Attic ventilation and a colder winter

Our house was built in the 1940s and as such the attic had no ventilation. After a particularly hot summer last year, this spring I installed a roof turbine and vents under the eaves (as well as replacing the two largest windows with dual-paned versions), which allowed me to keep the temp at a max of about 80F, instead of 90F the previous year. However, winter has come at a recent cold spell (I know, I know, 32F is nothing compared to others…) and the house seems to cool faster than normal (from 70F to 65F in around 2 hours). I had assumed that the dual-paned windows would help keep the head in more than normal (you could feel the cold air coming in through the single paned version), so my question is this:

Will covering the turbine with such tarps as I’ve seen such things at hardware stores keep the house warmer?

Two additional facts: The insulation appears to be blown in rock wool, the age of which I’m not sure, but would assume to be at least 10 years, since that when a pervious owner remodled the ceiling; and the roofing is composed of wooden shingles directly on top of the rafters, with two layers of cement shingles on top of them.

You could stuff and old sheet or blanket inside of it from below but that would defeat the purpose of it in the first place. Apparently you did a good job of venting your attic space without upgrading your insulation R-value. Having no idea where you live as far as temperate zones go or the configuration of your house its hard to give practical advise but basically keep your roof vented, add insulation without blocking the soffet vents and eliminate as much as possible, air exchange between your living space and attic area.
related website:
http://www.handymanusa.com/articles/icedams.html