Venting a clothes dryer to the outside isn't an option - it's a requirement. An unvented dryer puts all kinds of fibers and lint into the air in the house that will not only accumulate and make a heck of a mess over time, but can cause respiratory and breathing problems for the occupants. Even more important, the hot air in the dryer (as a result of combustion) may contain gasses such as carbon monoxide that are extremely hazardous. These need to be vented to the outside.
Luckily, installing a dryer vent is a pretty straightforward job. As long as you can measure accurately and use a power drill or jigsaw, you can install your own dryer vent.
Step 1 - Determining Where the Vent Will Go
The first thing to do is figure out where you want your dryer vent to be placed. If your dryer is in the basement, you need to drill through the wooden sill plate that sits on your foundation.
If your dryer is on the main or second floor, you need to determine where you can cut a hole through the wall. When you think you've found the proper location, drill a small pilot hole and insert wire coat hanger bent at 90 degrees and spin it around. If the hanger doesn't hit anything inside the wall, your location is fine; however, if it hits something in the wall you'll need to find another location.
Check the vent locations from the outside as well. Do this by measuring (on the inside) from the corner of the foundation or even a window to your chosen spot, and then go outside and use the same measurement to verify that your location is OK. You don't want to run into any existing shrubbery or gate posts.
Step 2 - Cut the Vent Hole
Once you've established where your dryer vent is going, go outside, and using a 4-inch hole saw, cut the hole for the dryer vent pipe. You can use a smaller hole saw and a saber saw to cut the hole, just be sure to mark the location of the vent pipe with the pilot hole in its center.
Step 3 - Install the Vent Hood
Install the vent hood or shroud to the side of your house using rust resistant wood screws, and caulk all around the pipe and the shroud. The vent hood should have a piece of pipe about 12 inches long already attached to it.
Step 4 - Run the Vent Pipe
On the inside, attach a 90-degree elbow to the protruding end of the vent pipe, and then run sections of vent pipe back to your dryer. At the dryer, attach an elbow where the exhaust comes out of the dryer and then connect the vent pipe to the elbow.
Your dryer vent is now basically finished. All that's left is to slide the dryer back into position and make sure it's level.
Use large hose clamps to attach the solid vent pipes to the elbows, and use foil tape to seal the joints between the pipe sections. Never use sheet metal screws to join the sections together - they will protrude into the pipe, where they will catch and hold lint that eventually could block the vent pipe.
One final word. Flexible plastic hoses were commonly used for venting dryers in the past. However, these hoses aren't strong enough to support their own weight, so they will sag, and lint will collect in the low spots, creating a possible fire hazard. Don't use them.