Environmentalists warn us about global warming and the toxic fumes that inhabit certain areas around factory towns and chemical manufacturing plants. But rarely does anyone bring up in conversation one of the most concentrated buildup of harmful chemicals, mold spores and carbon dioxide in one place: our homes.
Traditionally, homes were ventilated by openings that were later covered with windows. Even years later in roof-tight construction with windows and doors there were always portals in which air could be exchanged with fresh air from outside. As energy increased in cost home builders began making the homes tighter closing off all but a few vents in the home. This meant that the air inside the house could not be exchanged as readily and that pollutants were being kept inside for the occupants to breathe.
Home Air Exchange
Air quality dogged designers of ventilation and heating systems for years until 2003 when the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) came up with minimum standards for air quality for domestic structures. Their studies showed that air pollutants indoors could be as much as 5 times greater than the impurities outdoors. Their recommendation were as follows:
- Whole Home Exchange: Standard homes should have an exchange rate of 50 cubic feet per minute (CFM) and higher for larger homes. This rate can be less if ventilated from a centrally located air exchanger.
- Kitchen Range Hood: Because of the oil evaporates and other emissions from the cooking process ASHRAE has decided that a greater fan strength is needed in this area of the home - at least 100 CFM.
- Bathroom Exhaust Fan: The main concern in bathrooms is excess moisture permeating through the home. This vapor finds cracks and crevices and then condenses on the cooler surfaces providing a breeding ground for mold and mildew. The suggested fan rate is 100 CFM.
- Other Sources: Dryers and other appliances that need fans should be vented outside and care should be taken that they do not draw too much air from the home because it would create too much negative pressure.
Types of Home Ventilation
1. Exhaust Ventilation Systems
This system works on the principle that if a negative pressure is created in the home the impurities will be sucked out by a fan and fresh air drawn in. This is a simple, yet effective, method that does the job of changing the air in the home. However there are concerns that pollutants may be drawn in from within parts of the home: radon, dust from the basement and attic, gas and solvent fumes from the garage and fireplace.
2. Fresh Air Intake Ventilation Systems
The exhaust ventilation process is reversed with a fresh air system. Here, the air is drawn into the home creating a positive pressure build-up where the impurities are pushed out through the bathroom and kitchen vents. This system works best in warm climates because in cooler areas the intake of air may contain too much moisture and this could cause mold and mildew. A filter should be installed to clear the air of pollen and dust.
3. Balanced-Pressure Ventilation System
This system has fans on both the intake and the exhaust creating a flow and reduces any fluctuations in pressure. These ducts can either installed in every room or used as a whole-house system through a central ventilation system. However, because it draws air freely from the outside there is a chance of moisture build-up.
4. Energy Recovery System
Not only does this system replace the air in the home with fresh air it also adjusts the temperature of the incoming air with a heat exchanger. Within this device is a series of baffles (usually aluminum) which transfer the heat from the exhausted air (if it is winter) to the incoming, cool air which reduces the temperature loss and saves energy. Although the incoming and outgoing air do not come into contact with each other the exchanger can recover about 70% to 80% of the heat.
Energy recovery is divided into two main types:
HRV (Heat Recovery Ventilator): This process just transfers heat.
ERV (Energy Recovery Ventilator): ERV's work in much the same manner as HRV's except they have the quality of taking moisture from the exhausting air and transferring some of this to the dry, incoming air to maintain a relative humidity balance.
Filtration systems like Hepa filters cleanse the air of impurities and organic matter such as dust mites. However they do not get the fine particles. Adding an electrostatic filtration system will cleanse the air of the small particles that create allergies. These filters can be taken out and cleaned in a dishwasher.
Whatever type of dwelling people may inhabit, maintaining a safe and comfortable environment is extremely important to good health.Posted by: TrustedPros