prepare your window

Drafty windows? Stop the drafts before cold weather arrives!

Windows are part of your home’s thermal and building envelopes. Meaning, in the wintertime, your windows are designed to keep warm air IN and cold air OUT – and vice versa in the summertime.

windows in the winter windows in the summer

Did you know that drafty windows and doors are responsible for up to 40% of your home’s energy (heat!) loss?

The amount of heat potentially escaping through your drafty windows in the winter is the same amount of heat that would escape if you left 1 window wide open year round. That’s crazy!

If your windows look like this

icy windows in winter

then it might be time to ask yourself these questions…

  • Is your home always too cold in the winter?
  • Do you feel you’re paying too much for heat in the winter?
  • Can you feel the temperature drop whenever you walk past your windows?
  • Are your windows drafty?
  • Are your windows difficult to open or close?
  • Does the glass in your window panes rattle in the wind?
  • Do your curtains rustle even when your windows are closed?
  • Do you rely on storms (storm windows) to protect and insulate your windows in the winter?

If you answered yes to any of these questions, this could mean a variety of things:

  • The glass in your windows is energy efficient
  • If you have old window frames made of wood, aluminum, or a material that isn’t vinyl, your home’s building envelope may not be properly sealed
  • Your windows may not be properly insulated

If you’ve read up on your home’s building envelope, the two most important concepts for ensuring your home is prepared for winter are insulating and sealing (your home’s building envelope).

Why is insulating your windows important?

If your windows are not properly insulated, you may as well have a hole in the side of your house. If you can imagine a hole on the side of your home, it’s pretty easy to visualize the massive amounts of heat escaping, water invading, and cold air flowing in to your home.

You can buy the best windows in the world, but if they’re not insulated or installed properly, they will not do their job:

  • They will not keep your home sealed away from weather
  • They will not maintain your home’s internal climate control
  • They will not keep you warm in the winter
  • They will not keep you cool in the summer

How should your windows be insulated?

While it’s important to note that not every house is the same and, as a result, may require slightly different window insulation setups – in general, these guidelines are a good place to start.

If the space you’re trying to insulate in or around your windows is…

Less than an inch – the space should be insulated with a minimally expanding foam. This kind of window insulation foam might also be called slow expanding urethane foam or closed cell foam.

More than an inch – the space should be insulated with fiberglass. However, it’s important to remember that the fiberglass should not be compressed when installed. If the fiberglass is compressed or squished, it will not expand into the space it’s trying to insulate, which leaves open pathways for air to flow, defeating the purpose of insulation.

Just the right amount of insulation: It’s also important not to use too much insulation. While you want to fill any open spaces in and around your windows with the proper insulation, you don’t want to pack these spaces tight. All houses and products expand and contract, so you need to allow for this natural movement.

Insulating Window Weight Pockets

If you have old windows or you’ve replaced old windows with newer windows – you may have weight pockets.

What’s a weight pocket? Old windows used to move – and stay – up and down thanks to a pulley and a counterweight. If you live in an older home, then there’s a space around your windows that once housed the pulley and counterweight called the weight pocket.


(image credit: Washington State Historic Preservation)

If you have old windows and often feel drafts blowing through them or have trouble keeping the rooms with these windows at consistent temperatures – it could be because your weight pockets aren’t insulated at all. A lot of contractors will not insulate weight pockets at all in order to keep price and labor costs down.

How should your windows and building envelope be sealed together?

Once your windows have been placed and insulated, you still need to make sure that they are correctly sealed to your home’s building envelope. Your home’s building envelope is essentially your home’s shield against the weather. If there are any gaps or holes in your home’s building envelope, then there are opportunities for energy to escape and troublesome moisture to get in.

The best way to seal your windows into your home’s building envelope is with caulking. There are different kinds of caulk for different home sealing situations, the best kind of caulk to use for sealing windows on the outside of your home is a construction grade silicone caulk. And the best kind of caulk to use for sealing windows on the inside of your home is a paintable butyl.

Why your windows matter in the winter

Drafty windows and doors are the single biggest source of home energy loss. As much as 40% of your home’s energy loss occurs due to poorly insulated windows and doors. This equates to high energy bills and money wasted.

In an ideal world, your home has fully insulated energy efficient windows that are designed to be more thermally efficient and keep your home warm

in winter. If you don’t, just remember that a window is only as good as its insulation and installation.

Not sure if your windows are properly insulated and sealed?

Feel around your trim for drafts or give us a call and we’ll come out with our temp gun. We can let you know if your windows are properly insulated and sealed.

winterize windows