Written by Eric Gans
I have completed over 2000 Home Performance with ENERGY STAR® home energy audits in Maryland, and I like to write about my experiences.
One of the most common calls I get from homeowners goes something like this:
"My heat is running… but the house still feels cold."
Sometimes it’s a single room.
Sometimes it’s a basement.
But in this case, it was something more unusual.
The entire middle level of a townhouse was cold.
The homeowner had lived in the home for nearly 20 years and recently started noticing something troubling. Even with the thermostat set to 65°F, the living level rarely felt comfortable. To compensate, he had placed three electric space heaters around the room.
The heaters helped a little, but his winter utility bills were climbing over $400 per month.
That’s when he scheduled an energy audit.
What Is an Energy Audit?
An energy audit is essentially a diagnostic investigation of how a home loses energy.
Instead of guessing at the problem, we use a combination of:
The goal is simple:
Find where energy is escaping and identify the most cost-effective ways to fix it.
Many homeowners assume the problem is something obvious, like windows or HVAC equipment.
But most of the time, the real issue is hidden.
First Clue: The Stack Effect
Within minutes of walking through the home, one thing became clear.
This house was experiencing a classic building science phenomenon called the stack effect.
Warm air naturally rises.
When warm air escapes through the top of the house, it creates a pressure imbalance that draws cold air into the lower parts of the structure.
Think of the house like a chimney.
Heat escapes from the top.
Cold air gets sucked in from the bottom.
The result?
- Cold floors.
- Drafty rooms.
- And heating systems that seem like they can never catch up.
But to confirm the theory, we needed to check the attic.
What We Found in the Attic
The attic told the whole story.
As soon as I climbed through the attic hatch, several issues became obvious.
1. Missing Insulation Above the Bathroom
Because the home has vaulted ceilings, the roofline slopes upward across the house.
However, the bathroom ceiling below is only about 8 feet high.
This created a large hidden cavity above the bathroom where insulation had been installed incorrectly.
Instead of insulating the vertical wall separating the attic from the house, the insulation had simply been laid across the floor joists.
The result was a large, uninsulated pocket directly above the living space.
Warm air from the house was escaping directly into this space.
2. A Large HVAC Chase Open to the Attic
Next we discovered a major air leakage pathway.
The ductwork from the furnace travels from the basement up through a vertical shaft (called a chase) into the attic.
Unfortunately, this chase was completely open.
That means heated air from the home could freely travel up this pathway and escape into the attic.
Imagine cutting a hole in your ceiling and leaving it open all winter.
That’s essentially what was happening here.
3. Insulation Installed… But Not Doing Its Job
The attic did contain fiberglass insulation.
However, insulation only works properly when it sits on top of a sealed air barrier.
Without air sealing, insulation behaves like a sweater in the wind.
Air simply blows through it.
In several places, insulation had shifted or been installed incorrectly, leaving gaps where heat could escape.
The Blower Door Test
To confirm the problem, we ran a blower door test.
This test uses a large calibrated fan installed in the front door to depressurize the house.
When the house is under pressure, outside air gets pulled through every crack and gap in the building envelope.
That makes hidden air leaks visible.
During the test, we observed significant airflow entering through:
-
attic bypasses
-
rim joist areas
-
framing penetrations
This confirmed that the home was losing a significant amount of heat through uncontrolled air leakage.
Why Space Heaters Were Not the Solution
The homeowner had been using three electric space heaters to warm the middle floor.
Each heater produces about 5,100 BTU/hr.
Combined, the three units provide about 15,000 BTU/hr of heat.
But electric resistance heating is expensive.
In fact, electric space heaters can cost three times as much per unit of heat as natural gas heating.
So while the heaters provided temporary comfort, they were actually increasing overall energy costs.
The real solution was to stop the heat loss, not add more heat.
The Real Fix
The good news is that problems like this are usually fixable.
The most effective improvements for this home included:
1. Attic Air Sealing
Sealing the attic floor and all penetrations to stop warm air from escaping.
2. Closing the HVAC Chase
Install an air barrier around the duct chase to prevent heated air from escaping into the attic.
3. Correcting the Knee Wall Insulation
Properly insulating the vertical knee wall around the bathroom cavity.
4. Sealing Rim Joists
Air-seal accessible rim-joist areas along the exterior walls.
These improvements help transform the house from a leaky chimney into a controlled, efficient structure.
Why Energy Audits Matter
Many homeowners assume the solution to comfort problems is:
But in many homes, the real problem is the building envelope.
Energy audits identify the low-hanging fruit — the improvements that deliver the greatest benefit for the lowest cost.
According to the U.S. Department of Energy, air sealing and insulation improvements can reduce heating and cooling costs by about 15%.
But just as important, they make homes far more comfortable.
The Takeaways
This townhouse had a good heating system.
The equipment was not the problem.
The house simply had a few hidden pathways allowing heat to escape.
Once those pathways are sealed and the attic insulation is corrected, the middle floor should feel dramatically different.
And those space heaters?
They can finally be retired.
If you’ve ever wondered why your home feels cold even when the heat is running, an energy audit might reveal the answer.
Sometimes the problem isn’t the heating system at all.
Sometimes the house just needs a little help holding onto the heat it already has.
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