occurs, then insulating the vent connector and/or reducing the efficiency of the furnace may have to be done to raise the chimney temperature.
More detailed information may be obtained from the latest edition of the ASHRAE HVAC Systems and Equipment Handbook.
3. PROPER CHIMNEY HEIGHT:
The chimney shall terminate at least 3 feet above the highest point where it passes through the roof of a building and at least 2 feet higher than any portion of a building within a horizontal distance of 10 feet. (See Fig. 2a).
Fig. 2: Proper chimney termination height for pitched roofs
If the chimney penetrates a roof more than 10 feet from a ridge, wall or parapet, a minimum of 3 feet above roof or exit point must be maintained. See Figure 2b.
If the roof is flat rather than the normal residential pitched roof, refer to Figure 3 for proper clearances.
Fig. 3: Proper chimney termination height for flat roofs
4. PROPER VENT CONNECTOR PIPE/CHIMNEY CONNECTION:
The vent connector pipe should extend only to (and not beyond) the inside wall of the chimney (See Fig. 4). A thimble should be used to connect the vent connector pipe to the chimney so that the vent connector pipe may be readily removed in case of inspection or replacement.
Fig. 4: Proper insertion of the vent connector in the chimney.
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