How to heat a building biology-based flagship project? A subject that has plenty of options and even more opinions. After careful consideration, we decided on the following concept (design by Frank Hartmann, Building System Technician, Building Biology Consulting Office IBN):
- Heat generation: Primary pellet furnace, net power output of 10 kW (8 kW water, 2 kW indoor air), direct air supply to the combustion chamber of the furnace through the double-wall chimney. This furnace has been integrated into the partition wall between the showroom and the utility room. Thus visitors can enjoy the flames of the fire through a viewing panel, which spreads warmth and coziness; humans feel good when they are in contact with the four natural elements fire, air, water, and earth. The primary pellet furnace is connected to a buffer storage tank (400 l / 106 gal) and to a fireplace (insulation = foam glass).
- Heat transfer to the rooms: The building is divided into three heating zones and thus three heating circuits: Showroom with restroom (ca. 56 m2 / 603 ft2, ca. 1.1 kW) / suite (ca. 52 m2 / 560 ft2, ca. 1.1 kW) / offices with restroom and kitchenette on the upper floor (ca. 120 m2 / 1292 ft2 , ca. 3.2 kW). While the indoor air temperature of the suite is controlled by Variotherm wall heating elements (ca. 8 m2 / 86 ft2), all other areas (including the bathroom) are controlled by Lithotherm floor heating elements.
Why “temperature control” vs. “heating”? The heating demand of this building is extremely low (heating demand ca. 20 kWh/m2a = total ca. 4700 kWh/a). Based on calculations, it is assumed that one cubic meter of pellets is needed to meet our heating needs. Due to the large surface areas of the wall and floor heating systems, it is possible to facilitate the heat transfer from the heating elements to the rooms with very low supply temperatures, usually below 26°C (78.8) and a corresponding surface temperature of ca. 22°C (71.6). Therefore, the term “heating” in the classical sense does not seem to fit anymore and the term “temperature control” seems more appropriate.
With these low supply temperatures of the wall and floor heating systems, the combination with wood flooring is no problem because the flooring will be only slightly warmer than the indoor air.