latcheswindows
Getting a hernia trying to open these windows. I've unlocked them so they're either stuck or I'm doing something mindlessly wrong. Regardless, scratching my head trying to figure out what these latches are for? And the little boxy thing (alarm-related)? TIA for any info
It's a window latch and keeper. Unscrew a good one, head over the your local hardware store, and see if they have a match in stock. Pay close attention to the distance between the screw holes and the how tight the two parts are pulled together. They come in a lot of styles, e.g. this would work if the keeper was on a horizontal instead of on a vertical surface:
You can also look online, and worst case scenario, you'll have to go to the window manufacturer to get the replacement parts.
This is not meant to be a complete answer, but might help with your understanding of it. My understanding of the physics of windows is as follows -
Nearly all radiation (visible, UV, infrared, every other type too) that travels from outside the house into the house and is absorbed (not reflected back out again) is converted into heat. I would expect that exceptions (such as the energy from UV light causing a chemical change, such as when it fades your couch, or waves that induce a current in a conductor) are relatively negligible.
This means any radiation that can be reflected from the window to prevent it entering the house reduces the heat load. Also, if the radiation is absorbed into the window glass (eg through tinting it), then some of the heat from the window glass will be lost to the outside (through both conductance/convection and some radiated heat) which is an additional benefit.
A heated window pane would like lose more heat to the outside than the inside because the wind would help keep the temperature difference between the glass and the adjacent outside air larger than the temperature difference between the glass and the inside air.
Best Answer
In the second picture, the little thing that pops out (pointed at by the left-hand arrow) is a stop to prevent the window from opening more than about an inch. This way, when the window is open a little, nobody can open the window further from the outside to use it as a way of getting into your house. They can be a bit of a pain to latch down so the window can open further, if you desire to do so, but you push it flat, then slide it to the right and it should latch down, allowing the window to slide past it.
The two other items (pointed at by the arrow in the 1st pic and the right-hand arrow in the second) appear to be the locking mechanism that holds the window closed to prevent it from being opened at all. It appears that you pull down on the finger tab on the top one, and up on the tab on the bottom one, then slide the window open to the left. If these will latch into the open position, then you should be able to open each individually to leave the window unlocked, thus being able to open and close the window at will. They may, however, be spring loaded and require you to pull them both toward the center at the same time in order to open the window.
If these windows are several years old, there may be some of the general crud of life accumulated in them causing them to be a bit sticky and difficult to open. They may require a bit of force to open the catches, and possibly some cleaning.
In the pictures you've provided, it looks like the bottom catch is open, while the top catch is still latched shut.