best glass for double glaszing

I have a customer who whats to replace all his glass with double glazing in wooden frames we will use adapter glaze to go into the frames with the double glazing he is wanting to know the best type of glass to use as he is going for funding from the govt for his eco house as a trial .
he is also a aircon installer by trade so he tells me he will have the house filled with postive presure to push the air out any gaps in the frames .
so all i need to find out is the best glass to use !!
i have said we can use low e on the inside and evergreen on the out to keep the uv as low as poss
hope some one can help

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