WHAT IS COMPARTMENTALIZTION?

Besides being a long word that is difficult to say, compartmentalization is providing a robust separation between different spaces within a building including a separation between living or occupied spaces and interstitial spaces like framing cavities and shafts.  Compartmentalization is important to controlling the flow of odors, air, smoke, airborne contaminants, and pests between units and between units and other spaces within the building. 

An airtight enclosure around an apartment unit is needed to prevent airborne contaminants, smoke and odors in one apartment from spreading to neighboring apartments.   Likewise, and airtight enclosure around an apartment (or other space) will also prevent the ingress of airborne contaminants, smoke and odors from other parts of the building and building cavities.  With an airtight enclosure it is easier to control odors and other airborne contaminants within an apartment using ventilation.  Compartmentalization, therefore, is very important to indoor air quality.

An effective air barrier also supports pest control.  Generally, if air can’t leak through an enclosure, then it would be hard for pests to gain access to the space.  Holes at the base of a wall behind appliances and around pipes that penetrate through a wall provide opportunities for pest entry.  These also allow air, and anything carried in the air, to leak into the apartment.

The airtightness of individual apartments is also key to controlling air leakage for the overall building.  This is because compartmentalization prevents accumulation of forces acting on a building that move air into or through the building.  For example, the ground floor of a multi-story building would be less subject to drafts, and out-swinging doors would be easier to open in cold weather, if a building is well compartmentalized.  In this way, compartmentalization impacts comfort and energy performance.

Airtight enclosures also support the operation of conditioning and ventilation systems by making it easier to control the pressures and direction of air flow between spaces.  For example, if we want a corridor to be slightly pressurized relative to apartments so that odors from apartments do not migrate into the corridor, then it helps to have an airtight enclosure of that corridor space.  The more airtight an enclosure the less airflow is needed to pressurize or depressurize the space with the enclosure.  Therefore, with better airtightness it is possible to maintain the desired pressure relationships while using less energy and installing smaller ducts and equipment.  Ventilation, heating, cooling and dehumidification systems are more effective and are better able to meet set points within spaces if those spaces are well compartmentalized. 

What about Make-up air?

But wait a minute!  Don’t we need to allow fresh air into apartments so people can breathe!?

Exactly.  We want fresh, clean, good quality air to be delivered to people in our buildings.  That means we cannot allow the air to be leaking in from building cavities where rodents may live or have lived (expired), from under sinks, through maintenance closets with harmful chemicals and pesticides, from the apartment of neighbor who smokes, from the trash room...  To be able to have good quality, fresh air, we need to know where it is coming from.

Compartmentalization and Quality Assurance

Airtightness is sometimes regarded as a proxy for overall construction quality. The airtightness of a building and of apartments within buildings are properties that can be measured. 

The common method for testing and verifying the airtightness is through the use of a calibrated fan and pressure measuring gauges.  In the construction industry the common term for this testing apparatus is a “blower door”.  The widespread availability of blower door equipment and qualified technicians allows for quantitative airtightness targets to be established for new construction and renovation projects.

POAH encourages establishing a pre-renovation baseline airtightness for apartments and then measuring achievement at improving airtightness as various stages of the project.

Blower door diagnostics can also be used to evaluate specific air sealing measures and pin-point those which are most effective.  Thus, in a project involving repetitive scope or renovation work in a large number of similar apartments, it would be worthwhile to use blower door diagnostics to refine the compartmentalization scope to be included with the renovation project.