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Mylar Storms

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Posted by j on December 4, 2012, 3:12 pm
 
  An idea to pass along.

I've been making indoor storms. These are made out of 1/2" (1/2" is
about optimal air space) thick frames ripped from white pine 2 by stock.
2x6's seem to be made out of better wood than 2x4's, so I've been using
that. Half lap joints for the corners. Then, seal the wood.

Spray contact cement on one side of the frame and plop it down on a
sheet of mylar (I work on a glass top so I can cut with a blade right on
top of the glass, quick and easy). Cut the mylar to size and repeat for
the other side. 2 mil mylar works well (under $.20/SF), but 1 mil is
half the price. The contact adhesive has some working time so you can
pull any ripples out of the mylar using your fingers against the frame.

My friends and myself have old double hung windows, so the frames sit
against the window frame. What you wind up with is a poor mans triple
glazed window. IR temp measurements come close to the insulated wall
temps, the difference in room comfort is very noticeable. The U value is
higher than I expected.

Windows are dead clear, you may see some ripples at low angles at night,
otherwise you can't tell they are there. Mylar needs to be inside as it
deteriorates under UVB which ordinary glass blocks.

Just thought I would pass this along. For roughly the cost of replacing
one old school window you can get roughly the same thermal improvement
for the whole house. And they look good!

One mylar source:
http://www.usplastic.com/catalog/search.aspx?search=mylar&page=1

HTH

Jeff

Posted by Jim Wilkins on December 4, 2012, 4:16 pm
 


I made a set in 1981 and have mentioned them on alt.energy.homepower a
few times, generating no followup questions to fill in the details I
intentionally omitted. I got the idea and the Mylar from John
Stephenson who makes Warmlite camping gear and has played with Mylar
film insulation since the 1950's.

They work fine and most have survived without a tear. The window glass
has kept UV from noticeably yellowing the film. The only maintenance
has been replacing the closed cell weatherstripping that makes them a
snug press fit in the window trim. Instead of cement I used
double-stick tape and my wife and I stretched the plastic over the
frame the same way theatre flats are covered with canvas, ie working
from the centers toward the corners. Then we wrapped the edges with 2"
clear packaging tape.

Before covering the frames I stained them to match the windows so they
practically disappear from inside. From outside the reflection of a
few slight ripples shows at certain angles.

On the exposed upwind side of the house I added retainers made from
brass L hooks straightened, looped at the end and then bent 45 degrees
in the center to make thumb latches, two per window.

Infrared thermometer measurements of black tape on the plastic and the
wall show only a few degrees difference when the outside temp is well
below freezing. They seal the windows enough that winter-time humidity
remains above 40%.

It takes some cabinet-making skill to make invisible mortice and tenon
corner joints. Ten of the eleven window frames I made would hold
together without glue. The patio door frames were too big to stand
upright on the table saw so I dowelled them, which has held up fine.

jsw
.




Posted by j on December 4, 2012, 6:51 pm
 
On 12/4/2012 11:16 AM, Jim Wilkins wrote:
 >>   An idea to pass along.
 >>
 >> I've been making indoor storms. These are made out of 1/2" (1/2" is
 >> about optimal air space) thick frames ripped from white pine 2 by
 >> stock. 2x6's seem to be made out of better wood than 2x4's, so I've
 >> been using that. Half lap joints for the corners. Then, seal the
 >> wood....
 >>
 >> Jeff
 >
 > I made a set in 1981 and have mentioned them on alt.energy.homepower a
 > few times, generating no followup questions to fill in the details I
 > intentionally omitted. I got the idea and the Mylar from John
 > Stephenson who makes Warmlite camping gear and has played with Mylar
 > film insulation since the 1950's.

Very cool.
 >
 > They work fine and most have survived without a tear. The window glass
 > has kept UV from noticeably yellowing the film.

That's a long life!


  The only maintenance
 > has been replacing the closed cell weatherstripping that makes them a
 > snug press fit in the window trim. Instead of cement I used
 > double-stick tape and my wife and I stretched the plastic over the
 > frame the same way theatre flats are covered with canvas, ie working
 > from the centers toward the corners. Then we wrapped the edges with 2"
 > clear packaging tape.

I like that.

The contact cement should give more latitude. I had tried double stick
but it is hard to tug on the mylar.The contact slides until it sets. In
fact you don't have to be that careful of getting out the ripples
initially as they pull out easily after the mylar is on the frame.
 >
 > Before covering the frames I stained them to match the windows so they
 > practically disappear from inside. From outside the reflection of a
 > few slight ripples shows at certain angles.

Same here.
 >
 > On the exposed upwind side of the house I added retainers made from
 > brass L hooks straightened, looped at the end and then bent 45 degrees
 > in the center to make thumb latches, two per window.

Nice.
 >
 > Infrared thermometer measurements of black tape on the plastic and the
 > wall show only a few degrees difference when the outside temp is well
 > below freezing.

Same here, at least for as cold as we get! Seems like it works better
than expected.

  They seal the windows enough that winter-time humidity
 > remains above 40%.
 >
 > It takes some cabinet-making skill to make invisible mortice and tenon
 > corner joints. Ten of the eleven window frames I made would hold
 > together without glue. The patio door frames were too big to stand
 > upright on the table saw so I dowelled them, which has held up fine.

Your skills trump mine. I cut half laps with a dado and a stop. Then
pinned it together with a pin stapler while the glue set. Two half days
to do up a dozen windows.

Some of the pieces I've ripped have curved. What should I look for in
feed stock? I think the pieces with tighter/closer grain curve more. I
think the top grain is more critical than the edge grain. But I really
don't know.

Jeff
 >
 > jsw
 > .
 >
 >
 >



Posted by Jim Wilkins on December 4, 2012, 7:37 pm
 
I've been a theatre set builder and thus practiced stretching the
canvas. Since it's stapled before sizing it I could fix my beginner
mistakes without wasting material. The glue seems easier.


When I asked about the very large scrap pile I saw in a custom cabinet
shop the owner said he simply bought extra and used whatever warped
for firewood.

I got the Southern Yellow Pine as strips trimmed off doors etc from a
kitchen installer, and nowadays saw and plane my own furniture lumber
from local high-quality old growth that dies or blows down.

If you are limited to big box store wood you could buy extra, rip it
slightly oversize and pile it up indoors to season. Most of the
pressure-treated I've bought recently has dried pretty straight. I
rebuilt the outer frames and sills of my windows with it.
jsw



Posted by j on December 5, 2012, 12:53 am
 On 12/4/2012 2:37 PM, Jim Wilkins wrote:

I've given up on yellow pine. Everything I make is out of white pine, I
haven't had too much trouble, but I do get the occasional errant piece.
The white seems a good bit lighter too,I think not as strong, but strong
enough.

I've got a good bit of 1 x 6 tongue and groove cypress (I bought a
pallet Home Depot no longer wanted), it's my go to wood if the
dimensions are suitable.

The depot is not far and I can hang lumber out the car window and no one
cares. I brought home some 12 footers once and they stuck out 5'. A bit
too far for a comfortable drive home!

Jeff



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