No storm windows--happily (or sadly for lovers of seasons!) we're in Northern California, where the climate is pretty temperate. (To wit: we've been able to just lean a board over the opening where the window once was for the past week...) At this point we've ruled out insulated glass and are down to deciding between laminated glass and just sticking with single-paned. (We learned that insulated glass will look quite different because the muntins need to be shallower to accommodate the thicker glass; this is apparently less of an issue with the laminated glass because it's thinner.) Still not sure we will get enough benefit from the laminated glass to be worth the extra cost, so it may just come down to the final estimates, which I hope to have today--but still welcome any other thoughts! This post was edited by artemis78 on Mon, Mar 17, 14 at 14:34

It sounds like you have what is called a twin casement window, One opens to the left and the other to the right. In window replacement terms it is considered (1) twin casement. The vertical piece you see in the center is removed, creating a complete opening. The new twin casement will fit right into the same opening. I agree that Lowes or similar big box store would be ok for just one window. All the best, The Porch Guy Here is a link that might be useful: My Album

You betcha. Sounds like they have some decent options on that front and let us know what you figure out.

Sophie, the OP didn't say why he wanted to install a room air conditioner, and I think it's a stretch to assume it's because his home HVAC system isn't doing its job. Not everyone has or wants central air conditioning. As it happens, for example, I have 2 rooms with air conditioners in my house. That's intentional. One gets used regularly, the other only a few times per year. This setup works for me. And if someone (say, a guest in my home) tried to tell me that I should upgrade my HVAC system because my room air conditioners didn't meet his standards, he probably wouldn't get invited back. For the record, I agree that a mini-split would do the OP well. One of my air conditioners is a mini-split, and I like it. But it was outrageously expensive. I bit the bullet because I needed an especially quiet system. I hope installers have come to their senses since I had mine installed, but at the time, the installation cost over $1000. I had other quotations in the $2000 range. From what I could tell, they wanted about the same fee as they charged for a central air conditioner. In many other places I know of where mini-splits are popular -- Asia, South America, the Middle East, even Puerto Rico -- getting one installed usually costs around $100-300. I don't know about the EU.