Opening Restrictors

We had a request for more detail on the opening restrictors on the new windows. It took me this long to take reasonable photographs, and they are still kind of dark.

The background here is that the building code has some rules that are basically about preventing kids from pitching off of balconies and out windows to tragic ends. Any guardrail must be 42" tall, with no opening large enough to fit a 4" ball through. Windows with a sill height below 36" must also not open more than 4" wide.


The building code also requires egress windows in bedrooms. An egress window has an opening that is at least 20" x 24" (and a total opening size of 5.7 square feet) with a sill height no more than 44" from the floor.

This creates a look that is distinctive of our time, but not, maybe, a good match with a historic home. In our house, the original window sills are 18" from the floor, and the new windows have the same sill height as the old because I wanted to fit the new windows with the old look. So what do we do to both provide egress where required, and still restrict the opening of the windows so that no small children fall out of them?

Opening restrictor engaged

Enter the opening restrictor. This is on both sides of the double-hung window (the ones for casements or hopper windows look different, obviously). In its normal state, like this, the window sash comes up and hits it and the window cannot open any more than 4"

Opening restrictor disengaged

You just press the bottom on both sides, and the bottom wedge pops in and the upper part drops forward, like above. In this configuration, when you open the window it slides right open, but in the process the restrictor is re-engaged, so that then you close the window again it is back in restricted mode.

Here it is in action:

Restrictor in action

This is the window hitting the restrictor. The window is just less than 4" open at this point. You can't open it any more, and in fact you have to kind of push it down to disengage the restrictor.

Restrictor disengaged

This is a little hard to see, but I've pressed the bottom of the restrictor in on both sides of the window so I can open the window past the 4" mark. The top of the restrictor swings out when I do this to make a little switch.

Sliding past and re-engaging for next time

As I push the window further open, the window frame pushes in and switches that little switch and re-engages the opening restrictor, so if I close the window I don't have to think about re-engaging it; the protection is automatically there.

This is a little bit of a pain in the ass for those of us who do not have small children, but every line of the building code is written based on tragedy. A lot of kids died or were seriously injured before this was encoded. So there you have it.

(These are Marvin windows.)

posted by ayse on 09/10/16