Compartmentalization in multi-unit (multi-family) residential buildings

Published on May 03, 2017

Not surprisingly, in a large residential building, the last thing anyone wants is air leaks between the individual units. This is especially noticeable with cigarette smoke, as the second-hand smoke travels to all of the adjacent apartments. Also noticeable with cooking odours, these smells tend to linger and often remain in the air. To be sure, these are annoyances that are part of living in a multi-family residential building – but it doesn’t have to be that way.

From a building science point of view, there are ways to alleviate air leakage between units, and to stop the migration of smells, odours, and even sound. Sealing up gaps and openings in between units is the answer – it’s often referred to as “compartmentalization.” And while sealing up a unit is a good remedy, proper ventilation must not be overlooked. Simply put, air tightness must work in tandem with air ventilation in order to ensure optimum performance.

Barrier Sciences Group offers unit compartmentalization for condo owners, apartment dwellers, and low-rise multi-unit residential buildings. The benefits are far-reaching for every occupant:

•  reduced transmission of contaminants (and germs)
•  reduced spreading of odours (cooking and smoke)
•  increased capacity for fire safety (and containment)
•  reduced drafts for improved comfort in the unit
•  diminished sound diffusion from one unit to another

In larger residential buildings, a blower door test of an individual unit is often one of multiple approaches that can be used to assess airtightness (e.g. alternates being testing the entire building). Barrier Sciences Group does this type of unit testing using blower door tests. Testing individual units provides different and complimentary data to that of an overall building test. The blower door test is an excellent tool in determining the rate of air leakage in a unit. By identifying the source and scope of the leakage, a viable remedy can be considered.

In a single family home, air leakage is usually measured with respect to the exterior building envelope – professionals refer to this as “exterior leakage.” On the other hand, in a multi-family building, there are many air leakage pathways other than the exterior. A proper blower door test on an individual unit can measure air leakage from the outside as well as from unit to unit (“inter-unit”. Typically, multi-family buildings have a lot of “inter-unit” leakage.

Air leakage testing is technically challenging and time-consuming – it requires highly experienced operators, a comprehensive plan of attack, and equipment that can deliver accurate information and data. Good test results will quantify air leakage from the exterior walls, floors, and ceilings of a particular unit. With an experienced technician on hand, single-unit tests can set the stage for potential remedies that can correct and substantially improve air tightness.

Compartmentalization in multi-unit residential buildings is valuable for residents, landlords, and building owners alike. Even in terms of “fire-stopping”, preventing air leakage unit to unit makes abundant sense. A well-sealed apartment or condo can very effectively stop the passage of smoke and hot gases between individual resident units. At the same time, poorly sealed fire separations (even between floors) can spell disaster for unit owners and adjacent units.

Above and beyond the benefits of air sealing, ventilation must be incorporated into the remedy package when it comes to compartmentalization. This is particularly relevant in taller buildings because of the inherent air pressure differences and opportunities for air infiltration. Indeed, the well-sealed, well-ventilated unit provides a number of benefits with regard to indoor air quality – and often a serious improvement to built in central ventilation systems.

In many multi-family buildings, including newly built, it’s not unusual to find ventilation systems that are inadequately designed and installed. Air leakage is often a big problem, and therefore airflow from unit to unit could be uneven and imbalanced. Unless the ventilation system is well designed, and the ductwork well sealed, the tendency is for some units to get more fresh air than others – not that individual residents have an opportunity to compare.

Today, with so much development and construction of large multi-unit buildings, tenants have much greater expectations overall – and indoor comfort is climbing to the top of the list. Builders and contractors are therefore shifting focus on compartmentalizing individual units, allowing the residents to have more control over their indoor environment. As such, reduced air leakage and improved ventilation is less stressful on mechanical heating and cooling.

Whatever the approach to air sealing, industry research shows that compartmentalization in multi-unit buildings is highly effective in managing air movement, while controlling smoke, fire, odour, and sound. At Barrier Sciences Group, the focus with unit compartmentalization allows individual living units to operate more independently, and limit any external influences that may have negative impact on efficiency or comfort of individual living spaces.

As more and more people flock to multi-unit buildings, National Building Codes will require more stringent air sealing and air exchange specifications. The key, of course, is to create and develop new and improved techniques for air tightness, but at the same time address fire codes, sound issues, and even moisture problems. And although resident comfort is surely a priority, building owners must also have their priorities and addressed and delivered.

Overall, air sealing individual units can be a very cost-effective strategy, particularly with new construction, but as well when retrofitting existing multi-unit buildings. Besides the benefits of comfort and well-being, achieving higher energy efficiency for the entire building translates into a capital investment that is worthwhile. With the right products and a workable strategy, Barrier Sciences Group can deliver significant and measurable outcomes.

As building envelope specialists, Barrier Sciences Group offers every client the professionalism of an accomplished team of seasoned experts – from energy auditors to engineers, to technologists. When it comes to compartmentalization, BSG assesses the indoor environment of a given space and determines the added value of various retrofit solutions. Implementing incremental retrofits, BSG delivers cost effective remedies for building performance.

For more information, visit the BSG website at or contact a BSG expert toll-free at 1-866-333-3920. From low-rise MURBs to high-rise MURBs, building owners are in good hands with the professionals at Barrier Sciences Group.


The Canada Greener Homes Grant offers home efficiency renovation grants up to $5,000.

Homeowners Canada-wide are eligible for the Canada Greener Homes Grant, announced on May 27, 2021. This new incentive offers up to $5,000 in grants for home efficiency retrofit renovations, plus a $600 reimbursement for pre- and post-work EnerGuide evaluations. Eligible retrofit scopes include home insulation, heating, doors, windows, photovoltaic solar panels, resiliency measures, and thermostats.

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