Because of high costs and energy some European countries often debated if full air-conditioning of buildings is recommendable or should be prohibited by law. Of course air-conditioning will give better control of the indoor temperature and then improve comfort and productivity. But there also exist many examples of discomfort in air-conditioned buildings due to draught, noise and sick building syndrome. Alternatively the heating and cooling may be done by water based radiant heating and cooling systems, where pipes are embedded in the building structure (floors, ceilings, walls) or in the centre of the concrete slabs between each storey. The present paper will discuss the possibilities and limitations of radiant surface heating and cooling systems, and give some examples computer simulation of buildings with these type of systems will be presented together with measured performance.