat loss in homes is through the attic or uninsulated walls, not windows.
- Adding just 3 1/2 inches of fiberglass insulation in the attic has three times the R factor impact as replacing a single pane window with no storm window with the most energy efficient window.
- Properly repaired historic windows have an R factor nearly indistinguishable from new, so-called, "weatherized" windows.
- Regardless of the manufacturers’ "lifetime warranties", thirty percent of the windows being replaced each year are less than 10 years old.
- One Indiana study showed that the payback period through energy savings by replacing historic wood windows is 400 years.
- These houses were built hundreds of years ago, meaning those windows were built from hardwood timber from old growth forests. Environmentalists go nuts about cutting trees in old growth forests, but what’s the difference? Destroying those windows represents the destruction of the same scarce resource.
Cheap windows in old Dublin building. Now the whole building looks fake. Discussion here
Rypkema also points out that sustainable development is about, but not only about, environmental sustainability.
1. Repairing and rebuilding the historic windows would have meant the dollars were spent locally instead of at a distant manufacturing plant. That’s economic sustainability, also part of sustainable development.
2. Maintaining the original fabric is maintaining the character of the historic neighborhood. That’s cultural sustainability, also part of sustainable development.
The character of so many houses has been lost because charlatan window salesmen promise 40% energy savings with replacement windows but it rarely comes close. Furthermore you can fix the windows and get magnetic storm windows that go on the inside, so that nobody can even tell the difference.
When the Rocky Mountain Institute analyzed the return on investment of different measures one can take to save energy, upgrading to high performance windows was one of the least cost-effective things on their list, costing $133.88 per ton of carbon saved, five times as much as weatherizing (caulking and sealing) the windows did. (PDF here)
A Vermont study showed much the same result, concluding:
Preservationists Take Heart
"Our study of old windows showed that the energy savings are similar for a variety of retrofit and replacement strategies. Rates of return on investment for energy improvements are quite low when starting with typical or tight windows with storms in place, but are significantly higher when renovating loose windows with no storm.
The difference in annual energy savings between renovating an old sash and replacing it with a new one was very small--retrofits saved only a few dollars.
For preservations, the good news is that with a proper choice of renovation strategy and good workmanship, historic sashes can be almost as energy-efficient as replacements. Window renovators and homeowners can give more weight to comfort, maintenance, lead abatement, egress requirements, durability, ease of operation--and historical value--without sacrificing energy savings. For those of us who work with old windows, this is very good news indeed."
Source: Creating Windows of Energy-Saving Opportunity by Andrew M. Shapiro and Brad James
The character of these houses will be lost; good windows thrown out for lousy ones; more energy will go into making the windows than will ever be saved through their lifetime.
If you have crappy sashless sliders that are rotting away, replace them. But historic Edinburgh? Forget it. ::Donovan Rypkema
Read more on window repair in TreeHugger:
Building the Green Modern Home: Looking at Windows
Donovan Rypkema : LEED stands for "Lunatic Environmentalists ...
Renovation Uses Twice As Much Labor, Half as Much Material as New ...