I found couple posts / questions about glass (or window if you like) material in Unreal Engine 4, so I decided to make easy-to-use templates.
I used Nick Donaldson (https://forums.unrealengine.com/member.php?475-Nick-Donaldson) suggestion to achieve more natural glass look (on edges).
I’ve uploaded zipped package with UE4 materials on my blog: http://www.michalorzelek.com/blog/?p=322. Feel free to download it. Hope you like it.