Risk Management > Building Systems > Envelope (Thermal and Moisture)

Related Building Risks> Roof and Gutter Exterior WallsOpeningsFoundation and DrainageStructureElectricalPlumbing
Related Risks > Environment  • WaterPhysical ForcesCorrosionNatural LightPollutants

Insulation between joists, attic, Isaac Bell House.
• Blown-ininsulation was not always installed in accordance with standards; it may be inadequate; it may not have adequate — or any — vapor barrier; it has been moved by rodents; it may be adjacent to electrical wiring and units.

Attic, Isaac Bell House.
• This thermostatically-controlled fan helps to regulate the environmental conditions of the attic. Make sure all attices are adequately ventilated.
West window, second floor, The Elms.
• Many windows (see Openings) are inadequately weatherstripped: an operation needs as part of their repair and conservation.


The building envelope included other interrelated systems. It includes the structural elements that enclose a building (walls, roofs and foundations); materials within the envelope systems (such as insulation adn vapor barriers).  The building envelope provides the thermal barrier between the indoor and outdoor environment, and its elements are the key determinants of a building's energy requirements that result from the climate where it is located.

Building Envelope Components: The building envelope separates the outside from the inside. The building envelope is the structure that separates the building occupant from outdoor conditions. It's a major factor in determining a building's energy use. The components that make up a building envelope include:

  • Fenestration: Windows, Doors and Skylights
  • Insulation
  • Foundation
  • Wall Systems
  • Roofing

Building Envelope Components, Building Technologies Program, Office of Energy Efficiency & Renewable Energy,  U.S. Department of Energy


Incomplete documentation, analysis and understanding of the construction of exterior wall systems; the dynamics of infiltration adn exfiltration of air; the penetration of moisture from the exterior and the migration of moisture from the interior; the dynamics between related building systems.


Document and analyze select, yet representative, areas of exterior walls to ascertain their constriction, performance and condition.

"Moisture Buildup : Under certain conditions, water vapor can condense within the building envelope. When this occurs the materials that make up the wall can become wet, lessening their performance and contributing to their deterioration. To prevent this, place a vapor tight sheet of plastic or metal foil, known as a vapor barrier, as near to the warm side of the wall construction as possible. For example, in areas with meaningful heating loads, the vapor barrier should go near the inside of the wall assembly. This placement can lessen or eliminate the problem of water-vapor condensation.

"Weatherstrip all doors and place sealing gaskets and latches on all operable windows. Careful detailing, weatherstripping, and sealing of the envelope are required to eliminate sources of convective losses. Convective losses occur from wind loads on exterior walls. They also occur through openings around windows and doors and through small openings in floor, wall, and roof assemblies. Occupants can experience these convective paths as drafts. Older buildings can prove to be a source of significant energy loss and added fuel and pollution costs. Inspect weatherstripping and seals periodically to ensure that they are air-tight.

"Specify construction materials and details that reduce heat transfer. Heat transfer across the building envelope occurs as either conductive, radiant, or convective losses or gains. Building materials conduct heat at different rates. Metals have a high rate of thermal conductance. Masonry has a lower rate of conductance; the rate for wood is lower still. This means that a wall framed with metal studs compared to one framed with wood studs, where other components are the same, would have a considerably greater tendency to transmit heat from one side to the other. Insulating materials, either filled in between framing members or applied to the envelope, resist heat flow through the enclosing wall and ceiling assemblies."

Moisture Buildup within the Envelope, , Building Technologies Program, Office of Energy Efficiency & Renewable Energy,  U.S. Department of Energy

Undertake infra-red thermography of exterior walls and roofs to analyze air and moisture movement.

As required, seek means to provide circulation of closed cavity walls, attic spaces, basement spaces, and other area affected by moisture.

Make a commitment giving higher priority to reducing energy costs and protecting the environment. Monitor and measureme results to provide feedback on whether investments are producing the anticipated benefits.


Canadian Building Digest, National Research Council Canada

Building Envelopes Program (BEP), Oak Ridge National Laboratory (ORNL)

Building Envelope Components, Building Technologies Program, Office of Energy Efficiency & Renewable Energy,  U.S. Department of Energy

International Performance Measurement and Verification Protocol (MVP)

The International Performance Measurement and Verification Protocol (MVP) provides an overview of current best practice techniques available for verifying results of energy efficiency, water efficiency, and renewable energy projects in commercial and industrial facilities.

Download (free registration required) the following:

  • Volume I - Concepts and Options for Determining Energy Savings
  • Volume II - Concepts and Practices for Improved Indoor Environmental Quality
   © 2002-03 Philip C. Marshall and Preservation Society of Newport County