Simon Fairlie, quoted on Transition culture, makes a good point.  We are aspiring to triple glazed, passively heated homes where air is circulated via a heat exchanger.  This is to sustain our current love of indoor environments at 19degC (an increase by 5 degrees over 10 years).  Which is good for old people, but is expensive.

In the countryside, people often make do with old cottages, old caravans, old trailer homes.  Which are essentially zero energy containing.  They can then fuel their wood burners with logs from the plantation; which is cheap, renewable, and zero carbon. 

And the spiritual value of fresh air coming in through the window, and a real fire in the hearth, are immeasurable.