zehnder america a fresh look at indoor air quality
TRANSCRIPT
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
Home should be a place where you can breathe easy, but today that might not be
the case. Indoor air pollution can be worse than outdoor pollution, and people
spend about 87% of their time indoors, an average of 69% at home.
Environmental Protection Agency studies found pollution indoors could be two to
five times higher than outdoor levels, and in rare cases up to 100 times worse. In
this special report sponsored by Zehnder America Inc., we’ll outline causes of
indoor air pollution and discuss solutions available to create a safe and comfortable
indoor environment.
What’s in the Air?
While most people think of air pollution outdoors, the air inside our homes can be
filled with numerous particles and chemicals that can irritate the eyes, nose and
throat and in some causes cause or exacerbate severe health problems.
Causes of indoor air pollution include:
Allergens, such as pollen and pet dander.
Smoke, from tobacco and wood-burning stoves.
Gas-burning appliances.
Chemicals from household building materials, and furnishings. For
example, wood floor finishes, pressed wood products, draperies, wallpaper,
paints and even computers can emit formaldehyde.
Cleaners and pesticides.
Mold, mildew and bacteria. About half of U.S. homes have visible evidence
of excessive dampness or mold, and water leaks also are common in office
buildings and schools, according to Lawrence Berkeley National
Laboratory’s Indoor Environment Group.
Radon, a radioactive gas that is at elevated levels in nearly 7% of U.S.
homes.
The Centers for Disease Control and Prevention says indoor air pollution can do
more than irritate your eyes and airway; it can lead to asthma and other lung
diseases, chronic heart problems and cancer.
Many of the common types of indoor air pollutants can trigger asthma attacks, and
between 2001 and 2011, the number of people diagnosed with asthma in the
United States increased by 28%, the CDC says. Today about 26 million people in the
United States have asthma, including 10% of children, according to the Asthma and
Allergy Foundation of America.
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
Improving air quality does more than improve health. Studies suggest that in
offices, improving indoor air quality by decreasing pollutants and increasing
ventilation can increase productivity by 8% to 11%, the World Green Building
Council reported in Health, Wellbeing and Productivity in Offices: The Next Chapter for
Green Building.
Even meticulous attention to the materials used in building a home cannot keep
out chemicals, as Bill Hayward, CEO of Haywood Lumber, found after spending
thousands of hours researching products for a home he built. The house still had
chemicals in the indoor air until he turned on its ventilation system.
The Role of Ventilation
“Inadequate ventilation can increase indoor pollutant levels by not bringing in
enough outdoor air to dilute emissions from indoor sources and by not carrying
indoor air pollutants out of the home,” the EPA’s Indoor Environments Division
says.
“Dilution is key,” says Barry Stephens, director of business development and
technology for Zehnder America.
“The codes are requiring building and houses to be much tighter [and] healthy
home need better ventilation,” Stephens said.
“If too little outdoor air enters a home, pollutants can accumulate to levels that can
pose health and comfort problems.” EPA says. “Unless they are built with special
mechanical means of ventilation, homes that are designed and constructed to
minimize the amount of outdoor air that can ‘leak’ into and out of the home may
have higher pollutant levels than other homes. However, because some weather
conditions can drastically reduce the amount of outdoor air that enters a home,
pollutants can build up even in homes that are normally considered ‘leaky.’”
Energy Efficiency Leads to Air Quality Issues
Over the past few decades, builders have succeeded in making homes much more
energy efficient. One of the primary methods is by tightly sealing the “building
envelope,” from the roof to the floor, including windows, doors and exterior walls.
“It’s very easy now with the products we have to get buildings tight, like an
aquarium,” said Matt Belcher, a nationally recognized builder who serves as
director of the High Performance Building Research Center, part of the Midwest
Energy Efficiency Research Consortium at the University of Missouri-Columbia.
“Inadequate ventilation can increase indoor pollutant levels by not bringing in
enough outdoor air to dilute emissions from indoor
sources and by not carrying indoor air pollutants out of
the home.”
EPA’s Indoor Environments Division
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
Building Standards and Codes Adapting
Over the past five to six years, building standards and
codes have begun to reflect increased concern about
indoor air quality.
The American Society of Heating, Refrigerating and
Air-Conditioning Engineers adopted a residential
ventilation standard, ASHRE 62.2, for both whole
house and local exhaust ventilation. Over the past
two or three cycles of building code revisions, many
have begun to reference ASHRE 62.2.
Programs such as Energy Star and LEED homes also
require ventilation that, at a minimum, meets ASHRE
62.2.
International Energy Conservation Code changes
took effect at the beginning of 2015, and Matt
Belcher was involved in updating that code, along
with serving as chairman of the National Association
of Home Builders Green Building & Energy
Subcommittee and serving on its Building Codes and
Standards Subcommittee. “It would be very hard to
meet [the 2015 IECC ventilation requirements]
without a balanced system,” Belcher said.
LEED for Homes awards two points for projects with
ventilation systems that transfer heat between
incoming and exhaust air streams.
The U.S. Energy Department’s Zero Energy Ready
Program goes further than Energy Star version 3,
including Indoor airPLUS specifications that call for
ventilating the home with outside air at the highest
rate practical.
Standards from the International WELL Building
Institute include both indoor air quality and thermal
comfort, and the ICC 700 National Green Building
Standard also has a focus on fresh air and awards
extra points for Heat Recovery Ventilation or Energy
Recovery Ventilation.
Belcher noted that green building standards tend to
be a bit ahead of building codes.
Now a principal with the consulting firm Verdatek Solutions in Wildwood, Missouri,
and member of the National Association of Home Builders board of directors,
Belcher was a code official decades ago when the movement toward energy
efficiency began leading to problems he documented in a research report for his
boss: mold and respiratory problems causing what came to be known as “sick
building syndrome.” Inadequate ventilation is one of the causes.
A tight building envelope blocks the transfer of heat or cold, moisture and air.
While that is good for energy efficiency, it can create problems with air quality.
Interest Growing
“Indoor air quality is clearly a ‘sleeper issue’ today, with a niche group of experts
paying close attention to the sources, causes, impacts and solutions,” UL reported
in the white paper “Dawn of the Building Performance Era.” But with handheld and
home-based devices hitting the market to measure air quality, UL predicts that will
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
change rapidly. “Today, UL’s air quality scientists estimate we are easily within five
years of having robust and effective industrial and home detectors and monitors for
air quality that can alert people when dangerous chemicals, allergens and
particulate matter are present.”
Unlike the pollution and pollen levels outside, homeowners can directly control the
quality of the air indoors.
In looking at the future of the building market, UL said, “Most building owners and
operators will derive the biggest bang for their dollars by focusing on maintaining
and enhancing the building’s energy, plumbing and HVAC systems to achieve an
optimal level of energy conservation, water management and conservation, and
indoor air quality performance. The savings on energy and water usage combined
with the health and productivity benefits from occupants breathing clean air are
the most universally valuable to building owners and investors.”
When air quality data becomes more accessible in commercial buildings, employers
and employees also will take a greater interest in the health risks, UL Chief
Economist Erin Grossi said in releasing the report.
Opening a Window Isn’t the Answer
The traditional vision of opening a window to let in fresh air simply doesn’t provide
an effective solution to improving indoor air quality. Throw open a window and you
can throw off the temperature and moisture levels in a home, not to mention
introducing outdoor contaminants, such as pollen.
“Uncontrolled ventilation with outdoor air can allow outdoor air contaminants to
bypass filters, potentially disrupt the balance of the mechanical ventilation
equipment, and permit the introduction of excess moisture if access is not
controlled,” EPA says.
Home ventilation options generally fall into three categories:
1. Exhaust only, fans typically placed in kitchens and bathrooms.
2. Central-fan integrated supply (CFIS), with an air handler or furnace fan,
brings in outdoor air and routes it through he HVAC system.
3. Balanced ventilation controls both the intake of fresh air and the
exhaustion of stale air, plus it can recover energy and balance humidity.
Exhaust Effects
Turning on an exhaust fan in the bathroom or kitchen can remove moisture and
odors but add other problems.
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
First the money you spent to heat or cool air is going out with the exhaust, and new
air coming in will need to be brought to the proper temperature. But from where
will that air come?
When an exhaust fan draws indoor air outside, that creates negative pressure in the
home. So the air being exhausted is replaced with air drawn into the home through
cracks and leaks in the building envelope.
“Sucking air out of the bathroom doesn’t mean the bedroom is taking in fresh air,”
explains Stephens.
That can draw in more pollutants and cause the heating or air conditioning system
to work harder to bring that new air to the proper temperature. If air is pulled in
through a flue or chimney, such as from a water heater or wood-burning stove, that
“backdrafting” can draw carbon monoxide into the home.
The Cost of Exhaust Fans
The energy use of different ventilation systems can vary dramatically. Consider a three-bedroom, one-bath home
with a Passive House ventilation standard of 60 cubic feet per minute. Imagine the outside temperature is 30
degrees Fahrenheit and the indoor temperature 70 degrees.
Operating a bath fan for just two hours per day would use 10,416 Btus and draw in air at 30 degrees. In contrast, a
90% efficient heat recovery ventilation (HRV) system would use only 6,250 Btus while operating all day and
dispersing fresh air at 66 degrees. If an HRV or ERV system meets continuous ventilation requirements, the home
may not need a bath fan at all.
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
CFIS Benefits Limited
CFIS ventilation has a low up-front cost but is often more costly to operate that the
other two systems. Although you control the intake of air, you still lose energy
when air is exhausted, because that air has been heated or cooled and nothing is
recovered from it.
Balanced Ventilation
With Heat Recover Ventilation (HRV) and Energy Recovery Ventilation (ERV), you
can manage the intake and outtake, plus recoup up to 95% of energy from air
before it is exhausted. A balanced ventilation system removes stale and over-moist
air and replaces it with filtered, fresh air.
See more about the pros and cons of each ventilation option in the U.S. Energy
Department’s “Building America: Selecting Ventilation Systems for Existing Homes.”
HRV or ERV?
Both HRV and ERV systems offer great energy recovery in a ventilation
system. On cool days, they transfer heat from outgoing air to the air from
outside, preheating it with lower energy costs. On warm days, they cool
incoming air with the air being exhausted. (INSERT Zehnder diagram of
basic HRV/ERV operationXX)
While an HRV is more energy efficient, an ERV also includes a semi-
permeable membrane that regulates moisture. On a hot, humid day it can
remove moisture before air enters the house, and it can retain moisture
when the incoming air is cool and dry.
In designing a home ventilation system, you need to think about all the
factors that will affect indoor comfort and energy efficiency. For example:
In the hot, humid South, home builders often chose an ERV for the added
benefits.
Occupancy by people — and pets — can effect
humidity levels. For example, a home to one or two people in a cold, dry climate may benefit from
moisture that an ERV can provide in the winter.
In some cases, a unit with a removable core can convert from an HRV to an ERV and back at different times of the
year.
For more guidance, download “Selecting an HRV/ERV System.”
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
The 5-Degree Comfort Difference
The ability of an HRV or ERV system to bring fresh air into a home very close to the
temperature of the air being removed offers an additional benefit. If the
temperature difference is greater than 5 degrees, the air doesn’t mix as well.
Pockets of hot air will rise or cool air will go to the floor, Stephens explained. “If it
doesn’t mix well, it doesn’t distribute well.”
When the temperatures are within 5 degrees, the mixture of air maintains a
consistent and comfortable environment for the residents, along with the other air
quality and energy efficiency benefits.
Plan a Complete Solution
Attaining a healthy, comfortable and energy-efficient home requires all of the
design and systems to work together, including the air sealing, heating and
cooling, and ventilation. That requires calculating things like the desired frequency
of air changes in the home. In general, an HRV or ERV unit should operate
continually at 60% of its capacity.
Whether you are building a new home or remodeling an existing building, it is
important to consider from the very beginning of your planning how systems will
work together.
The Minnesota Sustainable Housing Initiative estimates that after accounting for
the ventilation systems own energy use a typical HRV or ERV recaptures 60% to
85% of the outgoing air’s heat, although a Zehnder HRV can recover up to 90%.
Because those units preheat or precool air, a home can require a much smaller
heating and cooling system than it otherwise would need. “Not only can you
downsize it, but you really need to,” Belcher explained.
“A lot of homes are built with oversized air conditioning units,” he said, causing
them to run for short cycles and making it difficult to maintain a comfortable
temperature.
With a properly sized unit, “You’re getting a much more comfortable house with
much less energy,” Belcher said.
Zehnder offers complimentary design services, to design an HRV/ERV system
layout and provide a quote.
HRVs and ERVs also take little energy to operate. The Cold Climate Housing
Research Center says a typical HRV takes the same amount of energy to run as a 60-
watt light bulb. Zehnder’s ComfoAir 350 HRV uses less than a 40-watt bulb.
The units are quiet too. In addition to the low volume and air movement in its duct
system, Zehnder adds silencers to its ducts, which are made of pharmaceutical
A Fresh Look at Indoor Air Quality
ProudGreenHome.com © | Sponsored by Zehnder America
system, Zehnder adds silencers to its ducts, which are made of pharmaceutical
grade polyethylene, so there is no off-gassing from them. When ductwork isn’t
properly matched with an HRV or ERV, it can sacrifice energy efficiency, cause
condensation and create noise levels so high that occupants will turn off the
system.
To ensure a system operates as designed, Zehnder offers technical support to
installers and, when the home is complete, does a quality assurance inspection to
ensure the system is balanced in bringing in and exhausting air. A system that isn’t
balanced can lose 30% to 40% of its efficiency, Stephens explained.
Proud Green Home: Fresh, Comfortable and Efficient
Indoor air quality was particularly important in
building the Proud Green Home of St. Louis, an
energy-efficient model for a family with three
children, one of whom has mild respiratory issues,
including allergies and asthma.
So with the HVAC system for the five-bedroom,
3,700-square foot home is a ComfoAir 550 ERV
(energy recovery ventilator) from Zehnder, which has
a separate exterior air intake and duct system.
The ERV exhausts stale air and brings in filtered fresh
air, transferring moisture between incoming and
exhausted air. In addition to cleaning the air, an ERV
or Heat Recover Ventilation system helps prevent the
growth of mold, mildew and bacteria. It is designed
to help exhaust moist, stale air from bathrooms, the
kitchen and utility rooms while ensuring clean air
constantly flows into areas including the children’s’
playroom and bedrooms, moving at low velocity
through silencers to be quiet.
Not only are the homeowners enjoying low energy
bills, but also the home’s appraisal came in above the
contract price, said building consultant Matt Belcher,
a principal with Verdatek Solutions and director of
of the High Performance Buildings Research Center,
two of the partners on the project.
With appraisers now trained in the value of energy
efficient systems, he said, “We can get appraisals 10
percent above the contract price.”
A well-designed and properly installed system can
cut energy, operations and maintenance costs in half,
Belcher said. That’s with the benefit of improved
indoor air quality and comfort.