How To Improve Your Window Insulation (Without Dropping $500)

by Erik North on October 7, 2011

Post image for How To Improve Your Window Insulation (Without Dropping $500)


With the calendar turning over into October, our thoughts turn to not freezing our butts off this winter. Your window, being a few slim panels of glass between you and the winter chill are the weakest point in the thermal envelope (outside your basement walls). How would you improve your window insulation?

As much as we’d like to have a six month autumn (wait, scratch that … I just envisioned half a year of tourist clogged traffic on Rte 1), your home’s insulation issues are best be dealt with sooner rather than the 10-degree-below-zero later. So let’s look at a few common methods for improving window insulation and reducing drafts: plastic films, insulated shades, window inserts and interior storms.

Window Insulation #1 – Plastic Window Films (as seen on TV!)

Everybody has seen (and used) the handy 3M Plastic Window Kits. And good news! For a very negligible cost (maybe $0.50 per window), a well sealed window can add about 1 to the R-value (the still air between the plastic and the window pane) and it significantly reduces air leaks. All good and easy to install too.

Window Insulation #2 – Window Inserts

The one big downside in that plastic films can, let’s be honest, look pretty tacky. A couple of low cost and more attractive alternatives are window inserts and insulated shades. Window inserts are light wood frames sized to fit on the interior frame. They’re fit with two layers of plastic films secured in a routed groove on both sides. The outside edges are fit with v-channel weatherstrips to produce a tight fit against the window frame. The food frames are painted to match the window frame, melding well with the home aesthetics. Window inserts add about 2 to the R-value and reduce air leaks. Wins all around! Wood window inserts are quite inexpensive and The main downside is that they’re not very durable. I installed three last winter and my 9-month-old puppy made short work of the plastic film.

Window Insulation #3 – Insulated Quilt Coverings

Another more aesthetic window insulation option is an insulated quilt covering. The fabric can be any color or pattern, allowing a lot of design flexibility. Traditionally, these are a simple fabric cover though modern variants include air and vapor barrier elements. These can add approximately 2 to the window assembly R-value. Insulated quilts don’t slow air movement as well as plastic window kit unless there’s some mechanism to maintain a tighter seal (side tracks, fasteners or a sealing frame).

And The Slightly Pricier Options – Interior Storms

Finally, there are interior storm windows (OK, I know weather can get pretty bad in New England but even we don’t have interior storms). These are a more permanent version of the window inserts mentioned earlier. Interior storms have insulated vinyl or aluminum frames with multi-paned glass panels. Now E-glazing can be added if appropriate for the climate. Their performance matches window inserts, tightening air leaks and adding about 2 in R-value.

Windows are the thermally weakest point in the building enclosure. However, high quality replacement windows, which genuinely improve performance, can be cost prohibitive and standard replacement windows can produce marginal improvements. Window inserts or storms are just two window insulation options for improving your heating bills and home comfort.

Previous post:

Next post: