Articles 12(1)(a) and 135(1)(j) of Council Directive 2006/112/EC must be interpreted as precluding a national law, such as that at issue in the main proceedings, which makes the VAT exemption on the supply of buildings subject to the condition that the first occupation thereof arises in the context of a taxable transaction. The same provisions must be interpreted as not precluding such a national law from making that exemption subject to the condition, in the case of the ‘upgrade' of an existing building, that the costs incurred have not exceeded 30% of the initial value thereof, provided that that concept of ‘upgrade' is interpreted in the same way as that of ‘conversion' in Article 12(2) of Directive 2006/112, namely as meaning that the building concerned must have been subject to substantial modifications intended to modify the use or alter considerably the conditions of occupation.