Tennessee Code Title 7. Consolidated Governments and Local Governmental Functions and Entities § 7-60-216

(a) When loans are made for the purchase of new houses, such preference in making loans as may be determined by the governing body of the county shall go to those houses incorporating energy-conserving design, construction or other energy-saving features, including solar heating or solar water heating. With houses incorporating such design, construction, or features, the amount of permissible loan may be increased to cover any extra cost such elements represent over the cost of a similar house without such elements.

(b) When loans are made for the purchase of older houses, such preference in making loans as may be determined by the governing body of the county shall go to those houses incorporating energy-conserving design, construction, or other energy-saving features, including solar heating or solar water heating. With houses incorporating such design, construction, or features, the amount of permissible loan may be increased to cover any extra costs such elements represent over the cost of a similar house without such elements.

(c) A reasonable percentage of new houses financed through this chapter shall be equipped with solar water heating units to supply all or substantially all of the heated water requirement of that household, the determination of the governing body of the county with respect to the reasonableness of such percentage to be conclusive. The applicable amount of mortgage money available to a person through this chapter shall be increased by an amount necessary to cover any added costs of such heater. Each county acting under this chapter shall determine the percentage of houses to be so equipped.