Bathroom fan draws cold air through furnace.

[KYRattler]

Hello all, please excuse if this has been answered somewhere on here. I'll blame the Google and forum search algorithms for keeping it hidden.

Anyhow, just like the title states, we have outside-temperature air being drawn into the coach while the bathroom/kitchen exhaust fan(s) are being used.

We are full timers in our 377FL, and as fall/winter presses in on us, I'm trying like a little Dutch boy to put a finger on all the gaps installed at the factory in Elkhart. I've filmed the single pane sliding windows and Reflectix'd all the bedroom windows. I've placed extra weatherstripping around the door frame gaps.

Between the electric fireplace, the main AC electric HEATER, and a radiant oil heater in the bedroom, I can keep it toasty when the frost hits... WITHOUT using the propane furnace. However, should we take a shower or "release any demons" in the bathroom, the awesome vent fan will draw an enormity of cold air through the intake of the furnace (which I'm sure is coming from the pass-through storage bay). I've checked this with an oil infuser in front of all the likely suspects of cold air. The furnace is the culprit.

Am I missing any secrets or RV lifehacks? My chilly-willy wife thanks you in advance!

PS: No, I will not stop using the fan... Moisture and "demons" are not friendly to small space living.