If the Commissioners shall find that the proposed Improvements or any Part thereof, whether with or without any Alterations by them required or sanctioned would effect a permanent Increase of the yearly Value of the Lands proposed to be improved, or of any Part thereof, exceeding the yearly Amount proposed to be charged thereon, they shall sanction such Improvements, or such Part thereof as they shall think expedient, if under the preceding Sections it shall be lawful for them so to do, by an Order under their Hands and Seal; and they shall by the same Order fix the Rate of Interest to be allowed on the Cost of the sanctioned Improvements, having regard to the Market Value of Money at the Time, but such Interest shall never exceed Five per Cent, per Annum.