What about installing a radiant barrier in cold climates! Installing a radiant barrier directly over the attic insulation will help reducing radiant heat loss. The problem quite honestly is that there is not that much radiant heat loss, to begin with. But here something most people are not aware of, that radiant barrier helps by making your existing attic insulation even more efficient and effective.
To explain; in a typical ventilated attic once has the roof, the attic space, then the attic insulation, and then the sheet of rock above the attic space. In a ventilated attic you have air entering through the soffit and exiting through the exhaust vents to help remove moisture and to keep the roof cold to prevent ice dampening. The only thing between the warm living space and the cold outside air in the attic is the layer of the sheetrock and the layer of insulation.
This is a huge mistake most make when it comes to building energy-efficient homes. The problem is that energy has been cheap and plentiful so energy efficiency was not a top priority. This method works ok if you're not worried about your heating cost. It's not smart to just blow air in insulation without a top barrier, but it's cheap and it's fast and too often it's the driving force when it comes to building homes. This problem can be easily fixed. So just like a jacket, one needs to install an outside air barrier to the ceiling insulation blanket on top of the attic insulation.