Getting the Most from Old Windows: A Tale of Attachments
July 21, 2011
Should you replace your old windows? Using attachments can get more life out of them, and improve performance.
Most of us approach poorly performing old windows with a step-by-step exploration from one less-than-optimal fix to the next. Improving existing window performance shouldn't be that way, and it doesn't have to with new online resources.
Home Sweet Home
In 2000, my wife and I moved into a nearly 100-year old home in New England, equipped with the original wood single- paned double-hung windows. These windows were supported by some pretty typical window attachments: triple-track exterior aluminum storm windows and opaque vinyl interior roller shades.
By and large, the windows themselves operated pretty well. All the sashes raised, lowered, and locked (more than you can say for a lot of 100-year-old windows). But the storm windows and roller shades were another story.
Conventional aluminum storm windows
You know these storms--the terrifically annoying, anodized aluminum, triple-track ones. Ours were rickety, with white dust (oxidation) all over the tracks, and most of them were barely operational. You typically risked damaging the storm panels or yourself when trying to raise or lower them. While these storms had apparently done a good job of sheltering the original wood sashes, they were frankly quite ugly and worked poorly. They definitely were headed to our local building salvage operation or metal recycling.
Dime-a-dozen roller shades
Our roller shades were essentially privacy shades. They were unattractive and brittle and made rooms horribly dark when deployed during the day. The roller shades were definitely coming out, in part because they were at the end of their service life but also because they were just not versatile enough.
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So if we were eliminating the existing exterior storms and interior roller shades, what did we do to improve our windows?
Decision #1--Keep existing windows, for now...
This first decision was actually dependent on our 2nd decision (see #2 below - high performance low-e exterior storm windows); the 100-year-old window sashes worked and looked just fine. Their problem was mostly thermal performance, something addressed by the storms.
And we did have both a shorter- and a longer-term plan: we would eventually do double-paned wood sash replacement kits for even better thermal performance. But more on this decision later; it turned out to be a bit more complicated than we thought.
Decision #2--Replace existing storms with low-e storms
Although this was our 2nd decision, it was our first purchase. The low-e, baked enamel, aluminum frame, triple-track Harvey storms were sturdy, smooth-operating, relatively air tight, and reasonable at about $100 - $120 per window (there are just two sizes of windows in our house--both 5 feet tall with one just over 2 feet wide and the other just under 3 feet wide). And perhaps most importantly, they continued the history of protecting the wood window sashes while bringing the overall thermal performance pretty close to that of an average new double-paned window.
Decision #3--Install "room-appropriate" interior window treatments
We thought we wanted our interior window attachments to do just three simple things: provide privacy, adjust for varying amounts of daylighting, and add some style and color to our windows. And the importance of each of these varied some from room to room.
So we purchased utilitarian white metal venetian blinds for the home office, where daylighting and adjustability for glare control were the most important. And then for the kitchen and various bedrooms, we purchased quality, heavy-cloth opaque roller shades with matching valances. We even bought bedspreads that matched the pattern of the window treatments for two rooms. The custom-fit venetian blinds were about $80 per window, and the fancy roller shades were about the same (both DIY installations).
Decision #4--Gradually replace sashes
The plan all along was to further improve the thermal performance of our windows by replacing the single- paned wood sashes with Brosco wood sash replacements. We could stain them to look almost identical to the original sashes and get them with low-e glass. While the white vinyl jambliners were a bit jarring, they were not all that visible and the closed-cell foam backing seemed like a thermal improvement over the cord-and-pulley system of the original windows. The sash replacement kits were about $200 apiece (DIY install--pretty simple except for removing the pulleys) so we did them as finances allowed over a 10-year stretch. (For more on understanding different window options and making choices, see Choosing Windows: Looking Through the Options.)
We paused in our purchasing and thought: that ought to do it...
Adding priorities and new options
We did not pause for very long. Window treatment selections turn out to be a lot like hangnails; you just can't leave them alone.
The home office is seriously overglazed, and we really needed better thermal performance from our interior window treatments.
In the kitchen and bedrooms, the lack of view or privacy, depending on how the roller shades were positioned, was frustrating, given how much we had paid for them. And those valances covering up nearly a quarter of the glass area, collecting dust, and covering up the beautiful wood window trim--what were we thinking?
And then we learned about insulated cellular shades with sidetracks that adjust top-down and bottom-up. They come in all kinds of patterns and light-filtering levels.
Changing to insulated cellular shades in the office worked well because the thermal performance of the insulated shades compared to the metal venetian blinds was amazing, and the top-down/bottom-up function gave us lots of combinations of daylighting, glare control, privacy, and view.
Insulated cellular shades (top-down/bottom-up) in the kitchen and bedrooms also gave us the right combinations of view, privacy, and daylighting. And they looked good; while venetian blinds are probably the best at combined view, privacy, and daylighting, they can't hold a candle to the look and feel of the insulated cellular shades, in our family's opinion.
But a closing note on insulated cellular shades--they are not cheap, particularly the top-down/bottom-up with sidetracks. We got ours at an uncommonly good price, about $250 per window.
An unintended consequence
After nearly 11 years of window attachment dithering, you would hope that we ended up exactly where we wanted to be, with the best performing windows possible. Almost.
It turns out that combining high performance window treatments with high performance glazing may create some problems. Both our low-e storm windows and our side-tracked insulated cellular shades, when combined with low-e double-paned windows and intense summer sun, may have resulted in some damage to the seals in the insulated glazing units (IGUs--these are the sealed, double-paned glass). The high-performance attachments combine with high-performance windows to trap quite a bit of heat inside the double-pane windows, enough to degrade the seals. At least that is what appears to have happened with the west-facing windows in our home; research into this issue is under way. (For some background on that and other research with Lawrence Berkeley National Laboratories, subscribers can read our feature story on window attachments: Making Windows Work Better.)
Lessons learned from living with these selections
We have spent quite a bit of money and learned an awful lot about how windows work, and how they don't.
- High quality, baked enamel, tracked, low-e storms work great; 11 years later, our storm windows look and operate as if they were brand new.
- Insulated cellular shades are just about as multi-functional as venetian blinds and look a hell of a lot better.
- Sash replacements need big, beefy seals to accommodate out-of-square old window frames.
- You pretty much get what you pay for; the best-performing, highest-utility window attachments are more expensive.
- Window attachments are like shoes--it's not really possible for one selection to do the trick for all occasions and conditions. You probably need multiple window attachments, just like you need multiple pairs of shoes.
- In terms of thermal performance, exterior attachments are the best at keeping heat out and interior the best at keeping heat in.
- Operable window attachments not only allow adjustment, they require it for optimal performance; this is particularly true for thermal performance.
- If you have high-performance windows and attachments, you may need to shade south and west windows to keep the sun out before it gets in.
By my calculations, there are around 17 types of window attachments and 24 attributes to consider in making your windows work better. You can meander about as we did, or, use the new resources at www.WindowAttachments.org, a website created and maintained by Lawrence Berkeley National Laboratory, BuildingGreen, and the U.S. Department of Energy. I guarantee that the Overview Summary Table alone will save you both time and money in your deliberations. And the monitored forums on the site will yield lots of experience and insight from the field.