How do you seal skylights for winter?

As winter approaches, it’s important to take steps to seal up your home against cold drafts. Skylights can be a major source of heat loss if not properly sealed for the winter months. Proper skylight sealing can help reduce your heating bills and prevent ice dams from forming.

Why seal skylights for winter?

There are a few key reasons why it’s important to seal up your skylights before winter:

• Prevent heat loss – Skylights are essentially holes in your roof that allow warm air to escape and cold air to enter. Sealing them helps insulate your home.
• Reduce condensation – Warm, moist air can hit the cold glass of an unsealed skylight and cause condensation or frost to form. Proper sealing prevents this.
• Stop drafts – Any air leaks around a skylight let cold drafts into your home, making it feel colder.
• Prevent ice dams – Warm attic air escaping through skylights can melt roof snow, leading to ice dams and water damage.

Taking steps to seal up skylights and reduce air leaks before winter starts can save on heating costs and prevent moisture issues in the home.

What you need to seal skylights

Sealing skylights doesn’t require any specialized tools. Here’s a list of what you’ll need:

• Caulk designed for roofs and windows – Look for a high-quality silicone, acrylic latex or polyurethane caulk with a 20 year or longer lifespan.
• Caulk gun – Either manual or pneumatic.
• Putty knife or caulk tool – For smoothing the caulk and getting into corners.
• Masking tape – Helps create neat caulk lines.
• Rags – For cleaning up excess caulk.
• Gloves – To protect your hands.
• Safety glasses – When looking up at a skylight, debris can fall into your eyes.
• Stepladder – To safely reach the skylight.

Make sure to read the caulk manufacturer’s instructions as well for any specific application tips or drying time requirements.

How to seal a skylight for winter

Sealing a skylight involves caulking around all the edges and joints. Here are the steps:

1. Clean the area – Use a putty knife to scrape away any old caulk or debris between the skylight and roof. Wipe the surfaces with a clean rag.
2. Apply masking tape – Tape along the edges of the skylight to create straight caulk lines and prevent mess.
3. Load the caulk gun – Cut the tip of the caulk tube at a 45 degree angle and load it in the gun.
4. Run a bead of caulk – Apply a continuous bead of caulk around the outside of the skylight about 1/4 inch wide. Make sure to hit all the edges and corners.
5. Smooth the caulk – Before it dries, use a putty knife or caulking tool to smooth out the caulk and make sure it adheres and spreads evenly.
6. Remove the tape – Carefully pull up the masking tape before the caulk dries.
7. Seal the interior – Apply caulk along the interior edges as well following the same process.
8. Let dry – Follow the manufacturer’s instructions for full curing time before exposing to weather.

Pay close attention to the mitered corners when caulking. Use extra caulk to fill any gaps or cracks in those areas.

Tips for effective skylight sealing

• Clean all surfaces so the caulk can adhere properly.
• Make sure the caulk makes full contact with the skylight and roof materials.
• Tool the caulk with a putty knife to help it fully seal any cracks.
• Apply in dry weather above 40°F for best results.
• Use a high quality outdoor caulk with excellent flexibility, adhesion and lifespan.
• Check for any interior gaps around the skylight frame and seal those too.
• Re-apply fresh caulk every 3-5 years for maintained effectiveness.

Extra sealing precautions

For extra protection against leaks and drafts, you may want to consider these added sealing steps:

Weatherstripping

Apply weatherstripping around the interior sides of the skylight frame. This adds a flexible barrier to stop air from getting through any cracks or gaps.

Plastic film

Temporary plastic film kits are available that can seal over the entire skylight in the winter. These are stretched over the outside of the skylight and help provide an extra layer of insulation.

Insulated coverings

For permanent insulation, you can have an insulated skylight cover installed. These specially designed covers seal over the skylight and have insulation inside to prevent conduction.

Bubble wrap

A budget solution is to cover the skylights with bubble wrap in the winter. Secure it tightly and it can provide an extra air barrier.

Signs you need to re-seal the skylight

Here are some signs it may be time to re-apply fresh caulk around your skylight:

• Visible light coming through cracks
• Noticeable drafts coming from the skylight
• Condensation or ice forming on the skylight
• Caulk looks cracked, dried out and shrunken
• Any gaps between the caulk and skylight materials
• Peeling or separated caulk
• Higher than normal heating bills

Re-sealing the skylight every 3-5 years can maintain its winterization effectiveness and prevent leaks.

Conclusion

Preparing skylights for winter only takes some simple caulking and sealing. By stopping drafts and preventing heat loss through skylights, you can save on energy costs and improve your home’s comfort all season long. With the right materials and techniques, sealing up skylights can be a quick weekend project before the cold weather hits.