"The Healthy House" (1) points to some concerns with modern building design and materials. Walls which breathe can exchange and filter the air and greatly reduce internal air pollution. Porous hygroscopic materials such as solid timber can take in and release moisture and so act as a natural air conditioner.

Building materials are ranked in order as suitable building materials for a healthy building. Here is a sample from the rankings of 25 building materials with 1 being the healthiest, and 25 the least healthy.

1	Beeswax as a surface for wood products
2	Solid timber and cork
3	Woodwool slab (compacted wood shavings)
19	Glass fibre
21	Polystyrene
24	Reinforced concrete
25	Aluminium foil vapour barrier

You can see more about Healthy Buildings under Buiding Research

1. 1."The Health House" by Sydney and Joan Baggs - Harper Collins 1996.