I, too, have experienced fogging inside the housing when the wind is cold but the sun is warm. I tried the anti-fog strips and found then slightly helpful. What I do now is make sure there is no excess humidity accumulated in the camera. I bought a 1 lb. box of silica gel. It was a kit made for drying flowers. I wrapped the silica gel in a cloth bag to keep the dust out of the camera. Put the camera, housing, and silica gel bag in a sealed plastic container. Actually, I always keep the silica gel bag in the plastic container to prevent it from accumulating moisture from the air. The night before my outing I put the camera in the housing but leave it open and put them both in the plastic container with the silica gel. Snap the housing closed as soon as you open the container. So far it works like a charm.
I have heard/read that keeping cameras humidity free in tropical areas is a continuing struggle. The camera itself can be full of humid air which will come out inside the housing and cause fog. A camera full of humid air can develop fungus on inside lens elements or corrosion on inside camera parts. Keep cameras in sealed containers with silica gel packets to absorb moisture.
Considering the types of environments we typically use GoPro cameras it's not surprising that humidity is a problem.
I also sometimes use a can of compressed "dust-off" with the plastic nozzle tube to displace the air inside the housing. With the camera in the housing but the housing still open just 1/8" I insert the spray nozzle and try to displace the air in the housing with the super dry gas from the spray can. Then snap the housing shut before any air gets back in.