(This article originally appeared in the July 26th, 2011 edition of the Century City News)
By Herman Kelting PhD
rciaq@verizon.net
Scope of three-part series about residential indoor air quality
In Part One of the series on residential indoor air quality (RIAQ), we discussed the effect of climate on indoor air quality and found that both outdoor temperature and humidity influence RIAQ, Part Two described source contaminants from the building structure, fixtures, and personal property, and the importance of air flow within and between the home, attached garage, and attic on RIAQ. We provided 14 guidelines for the management of personal property to improve RIAQ, described the effect of water damage to mold, and noted that mold must be eliminated, not killed, to improve RIAQ.
Now, in Part Three, I’d like to discuss the importance of conditioning the air and maintenance of the heating, ventilation, and air conditioning system (“HVAC system”) on RIAQ,
“Conditioning the air” defined
In order to improve residential air quality after particles and VOCs from the source contaminants listed in Part Two of this series have been minimized, it is necessary to condition the air. “Conditioning the air” or “conditioned air” refers to any air movement, air exchange, or air processing that improves indoor air quality and energizes the occupants. “Improves air quality” refers to reducing particles and volatile organic chemicals (VOCs). Energizing the occupants is important as an RIAQ standard because I have witnessed conditioned air that leaves a residual fragrance from filters that reduce occupant energy. And it is crucial for commercial establishments that conditioned air contributes to maximum work output,
“Conditioning the air” includes two types of processing, One of these is natural ventilation from open windows and doors, infiltration from leakage within the building structure, and makeup air taken in through the HVAC system in the absence of air conditioning (A/C) or other filtration, But open-window natural ventilation is distinguishable from infiltration or makeup air in the HVAC system because natural air exchange from open windows will duplicate outdoor air indoors, while infiltration or makeup air induced through the HVAC system may add contaminants from the building structure or from within the HVAC system; thus, it is crucial, for example, to assure the evaporator coils and HVAC filters are clean and are free of fragrances,
The second type of “conditioning the air” is physical air processing intended to reduce contaminants, This includes air conditioning in which contaminants are dissolved in the moisture on the evaporator coils or other types of filters such as electronic air cleaners, High Energy Particulate Arrest (HEPA) filters, impregnated carbon, etc. that remove particulates or VOCs.
Air conditioning to reduce temperature and humidity
Air conditioning (A/C) to reduce temperature and humidity during warm weather is one of the best types of conditioned air because the moisture on the evaporator coils absorbs many contaminants, It is helpful to utilize UVC lights (254 nm wave length) in the air flow system a few inches from the A/C evaporator coils to remove bacteria which collect on the A/C coils, and to clean the coils periodically to eliminate contaminate buildup.
Dehumidification
Dehumidification is useful to reduce humidity when the relative humidity (RH) is greater than about 50 percent (e.g., along the coast) and it is too cool to use air conditioning. Like air conditioning, it conditions the air by absorbing contaminants as air passes over moist coils; these coils must be cleaned with the same periodicity as A/C evaporator coils assuming no UVC lights in the HVAC system,
If you purchase a portable dehumidifier, be sure the coils are accessible for cleaning before you purchase; measure the electromagnetic field (EMF) with a three-axis EMF detector because some dehumidifiers create very strong EMFs. To avoid contact with the EMF, place the dehumidifier in a place that is outside the normal walking area. Portable dehumidifiers may also be used to provide heat in the winter because the output air temperature is about 84 degrees F, I provide about 95 percent of the heat in my housing unit with a dehumidifier.
Make-up air in the HVAC system
As a general rule, home HVAC systems do not have make-up air capability (i.e., fresh air drawn in from outdoors). Thus, engaging the HVAC system with only the fan on will not condition the air unless there are filters in the HVAC system (e.g., electronic air cleaners), If there is make-up air provision in the HVAC system, “fan-on” becomes an additional method of conditioning the air subject to our comments in the opening paragraphs,
Air filtering systems
There is a vast array of different air filters that are either portable or an integral part of the HVAC system. These systems are designed to capture particles and VOCs each of which requires separate systems to operate efficiently. Particle capture systems include HEPA filters, electronic air cleaners that operate at high voltages (e.g., 10,000 DC volts), ion generators which attract particles to surfaces, etc. VOC capture systems include impregnated carbon, potassium permanganate, zeolite, etc. to absorb VOCs. UVC lights in the air flow preceding the A/C coils also reduce bacteria on the A/C coils, Ozone oxidizes contaminants, but the oxides may be harmful and ozone should not be used with occupants present or with wood fragrances because ozone may combine with the latter to create harmful oxides.
Because there is such an array of these systems and because each manufacturer has product differentiation, it is impossible to discuss these in this article.
Open windows
Open windows are an excellent way of conditioning the air particularly if the HVAC system does not provide for make-up air and the outside air is of good quality. One measure of good outside air is the absence of sources of pollution and the density of trees, which capture pollution and add oxygen to the air. I suggest open windows for at least two periods of 15 minutes each every six hours during day-time hours with box fans in windows that draw outside air along a diagonal through the home; sleeping with an open window is also helpful, if the outside air is of good quality irrespective of make-up air in the HVAC system. Higher humidity air (e.g., 60% to 70%) contributes to better sleep; higher morning humidity over 50 percent in the home suggests dehumidification during the day.
Carpet cleaning
Carpets should be cleaned every four to six months to assure the best in RIAQ. It’s best to perform a manual cleaning with a carpet cleaner that has a dirty water return tank so that one can be assured of effective cleaning; be sure to purchase the extended warrantee. I have also found that using a good quality dish soap in the carpet cleaner assures that any residual soap is safe, particularly if children play on the carpet, If one uses a highly mechanized carpet cleaning system, it is a good idea to test clean with a manual, dirty-water return tank carpet cleaner to assure effectiveness.
Carpet cleanliness is very elusive in the sense carpets may appear to be clean when, in fact, they are quite soiled, If you haven’t cleaned your carpets for a year or two and you use a manual carpet cleaner with a dirty water return tank, the return water may be unimaginably filthy with an oil-like viscosity; several successive cleanings may be necessary before the viscosity and color of the water is normal,
Passive and active ventilation of attics
Attics may be sources of poor air quality because of construction materials or because outside humidity reacts with attic materials. The result is poor attic air quality that may enter the home from infiltration in the HVAC system or from cracks in the walls, Some combination of passive and active attic ventilation is desirable and it is important to consult with a design professional familiar with the home and the local climate. An active attic ventilation system is particularly important for a new home.
Maintenance of the HVAC System
Maintenance of the HVAC system includes cleaning the indoor evaporator coils, cleaning or replacing filters, and cleaning the ducts. The indoor evaporator coils consist of one or more flat plates about 14 inches square and three inches thick with parallel aluminum plates about 1/16” apart and copper tubes with Freon connecting the plates that act as heat exchangers. It is possible to reduce the frequency of coil cleaning by installing UVC lights in the air flow several inches in front of the A/C evaporator coils,
Air conditioning results in the accumulation of bacteria on the flat-plate A/C coils where water condenses. I suggest cleaning coils with a coil cleaner about every 60 days during A/C season in the absence of UVC lights; if the unit has UVC lights, I suggest 90-day periodicity of cleaning, Always clean the coils at the end of the A/C season because bacteria may continue to build up even with the end of seasonal use, Rinse the coil cleaner from the coils preferably with steam, otherwise with a spray bottle of water, even if the coil cleaner states “No rinse;” heat from the steam provides additional cleaning power against bacteria and also reduces the amount of coil cleaner required, Be sure to follow safety instruction on the coil cleaner because it’s toxic, Electronic air cleaners should be cleaned in the same manner and frequency as the A/C coils, Dust filters should be replaced every 30 days,
Frequency of conditioning of air
“Frequency of conditioning the air” refers to the number of hours in a 24-hour day that the air in a home is subject to the “Methods of conditioning of air” described elsewhere in this article, Notably, a recent article in Indoor Air, Volume 21, Number 3, June 2011, p. 191-204 entitled “Ventilation Rates and Health: Multidisciplinary Review of the Scientific Literature” indicated that a number of studies found that higher ventilation rates improved health and reduced Sick Building Syndrome.
The suggestions I offer in this section are only the most general guidelines subject to many variables such as climate, age, design, and materials used in the home, age of furniture, attic and attached-garage ventilation, etc. Older homes may require minimum conditioning of the air, Newer homes require minimizing source contaminants or any normal conditioning of the air may not be effective, Thus, the general suggestions in this section assume (1) that all material source contaminants have minimum off gassing based upon sound commercial and human standards, and (2) mold is not present in the home.
For an older home near the ocean, no new furniture, and full-day occupancy, I suggest about 14 hours of conditioned air per day consisting of eight sleeping hours with an open bedroom window and about six hours of dehumidification to about 45-50 percent RH in cooler weather. Use of A/C in warmer weather may reduce total conditioning to 11 hours including three hours of air conditioning. For any other home category, it may be necessary to provide considerably more conditioned air including the use of a variety of filters.
Michael Douglas Carlin is the director of the movies Luvicide and American Federale. Recently he completed a ten-year stint as the Publisher and Editor of the Century City News. Here his articles turned into three books: Rise a Knight, A Prescription for Peace, and Peaceful Protests.
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