Why natural stone?

How Infrared-C radiation is generated?

All warm objects release heat to the ambient room, either in form of radiation or in form of convection. In this context the object’s surface temperature is the decisive criterion. The higher the surface temperature the higher the portion of infrared-C radiation. In the first instance, the infrared radiation does not warm up the air but the solid objects in and around the room (walls, ceiling, floor, persons, furniture, animals, …).
In order to obtain a big portion of infrared radiation, the heater’s surface temperature has to be very high (for example: masonry stoves reach up to 150° C).


  • Natural stone is a material with low thermal conductivity. That means that touching a natural stone with a supposed surface temperature of 100° C will be unpleasant but the contact will not cause any injury. This is the reason why the VDE allows heaters made of natural stone or ceramic to have a maximal surface temperature of 100° C plus room temperature. For comparison: metal heaters only 40° C plus room temperature. Thus, with natural stone you can obtain a higher degree of efficiency.

  • The materials used for astra natural stone heatings either have a high crystalline content in the stone itself or an uneven surface due to the surface finish (diamond brushed, flame finished, …).
    Either the high crystalline content or the uneven surfaces procure nearly a 180° infrared-C radiation that can work all over the room and not only just in front of the heater.

  • When the relative humidity in a room is high, natural stones, especially marble and limestone, absorb this humidity (like a sponge). Afterwards, when the ambient air is dry they will slowly release it to the room. Therefore, rooms with astra natural stone heatings procure a comfortable and stable indoor climate. (Highly appreciated by asthmatic and allergic persons) (see: Health)