Is Your Building Burning Money? Air Sealing in Chicagoland

Sealed vs unsealed Chicagoland multifamily building comparison showing heat and energy escaping the unsealed building
Building Energy Experts

In real life, you cannot see which building is burning money. A sealed building and a leaky one look identical from the street. Same age, same brick, same brutal January wind off the lake. The difference only shows up on the heating bill, where one owner pays far more than the other for the exact same weather.

That difference is rarely the furnace, the thermostat, or the tenants. It is the building envelope, and whether or not it is sealed. And because you cannot spot it from the curb, most owners have no idea which building they own until someone actually looks.

The hidden leak in most Chicagoland buildings

Your building envelope is everything that separates the air you pay to heat and cool from the outdoors. The walls, the roof, the windows, the doors, and every gap, crack, and penetration in between. When that envelope leaks, conditioned air escapes and unconditioned outside air pours in to replace it. Your heating and cooling equipment never gets to rest, so it runs longer, burns more energy, and wears out faster.

This is not a rare problem. The U.S. Department of Energy estimates that air leakage wastes roughly 4 percent of all the energy used in the entire country, and ENERGY STAR reports that air leakage can account for around 20 percent of a building's energy use. For a multifamily property running through a full Illinois winter and a humid summer, that is real money leaving through the walls every month.

Why a Chicago winter makes it worse: the stack effect

Taller buildings carry a built-in disadvantage, and it has a name. It is called the stack effect. Warm air rises, so in winter the air you have heated floats up through stairwells, elevator shafts, and plumbing chases and slips out through gaps near the top of the building. As it leaves up high, it pulls cold air in down low, around entry doors, foundation seams, and lower-floor windows.

The taller the building and the colder the day, the stronger that pull becomes. On a frigid Chicago morning, the pressure moving through stairwells and shafts can feel like a steady wind. That is why top-floor units overheat while ground-floor tenants say they can never get warm, and why your boiler or furnace runs nonstop trying to satisfy both ends at once. Sealing the envelope is what finally breaks the cycle.

How much money is actually escaping

The numbers tend to be larger than owners expect. Department of Energy research has found that properly sealing and tightening a building can cut heating and cooling demand sharply, which shows up as utility bill reductions in the range of 20 to 40 percent. ENERGY STAR puts the waste from leakage alone near 20 percent of total energy use.

Put that against your own building. If you spend roughly $40,000 a year heating and cooling a multifamily property, a leaky envelope could be quietly costing you $8,000 or more every year. That is not a one-time hit. It repeats every season, and it usually gets worse as caulk fails, weatherstripping crumbles, and small gaps widen into bigger ones.

Signs you own the unsealed building

You do not need a full diagnostic to suspect a problem. A few patterns show up again and again:

• Heating and cooling bills that keep climbing with no clear reason
• Drafts near doors, windows, and baseboards even when everything is shut
• Units on different floors that are never the same temperature
• Tenant complaints about cold rooms in winter and stuffy rooms in summer
• Ice dams on the roof or long icicles hanging from the eaves
• A boiler or furnace that seems to run constantly
• Top-floor units that bake in July no matter how hard the AC works

If two or three of these sound like a building you own or manage, the envelope is most likely leaking. The only real question is how much.

Air sealing and insulation are not the same thing

These two get talked about as if they are interchangeable. They are not, and confusing them wastes money. Insulation slows heat as it moves through a surface like a wall or a ceiling. Air sealing stops air from leaking through the gaps and cracks around those surfaces. Add insulation over leaky gaps and you have essentially insulated a sieve. Most Chicagoland multifamily buildings need both, done in the right order, and the only way to know that order is to measure first.

What fixing it actually looks like

A real fix starts with an energy assessment, not a sales pitch. We call it a first look, and it is low impact with no disruption to your tenants. We find where the building is losing air, often using a blower door test that gently pressurizes the building to reveal exactly where it leaks. From there, the work usually includes:

• Sealing gaps and penetrations in the attic and roofline, where stack-effect losses are greatest
• Sealing rim joists, foundation seams, and utility penetrations near the base of the building
• Weatherstripping and sealing doors, windows, and common-area entries
• Sealing and testing any ductwork that runs outside conditioned space
• Adding or upgrading insulation so the newly sealed envelope holds its temperature

Done in the right sequence, these steps turn a building that fights its own heating system into one that works with it.

The payoff goes beyond the utility bill

Lower bills are the headline, but they are not the whole story. A sealed building is more comfortable, and comfort is what keeps good tenants renewing. It holds an even temperature floor to floor, so you field far fewer freezing-unit calls. It manages moisture better, which reduces the damp conditions that lead to mold, along with the complaints and remediation costs that follow. And because the equipment is no longer running flat out, it lasts longer and needs fewer repairs. For an owner or property manager, that is lower operating cost and fewer headaches inside the same project.

Rebates can cover much of the cost

Here is the part that surprises owners most. You may not pay full price, and some qualifying properties pay almost nothing. Illinois utility efficiency programs through ComEd, Nicor Gas, Peoples Gas, and North Shore Gas offer rebates and incentives for air sealing and insulation, and qualifying multifamily properties of three or more units can receive deeply discounted or even no-cost upgrades.

Timing matters right now. The federal Section 25C efficiency tax credit expired at the end of 2025, so the dependable path today is the utility programs, and the good news is that Illinois funding is live and active for the 2026 to 2029 cycle. These programs run on limited budgets that can fill up, so it is worth checking your eligibility while incentives are flowing. Working with a BPI-certified contractor that is approved for these programs is what makes sure the work qualifies and you capture the largest rebate available.

Find out which building you own

You can keep guessing, or you can know. A free multifamily energy assessment from Building Energy Experts shows you exactly where your building is leaking, what it is costing you, and which utility rebates you qualify for, all before you commit to anything. We are an ENERGY STAR partner and a BPI-certified contractor serving multifamily, commercial, and residential properties across Crystal Lake and the greater Chicagoland area.

Same weather does not have to mean the same bill. Book your free energy assessment and find out whether your building is sealed, or quietly burning money.

Frequently asked questions

How do I know if my building actually needs air sealing?

If you see climbing bills, drafts, uneven temperatures floor to floor, or constant comfort complaints, those are classic signs of a leaky envelope. A blower door test during your assessment confirms it and pinpoints exactly where the leaks are.

How much can air sealing really save?

Industry data points to energy savings in the range of 20 to 40 percent once a building is properly sealed and insulated. Your actual number depends on the size, age, and current condition of the building, which is what the assessment measures.

Is my building too old to bother?

Usually the opposite is true. Older Chicagoland buildings often hold the biggest and cheapest savings, because they went up before modern air sealing and insulation were standard. Age is frequently the opportunity, not the disqualifier.

Are the rebates really free money?

Qualifying multifamily properties can have a large share of the cost, and in some cases the full cost, covered by Illinois utility programs. Eligibility depends on your utility territory and building, which we confirm during the assessment before any work begins.

Will sealing the building make the air stuffy?

No, when it is done correctly. Good air sealing is paired with proper ventilation, so you control fresh air on purpose instead of relying on random leaks that also waste energy.