Crawl space vents are from an era when energy was cheap and not much thought went into crawl space construction. In cold climates, the best approach is to have an unvented space, with insulation on the walls and rim joist, and a reasonable vapor barrier to keep moisture from rising up through soil below. In addition code requires some air circulation, but many don't provide it and just install a dehumidifier.

Venting of crawl spaces is primarily intended to regulate moisture levels below the structure. It also serves to dilute any soil gases (e.g., radon) that would otherwise accumulate in the crawl space. You can find additional information about radon in MA homes here: https://www.mass.gov/info-details/radon-get-the-facts 

In MA, I'd build a sealed, conditioned crawl space as Seabornman described. And I would ventilate it at the code-required air flow rate of 1 cfm/50 SF of floor area or higher if needed to reduce soil gases to safe levels.

If you have a fuel burning furnace in the crawlspace you will need make up air. Using the vents. Even if you don't have any type of furnace, I would recommend opening them in the summer and closing them in the winter. Fresh air supply is a good thing

Not necessarily High-efficiency gas furnaces are sealed combustion units where combustion air is directly piped to the furnace from the exterior and exhaust gas is piped out. No air exchange from the crawl is required nor are crawl space vents.

Put down 6 or 10mil vapor barrier and top with pea gravel. No vents in winter.