In determining the maximum dollar amount of any federally assisted mortgage loan (as defined in subsection (b)) or the maximum per unit or other cost or floor area limitation of any federally constructed housing (as defined in subsection (c)), where the law establishing the program under which the loan is made or the housing is constructed specifies such maximum per unit or other cost on floor area limitation and the structure involved is furnished with solar heating or combined solar heating and cooling equipment under the demonstration program established by section 5503, 5504, or 5507 of this title, the maximum amount or cost or floor area limitation so specified which is applicable to such structure shall be deemed to be increased by the amount by which (as determined by the Secretary or the Secretary of Defense, as appropriate) the price or cost or floor area limitation of the structure including such solar heating or combined solar heating and cooling equipment exceeds the price or cost or floor area limitation of the structure with such equipment replaced by conventional heating equipment or conventional heating and cooling equipment (as the case may be).

In addition, in the case of a federally assisted mortgage loan, the cost excess specified in subsection (a) shall be fully taken into account in determining the value or cost of the structure involved for purposes of applying any statutory provision specifying the maximum loan-to-value or -cost ratio; except that, if the law specifies different rates of downpayment for successive increments of such value or cost, the lowest such rate shall apply to the additional cost attributable to the solar heating or combined solar heating and cooling equipment, and such equipment shall otherwise be excluded in determining the total value or cost of the structure.

is made in whole or in part by any lender the deposits or accounts of which are insured by any agency of the Federal Government, or is made in whole or in part by any lender which is itself regulated by any agency of the Federal Government; or

is made in whole or in part, or insured, guaranteed, supplemented, or assisted in any way, by the Secretary or any other officer or agency of the Federal Government or under or in connection with a housing, urban development, or related program administered by the Secretary or a housing or related program administered by any other such officer or agency; or

is eligible for purchase by the Federal National Mortgage Association, the Government National Mortgage Association, or the Federal Home Loan Mortgage Corporation, or from any financial institution from which it could be purchased by the Federal Home Loan Mortgage Corporation; or

is made in whole or in part by any “creditor,” as defined in section 1602(f) 1 of title 15, who makes or invests in residential real estate loans aggregating more than $1,000,000 per year.