Not entirely happy with a ventless gas heater

My house is over a hundred years old and not outfitted with conventional ductwork.

This makes temperature control a big challenge.

Living in the northern part of the country, the extreme cold weather necessitates a powerful heating system. We make do the best we can. In the kitchen, we rely on a ventless, natural gas heater. Because the heater isn’t vented, it creates an oily residue on the windows in the kitchen. I have a pair of antique French doors separating the kitchen from the dining room. Each of these doors has twelve small windows. Cleaning these windows is a labor-intensive, time-consuming and frustrating process. I’ve noticed that the windows rarely need to be washed during the summer. In the winter, they are constantly cloudy and require a thorough scrubbing. The heater is a single-stage unit, which means that it can only operate at one speed. When the temperature in the kitchen drops, the heater blasts at maximum capacity unit it reaches the thermostat setting. Then the heater shuts down and cools the inner workings with a fan that blows chilly air. The repeated on and off cycling causes unpleasant temperature fluctuations. The ventless heater is very sensitive to dust. The filters need to be washed at least once a week. If there is any debris clogging the air filters, a blinking red warning light comes out. When the warning light shows up, the heater will no longer shut on and off. It keeps blasting at high speed and I worry that it might overheat or become a fire hazard.

Hybrid HVAC system