Administrative Code

Virginia Administrative Code
5/28/2024

Part III. Passive Solar Energy System

13VAC5-200-110. Passive solar energy system defined.

An assembly of natural and architectural components including collectors, thermal storage device or devices and transfer medium which converts solar energy into thermal energy in a controlled manner and in which no fans or pumps are necessary to accomplish the transfer of thermal energy. Fans may be used to assist the natural convective air flow in a passive air heating system. The prime element in a passive solar system is usually some form of thermal capacitance.

Statutory Authority

§§ 36-97 et seq. and 36-137 of the Code of Virginia.

Historical Notes

Derived from VR394-01-8 § 300.1, eff. October 10, 1978.

13VAC5-200-120. South facing windows used as solar collectors.

Glazing material used in windows on the designated solar surface of south facing walls when it is part of a sun tempered design for the purpose of collecting direct solar heat in the cold season shall be considered solar equipment eligible for tax exemption. The area of south facing glazing considered to be solar energy equipment eligible for tax exemption shall be calculated as follows:

X - Y = Z

"X" - Percentage of glazing contained within the designated solar surface of the south facing wall in respect to the area of that wall.

"Y" - Percentage of glazing on nonsolar surfaces (north, east, west walls, and non-solar south walls) in respect to the area of those walls.

"Z" - Percentage of glazing considered to be solar equipment

The percentage of glazing considered to be solar equipment (Z), is then multiplied by the total invoice cost of the glazing used on only the designated solar surfaces of the south facing walls. The product of these calculations will be the dollar value of glass to be considered as "equipment" in calculating the solar exemption.

Wall heights used in the above calculations shall be considered the distance parallel to the wall from finished floor level to finished ceiling level.

EXAMPLE: A residence is constructed with fifteen percent (15%) of the north, east and west walls consisting of glass. The south wall, however, is eighty-five percent (85%) glass. The total cost of the glass used on the south wall was one thousand (1,000) dollars. To determine the percentage of that cost which is eligible for solar tax exemption, you would perform the following calculations:

85% - 15% = 70%

.70 X $1,000 = $700

(70% of $1,000 = $700)

Statutory Authority

§§ 36-97 et seq. and 36-137 of the Code of Virginia.

Historical Notes

Derived from VR394-01-8 § 300.2.1, eff. October 10, 1978.

13VAC5-200-130. Trombe walls.

The Trombe Wall is a south facing wall of the building envelope composed of a mass wall and exterior glazing. The mass wall functions as a combination heat sink and exterior wall, while the glazing creates a "heat trap" for penetrating solar radiation.

Trombe walls shall be considered solar equipment and all equipment used in the Trombe Wall, such as but not limited to vents, fans, movable insulation, controls, mass wall, glazing, shading devices and any other equipment peculiar to the solar system shall be eligible for tax exemption.

Statutory Authority

§§ 36-97 et seq. and 36-137 of the Code of Virginia.

Historical Notes

Derived from VR394-01-8 § 300.3.1, eff. October 10, 1978.

13VAC5-200-140. Greenhouses.

Glass, fiberglass, or other glazing materials, framing members, and foundations used to enclose south facing areas such as patios, atriums, or greenhouses for purposes of entrapping solar heated air shall be considered solar energy equipment, provided that the warm air be circulated through the principal structure by use of a permanently installed air movement system (forced or convective) and that adequate provisions have been made to prevent nocturnal heat losses and cold weather heat losses through use of insulating devices. Fifty percent (50%) of the invoice cost of labor and materials used in constructing a greenhouse or similar type structure, are to be considered solar heating equipment. The greenhouse is serving two purposes: (1) that of a solar collector, and (2) as a means of growing flowers or other plants. Equipment such as ductwork and fans used in circulating solar heated air accumulated within enclosed south facing areas such as patios, atriums, or greenhouses shall be considered solar energy equipment up to the point where such a system is integrated with a conventional heating system. Full credit will be allowed for movable insulation used to reduce nocturnal and cold weather heat losses.

EXAMPLE: Mr. Jones enclosed his south facing patio with fiberglass panels and movable insulation for the purpose of entrapping warm air which accumulates beneath the glazing. The warm air is then circulated through the residence using permanently installed ductwork and fans independent of his conventional heating and cooling system. The fiberglass, movable insulation, fans and ductwork Mr. Jones used in his solar heating system are considered solar equipment and eligible for tax exemption.

Statutory Authority

§§ 36-97 et seq. and 36-137 of the Code of Virginia.

Historical Notes

Derived from VR394-01-8 § 300.4.1, eff. October 10, 1978.

13VAC5-200-150. Thermal storage.

Devices constructed for the primary purpose of storing thermal energy collected and converted by a solar heating system shall be considered solar energy equipment. In passive solar heating systems the thermal storage is often incorporated into the building envelope in the form of thick concrete slab floors or masonry walls insulated on the exterior of the structure. If the thermal storage is serving a dual function as floor or wall of the structure, fifty percent (50%) of the cost of the floor or wall shall be considered solar energy equipment and eligible for tax exemption.

Statutory Authority

§§ 36-97 et seq. and 36-137 of the Code of Virginia.

Historical Notes

Derived from VR394-01-8 § 300.5.1, eff. October 10, 1978.

13VAC5-200-160. Movable insulation.

Movable insulation used to minimize heat loss largely caused by nocturnal radiation through areas used for direct solar heat gain during the daylight hours shall be considered solar energy equipment.

Statutory Authority

§§ 36-97 et seq. and 36-137 of the Code of Virginia.

Historical Notes

Derived from VR394-01-8 § 300.6.1, eff. October 10, 1978.

13VAC5-200-170. Shading device.

Any device designed primarily for shading a window or solar collector to prevent solar heat gain during the summer season shall be considered solar energy equipment.

Statutory Authority

§§ 36-97 et seq. and 36-137 of the Code of Virginia.

Historical Notes

Derived from VR394-01-8 § 300.7.1, eff. October 10, 1978.

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