A building construction formed as a dome has a transparent outer shell and an inner shell of flat cassettes which are turnable for regulating incident light radiation and light escaping from the dome. Air is circulated through a heat accumulator, arranged beneath the dome, and a collecting space in the peak of the dome through the cassettes, which have a shiny and a black side surface for maximum reflection or absorption of sunlight. The adjustment of the cassettes for greatest efficiency is automatically controlled. The dome has double or multiple transparent walls between which biomass is cultivated, e.g. green microorganisms in an outer and red microorganisms in an inner layer for maximum energy utilization. Light-absorbing salt solutions can be circulated through a layer, or parts thereof, when screening-off is desired to steer light radiation for optimum biological production.
