Weatherproofing Methods for Historic Windows

Jun 4

There are many ways to improve the weatherproofing of historic windows. Unfortunately, the vinyl window marketing machine has convinced many that the only solution is to replace the windows - this is simply not true. Not only would that be a temporary solution, considering many vinyl windows fail within 15-20 years, but it is a more expensive proposition that detracts from the character of the historic home or building. Instead, consider some of these options to maintain the character while achieving the weatherproofing benefits.

1. Weatherstripping

The MVP of window comfort. Weatherstripping closes gaps around sashes and frames, keeping out drafts without harming original materials.

Best Types for Historic Windows:

Bronze spring (long-lasting and invisible when installed properly)
Silicone or rubber bulb gaskets (flexible and low-profile)
Felt strips (easy to install, though less durable)

🛠 Pro Tip: Choose weatherstripping that can be removed without damaging the wood if future repairs are needed.

2. Storm Windows (Interior or Exterior)

Storm windows are like your historic windows’ secret superhero suit—they protect from wind, rain, and UV while keeping the original sash intact.

Interior Storms:

Easy to install.
Less visible from the outside.
Excellent for soundproofing and insulation.

Exterior Storms:

Provide extra weather protection.
Can be custom-made to match the historic look.
Available in low-profile aluminum or wood for authenticity.

3. Caulking & Sealing

Old houses shift and settle, which often leads to small gaps around window frames. Sealing these with paintable caulk (acrylic-latex or silicone for flexibility) blocks water and air infiltration.

🧽 Pro Tip: Don’t caulk the weep holes—windows need to drain water, not trap it.

4. Window Sash Repair

Loose joints or out-of-square sashes can lead to poor sealing and drafts. Re-glue, clamp, and square up sashes as part of the restoration process to ensure a tight fit.

5. Proper Glazing Compound

Failing or missing glazing putty around the panes allows air and water in. Scrape out the old compound and re-glaze with a linseed oil-based putty to seal and support the glass securely.

🖌 Bonus: A well-glazed window just looks better—it’s one of those small details that screams craftsmanship.

6. Insulated Curtains or Shades

While not a restoration solution per se, adding thermal curtains or interior shutters can dramatically reduce heat loss during the winter without altering the structure of your window.

🪟 Consider using Roman shades or wooden interior storm shutters for period-appropriate charm.

What to Avoid

🚫 Expanding foam or spray insulation – It’s messy, often irreversible, and can damage trim or framing.

🚫 Vinyl window replacements – They may promise efficiency but destroy your home’s authenticity and often fail within 20 years.

🚫 Improper sealing of double-hung windows – If done poorly, you’ll lose functionality and access for cleaning and ventilation.

Combining Comfort & Preservation

The goal isn’t to seal your windows up like a Ziploc bag. It’s to give them the support they need to do what they’ve always done—just more efficiently. When you weatherproof correctly, you: