What does your IREA stand for? It is the name of our local utility that I gave the finger to in 1997!!
http://www.earthship.com has the answer to greenhouse thermal mass.
There are billions upon billions of discarded tires in the world, and dirt everywhere. Of course, people have also used discarded 55 gallon drums for water or specially made colored water columns, and rock walls for thermal mass. Variations on the trombe wall.
Some use sheet metal or other piping with low power fans, and most natural convection.
I wonder about Germany. When I was stationed there, it was cloudy a lot. Not really the best place for solar PV or passive solar heat. They have more solar than the rest of the European countries. Has AGW changed their climate to more sunny since 1969?
Also, the numerous straw bale houses are super insulated and require very little heat and cooling inputs. Depends on the amount of glass and whether it is double or triple glazed.
Another thing of interest to you;
Ranges of small mammals extended northwards during Paleocene-Eocene Thermal Maximum
Northward range extension of a diminutive-sized mammal (Ectocion parvus) and the implication of body size change during the Paleocene-Eocene Thermal Maximum - Burger (2012)
Abstract: "An abrupt global warming event marks the Paleocene-Eocene boundary, known as the Paleocene-Eocene Thermal Maximum (PETM). The event is distinguished in the strata globally by a significant negative excursion of δ13C ratio values. The response of the terrestrial biota to the abrupt climatic change has been well studied in northern Wyoming in the Bighorn Basin, where it has been observed that the mammalian fauna during the global warming event is represented by smaller, but morphologically similar species to those found later in the Eocene. Various hypotheses have been proposed to explain the observation smaller body sizes during the global warming event. In this article, evidence is presented to support the hypothesis that the observed body size decrease during the PETM was influenced by the appearance of smaller southern species who extended their geographic range northward during the abnormal global warming event. Using disperse organic carbon isotopic ratios of bulk sediment, the negative excursion of δ13C was located in the Piceance Creek Basin of western Colorado, 400 kilometers to the south of the Bighorn Basin. Below the stratigraphic level marking the negative carbon excursion in the Piceance Creek Basin are five specimens of the phenacodontid mammal (Ectocion parvus), a diminutive species of the genus Ectocion restricted to the basal Eocene (Wa-0 Biozone) in northern Wyoming. The five specimens of Ectocion parvus are associated with a late Paleocene (Clarkforkian) mammalian fauna in Colorado, implying that the diminutive species extended its geographic range northward during the global warming event. This evidence supports biogeographic models that assume poleward biogeographic shifts during global warming events, and will have modern day implications for the conservation of species as global temperatures rise in the near future."
Citation: Benjamin John Burger, Palaeogeography, Palaeoclimatology, Palaeoecology,
http://dx.doi.org/10.1016/j.palaeo.2012.09.008.