Cost-Effective Solutions To Build Tight, Ventilate Right Contradictions
It's paradoxical, even as aggregate total outdoor emissions for carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), particulate matter (PM), volatile organic compounds (VOCs) and lead have decreased by 51 percent1 over the past 35 years, the quality of the air inside many American homes has become more toxic, more allergenic, more hazardous to infants, asthmatics, seniors and other at-risk population segments.
According to the American Lung Association, asthma is now the nation’s number one childhood disease, afflicting over six million children (and 14 million adults) in 2004. EPA research also indicates that indoor levels of common organic airborne pollutants are two to five times higher than outdoor levels regardless of whether the homes tested are in rural or urban areas.
Lifestyle changes have certainly had as much – probably more – to do with this deterioration in residential indoor air quality as any changes in building practices. Due to such factors as expanded home- entertainment options and increased work- at-home opportunities, the EPA estimates that the average American now spends 65 percent of his or her time at home. Looked at another way, that means over 60 percent of the air most people breathe comes from inside their houses.
Even in moderate climates, many residents tightly close and lock windows and doors when leaving for even short outings and rarely leave them open for extended periods even when at home. They prefer the controlled environment of heating and air-conditioning systems to the traffic noise, dust, loss of privacy and potential security vulnerabilities of an “open house.”
While tight building isn't, per se, a cause of increased indoor air pollution, it can acerbate the situation by limiting natural air changes. Indeed, a recent report by Restoration Consultants found that almost 80 percent of all mold problems investigated in the past seven years have been in newly constructed buildings and residences, and the condition colloquially known as “sick-home syndrome (SHS)” is rapidly achieving the perceived status of an actual disease.
All the evidence about indoor air quality, mold and moisture problems points to one conclusion: A greater-than-ever need for proper ventilation, air mixing , and air dilution in all types of dwelling. That said, there is little doubt that a disproportionate number of health and moisture-damage complaints are originating in post-energy-crisis-built homes.
Complaints, Callbacks and Courtrooms
A corollary of the increase in residential indoor air-quality complaints is a concurrent rise in the direct cost of contractor callbacks to investigate IAQ issues to an average of $400, over four times more than the difference in cost between a highly efficient, ultra-durable Panasonic ventilation fan and a lower output, far less reliable unit from a second- or third-tier maker.
Unfortunately, callbacks are among the least (and least costly) problems dissatisfaction with home ventilation systems and air quality can cause builders. A major cottage industry comprised of aggressively self-promoting attorneys specializing in indoor air quality health and mold-remediation litigation has grown up to exploit the difficulties inherent in trying to balance energy efficiency with indoor air renewal. Lawsuits alleging residential construction defects, the majority of them involving mold, moisture and other health issues, have increased exponentially since the year 2000 and the size of judgments entered against contractors have risen substantially.
For plaintiff and defense attorneys alike, to co-opt a phrase frequently and publically used by litigators for both sides, the “mold rush is the new gold rush.”
Ventilating Right as a Cost-Effective, Energy Star Answer
If mold, uncontrolled volatile organic compounds (VOC), and moisture-bred bacteria are not options, neither are energy-inefficient homes. New EPA Energy Star qualification guidelines that went into effect in 44 states on July 1, 2006 mandate that certified homes “perform significantly better than code” in such key energy-conservation areas as home envelope air leakage and recommend mechanical whole-house ventilation systems to “ensure consistent exchange of indoor air.”
The empirical fact is that much of the negative information about building tight that’s been circulating for the past five or ten years isn’t information at all, it’s disinformation, myth, urban legend.
Virtually every indoor air quality article written between 1974 and the end of the last century attributed the increased incidence of indoor air quality complaints to the tighter buildings constructed in response to the ‘70’s energy crisis. If you really look at the testing that's been done on those buildings, however, you’ll discover most of them aren’t really air tight at all.
Even some otherwise accurate professional websites still claim energy-conservation measures are responsible for poor indoor air quality while ignoring the vastly increased use of synthetic building materials, finishings, and furnishings, the proliferation of VOC-heavy personal beauty, cosmetic and hygiene products and some questionable design and construction practices that encourage formation of concealed moisture reservoirs.
Fortunately, we now have the means -- modern ventilation technology and a well-developed “roadmap” for using that technology – to provide high-quality, health-neutral indoor air without compromising heating, cooling or energy-efficiency objectives.
The ASHRAE 62.2 Guide to Good Air
Perhaps the best roadmap for ventilating right while building tight is ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) Standard 62.2. Published in 2004, ASHRAE 62.2 is being increasingly accepted as both a standard of care and a significant factor in defining what constitutes acceptable construction practices in mold-damage or other indoor-air-quality-related lawsuits.
In drafting 62.2, ASHRAE noted that “the Environmental Protection Agency lists poor indoor air quality as the fourth-largest environmental threat to our country,” that “asthma is the leading serious chronic illness of children in the U.S.” and that “moisture-related construction defects and damage are on the increase in new houses.”
ASHRAE 62.2 defines acceptable indoor air quality as “air toward which a substantial majority of occupants expresses no dissatisfaction with respect to odor and sensory irritation…” and air “in which there (is) not likely to be contaminants at concentrations that are known to pose a health risk.” The Standard’s authors conclude that “minimum residential ventilation can improve many of these indoor air-quality problems.”
"Minimum residential ventilation” is , of course, dependent on climatic factors, family size, floor plan, number of bathrooms, construction type and materials and a myriad of other factors. As an example, a two- or three-bedroom, 1500 square foot home, according to the Standard, requires fresh air intake of 45 cubic feet per minute.
In a home with a reasonably open floor plan and no specific pollutant sources, such as a basement hobby shop where someone does wood working and is generating pollution from volcanic compounds like adhesives, general house ventilation using a high-efficiency bathroom exhaust fan is usually adequate as long as there's sufficient make-up air to mix with and dilute existing indoor air enough to achieve acceptable quality levels as it is circulating through the house toward the exhaust port.
The Importance Of Balanced Air Flow
The major potential problem using the above solution, particularly in tight homes, is the possibility that the system will become unbalanced by more air being exhausted from the house than is being drawn into it.
Seals around windows, caulks, weatherization systems including home wraps, tight attics, and the lack of bypasses through the ceiling into the attic may severely reduce the natural intake of incidental makeup air unless provision is made for augmenting intake air flow via properly installed devices such as Panasonic’s multi-position passive inlet vents.
If more air is drawn out than in, the home could be put under negative pressure and back draft carbon monoxide and other toxins from combustible appliances throughout the house.
Back drafting is just one of the potential hazards of negative pressurization. If the dwelling is located in a humid area like Florida, or any climatic region (such as Chicago, the Carolinas and other coastal areas) with high humidity, negative pressure invites hot humid air to pass through the exterior of the house and infiltrate the exterior walls.
Given the appropriate conditions in such a building envelope, mainly a nutrient source in the wall cavity, moisture can condense between the interior and exterior wall and start mold growth. Unfortunately, a lot of organic building materials serve as very tasty nutrient sources for mold.
The opposite can occur if the home is under positive pressure. Montana and other Northwestern states, for example, are very cold and dry in the winter and many residents use humidifiers to compensate for both the natural lack of moisture in the air and the drying effect of natural-gas or propane forced air and fossil-fuel heating systems such as wood stoves.
The temperature and moisture differential between the inside air and the outside air may create positive pressure which can force the warm, most interior air to exfiltrate the interior walls and create the same mold-friendly conditions in the building envelope as negative pressure did in the Florida example.
Achieving Energy Efficiency and Air-Quality Equilibrium
Creating a ventilation system that provides sufficient air dilution and mixing in an energy efficient, temperature-regulated structure requires some pre-planning and design compromises, but is neither extremely difficult nor overly costly.
With a new home, the optimal course is usually to create a very tight exterior and use intentional ventilation as opposed to the old practice of building a loose house and counting on enough outdoor air leaking in to keep the concentration of contaminants down. That formula only creates huge energy bills during the summer and winter and results in homes with unacceptably large variances in temperature from room to room and area to area. It also stimulates mold propagation under high moisture and humidity conditions.
A far better solution is to utilize a weatherization system that includes a breathable home wrapper to provide an air and bulk water barrier, window and door flashing, caulked inlets and tightly sealed attics containing a properly designed ventilation system to help maintain neutral interior air pressure with minimal impact on energy efficiency.
Limiting air pollution at the source is also important. One way to do this is to use certified low-VOC-emitting interior materials. The more low-VOC finishes utilized, the less the likelihood of contaminated air in the home. “Green” homes, which emphasize the use of natural materials and non-toxic finishes in interior construction, are inherently less likely to be contaminated by VOCs than conventional homes using synthetic floor coverings and off-gas producing VOCs such as "non-green" wall paint or wallpaper adhesive.
Close attention should also be paid to combustion-fueled appliances such as hot water heaters, clothes dryers, furnaces, stoves and fireplaces to ensure that they're directly vented outside or, if necessary, power vented. Also, areas in which these appliances are installed should be designed to allow enough makeup air to prevent carbon monoxide buildup and in, in certain areas of the country, a dedicated ventilation fan should be installed to extract excess radon from basements.
Hardware Imperatives for User Acceptance
Once all the design and construction pieces of the balanced ventilation puzzle have been set in place, the most crucial issue becomes hardware selection, specifically what fan or fans should be employed as the system’s prime air mover.
Of the factors that go into this selection, the three most important are the fan's operating characteristics, its energy efficiency and whether or not people will actually use it. Of these three, the latter is by far the most important. Simply put, if the residents use the system it will work, if they don't it won't.
In considering whether or not residents will actually utilize any mechanical ventilation system often enough and long enough to generate sufficient air exchanges to adequately inhibit mold, bacteria and VOC buildup it is useful to think in terms of a threshold of obtrusiveness. The actual threshold beyond which a user will stop or decrease their usage of the system varies from individual to individual, but the twin components of the threshold are almost universal: Noise level and inconvenience.
Though personal thresholds in irritations differ widely, most studies indicate that excessive noise turns off more people – and their ventilation fans – than inconvenient operating controls.
Since the phrase “excessive noise” itself defies definition, it stands to reason that when it comes to the sound made by an operating fan what constitutes "too loud" and "quiet enough" will vary widely among individuals. It is reasonable to assume, however, that most people in our industrial society are pretty comfortable with the sound of a refrigerator gently purring in the background of their lives – a sound that is typically rated at about one sone. (Note: Since the sone measurement scale is linear rather than incremental, a two-sone noise is twice as loud as a one-sone noise and a three-sone noise is three times as loud.)
Most people find ventilating fans two or three times as loud as a refrigerator obtrusive, many find them so disturbing that they refuse to use them. Fans such as those in the Panasonic WhisperLine™, WhisperGreen™, WhisperFit™, WhisperComfort®, and WhisperCeiling™ lines, which are designed with such advanced noise-reduction features as fully enclosed condenser motors, over-sized double-suction blower wheels and two-sided intake inductions, are more likely to be used properly than louder fans in both intermittent room and continuous whole-house ventilation applications.
A phenomenally quiet fan such as the Panasonic WhisperGreen™ FV-08VKM1 operating at a full 80CFM while producing only 0.3-sones – so silent that the sound of a rustling shrub (0.5 sones) would drown it out -- coupled with a timer, humidistat or Panasonic’s integrated SmartAction™ motion sensor is an ideal package for both intermittent operation and continuous operation applications.
In the intermittent mode, particularly when equipped with the SmartAction™ sensor, which turns the fan on when a person enters the bathroom and turns it off 20 minutes after they leave, a fan quieter than 0.5 sone is unlikely to annoy anyone to the point of causing them to manually turn it off. In a continuous-operation system, such an extremely quiet fan quickly becomes part of the everyday aural ambiance of the home and is rarely even noticed.
Though noise is the main factor affecting mechanical ventilation system user compliance, operating convenience is also a significant issue. As in so many areas affecting indoor air quality, relatively recent lifestyle changes play a key role here.
We are no longer a dial-turning or switch-throwing society. It’s been a long time since a significant number of Americans regularly stood up, walked to the television, and spun a knob to change the channel. (We do use manual light switches because the penalty for not doing so – the inability to see anything in a dark room – is rather severe.)
Requiring occupants to manually switch on a bathroom fan when entering the room, leave it running for 20 minutes after use (as recommended by the Home Ventilating Institute), and return to the bathroom to turn it off is simply expecting too much of many users. Manual timers are an improvement, but control interfaces that require no user intervention – like the aforementioned Panasonic SmartAction™ motion sensors or humidistats -- are far better for intermittent spot ventilation and can be integrated with a programmable timer when whole-house ventilation using one fan is desired .
Energy efficiency is one factor which may not directly impact ventilation fan-usage patterns, but it can exert a major long-term influence on them.
In the world of ventilation fan economics, Energy Star certification is little more than a barely adequate protection against excessive electricity costs. Minimal investments in higher grade fans such as the Panasonic WhisperGreen™ models, which utilize DC motors to achieve energy efficiency ratings 75 to 400 percent better than Energy Star minimums, return maximum savings on utility bills.
All Fans Are Not Created Equal
Wall, ceiling and inline ventilation fans can be noisy, bothersome appliances that do little to alleviate the conditions they're intended to combat, or efficient, cost-effective solutions to numerous health and comfort issues. Since no two combinations of structural design, occupant lifestyle, heat-generating and cooling appliances, and climatic conditions are identical, installation can be tricky or straightforward and cost less than $100 or more than several thousand.
That said, there are some guidelines – such as adherence to the ASHRAE 62.2 standard – that home builders and contractors are generally well advised to follow. For example, one good rule of thumb is to never use two fans where one would do, three fans where two would do, etc.
A well-designed, precision -manufactured high-output fan will usually be only fractionally louder than a lower-output unit and is almost always significantly quieter than two smaller fans. Multiple fans also frequently require individual control systems, which could cause residents to use them less often, and generally use more energy than a single fan with a higher CFM rating. And, of course, using more than one fan increases both hardware and, because of the additional time and wiring required, installation costs.
In many applications, a good alternative to using multiple fans is to install a single fan so that it draws air from multiple inlets in one or several rooms. Panasonic Whisperline™ models improve on the multiple inlet capability of many competing fans by incorporating an adjustable input that regulates the airflow from all the inlets to create balanced air circulation.
Another excellent alternative, particular in those parts of the country with particularly hot summers and/or cold winters, is the recently introduced line of Panasonic energy-recovery WhisperComfort™ Spot Energy Recovery Ventilation (ERVs) fans. Using two ducts and a revolutionary capillary core, WhisperComfort™ fans simultaneously exhaust stale air and replace it with fresh outdoor air while recovering up to 75 percent of heat energy and maintaining balanced air pressure in the home
Other highly desirable fan attributes include built-in dampers to prevent outside air from coming in through the fan and creating unpleasant hot or cold drafts, non-heat-generating fluorescent lighting fixtures, and multi-tasking functionality such as that provided by Panasonic’s CustomVent™ Variable Speed Control, which runs the fan at a pre-set minimal CFM level continuously for whole-house ventilation and automatically elevates the speed to maximum output for a pre-determined time upon activation of a SmartAction™ Motion Sensor or other switch mounted in the room where the fan is installed.
A final major consideration in selecting a fan or fans for any specific project is the degree to which the units under consideration are installation-friendly. Though all installations are different, quality fan manufacturers like Panasonic attempt to minimize fitting and venting agony when designing their products. Other fan makers do not, which can frequently lead to increased costs in person hours and mounting hardware that far outweigh the apparent economy of buying a “bargain” fan.
Detachable adaptors, firmly secured duct ends, adjustable mounting brackets, detachable fan/motor units, simplified wiring, double-hanger bars and SmartFlow™ Optimum CFM Technology, which uses a computer chip to maintain fan performance at a constant CFM regardless of elbows and other flow-path factors, are just a few of the ways in which Panasonic strives to improve installer productivity.
Resolving The Inherent Contradiction
Fresh, healthy air in an environment free of excess moisture and mold growth. Home buyers are demanding it and an increasing number who believe – rightly or wrongly – that they are not getting it are seeking redress in law offices .
Energy efficiency and reduced heating and cooling costs. Home buyers, encouraged by utility companies and the government, are demanding that, too.
Fortunately for builders and contractors, carefully designed, correctly installed mechanical ventilation systems using today’s highly evolved, high CFM/ low-sone Panasonic exhaust fans provide a low-cost, builder-and-installer-friendly way to reconcile seemingly conflicting demands for better indoor air quality in a more tightly sealed, energy-efficient home.
1 EPA National Air Quality and Emissions Trends Report, 2003