Open Cell Spray Foam for Multifamily Buildings

Open cell spray foam is a two-component polyurethane sprayed in place at roughly half a pound per cubic foot. Its cells are interconnected rather than sealed, which makes the cured foam soft, vapor permeable, and rated at R-3.5 to R-3.8 per inch. Because it expands after it hits the substrate, it fills the shape it is sprayed into rather than a shape someone cut it to.

That is why it earns a place in older Chicagoland buildings: interior partitions with blocking and uneven bay widths, vaulted and cathedral ceilings, mechanical chases carrying pipe and conduit between floors, and the rough openings around windows and doors.

The sound benefit is real, and it is narrower than the word soundproofing suggests. Filling a partition cavity reduces airborne noise traveling through that cavity. It does not change noise moving through shared framing, the floor and ceiling junction, or a duct serving two units. If noise is why you are calling, ask for the whole assembly to be reviewed.

• R-3.5 to R-3.8 per inch, at roughly half a pound per cubic foot installed density
• Seals and insulates in the same pass, including around pipe, conduit, and irregular framing
• Vapor permeable, so vapor control in the assembly has to be designed rather than assumed
• Lower installed cost per board foot than closed cell spray foam
• Where it fits: interior partitions, vaulted and cathedral ceilings, mechanical chases, complex framing

The rig is truck or trailer mounted and has to park within hose reach, so the crew walks the access route with your maintenance contact before the first spray day. The substrate has to sit within the temperature range on the product data sheet, which in winter can mean temporary heat before anything is sprayed.

The sequence on a foam job runs the same way. Mask and cover what is not getting foam, set containment at the doorway, confirm the cavity is dry and clear. The foam goes on in passes to the thickness the scope calls for, sets quickly, then gets trimmed flush to the face of the framing with a saw so drywall sits flat. Trimmings are bagged and hauled out.

One detail surprises owners. Building codes generally require foam plastic to be separated from the interior of the building by an approved thermal barrier, most often half inch gypsum board, with limited exceptions where an ignition barrier or an approved coating rated for the application is accepted instead. Foam in a mechanical chase does not simply get left exposed. We confirm which method applies with the code official having jurisdiction, then name it in your scope along with who is responsible for installing it, before scheduling.

Spray foam affects the people living in the building more than most insulation work, so we are direct about it. The area being sprayed has to be empty of occupants during application and through the re-occupancy period the manufacturer publishes for that product. The crew ventilates the space mechanically during and after. There is an odor while spraying that fades as the space is ventilated.

In practice, foam inside an apartment gets scheduled at turnover, during a rehab, or in a unit the resident can be out of for the day. Attics, chases, ceiling assemblies, and unoccupied common areas are easier, because containment keeps the work away from people.

You get the re-occupancy time in writing before scheduling, not after. We work one area at a time, and we coordinate with the resident notice your office sends. The calendar is driven by prep, masking, and unit access far more than by the spraying itself.

You receive a written scope naming locations by unit, floor, or assembly, the product installed, and the thickness or coverage required, plus available photographs of each cavity before and after. Once drywall closes a wall, those photographs become part of the record of what is behind it.

Where foam is part of an envelope scope, diagnostic testing may be included if it is appropriate for the building and required by the scope or program. We do not promise a whole-building reading when the test would not represent the work performed.

What we need from you:

• Parking and a hose route for the spray rig
• A unit access schedule, and the resident notice that goes out under your letterhead
• A decision on who closes the walls and provides the required thermal barrier
• Heat in the space if the substrate is below the product's minimum temperature
• Disclosure of any active roof or plumbing leak, knob-and-tube wiring, or known asbestos or vermiculite

Building Energy Experts is an authorized contractor for the ComEd, Nicor Gas, Peoples Gas, and North Shore Gas efficiency programs. Insulation and air sealing measures generally require pre-approval before work starts. That is a common way an owner loses an incentive: the work gets done first, and there is nothing left to apply for.

The paperwork. We file it. Pre-approval, the documentation the program wants during the project, and the final submission afterward. For a foam measure that file is built from thickness, area, and the product's published R-value per inch, which is why the before and after photographs and the product data sheet get collected while the cavity is still open. Depending on the program and the address, foam work may be counted under an insulation measure, an air sealing measure, or both. Some upgrades are available at no cost for qualifying properties.

No web page can decide whether your building qualifies. That takes a property-specific review of the address, the utility accounts, the building type, and current program rules.

Open cell foam has a narrow lane, and putting it in the wrong assembly costs money or creates a moisture problem. Open cell foam is vapor permeable, so spraying it directly against roof sheathing in a cold climate needs a designed vapor control strategy, not a default assumption. And any active roof or plumbing leak gets repaired first, because foam will hide the evidence without solving the cause.

Otherwise the honest answer is a different material.

• Rim joists, crawl spaces, and basement walls: closed cell foam handles the moisture drive and brings its own vapor retarder at the thickness the scope calls for
• A closed wall cavity you would rather not open: dense-pack cellulose installs through small access holes with no tear-out
• An attic floor where cost per square foot decides it: blown cellulose usually reaches the same R-value at a lower material cost
• A unit that cannot be vacated for the spray and the re-occupancy window
• Any assembly with suspected asbestos or vermiculite that has not been assessed yet