DODGING [CHIMNEY] DRAFT PROBLEMS

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The venting system for a wood-burning heater is every bit as important as the stove itself.

Does your woodstove have the hiccups? Does your house smell of smoke much of the time? Do you have a heck of a time getting a fire started? If you have one (or even all) of these problems, don't blame the heater; your chimney is the most likely culprit.

There are actually two distinct (though related) factors affecting chimney performance: draft and capacity. Draft is the force behind flow, while capacity is the capability to handle flow. In most cases, more draft will equal more flow, but it's conceivable that you could have lots of draft but inadequate capacity if the diameter of your chimney is very small. The important thing to remember is that you'll get nowhere if you go after the wrong problem.

The object of this article is to help you diagnose and solve chimney problems related to airtight wood-burning heaters-without worrying too much about the physics of chimneys. (Open appliances, such as Franklin stoves and fireplaces, are separate matters.) Just pick out the SYMPTOMS you're suffering from on the list that follows, move on to the numbered PROBLEMS included with your symptom, and then proceed to the lettered SOLUTIONS mentioned with each problem.

SYMPTOMS

Fire is reluctant to start, smoke spills into room at start-up: Some chimneys perform adequately only after the first 30 to 60 minutes of burning. See PROBLEMS 2, 5, 6, and 7.

Stove back puffs powerfully on windy days: If this is the only time you have chimney draft problems, see PROBLEM 8.

Smoke spills to some degree under all conditions: If there is periodic (or even consistent) smoke spillage under almost any burn condition, see PROBLEMS 1 through 7.

Smoke spills at larger damper openings: If you get smoke leaking into the room when you open the damper for greater heat output, see PROBLEMS 1 through 6.

Heat output is too low: If, in spite of a wide-open damper, the woodburner doesn't become very hot, see PROBLEMS 1, 2, 4, 5, and 6.

Smoke odors are persistent, even when stove isn't in use: If your house constantly smells of smoke, even when you haven't lit a fire, see PROBLEMS 6 and 8.

PROBLEMS

[1] Chimney too small: Unless you have a very large wood-burning heater, it's unlikely that your chimney has inadequate capacity. It's generally safe to size a chimney to the recommendations of the woodburner's manufacturer. If you don't have that information, be sure that, as a rule of thumb, the chimney is about the same diameter (or has about the same cross-sectional area) as the flue outlet on the appliance. See SOLUTIONS A, B, and E for marginal improvements or SOLUTION H for the real fix.