My house is on the cooler side during winter months because I turn the forced air heating down while I'm out. I'm not sure if you have the same problem, but what I do is place all my bottles in a small room of the house, door closed, and make sure the air vent is fully open in that room so it stays warm regardless. I also find the yeast can settle and go to sleep in cooler conditions, but slowly turning the bottles over and back again helps immensely. I'll do this maybe 1-2 weeks into conditioning and it works a treat.