Section 101D. If a policy of fire insurance contains a reduced rate or co-insurance clause, and if, in case of loss, the parties do not agree as to the sound value of the property affected, such value shall be determined by the referees chosen to determine the loss. If the parties agree as to the loss, but do not agree as to the amount of the sound value, said value shall be determined by referees appointed as provided in and subject to the provisions of sections one hundred to one hundred and one G, inclusive, and of said standard form. An award in writing of a majority of the referees shall be final and conclusive on the parties as to the amount of the sound value.