Why do clothes dryers need to vent?

If the air isn’t venting, it would eventually become nothing more than steam. The clothes won’t dry.

Hot air holds more moisture than cold air. The saturation density for hot air in dryer at 50C is about 100 g/ cubic meter. If the volume of your dryer is ¼ cubic meter then the hot air will only hold 25 grams of water (less than an ounce). If your wet clothes weigh an extra pound (call it 500 grams for easy math) then the air must be exchanged a minimum of 20 times to dry them. It actually takes many times more than that since the air exchange is not perfect.

In cold weather I vent my dryer into my house. to save energy and add much needed moisture to the air. If you live in a hot, wet climate with air conditioning the dryer should be vented.

Note: there are “ventless” dryers that heat the air then run it through heat exchangers to cool it allowing the water to condense out. It is a clever but more expensive design and introduces more opportunities for failure: leaking heat exchanger, leaking water collector, potential water damage.

That is not just hot air. It is hot, moist air.
The water needs to go somewhere, you know.

@ragingloli I know ventless dryers are more common in the EU due to the energy savings and costs. I have never used one. Are the maintenance requirements more severe? Vented dryers usually have just one simple lint screen to clean. Do ventless dryers have screens over the heat exchangers as well? Where do they put the extracted water? Is it drained or plumbed to a sump pump?

I do not have a dryer. I just hang them on a rack.

Simple enough. We know where that water goes.

I looked up a ventless dryer commonly sold in Germany, LG Electronic Model # DLEC855W and checked:

“If your dryer is not connected to a household drain, then the water reservoir will capture the water from the drying process. This should be emptied every load.
If the container becomes full during a cycle, the EMPTY WATER light and alarm will be activated.”

If they couldn’t vent, their anger and frustration level would get real high, and potentially cause heart and emotional problems. Venting is healthy.

Additional maintenance over a conventional dryer:
The condenser must must be removed and cleaned 3–4 times per year.
The Ventilation Grill and Cool air Inlet grills need to be vacuumed.
From the manual :
“Use a vacuum cleaner to clean the front
ventilation grill and the cool air inlet in the back”

@LuckyGuy
“Use a vacuum cleaner to clean the front ventilation grill and the cool air inlet in the back” Yeah, like that is gonna happen on anything like a regular basis.

If you live in a cold dry climate and vent into your house, do you have to worry about the laundry room (usually a fairly right space) getting harmed by a lot of moisture while dryer runs? The drywall or paint getting too wet and risking mold or the paint peeling?

If I wanted to put a longer vent that put the wet air more towards the main room would it work? Or, would the air inside the vent start cooling too fast and there would be water in the vent rather than steam?

Also, if the dryer is gas is there any problems with the fumes being dangerous if you vent into the house? I don’t have gas, so I have no idea about those dryers.

Most, if not all, building codes require venting to the outside air and will not allow venting into a structure, even a garage.

@rojo Why?

warm, humid air=mould paradise

The International Residential Code says its specifications for dryer venting are intended to prevent fires, protect the dryer and ensure that warm, humid air from the dryer doesn’t cause damage to interior woodwork or mold-related health problems.

Why would fire be a risk?

Not sure, possibly lint accumulation and static electricity. Kind of like why they say you shouldn’t use a cell phone while pumping gas.

I should have mentioned I have an electric dryer, not a gas dryer.
In the winter I can use all the humidity (and heat) you can give me. In fact, most homes around here have humidifiers installed in their heating systems. I have a wood burning stove running in the basement, about 30 feet from my dryer and a circulation fan that blows air around the stove. My dryer vent runs near the ceiling attached to the plastic waste line from the bathroom. Attached to the vent is a stretched out leg from some old pantyhose. It acts as a lint filter and distributes the moist air a bit.
I do not have mold or mildew. My basement is wide open, no small dedicated laundry room.
In mid -spring when I don’t run my stove so often and don’t need the humidity, (April showers bring May flowers) I reattach it to the outdoor vent.

There is another advantage to internal venting in the winter. If the dryer vents outdoors, outside cold air is drawn in to make up the loss. For many months of the year that air is below freezing and needs to be heated.

@rojo Right. I can’t imagine people moving their dryer to vacuum the vents. The lint trap is easy. but pulling the condenser and vacuuming the back of the unit? No way.

Yes, I have known people that vented an electric dryer into a large, open basement in the winter with no problems. You can buy a divert with a sliding door and a screen.

Gas dryers make dangerous fumes, and small areas build up too much moisture.

I just realized that the ventless dryers are only “efficient” in the winter when you need the heat.
In hot climates they are significantly worse than vented. A vented dryer dumps the unwanted heat outside. A ventless dryer dumps all the heat into the home leaving it up to the A/C to work harder to cool it back down to comfortable room temperature.
On the other hand it does “reward” you with a little water that can be used to water your plants.

The lint is a concern for fire whether the line vents outside or not.

When there is a humidifier on a central air system does the humidity come out with the heat from the heat vents?

So, a ventless dryer is basically a swamp cooler for clothes?

@JLeslie Usually the humidifier element is mounted right in the hot air plenum. It gets hooked to the house water supply and has a humidistat that turns it on and off to maintain the desired level of comfort.

I WAS going to say: “Goodness!” and: “Heavens To Betsy!”
Everyone knows that people use a dryer just to heat up and make those cute little dryer sheets get all warm and toasty! Then they make everything smell like a forest. Or a bouquet of flowers. Maybe like a little fluffy bunny! However, now that y’all have given me a headache, I can only visualize deep, dark basements with colorful molds growing amongst the big spiders with giant fangs that glow in the dark!!!! Giant flexible hosey-things ( not with a W!!! ) waving around in the air like a mean version of the one’s at the downtown car lots! Ow- my brain is going to explode! I’m going to take the fluffy bunny, our bouquet of flowers and go out in the forest! Ow! And honestly, NO, I don’t know anyone by the name of Betsy!