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Musings of an Energy Nerd

Replacing Old Windows with Triple-Pane Windows

How to remove decades-old windows and replace them with high-performance units

The wood sills on my 40-year-old windows were rotting. It was clearly time to install new windows.

My home’s wooden windows are about 40 years old. Like most wood windows of that era, these Weather Shield windows lacked any exterior cladding. The double-glazed windows had no nailing fins: instead, they were sold with wood exterior casing already attached, so that the installer could fasten the windows in place by nailing the exterior casing to the wall sheathing.

The good news is that my walls never experienced any water entry problems, in spite of the fact that I neglected to flash the window rough openings when I installed the windows back in the early 1980s. The bad news is that Weather Shield decided to make the windows’ exterior sills from finger-jointed pine. Even though the sills were painted, they eventually started to rot—most noticeably on the east side of my house, which faces downhill and receives more wind-driven rain than the other exposures.

If you want to avoid water entry into your walls, rotten window sills can’t be ignored for long.

Assessing the condition of my window sills, I recently decided to replace seven windows.

Measuring new windows

You don’t have to remove your old window frames if you don’t want to. It’s possible to replace old window sash with new sash and new vinyl jamb liners; these components can be installed inside your existing window jambs. If you take this approach, you don’t need to remove the exterior trim, interior trim, or the window frame.

Window manufacturers (especially manufacturers of vinyl windows) also make framed replacement windows without nailing flanges; these units, consisting of a window frame and sash, are designed to slide inside your existing window frame after your sash are removed. This replacement window strategy leaves the existing exterior trim and interior trim in place, simplifying installation; the downside…

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14 Comments

  1. [email protected] | | #1

    Great article, Martin. Really nice work and having installed the windows in my house, also triple panes, I appreciate how heavy these things can get! I was also more than a bit surprised that the WeatherShield's were in relatively pretty good shape in your environment after 40 years. That's a testament to the owner IMO.
    You did mention that the new windows were aluminum clad, but the Elevate is actually hollow fiberglass on the outside with a solid wood interior (not a veneer), and from the pictures, those certainly do look like Elevates.
    Wondering if you might have been thinking of the Ultimate, which is a wood window with aluminum cladding on the exterior, when writing the article?

    1. user-1112646107 | | #2

      Oberon,
      Thanks for your helpful comment. You're right, of course -- Marvin Elevate windows have a fiberglass exterior. When researching window brands before my purchase, I looked at lots of different options. I forgot that the windows I chose had a fiberglass exterior. I have corrected the text of my article, and I appreciate the correction.

      1. [email protected] | | #4

        You're welcome Martin, and I forgot to mention in my earlier comment that the view through your new casement (and the doublehung, too) is spectacular!

        1. user-1112646107 | | #6

          That's Burke Mountain, which is almost due east of our house. To the southeast (not shown in the photo) we can see Mount Washington on a clear day. Using binoculars, I can even see the cog railway and the meteorological station on the top of Mount Washington.

          1. [email protected] | | #7

            Thanks Martin. As I recall the highest windspeed ever recorded in USA was at the Mt Washington meteorological station?

          2. paulmagnuscalabro | | #9

            Replying to Oberon...
            I believe the record has since been broken, but yes: something like 236 mph on the summit of Mt Washington. It probably helps that there is a permanent weather station on top of a mountain at the convergence of several storm paths... But even so, that's some scary wind.

  2. AntonioO | | #3

    Martin,
    What I confirmed from this article is how much window pricing varies. I have been quoting double pane casements that are not as large as the windows you installed (based on the window size relative to your size) but getting quotes of around $1,000 per unit. You got similar pricing for your tripple pane windows. Hmmm....

    1. user-1112646107 | | #5

      Antonio,
      I paid an average of $941 each (plus sales tax) for my windows. The quality of the Marvin Elevate windows I bought seems high. The windows close with a single lever that is connected to a vertical bar that engages three locking points -- at the top, middle, and bottom of the window. The interior wood is attractive, and the exterior fiberglass appears to be impervious to water. I would never pay $1,000 for a double-pane casement in light of the quality of these Marvin triple-panes.

  3. Expert Member
    MALCOLM TAYLOR | | #8

    I hate replacing windows. Glad to see Martin seems to be enjoying himself.

  4. bvillebound | | #10

    Dear Martin: First, thank you for this excellent article - and congrats for completing this major job yourself! We followed the same replacement path as you, with two different houses - on the first with Thermotech fiberglass triple-panes, and then Marvin fiberglass at our new place along the shore. In this tough marine environment, fiberglass is the only way to go. Plus fiberglass is significantly stronger than vinyl - a key factor with heavy triple pane windows. All of our windows are also casement or awning style, because double-hung windows cannot be effectively air sealed. Awning style also allows you to leave the window open a bit when it's raining - for fresh air and to hear the patter of the rain.

    Marvin also makes a marine / coastal line with tempered glass and doors with a more secure stainless steel, multi-point lock mechanism - to resist hurricane force wind. We ordered these for our french doors along the coast.

    Two suggestions:

    (1) You used Great Stuff Gaps & Cracks to seal the gap around the framing outside, and apparently to fill the gap inside through the holes you drilled. If you do remodeling, you will find that standard single-component spray foam like this hardens and often cracks - breaking the air seal. Everyone should use the 'Window & Doors' version of Great Stuff for applications like this. It remains flexible after it cures, to preserve the seal as things expand and contract. See the link below.

    Your readers should also know that Great Stuff and similar single-component spray foams from Loctite, 3M etc stick tenaciously to everything - and dried foam CANNOT be removed with any standard solvent. So tape off / mask everything nearby to avoid overspray and drips, e.g. on interior trim, floors, decking, carpet, etc. Great Stuff will also stick to your hands and cannot be removed, so wear gloves when you install it. Plus two cautions: (a) Spray foam will rapidly degrade in sunlight, so never use it to fill exposed holes, particularly outdoors. (b) Both liquid and dry/cured foam are extremely flammable, so DO NOT install any type of single-component spray foam near any source of heat. The dried / cured foam will ignite at just 240 degrees F, which is significantly lower than the temperature of burning paper - so do not use it to air seal around canned ceiling lights, HVAC exhaust ducts, or any surface that gets moderately hot. Spray foam should also NOT be used for fire-stopping, e.g. to fill holes in framing around pipes and electric lines - because it will ignite before the wood does.

    (2) For a job like this where you stop / start with spray foam and need precise placement, e.g. in the interior holes, a Great Stuff 'Pro' gun is much easier to use. This eliminates the straw, which tends to quickly clog with drying foam - and NO standard solvent will dissolve dried single-component foam, so you cannot clean the straw. The metal Pro gun has a trigger and a fine tip, perfect for the small gaps around windows and doors. I've let one site for days between uses without clogging, although Great Stuff / DOW sells a cleaner that you should blow through the gun before you put it away. See, for example:

    https://www.homedepot.com/p/GREAT-STUFF-40-oz-Window-and-Door-Insulating-Spray-Foam-Sealant-Kit-KTGS-7273/324683918

    https://www.lowes.com/pd/GREAT-STUFF-Window-and-Door-40-oz-Spray-Gun-Indoor-Spray-Foam-Insulation/5014497149

    https://www.homedepot.com/p/GREAT-STUFF-12-oz-Insulating-Spray-Foam-Sealant-Dispensing-Gun-Cleaner-259205/100550708

    1. user-1112646107 | | #11

      Bville,
      Thanks for your tips. I've been using canned spray foam for several decades, since it first appeared on the market in (I think) the early 1980s. I've opened up a lot of walls and looked at examples of my old sprayed foam, and most of it is in great shape. It's tenacious and long-lasting.

      Properly applied -- that is, carefully -- ordinary canned spray foam can be used around windows and doors, although low-expansion foam is safer, especially for the inexperienced. In theory, ordinary spray foam can cause window jambs to bow inward, but I've never seen that happen because of my careful installation techniques. In this case, I used ordinary canned spray foam to seal between the jamb extensions and the rough opening, and low-expansion foam between the window jambs and the rough opening.

      When I get spray foam on my skin, I clean it off as soon as possible. I use Comet cleaner and a stainless-steel wool pad. Basically I abrade it from my skin by friction. It works.

  5. bvillebound | | #12

    Dear Martin: Thanks again for your great article - and your quick reply. A few notes:

    (1) Ordinary / standard single-component canned spray foam is rigid when it cures, and will crack if there is enough expansion / contraction in the home's framing. This cycle is more extreme in some areas of the USA and other countries, less in others. If spray foam cracks, this obviously degrades the 'sealant' purpose. I have done remodels across the USA in a variety of climates, and can testify that this cracking occurs.

    (2) Frankly, 'careful installation' makes little difference. Great Stuff aggressively sticks to everything, expands and fills gaps; compared to most remodeling projects, installation is very simple.

    (3) The DOW team clearly agrees, and they make the product. Loctite also agrees:
    https://www.homedepot.com/p/Loctite-Pro-Window-and-Door-21-oz-Spray-Foam-Sealant-each-2865807/323836061

    (4) What possible reason would there be to use rigid / standard spray foam around windows and doors when flexible foam is readily available? The added cost for a Pro can of Great Stuff 'Window and Door' is just $2, compared to rigid 'Gaps and Cracks'.

    (5) The speed of cleaning spray foam off your skin makes no difference. It cures in seconds, particularly with the moisture and warmth of your hands. The only way to remove it is mechanical as you noted: rubbing with an abrasive pad. Much better to wear gloves! I've done a lot of this, and again can testify that gloves are a smart move - along with masking off the area nearby.

    In summary, I am surprised by your resistance to these reasonable suggestions.

  6. user-183982 | | #13

    Martin,
    I think it's important to remind readers that many wood windows were installed before yours are dense, old heart wood and often do NOT need to be replaced. Many professional field studies have shown that proper restoration can make old windows as energy efficient as replacements. They can be repaired, reglazed, and weatherized and further insulated with storm windows. They will last another 100 years before they need to be replaced. According to the warranties of all the replacement windows I researched, replacement windows are not expected to last more than 20 years and then need to be replaced AGAIN. How is that green and sustainable? Old window restoration can be done well by DIYers with the right tools and training.

    1. user-1112646107 | | #14

      User 1839,
      As my article makes clear, I replaced my 40-year-old windows because the sills were rotten.

      For a thorough discussion of the issues you raise, see "What Should I Do With My Old Windows?"

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