We are in the process of getting submissions to replace our windows,
and being in Ottawa (Canada), we are looking for the most energy-
efficient windows we can afford.

We've done our research (ain't Internet a great thing?), but we're
getting confused by the sometimes contradicting messages from the
tradespeople who've come to our house.

Examples:

One contractor suggested that we replace all protuding North-facing
windows by same size, flat windows. Better energy efficiency, he
said. Two other contractors saw the bow windows and didn't seem to
think they were a problem.

Internet searches indicate that Western Red Cedar was a good (albeit
expensive) choice for window frames, since it didn't rot. But even the
contractors who do sell it seem to try to convince us to go with "good
quality vinyl" (PVC) instead.

One contractor told us that aluminum-covered wood (pine) frames came
in two qualities: poor and good, the good being made of "extruded
aluminum", which meant that there was a space between the wood and the
aluminum so that air could circulate.

One contractor recommended INEX spacer bars. Another said that INEX
spacer bars were the worst, and recommended SUPERSPACER or INTERCEPT.

Can someone help us make sense of all this?

Also, most websites I've read deal with the windows themselves; they
don't talk about their installation which seems to me to be very
important as well.
What type of installation would be recommended? Sprayed
polyurethane? Insulating wool? Both?

Thanks for any help you can provide.

B.