Laura jeanne - I guess it is a cultural thing. Norms are different in the Texas and the climate too, and people who wear helmets may use ventilated ones like troxel.
People are right, that any helmet needs replacing after three years (the bubble wrap lining wears and flattens down from contact with your head when you ride). And any damaged helmet should be replaced at once.
I wear a heavy duty cross country helmet built to specs like that of a motor cycle crash helmet. You will see, I wear it always in the States. But I chose it after reading stuff and test results. Your OH is a great researcher. I'd suggest he read all the info and then choose for himself. And if that might take time, but him any hat just to ride in the interval.