Clean Air Inside

by Kim Kinrade

With the world clamoring for new standards to combat global warming very few people are looking into their own homes to help with the environment there. The air we breathe indoors id a potpourri of of very inflammatory substances that can cause a variety of ailments including an eroding of the immune system. Particles as small as mite and fly droppings mixed with minute, abrasive silica dust and the off-gassing of dozens of household products makes the air in our homes the equivalent of the atmosphere around a landfill.

Indoor quality concerns began with the closing in of our homes to keep warm, or in hot climates, cool. Before that time people used to open the windows and doors and let the air currents carry out impurities. In addition, more people walked to work or to school to get fresh air in their lungs and to expel the tainted particles in the lungs. Thankfully, the American Society of Heating & Air Conditioning Engineers has put forth a minimum standard for indoor air quality.

ASHRAE Requirements:

1) Whole House Mechanical Ventilation

The required rate for continuous ventilation for a domestic home is 50 cubic feet per minute (CFM), which means that every minute 50 cubic feet of air is being replaced and replenished.

2) Kitchen Mechanical Exhaust

Kitchen cooking odors and fumes are a major cause of indoor air pollution. Fats and burnt carbon become vaporized and float throughout the home which coats possessions and walls. Bacteria feeds off this film. ASHRAE conditions suggest a 100 CFM capability.

3) Bathroom Mechanical Exhaust:

Bathrooms require at least a 50 CFM fan to exhaust water-laden air from the area. However, a continuous system with 20 CFM capability is equally within the guidelines. This system is usually centrally located and exhausts the home as well.

Central Ventilation Systems

To change the air in the home there are basically four (4) systems that can be used.

1) Whole House Exhaust Ventilation:

The point of this system is to use a fan to draw out the air in the home. This creates a negative pressure in the house and fresh air is drawn in through special vents. This works very well and is inexpensive to put in and run. However, negative pressure can also pull in mold spores, radon, dust, gas fumes, flue and fuel gases from other areas of the home.

2) Whole-House Supply Ventilation Systems:

This system works in the opposite direction as the exhaust method. Fans draw fresh air in to the home while air is forced out of the home through bath and kitchen fan ducts and doors (when opened).Supply ventilation allows the homeowner to control and filter the air that is drawn in which is an improvement over the exhaust system as the high pressure prevents the drawing out of pollutants from the garage and fireplace areas. Fresh air coming into the home has its faults. For example, the home can slowly be infiltrated with excess moisture, and unless a dehumidifying option is attached, may attract mold and rot inside. As well, with an energy recovery system cold air is drawn in in the winter causing high heat bills.

3) Balanced Ventilation Systems:

A balanced ventilation system combines the exhaust and supply systems. There are usually two fans and two exhaust vents which distributes the fresh air from vents installed in one or every room in the home. In addition, because the balanced system allows for the use of filters for the air coming from the outside to remove dust and pollen. As in the case of both supply and exhaust systems balanced ventilation systems do nothing to remove moisture from air entering the house. And because the air comes in at its outside temperature look for high heating and cooling costs.

4) Energy Recovery Ventilation Systems

With energy costs climbing every month, an energy-recovery system is becoming the norm for ventilation.

There are two (2) types and, like the balanced systems, they both have fans to both push and pull the air through the system.

1. HRV - Heat Recovery Ventilator: HRV's use separate blowers to move in fresh and exhaust stale air from the home. In the process the specialized core made from very thin aluminum transfers heat from the outgoing air to the incoming air while keeping the two separate.

2. ERV - Energy Recovery Ventilator: This type of ventilator wordk like the HRV but with an addition. The ERV transfers a certain amount of water moisture from the exhausting air to the incoming, dryer air. This also keeps the heat exchanging system warmer lessing the chance of a freeze-up. In summer, an ERV keeps an equilibrium in the relative humidity of home also by the same method, by transferring water vapor to the dryer air coming in. If the incoming air has more moisture than needed the excess will be drained off. In both cases the core has to be cleaned every year to prevent mold build up.

Filters

Standard air and furnace filters collect allergens, spores and dust mites from the air but are not fine enough to rid the harmful effects out of all the air. An electrostatic filter can get the minute particles that even Hepa filters can't get.