I'm getting glass block windows to replace my old basement windows. I've been looking around and concluded that everyone basically uses Pitt. Corning glass blocks. And everyone charges about the same to install. approx $48-50 per window, plus $25 for an optrional air vent or drier vent. Two questions. 1)They offer either a silicon bond to hold the blocks together or a mortar base. Which one should I go for? pro and cons for both. 2)Does it really matter who installs it, I don't have to pay until they are installed, and everyone has about a 5 year warranty on leaks and cracks, not including Pitts. Corning's warranty. As long as they have a decent reputation can you realy mess up this job. Thanx for the input.