If a person carrying on a trade has after 12th November 1974 incurred expenditure in adding any insulation against loss of heat to any industrial building or structure occupied by him for the purposes of that trade, Chapter I of Part III of the [1971 c. 68.] Finance Act 1971 shall apply as if the expenditure were capital expenditure incurred on the provision of machinery or plant for the purposes of the trade, and as if the machinery or plant had, in consequence of his incurring the expenditure, belonged to him and had been in use for the purposes of the trade, and as if the disposal value of the machinery or plant were nil.

If a person has after 12th November 1974 incurred expenditure in adding any insulation against loss of heat to any industrial building or structure let by him otherwise than in the course of a trade, Chapter I of Part III of the [1971 c. 68.] Finance Act 1971 shall apply as if the expenditure were capital expenditure incurred in providing machinery or plant first let by that person, otherwise than in the course of a trade, at the time when the expenditure was incurred, and as if the property comprised in the lease of the building or structure had as from that time included the machinery or plant, and as if the disposal value of the machinery or plant were nil.

This section shall be construed as if contained in Chapter I of Part III of the Finance Act 1971 ; and in this section " industrial building or structure " has the meaning given by section 7 of the Capital Allowances Act 1968.