Sense Blog

Five Ways to Weatherproof Drafty Windows Right Now

The polar vortex has been rattling windows and increasing heating bills across the country in these last cold weeks of winter, but it’s not too late to stop the drafts. Houses lose about 30% of their heating energy through windows. When you consider how little wall space is taken up by windows in most homes, it’s clear that they have a real impact on your heating (and cooling) bills. So let’s tackle those drafts. Here’s a list of five things you can do right now.

1. Check for air leaks

The best way to find out about leaks around windows and doors is with a professional energy audit, and winter can be a good time to have it done, but in Covid times this approach may not be healthy. Instead, you can inspect your own windows. Examine each window and see if you can rattle them – any movement shows possible air leaks. You can also hold a candle flame near the window to see if it flickers, and look for light around the window frames, since air can move through those cracks.

You’re more likely to find these issues with older windows, and you can address them by caulking cracks less than ¼ inches in width on the non-movable parts of your window or weatherstripping to stop the flow of air around the window sash. These are projects you can do over a weekend if you’re handy with tools.

2. Close the curtains

There’s a reason our ancestors slept in four-poster beds with curtains: they’re an effective way to keep out drafts at night and reduce heat loss by as much as 25%. Choose window curtains made of tight, heavy cotton or insulating fabric that extend to the floor to shield against night-time drafts. Lined with white fabric to prevent fading and reflect sunlight, curtains can reduce solar heating in summer, too.

3. Install insulated shades

Insulated shades and window quilts are relatively inexpensive ways to control drafts. Insulated cellular shades have air pockets that act as insulators, and installing them on side tracks will increase their effectiveness. In fact, tightly installed cellular shades can lead to 20% heating energy savings. Cellular shades come in a range of styles and prices.

Window quilts are installed on side tracks, too, to create a pocket of insulating air at night. Keep in mind that shades won’t solve the problem of air leakage around the windows because they’re mounted inside the frames.

4. Invest in exterior storm windows

Late winter may not be the best time to install storm windows if there’s slippery snow on the ground, but it’s a good time to research your options. Traditional storm windows are installed on the outside of existing single-glazed windows to add a strong layer of protection against air movement. This approach can reduce heat and cooling loss at about a quarter of the cost of replacement windows.

Old storm windows were just clear glass, but newer ones have low-e coatings with good energy performance ratings. Low-e, which stands for Low Emittance, is a coating applied to window glass that blocks infrared and UV light, improving energy efficiency. (For a detailed analysis of the effectiveness of low-e storm windows, see this report from EnergyStar.) For homes with older windows, installing storm windows over well-maintained primary windows can actually yield better insulating properties than double pane windows, at less expense.

Fifty years ago, homeowners had to install their exterior storm windows in the fall and remove them in the spring. Today’s storm windows can be permanently installed with multiple tracks that make the transition to warm weather easy: the bottom pane of the storm window can be moved up in the spring and a screen moves down to allow air flow. Professional installation can be a significant part of the overall cost of exterior storm windows, so include it in your considerations.

5. Add storm windows on the inside

An alternative approach is interior storm windows that are put in place for the winter and removed in warm weather. Designed to fit tightly inside the window frame, these windows can be easily installed by the homeowner and are held in place by magnets or the tight fit. It’s important that interior storms be correctly sized to ensure a good seal.

An ultra low-cost way to stop drafts is a window insulating kit from the hardware store. These kits work for the same reason that insulated shades work – they use plastic film to create a sealed air pocket next to the window. To be most effective, be sure to shrink wrap the plastic film with a hair dryer so it’s tight.

Evaluating Storm Windows

While storm windows are generally less expensive than replacement windows, they’re still a significant investment in your home, so you need to do your homework before buying. Be sure to check the energy ratings for all storm windows before purchasing.

The National Fenestration Council has a rating system that helps you compare the efficiency of windows. It rates windows for U-factor, solar heat gain coefficient (SHGC), visible transmittance and air leakage. The U-factor measures how well a product can keep heat from escaping from the inside of a room. The air leakage rating tells you how much air will enter a room 

through a product. For both these ratings, look for a lower number to keep your home cooler in winter.

But what if your drafty window faces south and the sun heats up your room in the summer, making your air conditioner work harder? Look for low numbers for the solar heat gain coefficient. And if you want bright sunshine in your room, look for a higher number for visible transmittance.

You might guess that some windows are better suited to specific climates, and you’d be right. Find your state on this map to see which U-factors are best suited to your climate.

Another rating system, from the Attachments Energy Rating Council, addresses the same question by telling you how well suited a particular window is to cool or warm climates. Look for higher ratings in your climate zone.

Cold winter winds are blowing now, but the first day of spring is only a month away on March 20 when warm days will start to return. Tightening your home’s envelope will reduce both winter heating and summer cooling costs, so weatherproof windows are a solid, year-round investment for your home.