Why is my upstairs so much hotter than downstairs even with AC on in Lake Stevens?

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What's actually happening

Heat Rises and Your AC Is Losing the Battle: The Duct Problem Most Techs Miss

Your AC is on.

Thermostat is set to 70.

Downstairs feels fine.

Then you walk halfway up the stairs, and you feel it immediately.

Upstairs is hotter. Bedrooms don't cool. Air feels different.

This is one of the most common things we see in Lake Stevens, especially in older homes around Old Town near North Lakeshore Drive and Hartford, where many houses were originally built in the 1920s and 1930s.

And most of the time, the AC unit isn't the problem.

Before you spend thousands

Before You Spend Thousands: Try These First

If your upstairs is 5–10 degrees hotter, don't guess, start here.

Before you spend thousands on a new AC unit, try these 5 local "Old Town" fixes that most sales techs won't tell you about:

Here is how you actually fix those specific red-flag issues without just calling a salesperson:

1
The "Single Thermostat" Trap (The #1 Culprit)

In most 1920s–1930s homes in Old Town, the thermostat is downstairs. Once the living room hits 70°F, the AC shuts off, while your upstairs bedrooms are still at 78°F.

The DIY Fix

Buy a Smart Thermostat with Remote Sensors (like Ecobee or Nest). Put the main unit downstairs and a sensor in the hottest upstairs bedroom. Tell the system to "average" the temperatures or prioritize the upstairs sensor during sleep hours. This forces the AC to stay on until the upstairs is comfortable.

⚠️ The "Ice Box" Disclaimer

Because you're forcing the AC to stay on until the upstairs is cool, your downstairs will likely plummet to 62°F (the "Ice Box Effect"). Since 1920s ductwork can't "aim" the air, it goes everywhere. This isn't an efficiency fix, it's a comfort fix, so expect your bill to rise as the unit runs longer to fight that 150°F attic heat.

⚡ Pro-Tip: The "Better Together" Strategy

To make this work without freezing out the ground floor:

  • Partial Block: Use magnetic vent covers to partially close a few downstairs vents, forcing more air pressure upstairs.
  • Insulate First: If you combine this with the R-49 attic insulation mentioned above, the upstairs won't get as hot in the first place, and your AC won't have to work nearly as hard.
2
The "Return Air" Ghost (Why the heat stays trapped)

Older homes were built for heating, not cooling. They usually have vents that push air in, but not enough vents to pull hot air out of bedrooms. If you close a bedroom door, you create a "pressure box" where cold air can't get in because the hot air has nowhere to go.

The DIY Fix

The "Door Gap" test. If your upstairs bedroom feels significantly hotter with the door closed, you have a return air issue. Keep the doors open, or install "Transfer Grilles" (vents in the wall or door) to let the hot air escape to the hallway where the main return vent usually is.

3
The "Manual Damper" Hack

Many Lake Stevens HVAC systems actually have manual levers on the ductwork near the furnace (usually in the crawlspace or garage).

The Fix

Look for small metal handles on the large round pipes. In summer, partially close the dampers leading to the downstairs vents and fully open the ones going upstairs. This physically forces more cold air to the second floor.

Note: Never close a damper 100% or you might freeze your AC coils.

⚡ Pro Tip

Mark your "Winter" and "Summer" settings on the pipes with a Sharpie so you don't forget where they go when the Lake Stevens snow starts falling.

Manual Damper: Winter vs Summer
WINTER main duct handle open (parallel to pipe) heat flows down W SUMMER main duct handle angled (partially closed) cool air goes up S CRAWLSPACE / GARAGE Look for the metal handle on the large round pipe SHARPIE MARKS W = Winter position S = Summer position Mark with Sharpie so you always know which is which
4
The Attic "Radiator" Effect

In those Old Town cottages, the attic insulation is often original (wood shavings or thin fiberglass) or nonexistent. The roof gets to 150°F, and that heat radiates through your ceiling like a giant heating pad.

The Local Solution

Before spending $10k on a new AC, spend $1,500 on blown-in cellulose insulation in the attic. Aim for "R-49" or "R-60" depth. In Lake Stevens, Snohomish PUD often offers rebates that can cover a chunk of this.

5
The "Lake Stevens Humidity" Problem (Why AC feels "Weak")

Since we live near the water, our "hot" days are often muggy. If your AC fan speed is set too high, the air moves across the cooling coils too fast to drop its moisture.

The Professional Fix

Ask an HVAC tech to lower the fan blower speed for the cooling cycle. Slower air stays on the cold coils longer, removing more "lake humidity" and making 72°F feel like 68°F.

Which of these fits your house best? For example, do you still have original lath-and-plaster walls, or has the house been remodeled with drywall?

The real cause

This Isn't a Broken AC: It's How These Homes Hold Heat

Heat rises. That part doesn't change.

But in Lake Stevens homes, especially older ones, it gets worse.

Your roof absorbs direct sun all day. The attic heats up and acts like a radiator. That heat pushes down into the second floor while warm air from the rest of the house naturally rises and collects upstairs.

So before your AC even starts doing its job, your upstairs is already hotter.

Now the system has to fight against that.

The thermostat trap

Why Your Thermostat Says It's Fine, But Your Upstairs Isn't

Your system is doing exactly what it's told to do.

The problem is what it's being told.

Most homes here run a single thermostat, usually downstairs.

The downstairs cools quickly. The thermostat hits the set temperature. The system shuts off.

Meanwhile, upstairs never actually reaches that temperature.

So you end up with a system that works… just not for the part of the house you actually need cooled.

Airflow

The Air Isn't Reaching Where You Need It

Even when the system is running, the air doesn't always make it upstairs properly.

In older Lake Stevens homes, especially in Old Town and Hartford, ductwork was never designed for balanced cooling.

In some cases, air is lost inside wall cavities before it even reaches the second floor.

Long duct runs reduce pressure. By the time that air gets upstairs, there's not enough of it left to do the job.

What most techs miss

The Part Most People Miss, And Most Techs Don't Check

Upstairs heat doesn't just need to be cooled.

It needs to be removed.

A lot of these houses have one return vent upstairs, usually in a hallway.

That means:

Bedrooms trap hot air
Air can't circulate properly
The system can't pull that heat out

So even when cool air is coming in, the heat isn't leaving.

Book a Same-Day Diagnosis in Lake Stevens

Clear answer before any work. No pressure.

Call (425) 728-7427
Free resources

You Can Get an Energy Audit: But It Won't Solve This Quickly

Some energy providers offer home energy audits.

To get a free energy audit in Lake Stevens, Washington, contact your local utility providers, specifically Snohomish County PUD (electricity) and Puget Sound Energy (natural gas). They offer free home energy assessments, efficiency tips, and sometimes free energy-saving kits to help reduce costs.

Snohomish County PUD (electricity)
Visit snopud.com and search for "energy audit" or "home assessment" to find current offerings.

Puget Sound Energy (natural gas)
Visit pse.com/homeassessment. PSE offers a free assessment where they analyze your energy use, provide recommendations, and can install energy-saving products at no cost.

They'll:

Analyze your energy usage
Check for air leaks
Review insulation levels
Look at your HVAC system

And they'll give you a detailed report.

That can be useful.

But it takes time to schedule. And it doesn't fix anything immediately.

If your upstairs is already uncomfortable, that's not the fastest path to a solution.

A direct HVAC diagnosis will give you answers faster, and show you exactly what needs to be done.

What it costs

What It Costs to Figure This Out

Most HVAC companies will charge somewhere between $0 and $100 to come out and evaluate the system.

And that's the key step.

Because this could be:

Airflow
Duct layout
Return imbalance

You don't know until it's actually checked.

Why this is so common here

Why This Is So Common in Lake Stevens

Older homes in Old Town and Hartford
Two-story layouts
Attic heat load
Systems designed for heating, not cooling

This isn't unusual here.

Why Good Guys

Why Homeowners Call Good Guys for Hot Upstairs Problems

We don't just check the AC unit and leave.

We look at:

01

Airflow

Measured at every vent, not estimated.

02

Duct layout

Where the air is going and where it's getting lost.

03

Return system

Whether hot air can actually leave your upstairs.

04

Real performance

What the system is actually doing versus what it should be doing.

Because that's where the issue actually is.

You get a clear answer before anything is done. No guessing. No upsell.

Same-day / same-week availability

Book a same-day diagnosis in Lake Stevens

Clear diagnosis before any work. No pressure.

Same-day / same-week availability
Clear diagnosis before any work
No pressure

Good Guys Heating, Air & Electrical  ·  8431 30th St SE, Lake Stevens, WA 98258
Serving Cavalero · Fobes Hill · Bunk Foss · Machias · Sonterra · Glenwood · Hartford

Frequently Asked Questions

Frequently Asked Questions: Why is my upstairs hot?

A powerful AC is only half the battle; the other half is delivery. Think of your AC like a high-end sink faucet, if the pipes (your ducts) are too small, leaky, or poorly routed, it doesn't matter how much water you turn on; it won't reach the second floor. In Lake Stevens, we often find that installers swap the unit but ignore the static pressure issues in the original ductwork.
Rarely. Most "hot upstairs" issues are airflow problems, not "cooling" problems. We can often bridge a 5–10 degree gap by sealing duct leaks, adjusting blower speeds, or installing a smart zoning system. Replacing the AC without fixing the ducts is like putting a bigger engine in a car with flat tires.
Be careful! Your AC system is designed to "breathe" a specific amount of air. If you close more than 20–30% of your vents, you create backpressure. This can cause your indoor coils to freeze into a block of ice or, worse, burn out your blower motor. A partial adjustment is fine, but "forcing" air is a recipe for an expensive repair bill.
These homes were built for natural convection. They were designed to let heat rise and escape through attic vents because they didn't have AC. When we retrofitted them with ductwork decades later, those ducts were often squeezed into tiny wall cavities meant for plumbing, not high-volume airflow. They simply weren't engineered for the 90°F+ summers we're seeing now.
Set your thermostat fan from "AUTO" to "ON." This keeps the air moving 24/7, even when the AC compressor isn't running. It won't perfectly balance the house, but it prevents the upstairs air from becoming "stagnant" and gives the return vents more time to pull that hot air out of the bedrooms.
We don't just look at your AC unit. We use specialized tools to measure CFM (Cubic Feet per Minute) at your vents and check for thermal "hot spots" in your ceilings. We look for disconnected ducts in the crawlspace and "pinched" lines in the attic. You'll get a clear map of exactly where your cold air is getting lost before it reaches your pillow.