One failed unit is a fix. Twenty failed units are a schedule problem. On production builds, air leaks often repeat from one floor to the next because the same detail gets missed the same way. Party walls, floor lines, and shaft penetrations tend to cause most of the trouble. That’s why multifamily ACH50 air sealing depends more on sequencing than on extra caulk at the end.
In this blog, you’ll learn where stacked and townhome envelopes usually leak and how to order air-sealing work between trades. You’ll also see when to verify before drywall and which checkpoints keep retests off your calendar. Keep reading to build a plan your crews can repeat on every building.
Every unit is its own test zone. When we run a blower door on an apartment, air can leak outside, but it can also move into the unit next door, above, or below. Most unguarded unit tests count all of that leakage. As a result, shared walls and floors carry as much weight as exterior walls.
Targets depend on your code edition and climate zone. Some newer editions offer an alternative metric based on enclosure area for attached units. Confirm the exact target and any sampling rules with your AHJ before framing starts. Strong production-build airtightness comes from treating every unit boundary as part of the air barrier.
Good apartment air sealing sequencing follows the trades. Seal top plates, rim joists, and bottom plates right after framing and before MEP rough-in crowds the cavities. Once plumbers, electricians, and HVAC crews finish, seal every penetration they leave behind. Do this before insulation goes in.
Stacked buildings share the same weak spots. Most stacked unit air leakage shows up at floor lines, in plumbing and duct chases, around sprinkler lines, and behind tubs set against exterior or party walls. Install air barrier backing behind tubs before they’re set.
Townhome air sealing adds its own traps. Watch the attic gap at the top of party walls, kneewalls at bonus rooms, and ceilings over tuck-under garages. Assign each detail to a named trade so nothing falls between crews.
Pre-drywall is your cheapest chance to fix a leak. Once walls close, every repair means cutting board and pushing back finishes. Schedule a visual air-sealing check on each building after rough-in and air sealing are done, before insulation covers the work.
On the first units in a new building, run a pre-drywall blower door test. Those results show whether your sequence works before you repeat it 50 times. Adjust the scope, then lock it in for the rest of the site.
Multifamily blower door volume testing runs best on a set path, floor by floor or building by building. That keeps our crew moving and gives you fast unit-level results. When a unit fails, check the same detail in nearby units right away. The pattern usually repeats, and catching it early prevents a round of retests.
These checkpoints turn air sealing into a repeatable routine. Build them into your schedule from the start.
List every seal each trade owns, from top plates to chase penetrations. Share it at the preconstruction meeting and post it on site. Clear ownership stops the “I thought they had it” gaps that show up in failed units later.
Test one representative unit before drywall on every new building. Pick a corner or top-floor unit, since those carry the most exterior exposure. If it passes with room to spare, your sequence is working. If it’s close, adjust before crews move on.
Confirm power is live, mechanical systems are fully installed, and intentional openings are ready to seal. Walk a few units before test day. A short readiness check prevents wasted trips and keeps final testing on a steady pace.
Air Tight Solutions is a leading provider of energy efficiency testing and compliance services for new construction. Our BPI-certified team knows IECC requirements from 2009 through 2021, and we’ve tested units on garden-style complexes, townhome rows, and affordable housing sites. We help builders plan multifamily ACH50 air sealing around the way their crews actually work.
We see ourselves as part of your team. We review your details, test benchmark units early, and flag repeat patterns before they spread. Our reports stay organized by building and unit, so closeout moves fast. Pair your envelope tests with our multifamily duct leakage testing for one coordinated testing plan.
Yes. We can usually schedule testing for the next day. On larger sites, we’ll build a testing calendar around your phase and turnover schedule.
Each unit needs working power, and all mechanical systems must be fully installed. Air handlers, exhaust fans, and registers should be in place before we arrive.
Yes. The base price includes the test and all required documentation. You receive organized results for each unit that your team can share with the AHJ.
We don’t pull permits, but you can submit our documentation directly to the county for final inspections. That keeps your closeout process simple.
Pricing depends on building size, unit count, and test complexity. Contact us to schedule, and we’ll send a custom quote that includes detailed reporting.