The Hearth in the House as a System
Very few things in this world are perfect, but it is worth describing perfection so that one can tell just how bad any given thing is. By defining perfection in chimney venting terms, we become less accepting of flawed systems because the flaws tend to stand out more.
When designing or troubleshooting systems, consider the extent to which they stray from perfection. That is, assign a demerit point for each characteristic that does not conform to perfection. Think of each of the following as a 'driving' characteristic and each flaw in a system as an 'adverse' characteristic.
- The system is installed in a house that may be fairly 'tight' but which has a balanced ventilation system.
- The chimney runs inside the building envelope and has no offsets.
- The chimney flue is insulated and is the correct size for the appliance.
- The chimney penetrates the highest part of the house envelope.
- The chimney is tall enough and is clear of obstacles to wind flow.
- The flue pipe assembly runs straight up from the appliance flue collar to the base of the chimney.
- There are no large exhaust ventilators in the house, or if one exists, it is interlocked to a fan-forced make-up air supply.
- The appliance and venting system are reasonably well-sealed.
- The appliance is EPA certified or has equivalent characteristics (ie. unlikely to smolder).
- The appliance is operated by an informed householder.
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