Low Emissive Window Glazing Materials?

Low Emissive Window Glazing Materials

I need to cault or reglaze some windows, an article on your site recommends as follows:

"Replacing Sashes & Reglazing Replacing sashes or reglazing windows can be cost effective alternatives to replacing entire windows. Select sash material with a high insulating value and glazings with a low emissive coating."

But none of the window glazing materials I've seen seem to be "low emissive," and they all recommend preparing the sash by priming with oil-based primer. I want to do all of my home improvement projects in as environmentally friendly and healthy way as possible. What do you recommend?

Jen