A cost-effective way to winterize windows

D’Arcy Norman asks:

If there’s a better way to winterize windows than just taping plastic to the frame, I’d love to hear about it.

Indeed. In New Hampshire, when fuel prices first skyrocketed, we did that for a couple of years. It’s an incredibly effective way to stop the leaks that suck precious warm air out of your home. But it’s a royal pain to install the plastic sheeting every fall, and when you remove it in the spring you inevitably pull paint chips off your window frames.

The solution is interior storms, a really nice hack I learned about from John Leeke. He’s a restorer of historic homes, and — what brought him to my attention — a narrator of that work. Interior storms are just removable frames, surrounded by gaskets, to which you attach your plastic sheets permanently. Once made they pop into your window frames in a few seconds every fall, and pop out as easily in the spring.

Achieving that result is, however, not trivial, at least it wasn’t for me. My first generation of interior storms, based on John’s instructions, were suboptimal. The round backer rod material he recommended had to be split lengthwise to form a D profile. I wound up making a jig to do that by drilling a backer-rod-diameter hole in a piece of wood, splitting it in half, embedding a razor blade on an angle, and joining the pieces. Great idea in principle, but in practice it was still hard to draw hundreds of feet of backer rod through the jig and achieve a clean lengthwise split. It was also hard to apply hundreds of feet of double-sided tape to the split material.

The backer rod I used also turned out not to be sufficiently compressible. The critical thing with interior storms is a tight fit. When you tape plastic to your windows you’re guaranteed to get that result, which is why it’s so effective. Interior storms need to press into their surrounding window frames really snugly to achieve the same effect. Inconsistencies in the width of my split backer rod, and the relative incompressibility of the material, resulted in storms that didn’t always fit as snugly as they should have.

Another problem with the first-generation storms was flimsy frames. I ripped pine boards lengthwise to create inch-wide frame members. They really should have been inch-and-a-half.

So last year I rebooted and created second-generation storms. I started with inch-and-a-half wide frame members. Then I ditched the backer rod and went with pretaped rubber gasket. It’s a much more expensive material but it obviates the need for do-it-yourself taping and has the compressibility I was looking for.

Yet another problem with the first-gen storms was that I made all the frames from the same template. The windows were nominally all the same dimensions, but it turns out there were minor variations and those matter when you really need to achieve a snug fit.

So the second time around I customized each frame to its window. Yes, it was tedious. But for our house it was necessary, and it might be for many old houses. Here’s the algorithm I came up with:

1. Cut short dummy pieces from spare inch-and-a-half-wide frame members.

2. Attach gasket to one side of each dummy piece.

3. Make all long and short frame members a bit longer than needed.

4. For each frame member:

– Place dummy pieces on either end

– Place frame member between dummy pieces

– Compress the gasket at one end

– Mark frame member at the other end (accounting for gasket compression on that end)

– Cut frame member

– Label frame member (“living room west wall”)

Once the frame is made, you attach the plastic sheet in the usual way. I used Warp Brothers SK-38 kits which come with double-stick tape. You tape around the edge of the frame, lay down the plastic, smooth it by hand, press it down, trim the edges, and use a blow dryer or heat gun to shrink it tight.

Ths is the kind of job I hate doing. You spend lots of time climbing the learning curve, and then once you’re done you never reuse the knowledge you’ve painfully acquired. Since the method is so effective, though, I’ll toss out an idea that’s been percolating for a while.

Consider an older house in a northern climate, with older windows and storms, and adequate attic insulation. The walls may or may not be adequately insulated, but the first line of defense is to tighten up those windows. It’s expensive to replace them, and the replacements are going to be vinyl that will ruin the aesthetics of the house and won’t age well. It’s even more expensive to hire a restorer to rebuild the old windows.

Let’s say that interior storms deliver 80% of the benefit of replacement windows for 10% of the cost. Deploying this solution to all the eligible houses in a region is arguably the most cost-effective way to tighten up that population of houses. But the method I’ve described here won’t scale. It entails more effort, and more hassle, than most folks will be willing to put up with.

How could we scale out deployment of interior storms across a whole community? I’d love to see high schools take on the challenge. Set up a workshop for making interior storms. Market it as a makerspace. No, it’s not 3D printing, but low-tech interior storms deployed community-wide will mean way more to the community than anything a MakerBot can print. Also, turn the operation into a summer jobs program. Teach kids how to run it like a business and pay themselves better than minimum wage.

Since I am now living in Santa Rosa, winterization of windows is no longer a big concern. But I’ve been meaning to document what I learned and did back in New Hampshire. And I would really like to see John Leeke’s idea applied at scale in places where it’s needed. So I hope that the new owner of the house we sold in Keene will be successful with this method, that D’Arcy Norman and others will too, and that communities will figure out how to make it happen at scale.

9 Comments

  1. Following your original article, I did this for one of my windows (with only 2mm glass), and in fact, I leave the frame in place all year now – the actual window is painted shut and not one I’d ever want to open.

    Like you, I found it easier to use “pretaped rubber gasket” (sold on long rolls to use for draught-proofing doors etc) which is available in a range of different profiles. But rather than use the shrink wrap, I cut a piece of perspex to the frame once made, and then screwed this to the frame.

    The seal might not be perfect but I can still apply tape if needed to seal the wood-perspex gaps, and the perspex makes the frame stronger. The perspex is on the window side of the frame (to hide the screws) which is a reduced air gap slightly, but now I can clean the screen if needed.

    If I was really keen, I could then also apply the shrink plastic to the non window side of the frame to get a triple gazed effect with two airgaps.

    But I was wondering if you could make these to be easily adjustable, with something like the “twist to lock” metal tubes and simple corner brackets, so you easily pick up 4 sides that span the lengths required, 4 corner pieces, and then apply the film. That would separate the job of manufacture from the task of getting a snug fit to an arbitrary window… making the sort of community wide deployment much more feasible.

  2. As I was reading your description the thought of using a laser system to map the existing window openings popped into my head. Going with your maker thought, it might be an interesting project to build a “window scanner” that would drop out the exact dimensions needed for the frame cuts. It would really simplify the process.

  3. Both good suggestions. My first-gen frames were sort of adjustable. The middle cross-member wasn’t permanently attached, just pressed into place, and I put flat-top screws on the ends so I could adjust the tension.

    I thought about something like that for all the joints on the second-gen frames, but nixed the idea because spreading things apart leaves unsightly gaps. But I should have consulted my design genius friend Gary Spykman (http://www.sebbidesigns.com/about-people/) about that, I bet he’d have figured something out.

    Scanning the exact window dimensions is a really interesting idea! Outside my domain of expertise but if it becomes a reality I’d love to see it happen!

  4. Could you please explain to me what the shrink plastic is and where I can purchase it in Australia. Is it toxic?

    Thank you

  5. Having just purchased a historic home in Detroit and weathered our first Winter in it, I would have never expected finding myself landing on your site for advice on internal storm windows. But, I’m glad you wrote this post! :)

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