Actually, the pointed roofs have *more* surface area than the flat ones.

The majority of modern buildings are derived from the historical designs built before them, which may explain the flat roofs in hot climates and pointed ones in wet climates. Generally traditional buildings in hot climates had flat roofs because they're cheaper to build and water resistance isn't such a concern, in fact traditional masonry houses in Spain don't even have a damp proof course. However, the houses in climates with lots of rain needed pitched roofs as the slope helped their fairly primitive roofing systems (they didn't even have underlay back then) to shed water better. Things have changed a lot and modern building materials mean you can have a long lasting totally water proof flat roof in any climate, but people continue to build mostly traditional looking structures.

However, a flat roof is the most energy efficient option as it has the least surface area to loose or gain heat from. They're also a fraction of the cost of a pitched roof.

Also, SIPs are strong enough to build most any normal house. They're substantially stronger than normal framing. You can apparently build up to three floors with them (further, with extra supports), and even use them for floors and roofs.

Ventelation is a concern in most all modern buildings as air exchanges per hour continue to reduce, so the problem isn't specific to SIPs, although they do offer a potentially very air tight building. The low-tech option would be to open a window, but you can also fit heat recovery ventilation, which is simply a heat exchanger which transfers about 85% of the heat from air leaving the building in to the fresh air entering it. They also work in reverse when you're cooling the house. Another angle that isn't mentioned half as much is that indoor air only becomes polluted when we release unhealthy things in to it. The fact that some building materials and furniture off-gas chemicals, and poorly designed appliances which don't use sealed combustion pollute the house, is not really a good reason to keep building leaky energy wasting houses, instead it's a good reason to re-evaluate using them items in the house at all.