Gardenia's in general don't like the dry air created by heating systems. Your gardenia would fare better if placed in a cool location, preferably a well lit unheated room.

That said, you don't indicate what zone you're in or which variety of gardenia you're growing. "Chuck Hayes" & Kleim's hardy are the hardiest of the gardenia's. These are hardy to zone 7.

Can you provide more info?

There are several Gardenia that are referred to as "ever blooming gardenia". I would first find out which variety you have and if it is possible to grow it outdoors in your climate zone. G.jasminoides in general only fare acceptable for a short duration while in the indoor environment.

I have overwintered a gardenia for about 7 years now and aka_peggy is correct. No drafts, in a cool room, and mine is in a west facing window. Misting may also help, especially if you have forced-air heating, but water sparingly. Since my tap water comes from Lake Michigan and is a bit alkaline, I also found that by sprinkling some elemental sulfur on top of the soil and covering it with a pine bark mulch helped cure my chlorosis.

tj