That is an important question.  For many years we at Stearns Design Build (Stearns Construction at the time) insisted on only remodeling, or, as we like to put it, recycling homes.  We have since justified designing and building new homes.  The justification is that new building stock is necessary.  The fact is that we just love designing and building new homes that save energy and create happiness. But we still love restoration and modernization of older homes too. Here is a great blog post on this topic from Christopher Davis at the USGBC.