I recently moved into a home that was built with radiant heating which uses a gas-based water heater (a Vertex model) - house was built around 2007 or so. We also have a portable air conditioner from the summer months. And unfortunately, the house did not come with any instructions on how everything worked, so I'm trying to figure some of this stuff out. Now, our energy bill skyrocketed in September because all of a sudden, there was a lot of gas being used (the only gas appliance is the water heater), so it seems like the water heater wasn't really doing much during the hotter months, and now that it's getting colder, it's apparently running a lot. Since it's almost always below 70 degrees outside now, I'd like to just shut off the air conditioner and put it away but without it, the house gets uncomfortably hot. It's as if the radiant heating is in overdrive or something. I've adjusted the thermostat to as low as it can go, but that doesn't seem to really do anything at all. The water heater was at an operating temperature of 130 degrees with 2 degrees differential, so I tried lowering that to 122 degrees, but I'm not noticing much difference (and to be honest, I'm not 100% certain what else might be impacted by lowering that number). This situation is ridiculously inefficient, so does anyone have any tips on how I can "turn down" the radiant heating a little bit? This is my first house with radiant heating, so that might be a ridiculous question. Whatever information you can provide would be greatly appreciated!

Is your thermostat actually working? Does circulation stop when you don't need heat?

Well, the thermostat seems to be reporting the temperature between 70-80 at most times, so I'm assuming it's at least partially working, but I have no idea how to test it any further than that.

I also am unsure how to know if the circulation stops (I'm assuming you're talking about hot water circulating as part of the radiant heating system). Is there a way to tell?

Find the pumps for the radiant and just feel them (with a gloved hand, or bare handed gingerly) to see if they're vibrating. You can usually hear if it turns on/off.

Sounds like the pumps are either running all the time due to a control fault, or the thermostat's setpoint is turning it on at a higher temp than it's telling you on the display.

Turning down the water temp is fine, but if it's too low it may not be able to keep up with the heating load on the absolute coldest of nights.