What do you define as 'real demand'? There are three main areas of demand for housing property:
1. People requiring shelter (i.e. people who will purchase a property to live in themselves) or
2. People purchasing property to extract rents (landlords) or
3. People purchasing property to later on-sell for a greater amount (property investors)
It's the third class of buyer that many believe is driving demand, and there's certainly a strong argument that the property investor class is bigger today because of depressed interest rates. Because of this increased demand, prices increase. But that price increase is driven only by the perceived future sale value of the property. This is why it's a bubble - The returns are predicated only on continued buy-in to the market. It's little more than a ponzi scheme.
This assertion falls apart if you don't accept the premise that current activity is being driven by investors, of course.