Installing and Venting Fireplaces
Installing the venting for a fireplace is not a task for the faint of heart. Even the simplest operation can take several hours for those who know what they're doing. Making a mistake can lead to smoke billowing into your living room or carbon monoxide silently filling the air. This mistake may be as simple to correct as a leak that needs to be sealed. Or it may be as complicated as re-routing the entire venting system. You may want to have a professional installer do the job. If you want to tackle it yourself, make sure you have smoke and carbon monoxide detectors in working order.
Vent-free fireplaces are the easiest to install since you don't have to give them any connection to the outside world. However, some states do not allow the installation of these fireplaces. And although they are generally safe, they can output a fair amount of moisture that can lead to mold and mildew in more humid locales.
A direct vent gas fireplace can be the easiest vented fireplace to install since it doesn't require a chimney. It uses a single 7 inch pipe with a 4 inch pipe inside. Air is taken in through the outer pipe to fuel the fire. Fumes and smoke are exhausted through the inner pipe. In its simplest implementation, the venting heads straight back from the fireplace and through the exterior wall to the outside. The pipe fits onto the fireplace with an adaptor, is secured to the wall with a thimble cover, and sets close against the outside wall with a cap that allows air to be drawn in from above and below.
This design can be adapted to run up the wall a ways to an angled pipe that takes the venting out to where the air is. Or it can run all the way up the inside air and end on the roof with a standard flue and chimney cap.
Pellet burning stoves can also be vented directly out the back or with venting that runs up and then angles out. Most pellet burning stoves come with a fan that blows exhaust products out to help with the venting process.
Fireplaces and wood burning stoves are simple to vent if your home already has a useable chimney. If not, installing your own chimney can require a bit of effort. The venting can run straight up from the unit into the chimney proper, or it can run out the back, head up, and then angle again to the chimney along the back wall.
The chimney should have a ground level access door on the outside for cleaning out the ash and soot that settles to the bottom. The vent pipe should be surrounded by a larger round or square insulating box to keep the hot pipe from setting fire to your home. As it goes through each floor it should additionally be protected by a firestop radiation shield. It should be secured to the wall with an adjustable wall strap. In the attic, you'll need an attic insulation shield and a round ceiling support that is kept at least 3 inches from the ceiling by a square ceiling support box. This can emerge into a chase top with flashing and a minimum of 6 inches clearance between that and the chimney top. A roof support bracket is optional but it may help to hold your chimney in place.