Richard Donnell (, 25 May) sensibly argues that the mix of new housing should be decided at the local level – top-down density or mix targets cannot possibly produce the right housing.

However, he is not right when he says “what we need are smaller homes”. Research published by the Home Builders Federation in March 2005, involving the most comprehensive analysis ever between household growth and the size of homes, found that we will need more large homes over the next 20 years.

There are several reasons for this, the most striking being the impact of an ageing population. In early adulthood, people tend to trade up until they occupy a large family home, usually in their forties. However there is a much weaker tendency to trade down in later life, so the stock of larger homes remains in the hands of the over-forties.

Unless someone finds a way to persuade large numbers of baby boomers and retired owner-occupiers to trade down, pressure for more larger homes will remain strong.

John Stewart, director of economic affairs, Home Builders Federation