I am constantly being asked what Hoyas do well in cooler house conditions. Now that I know longer heat with wood pellets I am keeping my house no warmer than 68°F (20°C) during the day and 65°F (18°) at night. The key to keeping Hoyas this cool is to not over water and keep the plants on the dryer side. I would have to recommend Hoya pauciflora as a strong candidate for these cooler conditions. Here is a photo of the plant happily living with other members of its genus, a Jade Plant, and a mounted Orchid in my dining room window.