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Note this page is deliberately narrow to make it printable in portrait format.
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BUILDING INTERIOR WINDOW INSULATION
PANELS
I will be offering public demonstrations and training on how to assemble these window panels: Public training to make window insulation panels for local residents November 8+9 Saturday: training 9:00-11:00 assembling 3:00-5:00 and Sunday 1:00-3:00 (assembling) UCC Church, Bath, Maine Register by calling 443-2187 or email faithcommunity@faithinbath.org Materials Sources Construction overview Assembling the frames Applying film and weather strip
As home heating costs began their rapid climb this
year (2008) I decided to address one of the principal
sources of heat loss in homes. Windows.
Topher Belknap
is a fellow member of the
Midcoast Green Collaborative
here in Maine and he came up with a very
simple design for double pane
thermal window panels that simply push into the widow frame
with foam insulation around the edges. Topher says
that these panels
will increase the R-value of your windows by around 2.3,
however on a southern exposure they will reduce the solar heat gain by about 15%.
For most windows, this is a good tradeoff.
The panes are made of clear polyolefin shrink film. The simple wood frame can be constructed inexpensively from either natural or pre-primed lumber. The net cost of material per window is under $1.00 per square foot and it takes 2 people about 40-45 minutes per window to make them up. These window panels serve 2 functions, as a double barrier they will more than double the R value of a single pane window and they also completely block all air movement through the window. So they block both drafts and transmitted heat, cutting heat loss in half or better. The projected savings for single pane windows in Maine is between $4 and $10 per square foot of window per heating season, depending on your windows. This assumes you are paying over $3.50/gallon for oil. Drafty single pane windows will reap the most benefit from the new panels. In more moderate climates it may take longer to recoup the investment. You can use this tool to calculate your estimated energy savings. Be advised that the panels are inexpensive in materials, but costly in time to make. Count on investing at least 45 minutes to actually build each window, plus a few hours for measuring and ordering or buying the materials. An average home can have around 20 windows, so that's a commitment of over 10 hours in time to make them. Last year we invested in commercial versions of these windows for our home -- at over $9.00 per square foot these nice aluminum framed units are white finished and very well made. They are effective but also expensive. I wanted to see how inexpensively I could make them and then share this information with the world so we can all save on heating costs and live more sustainably. We swap these panels out when we install and remove screen windows in the spring and fall. Removing the screens in the fall will allow 3-4% more solar gain so remember to remove them and clean the windows to get as much light as possible. Some panels can be left in place all year if desired if they are hard to get to or the window is never opened. |
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| Materials Sources: | ||||
| what | retail | cost | volume | cost |
| 1X4 clear pine lumber or pre-primed | Big box hardware store | $.95-1.50/ft. | Ask your lumber yard for a discount many will give you a break for more than 100 feet. | $.95-1.50/ft. |
| Polyolefin heat shrink film | A variety of kits that include shrink film and double stick tape are available in hardware and big box stores. Shrink film also comes in wide rolls. | $9.99 |
Uline 20" x 3,500ft. 75ga Polyolefin Shrink Film Roll (will do hundreds of windows) |
$200.00 |
| 1/2" wide double stick tape | double stick tape by the roll be sure to get 1/2" wide tape! | $3.00 |
Scotch Adhesive Transfer Tape,
1/2 Wide X 36 Yards (requires dispenser gun) |
$7-10.00 |
| 2.6 mil 2"
clear packing tape and dispenser |
StaplesŪ Clear View Packaging Tape, Clear, 1.89" x 54.7 yds, 6 Rolls will do hundreds of windows | $15.99 | StaplesŪ Clear View Packaging Tape, Clear, 1.89" x 54.7 yds, 6 Rolls will do hundreds of windows | $15.99 |
| .5 X .5" open cell foam weather strip | Get OPEN CELL poly foam that is grey - not white! | $4.21 | Ether Foam Tape
from
Foamtapes.net (case of 12 70ft. rolls) |
$50.52 |
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Materials notes:
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Applying film and weather strip
This part takes 2 people about 30 minutes per window
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A large work table is essential. I used a full 4X8 sheet of MDF on top of my table saw, or on saw horses. It is good to have a clean flat surface. If you use plywood I recommend covering it with paper and taping the edges so your clothing will not snag on it. |
I
bought a 3700ft. roll of film so I could do a lot of panels for friends
and neighbors. This huge 40lb roll is 20" wide, but the film unfolds to
40". If you use store bought sheets or rolls of film, be sure to keep the inner
surface off the work table so it does not pick up dust. |
I us e a commercial adhesive transfer tape dispenser
to put double sticky on
the outside edge of the whole frame. These
guns hold 100 foot rolls and are very convenient. If you use
double stick tape then just apply it firmly and peel back the backing just before
applying the film. |
The film on the roll is
folded in half and separating the 2 layers is hard, the trick is to use
2 small pieces of blue masking tape right at the corner to pull the 2
layers of film apart. You may have the same issue with store
bought rolls of film too. |
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Cut a length of the film so that you have at least 4 to 6" extra all around the frame.
Unfold
the film and smooth it out to it's full size, then lay the frame on
top centering it carefully. If you used double stick tape then now is the time
to remove the backing. Begin at one end and carefully lift the film up and over the frame so that it sticks to the edge, rub the edge to ensure that it is well adhered. Then do the other end being sure to pull it tight to take out any wrinkles. On the longer sides it is best to have 2 people doing this together so that you can tension the film to prevent wrinkles. I find it easier to start at one end, then pull the film tight to the other end before doing the longer sides. It is important to watch for wrinkles and try to pull them out before the film sticks. Pay attention when pulling the final side, you need to pull firmly to ensure the film is stretched tight. The film will only shrink about 1%. |
After each edge of the
film is stuck, you will need to cut off the
excess. By pulling the film upwards, you can slide a utility
knife along the frame to cut the film off flush with the wood. It
takes practice to get the knife to cut well, a 45 degree angle works
best as shown with the blade just resting flat on the wood. This takes
practice to do well and requires a very sharp blade. The knife
should just glide along easily without encountering resistance. |
| Now repeat the steps above to
apply more double stick tape all around the edge over the film you just
applied and then apply the film
to the opposite side. Keep in mind that this film is both strong and resilient and also very fragile when exposed to sharp objects. Small tears can be repaired with clear packing tape, larger ones may require removing all the tape and film and re-applying it, so handle them carefully. |
Next use the packing
tape gun to wrap the entire edge of the frame. I use high quality clear
tape for it's strength and clarity. This tape protects the film at the edge of
the frame during handling and insertion and removal from the windows. I
have found that it is simplest to do each side separately. Start by
pulling out a bit of tape and wrapping an inch or so over the edge being careful
to center it on the frame. |
Now pull the tape out to a few inches past the other end and lay it down
so that the entire length centers on the frame. Cut off the tape and wrap
it over the end. Now smooth the tape firmly down along the whole edge.
Then begin at one end and fold the tape over and down the sides. You need
to make a tight fold here or you will get bubbles in the tape. If bubbles
get trapped you can puncture them with a knife then rub them out. Rub the
tape down firmly so it disappears.
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NOTE! Now is the time to
install pull tabs made from clear packing tape. Use a short length
of tape and stick it to the outer edge then fold it over and stick about
1" to the inside surface. Locate them where they will be easy to
reach - typically a foot or so from the bottom. These panels will
be VERY difficult to remove without a tab. (Note the picture shows
the foam already applied, but do this step before applying the foam strip).
You can add a label onto the tape using a white address label that says "pull to
remove" if you want to make it easier to find. |
Use a hair dryer set on high to shrink
the film. I have found that starting in the middle and working out
to the edges works best to remove wrinkles. Keep the hair dryer
moving at all times and be sure to heat every part of the film so you
don't have loose spots or wrinkles. Don't use a heat gun - it will
melt right through the film! |
The open cell foam
weather strip that I use is 1/2" by 1/2". I first measure it to
length and cut it an inch or so long. Note that I made a jig to hold the frame vertically on the floor.
I glued 3 pieces of 1X lumber together. 2 wide ones and a narrow
one with a layer of thick paper in the glue joint to space it out a bit.
This forms a long U channel that holds the frame snugly allowing for the
thickness of the film and tape. The channel is then glued to a
larger board for stability. |
Peeling the backing off
the foam tape is tricky. This is annoying as it is hard to get it
to start, but if you get your fingernail right up against a corner and
pull the foam off the backing tape it will come off fairly easily.
Now peel back a few inches and stick that down to the end of the frame
with a slight overhang at the end. |
Slowly
pull the backing tape off as you guide the foam so that it sticks in the
center of the edge of the frame. One person can lead by pulling out the
backing tape as the other centers the foam and presses it down. |
Apply foam to 2
opposite sides first. Then when you cut the foam off of the ends
be sure not to undercut. You want the foam to hang over the end
slightly so that the foam can overlap and stick to the foam and form a
square edge. |
I tried just wrapping the foam around the corners but it leaves
a rounded gap that looks unsightly and leaks air. The point here
is to eliminate all drafts. Here's how it looks before you cut off
the edge. |
| That's it! Repeat as needed for all the windows in your home. Then in the spring review your heating energy bill and SMILE! |
Materials Sources
Construction overview
Assembling the frames
Applying film and weather strip
This
page was substantially revised on October 6, 2008 based on my experiences
training many groups to make these window panels. I have endeavored to
simplify the process for the average home handyman. Please
contact me if
you have
questions or
suggestions for
improvement.
visits since 7/30/08