Building cavities are the empty or interstitial spaces found within the structure of a building, often located within walls, floors, or ceilings.
Specifically, cavities (or interstitial spaces) within walls are sometimes utilized as pathways for supply- or return-air in building systems. These spaces are inherent parts of the building's construction, typically formed by framing elements like studs, joists, or rafters.
Understanding Building Cavities
In the context of building mechanics and air distribution, these cavities serve as channels for air movement. However, using these structural spaces has implications:
- Air Connection: As highlighted in the reference, these cavities often create a connection of inside air with outside air from an attic or crawlspace. This means that air flowing through these pathways can be exposed to outdoor conditions or air from unconditioned spaces.
- Airtightness Challenges: It is notably very difficult to make such cavity spaces airtight. This lack of airtightness can lead to:
- Air Leakage: Uncontrolled air movement between conditioned indoor spaces, unconditioned spaces (like attics or crawlspaces), and the outdoors.
- Energy Loss: Heated or cooled air can escape, and unconditioned air can enter, increasing energy consumption for heating and cooling.
- Moisture Issues: Air leakage can carry moisture, potentially leading to condensation within the wall cavity and promoting mold or material degradation.
- Reduced System Performance: The intended airflow for heating or cooling systems can be compromised by leaks in these cavity pathways.
Practical Considerations
When building cavities are used for air distribution, it's crucial to be aware of these challenges. Best practices in modern construction and HVAC design often prefer dedicated ductwork sealed to be airtight, rather than relying on building cavities, to ensure efficient and controlled airflow.
Understanding the nature and limitations of building cavities is essential for proper building performance and indoor air quality.
