Alliance for Healthy Housing working for affordable healthy housing for all.

September 29, 2010

Ventilation and Indoor Air Quality

Proper ventilation helps improve indoor air quality. Ventilation can control indoor humidity and airborne contaminants, both of which either contribute to or act as health hazards. The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) and several states (Minnesota, Washington, and Vermont) have ventilation standards designed to ensure acceptable indoor air quality.
High indoor humidity can spur mold growth. High humidity may result from poor construction/rehabilitation, site design that does not properly manage water, and/or inadequate air exchange. A reasonable target for relative humidity is 30-60 percent. A low cost hygrometer, available at hardware stores, can be used to measure relative humidity. In cool climates, inadequate ventilation in the winter can contribute to excessive moisture and humidity because normal activities create moisture (cooking, bathing, breathing), and there is insufficient natural ventilation (opening windows) or mechanical ventilation (fans, exhaust systems) to remove the moisture. In warmer climates, the heating, ventilation, and air conditioning (HVAC) system can pull warmer, humid air inside. In this case, the ventilation system may help create indoor humidity problems unless the system also dehumidifies the air.

Common sources of airborne contaminants include:

Indoor contaminants. These include chemicals used in the construction or renovation of buildings (e.g., glues, off-gassing from carpets, emissions from particle board, cleaning compounds). In addition, appliances that burn gas can produce particulates and carbon monoxide. Incomplete combustion and poor ventilation of these appliances (cook stoves, gas furnaces, gas boilers, and gas water heaters) can contribute to indoor contaminants. Gas cook tops should be used with fans that send exhaust outside. Gas-fired heating appliances should be sealed and power-vented systems installed to remove products of incomplete combustion. Wood-burning stoves can also create particulates and must be vented outside.

Outdoor contaminants. Outdoor particulates can be drawn inside when the heating or cooling system draws air into a home. Particulates and allergens found in outdoor air can be asthma triggers. Filtering incoming air for HVAC systems effectively filters particulates. Experts recommend using filters with a MERV 6-8, but higher MERV levels trap smaller particles and generally are more appropriate for those with allergies or where the indoor environment has a high concentration of mold spores, dust particles, or other allergens.

Two types of ventilation can help control harmful air contaminants and humidity: spot ventilation and dilution ventilation. Spot ventilation draws air from a particular location (e.g., bathroom, kitchen) and exhausts it to the outside. Dilution ventilation address low-level contamination throughout the home.

Spot Ventilation. Exterior exhaust fans should be installed in all bathrooms and kitchens. These fans remove humidity and carbon monoxide. The most effective fans are quiet and durable. Use fans that operate at one sone or less and exhaust to the outdoors. Fans equipped with timers or de-humidistat controls are useful to ensure the fans run for a sufficient period of time. A good rule of thumb is to run a bathroom fan for about 45 minutes after a shower.

Dilution Ventilation. Dilution ventilation addresses the entire living space. Air changes (exchanging indoor air with outdoor air) and air cleaning help determine the effectiveness of dilution. Air changes result from a combination of natural ventilation (infiltration; leakage; windows) and mechanical (controlled) ventilation. Air cleaning occurs when particulates are filtered and when air is dehumidified to remove moisture. The goal is to provide sufficient changes to ensure a healthy environment. There are several types of heating and cooling systems with filtration that can be installed to accomplish this. A common element necessary in all systems is duct sealing, particularly on the return side (side drawing in the air). The Air Conditioning Contractors Association (ACCA) provides guidance on duct sealing in its Manual D: Duct Design.

Sizing HVAC Systems

It is important not to oversize a system. Oversizing can contribute to poor air distribution and insufficient dehumidification, creating an environment that promotes mold growth. Oversized heating systems can “short cycle,” meaning that the system does not run long enough to turn the fan on for a sufficient period to distribute new air. Systems that short cycle during air conditioning will deliver cold air in short bursts but not necessarily dehumidify the air. The resulting cold, clammy environment can encourage mold growth. Some contractors oversize HVAC systems to compensate for duct leakage and to minimize complaints about heating or cooling delivery. The ACCA provides guidance on system sizing in its Manual J.

HVAC Systems Can Contribute to Air Quality Problems

HVAC systems can also exacerbate indoor air quality problems. The HVAC system may be contaminated (because of mold in duct lining or bacteria on coil or filters, for example), and the system may spread these pollutants throughout the home. Second, the HVAC duct distribution system can spread pollutants from one portion of the home to another. Regular maintenance and duct sealing can help minimize these problems.

Sources and Additional Information:

Air Conditioning Contractors Association (ACCA) –

American Society of Heating and Refrigerating and Air Conditioning Engineers, Inc –

Building Science Corporation –

Home Energy Magazine –

Minnesota State Regulations – Ventilation –

Washington State Regulations – Ventilation –

Alliance for Healthy Housing

September 29, 2010

About Health and Housing

A century ago, advances in housing — everything from indoor plumbing to vented combustion appliances — were driven by the need to protect health. Today, the link between good housing and good health is often overlooked or taken for granted. However, housing directly affects everyone’s health, and conditions in our homes can cause or contribute to many diseases and conditions. Many common health hazards in housing are also environmental problems that can place young children, the elderly, and even entire communities at greater risk.

Housing Is a Health Issue

Because most individuals spend so much time inside, our homes typically account for a major share of exposures to toxics, irritants, allergens, and gases that can cause disease and hurt our health. For example:

mold, mildew, and pests (such as cockroaches, rodents, and dust mites) can trigger asthma, the leading cause of absences from elementary school;

carbon monoxide poisoning from combustion appliances, such as stoves, furnaces, and gas heaters, claims several hundred lives each year in the U.S. and causes flu-like symptoms at lower levels;

lead-based paint in older housing is the primary cause of childhood lead poisoning, which reduces children’s intelligence, interferes with learning, and causes behavior problems;

exposures to asbestos particles, radon gas, and second-hand tobacco smoke, all of which can cause cancer, are far higher indoors than outside; and

pesticide residues in our homes can pose significant risks for neurological damage and cancer.

Health care providers, government officials, property owners, and consumers all need to realize the importance of decent housing to good health. A growing body of scientific research has demonstrated that children who live in homes that are well ventilated, dry, and free of pests, poisons, and dangerous gases will be healthier and lead fuller lives. In particular, the current preoccupation with drug therapies for asthma needs to shift to give greater emphasis to reducing children’s exposure to asthma triggers and sensitizers in the home environment.

Addressing housing-related health hazards can significantly improve occupants’ health and quality of life while saving billions of dollars in health care costs.

Housing Is an Environmental Issue

Everyone knows that pollutants in our environment directly affect our health. Though we usually think of the environment as the outside world, scientists have long known that indoor exposures far exceed outdoor levels for most pollutants. Because toxic substances (such as lead and asbestos) and harmful gases (such as carbon monoxide and radon) build up in confined spaces, indoor levels are at least 10 times higher than outdoors for many pollutants of concern.

While protecting our air, water, and land from environmental pollution has become a top national priority, environmental health risks in our homes have been largely overlooked, despite the fact that most people spend about 90 percent of their time indoors.

Young Children and the Elderly

Infants and toddlers, whose developing systems make them most sensitive to pollutants, spend lots of time at home. Substandard housing is, in fact, the nation’s #1 environmental health threat to young children.

The elderly also tend to stay at home more than members of other age groups, putting them at heightened risk for health hazards in the home environment.

Low-Income Communities of Color

While homes of any age and value can harbor serious environmental hazards, older, low-income properties that are in substandard condition typically present the greatest risks. These homes are more likely to contain toxic substances, such as asbestos and lead-based paint. In addition, deferred maintenance in these properties often results in moisture and water leaks that encourage infestations of mold, mildew, dust mites, cockroaches, rodents, and other pests. Millions of American families live in physically substandard homes or have insufficient income to support basic property maintenance.

The fact that older, substandard housing is often concentrated in low-income communities of color makes housing-related health hazards a pressing environmental justice priority as well.

Help us work for healthy affordable housing for all—make your tax-deductible contribution to the Alliance today!

Alliance for Healthy Homes and National Center for Healthy Housing Announce Merger

September 29, 2010

On January 20, the Alliance for Healthy Homes and the National Center for Healthy Housing announced a merger between the two organizations in order to better serve the shared mission of promoting healthy, affordable housing.

The consolidated organization will continue to operate as the National Center for Healthy Housing, with offices in Columbia, MD and Washington, DC.

From now on, please visit to find information about healthy housing.

How can I control the humidity in my home during the summer?

September 28, 2010

Humidity has an important effect on comfort during the summer. Some weather forecasters in the summer talk about the comfort index, which attempts to show how much hotter the air temperature is likely to feel to you because of the humidity. The higher the humidity, the hotter you will feel. One of the ways air conditioners operate is to remove humidity from the air, which makes you feel cooler.

If you live in an area with high humidity, be careful about leaving windows and doors open during the summer. This will allow moisture from the outside air to enter your home. A way to control indoor moisture during humid summer months is to run an air conditioner and/or a dehumidifier. If you use a dehumidifier, clean it often. Also, empty it daily or have it drip directly into a drain.

Warm air can hold more moisture than cold air. Therefore, when your home is warm in the summer, more moisture is likely to stay in the air rather than condensing on the surfaces of walls and windows. In most climates, keeping an indoor humidity level below 60 percent in the summer probably will prevent condensation and mold growth.

Even though your air conditioner removes moisture from the air, the areas around your air conditioning system can be a source of water build-up. Make sure the drip pan on your air conditioner has not overflowed, and check near your air conditioning system for traces of dampness where mold can grow.

How can I determine the level of moisture in my home?

September 28, 2010

Weather forecasters talk about the relative humidity outdoors. Likewise, the inside of your home has a relative humidity, which is a measure of the moisture content in the air. Hardware stores sell instruments to measure the humidity inside your home.

Humidity is an important factor affecting the comfort level in your home. Have you ever awakened in the middle of a winter night to discover that your throat and nose feel very dry? That could mean the humidity in your home is too low. To remedy the problem, some people use humidifiers, which are designed to raise the humidity in a home. Your goal should be to have enough humidity in the air so the members of your household can stay healthy and comfortable.

Too much humidity can cause droplets of water to form on your walls, floors and windows, which can lead to mold growth. This formation of water droplets is called condensation. It occurs when warm moisture comes in contact with a cool surface. If you pour a glass of ice water and leave it on your kitchen table, the glass soon will begin to sweat. The sweating does not come from inside the glass. It is created when moisture from the air condenses when it comes in contact with the cold outer surface of the glass.

A sign of excessive humidity in a home can be condensation on the inside of windows, especially if you have double- or triple-pane windows. If condensation is present for prolonged periods, take steps to reduce the level of moisture or increase ventilation in your home. Condensation also can result from the use of unvented fuel-burning appliances, such as kerosene heaters or wood-burning stoves. If you use such appliances, have them inspected by a professional contractor or a utility company representative.

Another sign of excess moisture could be the warping of floors or difficulty in opening wood windows and doors. In such cases, the moisture from the air is absorbed into the wood, causing it to expand.

5 tips to improving your home’s indoor air quality

September 26, 2010

When you’re stuck inside because it’s too hot to go outside, you’ll be grateful if the air in your home is clean and comfortable.

As long as you’re indoors, why not spend time making sure it is?

A few simple changes and chores can upgrade the quality of your indoor air, make your family feel cooler on the hottest days and spruce up the look of your rooms. Here are five tips:

1. Upgrade your ceiling fans-or add fans if you don’t have any.
Installation is an easy do-it-yourself project. Newer models are far more energy efficient, and it’s easier than ever to choose one that conserves electricity. Here’s how:

• Look for a fan with a label that says it uses few watts per cubic foot of air. Older fans use as much as 60 to 70 watts.

• Buy a fan with five blades. The more blades your fan has, the more efficient it is. Newer fan blades are pitched so they create a vacuum when they spin, which helps them propel with less electrical energy. That increased pitch also makes the movement quieter, so there’s less of that helicopter like chopping sound.

• If you raise your thermostat by 4 degrees and turn on the ceiling fan, you probably won’t feel any difference in comfort, but you could see a difference for the better on your cooling bill.

2. Update your window treatments – but don’t stop with the drapes and blinds.
The sun will fade and ruin them unless you also add sunscreens, especially on the west and south sides of the house. You can mount sunscreens on the inside of the windows under your drapes. Or, invest in honeycomb shades with double cells, which are easy to install, reasonably priced and come in variety of colors.

A tip: Choose a style that allows you to lower the window cover from the top down instead of raising it from the bottom up. You’ll still get a lot of light and have a nice view of the sky without letting direct sunlight into the room or sacrificing your privacy. Other tips:

• If you have a skylight, cover it with a motorized cellular shade or screen to keep the hot sun from beating down on the room in the early afternoon. Just push a button to open and close it.

• For bedrooms and home theaters, consider blackout shades with a sliding track system on the sides to close the gap between the fabric and the window. The plastic track locks out the light and can reduce the loss of your cool, indoor air by up to 65 percent.

3. Switch all light bulbs to compact fluorescent lights or LEDs (light-emitting diodes).
They cost more than incandescent lights, but they last far longer and use a fraction of the energy. Plus, they don’t get hot when they burn, unlike incandescent bulbs, which spend about 90 percent of their energy producing heat rather than light. Consider:

• Trying out a few LEDs in the kitchen to see if you like them. Good places: in a pendulum light over the kitchen island and under cabinets.

• Dimming your lights so they use less energy. Look into dimmer switches if you’re still using incandescent lights, and into whole-house lighting controls that allow you to turn the lights on or off from anywhere inside or outside of the house. Motion sensors also save energy because they switch lights off when nobody’s in the room.

4. Switch to non-toxic cleaners for big and small jobs.
If you’re having your carpet professionally cleaned, hire a contractor who freshens the rugs with eco-friendly cleaners. And try mixing white vinegar with water to clean windows, floors, and kitchen and bathroom surfaces. In most cases, it works as well as chemical cleaners, and it does a great job of removing set-in odors.

5. Have your air-conditioning system checked.
Hire a pro to check your ductwork for blockages and leaks, to inspect your clothes-dryer exhaust duct to make sure it’s working properly and to clean your air-conditioner’s air handler and coils. If you don’t clean the coils, there’s no sense in cleaning the air ducts.

• Toss your cheap, fiberglass air-conditioner filter and upgrade to a pleated filter with a MERV 8 rating (for Minimum Efficiency Reporting Value, which is a rating system of the American Society of Heating, Refrigeration and Air Conditioning Engineers). The higher the MERV rating, the smaller the particles it will remove from the air.

• Change the filters every month, even if the manufacturer says you can go two or three. Arizona is a hot, dusty place, so the filters don’t hold up as long here as in other parts of the country.

• If you have a reusable electrostatic filter, clean it often. The most expensive reusable filter is less efficient than a $5 or $7 disposable filter if you don’t clean it.


September 26, 2010

Teachers have a significant role maintaining good air quality in classrooms. Below are a few tips for teachers that if followed can assist in maintaining or improving the air quality of classrooms.


Classroom air supply systems are critical to the classroom environment. It is important that air systems are not manually turned on or off and are not blocked. Classroom air systems will not work properly when the system is even partially blocked. If there are issues with your air supply system, ask the front office to enter a work request for Building Services to address the issue on your behalf. If you are storing materials like the ones shown below finding alternate storage space will allow the system to better perform.


Cloth furniture, stuffed animals, pillows and other such articles are reservoirs for allergens and asthma triggers. It is important to wash these types of materials out of the classroom or cleaned regularly to keep allergens to a minimum.


Dust can be a serious problem for asthmatics or others with upper respiratory sensitivity. Keeping clutter to a minimum will allow your custodian to take better care of your room. For instance, keeping stored materials in plastic boxes with lids allows them to be dusted. Your custodian takes good care of your room. However, the hygiene of personal items, media carts, computers and stored materials is the responsibility of the teacher(s) using or storing these items.


Furry animals produce dander which can be both an allergen and asthma trigger. It is best not to have furry animals in the classroom. If animals are required for curriculum the cages should be cleaned on a daily basis and more sensitive children should sit on the opposite side of the room from the animals. Animal food should be stored in sealable vessels. You should never be able to smell the presence of the animals in your classroom.


Masking agents introduce substances into the air that may smell nice to some, but may be offensive or upper respiratory irritants to others. It is best not to use masking agents in classrooms. If there is a building related problem causing odors, the masking agent makes it harder to find the problem. There have been a number of response actions conducted by district personnel where simply removing the masking agents out of the building resolved staff and student upper respiratory irritation.


It is important that classroom air systems are allowed to run as designed. Tampering with the air system not only impacts your room, but may start a domino effect that impacts other classrooms too. If your classroom is not within the accepted temperature range contact the front office to request support.


Do not store or prepare food in classrooms unless there is a specific medical or curriculum need to do so. Food spoils, attracts pests and should be prepared in appropriate spaces. Home appliances are not intended for use in school buildings and generally do not have the appropriate ASTM rating.


Perfumes, aftershave and colognes may be serious upper respiratory irritants. Reduce use to a minimum while at school to avoid triggering asthma attacks or causing upper respiratory system irritation.


Report floods, water leaks, or water spots to the front office promptly. By reporting these issues early the initial problem can be addressed by Building Services before the moisture becomes a more serious event.


Empower yourself to improve the indoor environment by reading up on IAQ at the USEPA Tools for Schools IAQ Website.

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