Which is better, having windows open or closed when Sandy hits?
My concern is not water. A flood may occur of this I’m sure. My concern is wind.
I have a garage which has broken windows on three sides of the structure. Should I board up the windows with plywood or should I just let the wind flow through?
The wind is not likely to be all that extreme. Nothing like a tornado or high category hurricane. Close your house windows and try to keep dry. If it were me I’d board up the garage windows to keep most of the water out.
The boarding and taping you've seen in news reports of hurricane preparation are not likely to be anything you need to do. Boarding is beneficial in dealing with large wind-borne debris. Taping prevents high wind from flexing and cracking larger panes of glass by giving it a little more support, and it also minimizes flying glass if it actually does break.
Get any items that the wind could conceivably pick up and toss around put away. Lawn chairs, tables, decorative items, kid's toys, that sort of thing. If you've got any large trees near your house that could fall on it, occupy a section of the house that is away from it.
Drains, gutters and the like, clear them, there will be a lot of rain. A lot. Windblown rain can get driven into unusual places, such as through gable vents in the attic. Might want to check it out and cover them temporarily with plastic sheeting affixed with duct tape.
If you have an older roof, there may still be time to check that. Loose shingles will very likely be blown off.
It'll be a little scary for a while, then calm, then the wind will reverse direction and you'll go through it again. Then it's over except for flooding and any damage that might have occurred. You should be OK unless your house is in a flood plain. I'd go somewhere else for the duration if it is.
I am no expert but just on the face of it, I wouldn’t recommend opening windows through a tropical storm.
I’d say board it up.