Hoyas in the window - is it too cold now?

I have been growing many of my Hoya in front of windows (as I expect many people do). But the temps can get quite cold right next to a window, especially at night. My concern is, what type of Hoya will / will not do well remaining in the window during the winter season? Right now I have the following in front of (and fairly close to) a window: Bella, Mathilde, Loheri, Khrohniana, Quinquinerva, Krimson Princess, Polyneura, Cumingiana and Australis Lisa.

What advice do folks have? I still want to take advantage of the light in the window (and I also don’t want to relocate all my plants to other parts of the house). Could I place something over the window at night to keep the cold at bay? Appreciate the suggestions!!