WiFi through glass

[RedDoor]

I am just setting up a home WiFi network. Our "home" is really two farm buildings that we renovated. They are quite close together. My wireless broadband comes in on the 1st floor of one bulding. My office is on the ground floor of the second.
My best wifi connection is with the WiFi router sitting in a window about 10 feet higher and 40 feet away from the WiFi antenna which is also sitting in a window.
If I open the window and put the router out on the porch I get great reception. Inside the window I get a low or very low signal strength. The windows are double glazed K glass.
Is it the window pane(s) that are causing the slowdown? My only other choice is through concrete walls and that is no better. Also the roofs on both buildings are metal.
What am I asking? 1) Is glass a good or bad "transmitter" of WiFi. 2) Would changing the channels help any? 3) Does signal strength affect transmission speed? 4) Do repeaters really work?

Thanks all.

[swoodworth]

Pilkington K Glass is coated on the inside surface of the inner pane with a coating that is (according to Pilkington) opaque to longer wavelengths so that it reflects heat internally while letting light through from the outside. It's possible that the coating also attenuates radio signals though I can't find confirmation of that. If it does attenuate radio signals, then changing channels might not be much use though there's no harm in trying.

What about a repeater or access point with an externally mounted antenna?

Simon.

[RedDoor]

I'm just guessing on the K glass as well. But, I do note that when I set the wifi router outside I got great signal strength.
Hadn't thought about the external antenna. Any idea which is cheaper - external antenna or repeater?