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Radiant Barrier and Ridge-and-Soffit Venting

Sponsored in part by:

Eco-Wise globe

Eco-Wise

110 W. Elizabeth
Austin, TX 78704
(512) 326-4474
(512) 326-4496 (Fax)

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Radiant Barrier and Ridge-and-Soffit Venting Contents:

CSI NUMBERS
DEFINITION
CONSIDERATIONS
COMMERCIAL STATUS
IMPLEMENTATION ISSUES
GUIDELINES

RESOURCES

CSI Numbers:

DEFINITION:

 A radiant barrier is a layer of metallic foil that blocks radiated heat, assisting in the energy performance of a home.

A ridge-and-soffit venting system is a continuous, weather-shielded opening at the peak of the roof in combination with continuous screened openings along the eaves of the house. This system provides air movement under the roof that washes the underside of the roof with air that is exhausted out the top of the roof through the ridge vent.

CONSIDERATIONS:

A radiant barrier is used in our area principally as a cooling strategy. Buildings gain heat in three ways - conduction, convection, and radiation. A radiant barrier is useful in preventing heat gain from radiation.

Emissivity is an indication of a surface's ability to emit heat by radiation. The lower the emissivity, the better the radiant barrier qualities of a material. Emissivity is measured on a scale of zero to one. Most foil type radiant barriers have an emissivity of 0.05 or below, which means 95% of the radiant heat is being blocked.

A radiant barrier is typically placed beneath roofs in our area to block the heat gain radiating from hot roofs. Temperature reductions of 10 degrees or more are typical during peak summer days. The reduction of attic temperatures is considered less important in highly insulated attics (R-30 and higher), in respect to conduction through the ceiling. If air conditioning ductwork is located in the attic, lowering the attic temperature reduces heat gain on the ductwork.

A continuous ridge-and-soffit vent system is the most effective means to ventilate an attic. It is a passive system (no fans) and can outperform fans. The effect of pulling air from the eaves and out at the ridge is an example of the thermal chimney effect (discussed in the Passive Solar Design section).

Commercial
Status		 Implementation
Issues
technology suppliers cost financing public regulatory
Radiant Barrier
Ridge & Soffit Vent
Legend
green Satisfactory
yellow Satisfactory in most conditions
red Satisfactory in Limited Conditions
black Unsatisfactory or Difficult

COMMERCIAL STATUS

TECHNOLOGY:

Well-developed.

SUPPLIERS:

Well-developed.

COST:

Radiant barrier varies according to the type of radiant barrier material selected, with lower costs around $0.10 per square foot. Ridge vents can cost $2.00 - $3.50 per lineal foot. These costs do not include installation.

IMPLEMENTATION ISSUES

FINANCING:

Not an issue.

PUBLIC ACCEPTANCE:

There is moderate interest in radiant barriers and continuous ridge-and-soffit vents among energy conscious buyers.

REGULATORY:

Not an issue.

GUIDELINES

  • 1.0 Radiant Barrier

    • An airspace must be adjacent to the radiant barrier for it to work. (This is true for all radiant barrier applications.)

  • 2.0 Continuous Ridge-and-Soffit Venting

    •  A continuous ridge-and-soffit attic ventilation system is a passive system that is considered the most effective means of ventilating an attic. This type of venting system can operate effectively regardless of wind direction and velocity. Airflow in an attic created by this type of venting will be a continuous wash of air directly under the roof moving upward from the eaves (soffits) to the ridge.

    RESOURCES

    PROFESSIONAL ASSISTANCE

    COMPONENTS / MATERIALS / SYSTEMS

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    This document was adapted to HTML by Bill Christensen, sysop and environmental editor of Texas InfiNet, an online community for progressive information.

    Sustainable Building Sourcebook web version copyright Sustainable Sources 1994-1999.