The guy at the bike shop recommended the Brentwood to me because that had the best ventilation out of all the Bern helmets in the store. Two vents in the front, 5 in the top, and 4 in the back.

Earlier this week, the temperature high was around 33 C. I usually cycle when I get home from work - thanks to our daylight savings time I usually get about 1.5 to 2 hours of cycling before the sun sets. Thus, the temperature was below the max at that time, but I did sweat a lot. But I have say that I sweated just as much wearing a racing style helmet under similar conditions, and that was when I was just trying to balance on the bike. With the Bern on my head it was hot weather and I was also putting in effort to "climb" (cycle up inclines - my house is on a hill, so every street has incline/decline) - I don't think I sweated any more than I did in the racing helmet. Actually, what gave me more trouble was the sweat causing my sunglasses to slip from my face. I have Wayfarer style sunglasses and would have gotten Oakley or similar brand sunglasses with the rubber nose bridge and temples if I'd known I would take up cycling just 4 months later.

Like you, I was reluctant to buy a helmet online and was glad to have gone to a bike shop to buy the helmet. I was originally interested in a Nutcase helmet, but the bike shop guy said that the Bern Brentwood had much better ventilation.

BTW, I'd say about half my colleagues who cycle to work wear urban style helmets. What most of them seem to do during warmer months is wear shorts or short dresses/skirts while cycling, carrying their work clothes in panniers or backpacks, and when they arrive at our office building, they use the building's locker room to take showers, then put on work clothes. It seems like a lot of them take showers regardless of style of helmet. In colder months they wear base layers/stockings/whatever under their shorts/dresses/skirts.