Double up on storm windows?
I’m onto the final details of my 1869 Farmhouse renovation. This was a down to bare studs renovation, and air sealing + insulation was done meticulously and thoroughly.
However, I could not bring myself to remove the historic windows. I planned on installing low-e storms and air sealing everything. I see they make interior storms as well as exterior, would there be benefit in using both for what would essentially be a triple pane window? I realize they’re not vacuum sealed or anything.
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A Gouch, I don't think doubling up on storm windows would save enough energy to make them a good financial investment. But if you're in a cold climate, like any triple-glazed window they will make the interior more comfortable in cold weather because the interior surface will be relatively warm, resulting in less radiant heat loss.
Hi Gouch. I'm in a similar situation. Restoring / weather stripping some of my old double hungs and updating the storms. I'm curious which storms you are considering. I'm looking at Allied single track at the top of the price range, with Quanta and Larsen double tracks less expensive. Harvey generally has a good rep, but I'm not digging the depth of the triple track.
The Allied single track has been my go-to so far. I’m not dead set on it, but if I was ordering tomorrow without reading another word, that’s the way I would go.
>" I planned on installing low-e storms and air sealing everything. "
That's a good plan.
Tight low-E storms over a reasonably tight wood sashed single pane brings the performance of the assembly to the U0.31- U0.34 range, pretty close to current IRC code minimums. This has the advantage of ample drying capacity toward the interior for the original sashes, and keeps those sashes warmer (close to room temp), which lowers the average moisture content of the wood, and thus less susceptible to mold/rot.
>" I see they make interior storms as well as exterior, would there be benefit in using both for what would essentially be a triple pane window?"
An interior storm limits the drying toward the interior for the antique originals, and may raise the moisture content of the old sashes if there is also a tight exterior storm. There would be only a marginal thermal performance gain, and NOTHING like the performance of argon filled double low-E triple panes. Interior storms are definitely not "worth it" if there are low-E exterior storms.
Making the original windows as air tight as possible is worth it. Getting rid of sash weights for double hungs and installing coil-springs instead allows filling the weight pockets with insulation, and makes the assembly more air tight. If keeping the sash weights, inexpensive sash pulley seals can reduce the size of the air leak into the weight pockets by a significant amount too. Spring-bronze seals for the sashes are pretty tight too.
I appreciate it Dana. I wish I’d know about the coil springs. I realized the pocket in which the old weights resided were very leaky, so I removed the weights entirely and filled the cavity with spray foam.
I'm going with a middle ground for the sash weights. The upper sash will be fixed, the upper sash weights replaced with about an inch of foam, the bottom sash operable as usual. This, a good storm on the outside, and thorough weatherstripping of the sashes.
I'm taking the restoration advice from Scott Sidler and Wood Window Makeover.
I like that plan. I’m certainly not thrilled my windows are inoperable, it was just the best solution I could think of at the time when factoring in all options. I have a mini split system coupled with all led lights and efficient appliances, so I wanted everything as efficient as possible so I can convert to solar at some point.
Making the original windows as airtight as possible is also important to limit condensation inside the storms. Without good air control, condensation can put enough water in the space between the windows to rot the sills in short order. There are some good retrofit kits for installing gaskets and seals on old wood windows. you have to take them out and route some grooves for the gaskets, but this makes a big difference. For windows that you don't intend to open and close, you can caulk the entire perimeter. Caulk is removable if you change your mind, but can make them effectively airtight.
Appreciate the input. I’m OCD by nature, but I’ll take particular care to get them sealed well. I actually do plan on caulking everything. I don’t intend to open these windows. I get plenty of fresh air through my HRV, and if the weather is EXTRA nice, I have a few windows I was forced to replace I can open up :)
There are thin dual pane IGUs that you can get that can be made to fit. I've done this for retrofitting older entrance door glass. Means a bit of router work but much less work than full replacement, plus you don't effect the character of the house.
It would let you skip the exterior storm windows and if your window air sealing details are good, it will preform pretty well.
So in this scenario, the thin igu would go on the interior side of the existing single pane window?
No, you replace the current glass pane with the insulated IGU. That, along with good weatherstripping can make an old window perform pretty close to a new one.
Ohhh, I see. In my case, that would involve lots and lots of very small IGU’s though haha. Each window is 9 individual panes of glass. 18 if you include the top and bottom of the double hung.