You may have already found this, but there are some things you'll want to know about how dg units need to have their edges kept dry, so they don't mist inside.
This site http://www.thewindowman.co.uk/ has an "e-book" on the subject
at http://www.double-glazing-web.co.uk/eBooks/wooden_windows_drainage_old.pdf
Also, Jeff Howell is worth reading on the same topic:
http://www.askjeff.co.uk/double_glazing.html
This site http://www.thewindowman.co.uk/ has an "e-book" on the subject
at http://www.double-glazing-web.co.uk/eBooks/wooden_windows_drainage_old.pdf
Also, Jeff Howell is worth reading on the same topic:
http://www.askjeff.co.uk/double_glazing.html