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Fitting window opener to cold frame

Posts: 489
Location: Dawson Creek, BC, Canada
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In the roundwood forum, there was a topic on wood treatments I had commented on.  


This is related to the cold frames. I've never worked with window openers before, or looked at greenhouses to see what they do.

The body of the cold frame is vertical 2x6's (some are 2 boards tall in front, one is 4 boards tall in front.  The "wedge" side pieces are 34.5 inches, which is just a hair over 9 degrees.  The window open in question is a DecDeal HX-T319 (dual springs).

The cold frame is 3x6 feet on the outside.  The "window frame" is slightly bigger than this (sort of to hide the fact that these cold frames are not quite square ).  What seems to work, is to recess the door hinges into the bottom of the window frame.  The frame is made from 1x4 western red cedar, with 90 degree internal steel angles on the 4 interior corners, and a 4 (4.5?) inch long #10 screw installed into predrilled holes to join the body of the "mitre" corners (it really helps the stiffness).

Because the window frame is slightly bigger than the cold frame, and is mounted flush at the back, it sticks out over 3 sides, and because of the 9 degree slope on the window when closed, the bottom edge should act as a drip edge.

The intention is to apply a layer of 6 mil poly on the underside and the topside of this window frame.

[ The kit comes with 2 steel "clamps" and 4 machine screws to mount the clamps on the mount body.  But how this is intended to work completely eludes me. ]

It seems that you should be able to slightly open the window by pulling it up when closed (working against the dual springs).  To actually open the window all the way, I guess you reach in, and squeeze the two "arms" attaching the opener to the body of the cold frame, which releases the bottom of the opener.  So that lets you get inside to water plants or harvest crops or whatever.

In the basement now, it is cool enough that for the current "setting" of the lift cylinder, if I measure down from the arm which would attach to the window frame, the lower frame is down about 2 inches, and the bottom of the lift cylinder is about 9 inches down.  Which would mean that this particular window opener would not work if the front body height was less than 9 inches (it is currently 11 inches), and the cylinder would be hitting the ground inside?

So, the fact that some mornings in the rest of this week, the temperature should be something like 4C in the morning is a good thing, for installing one of these things?  I directly screw the bottom arm mounting plate to the body (on the centreline) about 2 inches below the top of the cold frame body.  That mounting pad has a number of holes, maybe they will take a #8 x 1.5 inch screw?  Or maybe I have to use #6 screws?  The mounting pad to the window frame, has slots, so I guess I find a screw which will go through the slots, and is short enough to not penetrate the top of the 1x cedar frame.

These openers will be closed below some temperature which depends on the actual installation, and then at some point they will start to open?  And then the amount of opening is a function of how much the temperature has risen above some set point?

At some temperature (T_level), the window will be open 5.5 inches, at which point the front of the window frame will have the same elevation as the back of the window frame.  While winds are typically from the west here, west can be SSW to NW.  These windows will open to the south (as I live in the northern hemisphere).  For winds that are not too strong, at temperatures below T_level, the wind will be trying to close the window if it has any amount of "south" to it?  And for temperatures higher than T_level, it should be trying to further open the window?

I would imagine the window will have the aerodynamics of a (very light) sheet of 3/4 inch plywood?  Should a person put aerodynamic devices (spoilers, ...) on top of the window frame, to try and keep strong winds from ripping the window frame off the  body?

How should one attach the 6 mil poly to the frame?  My guess is that you put a bead of acoustic sealant near the inner edge, place the sheet of poly on, and then staple it frequently outside of the acoustic sealant edge.

I don't know what the R value of 2 sheets of 6 mill poly 3/4 of an inch apart is, but it has to be higher than a single sheet of 6 mil poly.

Or am I doing something wrong?

The picture shows my first cold frame, which is slightly oversize but it has a "window frame" mounted on it, with a proper size cold frame in the background.  Bottom 2x6 is western red cedar, the "2x2" corner boards are cedar (ripped from 2x boards) and the other wood is 2x6 SPF.
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