An Interior Window
Reduces Drafts, Saves Money
Bruce W. Maki,
The idea for this window cover occurred to me in 1980 or 1981.
When I was a college student, I saw a display in a shopping mall for
an interior "storm window" product that was customized for
the size of each window. They wanted over $100 for a medium-sized
window cover made of Lexan (a thick plastic sheet) that used a
magnetic strip around the perimeter to attach to the window trim..
3M Corporation had just released a window film product that was
intended to be adhered to the window trim every autumn and removed
in the spring. The film was not reusable. After applying the film,
you warmed it with a hair dryer to make it shrink tight and cause
the wrinkles to disappear. It was (and still is) a good product.
But I wanted to avoid the expense and hassle of applying film to
windows every year. So in 1990, when I bought my first house,
I tried making a simple frame of 1x2 lumber, custom-cut for each
window jamb opening. I stained and varnished the frame, and
then applied the window film to the wood. With a few other touches,
I had a successful window cover that held back the drafts.
||This window cover, made in February 2000, is
barely noticeable, even when the curtains are removed.
|This frame is quite large, about 4' wide by 5'
To prevent the sides from bowing inward, I added the
horizontal cross piece. This piece is positioned to lie
directly in front of the junction of the upper and lower
window sashes, so it does not interfere with the view.
This frame was made from 1x2 red oak. But I have made other
window covers from 1x2 clear pine and even 1x2
"whitewood", which is usually spruce, a low-grade wood
prone to warping.
I made each frame about 1/8 inch shorter and narrower than the
window jamb opening. This left about a 1/16 inch gap all around the
frame. There is no point in trying to make a perfect fit.
The corners were mitered and joined with glue and brad nails. The
first frames I made a decade ago were assembled with a single wood
screw at each corner, which helped hold the joint together while the
wood glue dried. Another good way to join the boards together
is to use miniature biscuits, but this requires a special
biscuit-slot-cutting power tool.
After the glue dried I applied a coat of urethane varnish. This
is necessary because a non-porous surface is needed for the
double-sided adhesive tape. Semi-gloss paint could also be used, but
first the bare wood must be primed.
After I made my first window cover ten years ago, there was still
a small gap all around the frame. I experimented with different
gasket materials. Foam weather-strip tape didn't work... it would
roll off the wood as I pushed the tight-fitting frame into the
window opening. Then I tried placing the foam strip inside a
rolled-over strip of plain polyethylene plastic. That was too bulky.
So I tried just a long scrap of polyethylene plastic, folded over
and stapled to the back of the frame. That gasket design worked
great and cost almost nothing! I have made at least ten window
covers with this simple gasket and find that it does an excellent
job of sealing the frame to the window jambs. And when the cover is
installed in the window, you can't really see the gasket.
||A scrap of plastic, folded over and stapled to
the back of the frame, makes the gasket.
|There is one piece of gasket for each side. At
the corners I simply overlap the gasket strips.
I let the loop of plastic extend out about 3/4 inch, so it
folds over the narrow dimension of the wood when the frame is
pushed into the window opening.
||This loop handle helps to remove the
tight-fitting window cover, otherwise there is nothing to grab
The handles are just plastic strapping from some packaging
that was going to be thrown away. (It pays to be a pack-rat!)
I just stapled them to the back of the frame and folded them
||To keep the window cover from blowing into the
room, I screwed some small scraps of wood to the window jambs.
I'll admit these cleats look sort of cheesy, but you can't
see them when the curtains are in place. I could have spent
more time making nicer looking blocks.
||I labeled the back side so it would be obvious
which cover belonged to which window. I also labeled the top
end because the cover may not fit upside down.
Storage of these covers during the summer season could be a
problem. The plastic film is very fragile and cannot tolerate
much abuse. I recommend an out-of-the way place where
children won't be able to reach these. I used to have a space
behind the furnace where these covers would not get damaged.
One time my big 'ol Labrador Retriever put her paws up on a
window sill and poked a claw through the window cover. I patched the
hole with clear packaging tape and never bothered with any further
You Know They Work When...
These window covers can be so air-tight that they must be pushed
into the window opening s-l-o-w-l-y to allow the trapped air to
When the wind blows, the plastic film may bulge inward a little.
During strong winds I have seen this large window cover bulge inward
by over 2 inches. I can tell the direction of the wind by
which room's window covers are bulging inward.
How About The Money?
The wood for these frames can cost a little or a lot, depending
on the type and quality used. The plastic shrink-film may cost as
much as $10 for a large window like this. Some large sheets might be
enough to cover two or three windows. I can't imagine spending more
than $25 for a window cover like this, unless exotic woods were
used. I have built smaller covers for around $7 each. For basement
windows I have used polyethylene for the window film, which
renders the window impossible to see through. Combined with ordinary
lumber, that is a really cheap solution, under 2 bucks.
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What's New Project
- Cordless Drill/Driver
- Miter Saw
- Staple Gun
- Basic Carpentry Tools
- Lumber, 1x2
- Plastic Window Covering
- Double-Sided Sticky Tape
- Polyethylene Plastic Sheet
- Plastic Strapping (For