Q: Is it a good idea to get a device that attaches to the dryer vent, collects lint and directs air into the house instead of outside?
A: Dryers are significant users of energy. They suck air from the house into the dryer, heat it up with an electric element or gas burner, and blow the hot air — along with the moisture from your clothes — out the vent pipe. All of the heat produced by the dryer is “lost” when you blow it outside.
Any time you exhaust air from your house, an equal amount will be sucked in to make up for it. This “makeup” air will come in through every available hole and crack in the house, mixing with the air you’ve already heated or cooled and causing your furnace, air conditioner or heat pump to work harder.
In the summer, the air sucked in by the dryer tends to be hot and humid, making the air conditioner work harder. In the winter, the air tends to be dry, making the air in your house dry. If your house is already leaky and dry, this will just make it worse. Some people try to counteract the dryness by installing a humidifier to add moisture, but spending that money sealing the house instead will make it less dry and reduce energy bills.
Overall, dryers can cost a lot to operate and create serious issues with moisture, comfort and even health.
So, does it make sense to bypass all of this and reroute the dryer vent to the inside? First off: DO NOT CONSIDER THIS IF YOU HAVE A GAS DRYER. The exhaust vent is also the combustion vent. You do not want the products of combustion (e.g., carbon monoxide) in your house.
If you have an electric dryer, there may be some houses during some times of the year where using this strategy could be beneficial. The problem is determining which houses and when. How do you know when the added moisture will make you more comfortable or lead to mold growth or even rot? This depends on a number of factors, including how tight your house is, how big it is, what it’s made of, how much laundry you do and what the weather is. Keeping track of all of this information to decide whether to vent the dryer inside or outside is often more trouble than it is worth.
There are other solutions, though. In Europe, condensing dryers have been used for years. They don’t exhaust air at all, so the problems associated with conventional dryers are eliminated. However, they tend to be smaller than the units Americans are used to and take longer to dry. You can also go with the solar approach and dry clothes outside to save more on energy.