Preserve, Reuse, and Pass Forward Oregon's Historic Resources...
A couple of weeks ago Mark Bell of Classic Sash & Door came out to give Drew and I an estimate on traditional wood storm windows. Well, not all traditional. We asked him to include an estimate for the Marvin wood storms that have a metal insert with a screen, allowing for full ventilation without removing the storm windows. We are in a big old foursquare and intend to stay here, so as we get older we may not want to be scrambling up and down ladders with storm windows and when we do get that unexpected 70 degree day in February or March, we'd like to air out the house a bit. We will, however, use the fully traditional storms on the front of the house and the side by the deck where they will be seen from the street or up close and we can either stand on the porch or deck to remove them or on the roof of the porch.
Mark was gracious enough to talk a little about storm windows and the process for buying and installing them on camera (about 10 mins):
One of the things I am most looking forward to is the increased quiet. As you can hear, we are on a reasonably busy street (with a bus line).
The estimate came back at about $4,900 for the whole house with the fancy schmancy storm/screen combos. Mark agreed that it would probably cost between $25K and 30K to replace our windows with high quality wood windows with similar architectural details (take this as a very loose estimate). That's a big difference in price and add the interest you'd pay if you have to take out a loan or the interest you'd lose if you have $20K sitting around. It makes you wonder if the difference in energy savings is worth $20K.
I've been attempting to find a good neutral calculation for what we would save in heating bills with replacement windows vs. storms and one of the issues I've come across is that a lot of companies use a Department of Energy figure that states "Increasing the R-value from 3 to 5 reduces average heat loss through the window by 30% to 40%." The important words are through the window. It does not mean that your overall heating bill will be reduced by that amount, but many of the online calculators ask you to type in your yearly heating bill and their "calculator" just cuts it by 40% without considering how many windows you might have or how large they are or whether the rest of your house is insulated.
As you can see from the chart (right) from the Department of Energy,(http://www.energysavers.gov/tips/air_leaks.cfm) only about 10% of air leakage is from windows. No way would we be able to save 40% of our energy bill by replacing our historic windows even if they accounted for 15% of air leakage. We would do better by insulating around plumbing penetrations or closing off our fireplace(not gonna happen). We are working on re-insulating the attic, removing old tamped down insulation and putting in new fluffy stuff. And we will now look at plumbing penetrations and ducts as well.
But what is the difference in efficiency between replacement windows and storm windows? I found this chart from the Oak Ridge National Laboratory showing the relative efficiency of storm windows and replacement windows with and without Low-E glass:
Our estimate doesn't say anything about Low-E glass, so we will have to go back and discuss that. It also seems that interior storms do an even better job than exteriors.(We've planned for interior storms on 3 windows - the swing-out casements on the sleeping porch and the 12-light window in the attic dormer. But that's another blog post.)
We're going to get some more estimates, including interior storms and will continue to share our storm window adventure right through installation.