Giro and Bell do have some models that have decent airflow and for inexpensive helmets they have some highly rated in the crash tests. And it was a Giro interceptor that saved me in my one and only trip to the ER.
Everyone else is about the same with some that don't have much ventilation and many that do have a lot of ventilation. You just have to look and imagine how the air flows through them. Poc might be the one that impressed me as not having a lot of ventilation for such well speaking reviews. But perhaps the shop I was at only had those that didn't have much ventilation. I don't think I've ever looked on Poc's site.