**5. Conclusions**

First, the optical and the thermal mechanism of volumetric S. R. collection incident upon an opaque house covered by a composite surface were explained. Second, on a "South-North model" and a "East-West model" of the opaque house, under new concept of volumetric solar heat collection, the working performance of the opaque house was calculated applying S. R. database at the proving test site. As a result, one of the performance factors, ηVC of both houses, which was defined as efficiency of volumetric solar heat collection, attained 140 % of averaged value through the year. The rate of solar heat collected was 1.4 times of S. R. incident on the floor of the opaque house. Thirdly, applying a normal calculation method, using S. R. measured at the proving test site; Ashoro, a volumetric solar heat collected QVC of the opaque house constructed on the site was calculated, the proving test on larch lumber drying was carried out in cooperation with all staffs, and drying performance was verified to be good. Where, an electric power was supplied to feed pumps for auxiliary heat and fans to agitate inside air in the opaque house was 400 W maximum which was negligibly small. Thus, a "fully passive-type solar lumber drying house" proposed by us, could be achieved to dry out larch lumber under the conditions of low temperature and low humidity inside the opaque house.
