A Constant Supply of Warm Dust

A retired couple contacted John Banta because they were experiencing eye irritation and diffi­culty breathing caused by dust in their home. In spite of frequent vacuuming and dusting, an un­usually heavy deposit of dust was noted on the furnishings during the house inspection. John suspected that the furnace system was the source of contamination because the heat registers in the home were lined with a fine dust and the clients’ symptoms worsened when the furnace was on.

John was puzzled, though, by the lack of dirt on the cold air return filter and the absence of air movement. He opened the cold air return and ex­amined the inside wall to see if there were any vis­ible obstructions. To his surprise, he found no duct at all. The cold air return was a dummy and went nowhere.

Further investigation revealed that the fur­nace and duct system were located in the crawl space under the home. John inspected the crawl space, where he discovered that there was no con­nection between the cold air return port on the furnace and the rest of the house. In fact, the fur­nace was taking cold air from the crawl space and blowing the unfiltered, contaminated air directly

can influence the ultimate outcome. For this reason we have provided specifications for the contractor where relevant. Finally, a regular cleaning and maintenance program is essen­tial for optimal efficiency. This task will ulti­mately fall to the owner and may influence your choice of HVAC system.

Choice of Fuel Source

Gas and other sources of combustion fuels can pollute the airstream if you do not plan care – into the house. Consultation with a heating and air conditioning company was recommended to cor­rect this construction defect.


HVAC duct systems should always be leak-tested to ensure that they meet specified standards. The stated industry standard for a sealed duct sys­tem is less than 3 percent leakage, which is rarely achieved. The furnace itself will account for much of the leakage since it is difficult to seal. The fur­nace should be mounted in a clean, easily acces­sible area such as a mechanical room and not in an attic or crawl space.

Leakage also occurs at unsealed joints where the metal ducts fit together. Since the return side of the furnace is sucking air back into the furnace, it will suck contaminants through leaks in the duct­work. If the unsealed ducts pass through walls or attics containing fiberglass, fiberglass particles are sucked into the ducts and blown into the house. If the unsealed ducts are in a crawl space under the home, then moldy, pesticide-laden or dusty air can be sucked into the furnace system and blown into the house.

fully. Electric heat is often considered “cleaner” heat because combustion does not occur in the home. However, environmental pollution from electricity generation plants must be ac­knowledged. Moreover, electric heating ap­pliances generate electromagnetic fields, an invisible and often overlooked source of pol­lution. Whatever your choice of fuel source, there are several strategies that can be em­ployed in the mechanical room that will make heating healthier.

Mechanical Room Design

• The mechanical room should be a dedi­cated room, insulated and isolated from the living space either in a separate build­ing or in a well-sealed room that ventilates to the outside. It should be easily accessible for regular routine maintenance.

• The equipment in the mechanical room may produce elevated levels of electro­magnetic fields and should not be located adjacent to heavily occupied living spaces.

• Ensure the supply of adequate combustion air to the mechanical room.

• We recommend that you locate a fire alarm in the mechanical room.

• If there is a water source in the mechanical room, there should also be a floor drain.

Heating and Cooling Appliances

We recommend the following guidelines for choosing, locating, and maintaining heating equipment:

• Purchase equipment designed for back – draft prevention.

• Use sealed combustion units to prevent transfer of combustion byproducts into the airstream. This is especially important where the mechanical room must be ac­cessed directly from the living space.

• If you are using a forced-air system, we strongly recommend adding a good com­bination filtration system that will filter out both particulate matter and gas.

• If possible, choose a heating system that does not run hot enough to fry dust. Hy – dronic systems and heat pumps meet this requirement.

• Institute a regular maintenance program to clean components, change filters, and purge mold or mildew growth.

Hydronic Heating

Hydronic heating, delivered through hot wa­ter, is usually a wall-mounted baseboard or radiant floor system. Baseboard systems are usually made of copper tubes and aluminum radiating fins with painted steel covers. Base­board radiators can be noisy if not maintained, and they can become traps for dust and dirt. Some baseboard units are subject to outgas – sing at first, when the factory-applied paint on them gets hot. Verify with the manufacturer if this will be a problem with the model you are considering.

Hydronic radiant floor systems are usu­ally made of plastic, rubber, or copper tubing installed within or under the floor. Hot water circulating through the tubing heats the floor mass and the heat then rises through gentle convection. Radiant systems are silent and clean. Because this form of heating heats feet, occupants are comfortable at lower operat­ing temperatures. The water running through the piping is not hot enough to fry dust. Note that hydronic radiant floor heating should not be confused with radiant electric heating, in which the heat source is heated electrical wir­ing. We do not recommend this type of heat­ing because it will distribute a magnetic field throughout the home when in operation.

At one time, radiant floor heating used copper tubing almost exclusively but the ris­ing price of copper, combined with the intro­duction of plastic and rubber tubing, made this a less common option. Metal tubing, such as copper, can conduct electromagnetic fields through the structure if it becomes charged at any point along its route and for this reason we do not recommend it. Some in-floor systems use very odorous rubber products. While this is not a problem where they are embedded in concrete, it can be a source of indoor pollution where the tubing is exposed at access points. Wirsbo Hepex, a crosslinked polyethylene tubing, or Kitec, a crosslinked polyethylene tubing with an aluminum core, are odorless products for radiant floor heating.

The advantages of a hydronic system in­clude slightly lower operating costs, even heating, quieter operation, ease of zoning, and independent room-temperature control. Disadvantages of the hydronic system include slow response time and higher installation costs compared to forced air because of the number of mechanical components.

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