You load the dryer, hit start, shut the laundry room door—and within minutes the room feels like a sauna or the dryer seems to struggle. You’re not imagining it. A typical vented dryer can move 150–200 cubic feet of air per minute. If that air can’t get into the room, the dryer pulls a vacuum, runs hotter, and takes longer to finish. That wastes energy and can be risky with gas appliances. This topic matters because poor airflow isn’t just about comfort—it affects safety, efficiency, and how long your dryer lasts. You’ll learn when it’s smart to leave the door open, how to tell if your setup has enough makeup air, and practical fixes that don’t require a remodel. I’ve seen perfectly good dryers underperform for years simply because the door stayed shut in a tight room. A few small changes can make a big difference.
Quick Answer
Leave the laundry room door open if your dryer is vented and the room is small, tight, or gets hot and humid during a cycle. You can keep the door closed only if the space has adequate makeup air—such as a louvered door or transfer grille providing roughly 60–120 square inches of free area—and the dryer vents properly outside. Ventless (condenser or heat-pump) dryers also benefit from the door open to dissipate heat and residual moisture.
Why This Matters
When a dryer runs, it has to pull in as much air as it exhausts. Starve that air and you get longer dry times, higher energy use, and extra wear on the machine. With gas dryers, a tight room can also lead to backdrafting, where exhaust from a water heater or furnace gets pulled into the home instead of vented outdoors. That’s a serious safety risk.
Humidity is another big one. Even a vented dryer releases some heat and moisture into the room. Close the door on a small laundry closet and relative humidity can spike past 60% within minutes. That’s prime territory for mold growth, musty odors, and peeling paint. I’ve measured rooms jumping from 45% to 68% RH in a single cycle with the door closed, while staying under 55% with it open.
Finally, airflow affects performance. If your dryer moves 150–200 CFM but the room provides only a fraction of that as makeup air, the motor works harder and the moisture sensor keeps the cycle running. Over a year, that can add dozens of extra hours of runtime and noticeable dollars to your utility bill.
Step-by-Step Guide
Step 1: Identify your dryer and room type
Know what you’re working with. Vented electric or gas dryers exhaust air outdoors and need makeup air. Ventless condenser and heat-pump dryers don’t exhaust outside but still add heat (and a little moisture) to the room. Also note the space: Is it a large room with a window, a small interior room, or a tight closet? You might find lint alarm for dryers helpful.
- Vented gas: highest priority for makeup air and carbon monoxide safety.
- Vented electric: needs makeup air for performance and humidity control.
- Condenser/heat-pump: needs room to shed heat; door open helps comfort.
Step 2: Check makeup air and openings
With the dryer running, close the door and see if it pulls shut hard or you feel noticeable suction. That’s a sign of poor makeup air. Look at the door undercut: a 30-inch-wide door with a 1-inch gap provides around 30 square inches, and actual free area can be less. Louvered doors or transfer grilles increase airflow.
- Target roughly 60–120 square inches of free area to support most vented dryers in small spaces.
- For gas dryers, ensure there is a clear path for combustion and makeup air; many installers use two grilles (high and low) to adjacent spaces.
Step 3: Inspect and optimize the vent path
Restricted exhaust makes everything worse. Use 4-inch smooth rigid metal duct, keep the run as short and straight as possible, and minimize elbows. As a rule of thumb, each 90° elbow adds about 5 feet of “equivalent length.” Many dryers are rated for about 25 feet total equivalent length before performance drops. You might find dryer vent hose helpful.
- Confirm the exterior hood opens fully and isn’t blocked by lint or nests.
- Avoid flexible foil or plastic duct; they trap lint and restrict flow.
Step 4: Run a quick performance and comfort test
Do one load with the door open, one with it closed, and compare. Note dry time and how the room feels. If dry time increases by 10% or more with the door closed—or if the room gets hot and sticky—you don’t have enough makeup air.
- Use a simple hygrometer; aim to keep laundry room RH under 55% during cycles.
- Hold a tissue at the bottom of the door; strong inward pull indicates negative pressure.
- Gas dryers: make sure you have a working CO alarm nearby as a safety check.
Step 5: Fix the root cause
If the room is tight, the simplest fix is to run the dryer with the door open. For a permanent solution, add airflow: install a louvered door, cut in a transfer grille to a larger room, or increase the door undercut (where allowed). For ventless units, consider a small booster fan for room air circulation or a dehumidifier if RH climbs. You might find dryer safety kit helpful.
- Seal and shorten the vent to factory specs to reduce backpressure.
- If the home is very tight, a dedicated makeup air duct for the laundry area can solve negative pressure—keep it separate from HVAC returns.
Expert Insights
Dryers are basically small exhaust fans with heaters. Most residential models move 150–200 CFM; some compact units run a bit lower, but the principle is the same: what goes out must come in. In airtight homes, it takes as little as 5–10 Pascals of negative pressure to backdraft a naturally vented water heater. I’ve seen that happen in laundry closets where the door stayed shut and there were no grilles.
A common misconception is that closing the laundry door saves energy by keeping conditioned air in. In reality, starving a dryer of air often lengthens cycles and uses more energy than any small loss from leaving the door open. Another myth: an electric dryer doesn’t need makeup air. It does. It still exhausts a large volume of air and fights itself if that air can’t be replaced.
Pro tips: vacuum the lint screen housing with a crevice tool a few times a year; a thin lint mat on the screen can increase dry time by 10–15%. Check the exterior hood while the dryer runs—if the flap barely opens, you’ve got restriction. For ventless dryers, give them space and airflow; heat-pump units are efficient but still warm the room and appreciate an open door or a transfer grille.
Quick Checklist
- Open the laundry door during cycles if the room is small or feels hot and humid.
- Provide 60–120 sq in of free air (louvered door or transfer grille) if you want to keep the door closed.
- Use 4-inch smooth rigid metal vent duct; keep total equivalent length within the dryer’s rating.
- Limit elbows; count each 90° elbow as about 5 feet when totaling vent length.
- Verify the exterior vent hood opens fully and is lint-free while the dryer runs.
- Keep room humidity under 55% during operation; add ventilation or a dehumidifier if needed.
- Install and test a CO alarm near gas appliances; ensure adequate combustion air.
- Clean the lint screen every load and vacuum the lint trap and vent path periodically.
Recommended Tools
Recommended Tools for should you leave the laundry room door open when running a dryer
Frequently Asked Questions
Will leaving the laundry room door open waste heating or cooling?
There’s a small impact, but it’s typically outweighed by faster dry times and less heat buildup. A starved dryer can run 10–20% longer, which costs more than the slight loss from opening the door. If you need to close it, add a louvered door or transfer grille for makeup air.
Is it safe to keep the door closed with a gas dryer?
Only if the space has adequate makeup and combustion air. A tight room can create negative pressure and potentially backdraft a water heater or the dryer itself. If in doubt, open the door during operation and add permanent openings to meet the manufacturer’s airflow requirements.
Do condenser or heat-pump dryers need the door open too?
They don’t exhaust outdoors, but they still add heat and a little moisture to the room. Keeping the door open helps comfort and prevents humidity spikes. In small closets, many manufacturers require a minimum room volume or louvered openings—so an open door is the simplest fix.
How big should the airflow opening be if my dryer is in a closet?
As a practical rule, aim for 60–120 square inches of free area via louvers or grilles to support typical vented dryers. Some setups use two openings (high and low) to an adjacent room for better circulation. Always check your dryer’s installation guide for the exact requirements.
Why does my laundry room get so hot and humid when the door is shut?
The dryer is pulling air out but not enough is coming in, so heat and moisture build up. Restricted exhaust ducts can make it worse. Open the door during cycles, improve the vent path, and consider adding a transfer grille to stabilize temperature and humidity.
Can I add a duct just for makeup air to the laundry room?
Yes, a dedicated makeup air duct can work well in tight homes. Keep it separate from HVAC returns and use a screened intake to the outdoors. In colder climates, a controllable damper helps limit drafts when the dryer is off.
How can I tell if my dryer is starved for air?
Signs include longer dry times, hotter exterior cabinet, linty or musty smell in the room, and a door that’s hard to close due to suction. At the exterior hood, a weak or barely opening flap while the dryer runs indicates high restriction and likely poor makeup air.
Conclusion
If the laundry space is small or tight, keep the door open while the dryer runs. If you want the door closed, provide a clear path for makeup air with a louvered door or transfer grilles, and make sure the vent is short, smooth, and clean. Watch your dry times and humidity—both are honest feedback. A few small adjustments improve safety, comfort, and efficiency, and your dryer will thank you with faster cycles and fewer headaches.
Related: For comprehensive information about Ventisafe, visit our main guide.