Q: We are switching over from a wood stove to a pellet stove. We have the stove and the pipes to go from the stove to our existing chimney. Some people say that we need a liner for the chimney or we can put it through the wall of the house. What do you recommend? –Linda K.

A: You can vent a pellet stove either through a wall or through an existing masonry chimney. If you’re going through the wall, there’s a through-wall fitting that’s used to provide the proper clearance to combustibles, then the vent pipe is passed through that. If you’re venting through the chimney, you need to inspect it to be sure it’s clean, solid, and meets all local building codes. Some chimneys also require the installation of an approved metal liner that the pellet stove vent pipe passes through.

An improperly installed combustion heating appliance of any type — including a pellet stove — is a definite health and fire hazard. You’re also setting yourself up for liability issues if you don’t have the proper permits, both from a resale standpoint and also with your homeowners insurance company. For that reason, unless you’re experienced in this type of installation and are willing to obtain the necessary building and mechanical permits from your local building department on your own, I would definitely leave this project in the hands of a licensed stove installer. You can find a qualified person through the dealer where you purchased the stove.

If you got this stove used through a private party instead of new through a dealer, then I honestly wouldn’t recommend installing it at all — you don’t know anything about its condition, and you could be installing an appliance that doesn’t comply with local or state requirements.

Q: I read your tips all the time and they are great. Now it’s my turn.

We remodeled our kitchen a few years ago. We replaced the re-circulating stove hood and installed a better system that vents to the roof. I don’t recall if they used 6-inch or 8-inch piping, but it was the size recommended by the manufacturer. The total amount of piping is probably about 12-15 feet from fan to roof vent. I think the bigger problem is that this ventilation piping takes a few turns via a few 45-degree turns before it exits the roof.

The fan mounted in the stove hood was very powerful (based on the manufactures specs), but I think the turns and pipe lengths are impeding the airflow, and it’s an inefficient system. The amount of air that leaves the stove vs. the noise it produces makes it easier to tolerate the smoke since it does very little.

Reconfiguring the vent piping is nearly impossible although access to the attic is very possible. I was considering a roof-top ventilator. Instead of attempting to push out the air through a fan, this device works more like a vacuum and pulls the air out from the roof. A little extra power and noise would not be a problem since it would be mounted outside on the roof and the existing vent pipe would remain. The old fan would come out and the metal filters would remain.

Any recommendations or am I wasting my time? –Patrick G.

A: First, let’s look at the situation with the existing range hood. Contained within the instructions and specifications that came with the hood will be a chart of some sort that lists the maximum length of duct that is allowable for that particular unit. The chart will also tell you how much equivalent length is taken up by a fitting — for example, it may say that an elbow is the equivalent of 4 additional feet of duct. So if you add up the actual number of feet of duct and then factor in the number of feet that’s added by the fittings, you can determine if what you have exceeds what the manufacturer recommends.

You mentioned "they used," so I assume you had this done by a contractor. If the contractor did not install the hood to the manufacturer’s specifications, you may have some recourse there for getting them to make some repairs or adjustments. All that being said, however, you may still not get the type of exhaust results you’re hoping for with the existing hood, even if the duct is redone to fall within the manufacturer’s specs.

Which leads us to your idea of an exterior vent motor, which I think is a great idea. (I’ve had one for years with very good results). Exterior vent motors that pull instead of push work very well, for the two reasons that you mention. Because they are outside, the motors can be considerably larger than what is possible inside a range hood. And the exterior mounting means that the noise the larger motor generates is not nearly as much of an issue. It’s why you almost always see restaurants and other commercial applications utilizing exterior vent motors.

The downside is typically one of cost. The exhaust motor is more expensive, and it requires more labor to cut and flash it into the roof, and to run the necessary ducting and wiring. If an exterior vent motor fits into your budget, then I would certainly recommend making the change.

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