Breathe Easy: Taking a 'Whole House Solution' Approach to Indoor Air Quality
Accumulation of biological pollutants can result in hazardous health effects for occupants, as well as structural damage to the building.
- By Jim Shelton
- Sep 01, 2017
They say ignorance is bliss. But today, with mounting evidence showing the harmful health effects of poor indoor air quality (IAQ), consumers and businesses alike are making considerable changes to reduce their carbon footprint. According to the Environmental Protection Agency, each year, more than 7 million people across the globe die because of exposure to indoor and outdoor air pollution. Of those 7 million premature deaths, 3.8 million are caused by exposure to indoor air pollution.
In the 1970s, rising home energy costs led to tighter building construction. To obtain these airtight designs, builders used newly designed windows and doors, sealing caulks and other insulating materials to create better energy efficiency. The resulting benefit was fewer drafts and therefore, smaller heating and air-conditioning costs. However, a new problem emerged: the extra pollutants retained in airtight buildings showed to be hazardous to occupants due to the buildup of pollutants and uncirculated stale air.1
Today, the need for mechanical ventilation, allowing even the most tightly built home to "breathe" in fresh air and exhale any pollutants in a controlled and monitored way, while still maximizing energy efficiency, is at the forefront of modern building science discussions. As building codes require tighter, more energy-efficient homes, third-party certification programs like EPA's ENERGY STAR® enable and encourage builders to have a profound impact on the comfort and safety of residents (by improving IAQ), as well as the cost of construction and the cost of operating the home.
Think of mechanical ventilation as the lungs of the home. Without air systematically supporting the body with oxygen and exhausting the carbon monoxide, the human body would not function in a healthy manner. The same is true for ventilation in the home. As an industry, we have an obligation to consider home health and IAQ as a primary driver in any home ventilation plan. While exterior pollutants such as smog and carbon monoxide may receive more attention, IAQ within a home can have serious effects on our physical and mental health, as well. Unsettling as it may sound, your home could actually be making you sick, leaving builders and manufacturers vulnerable to damaging and costly reputational harm and possible litigation. Here are common unresolved issues that lead to IAQ problems and "sick homes."
- Toxic molds. Biological pollutants, including mold, mildew, pollen, dust mites, pet dander, viruses, and bacteria, are found in all homes. In fact, 28 percent of American homes rated as unhealthy report problems with mold, mildew, and/or rot. Accumulation of these biological pollutants can result in hazardous health effects for occupants, as well as structural damage to the building.
- Formaldehyde. Many airtight homes are built or remodeled using synthetic building materials that may release harmful chemicals into the air. These harmful gasses are known as Volatile Organic Compounds (VOCs), carbon-based compounds that easily evaporate. Formaldehyde and other types of gases can also be released from building materials, carpets, furniture, and many other household items as part of aging, decomposition, or curing, all of which are natural processes known as off-gassing; 98 percent of new homes have indoor formaldehyde levels ranging from 4ppb (parts per billion) to 120 ppb, with a median of 29 ppb for the first 2-5 years.
- Carbon monoxide. Because it is impossible to see, taste, or smell the toxic fumes, CO can cause harmful effects before you are aware it is in your home. The effects of CO exposure can vary greatly from person to person depending on age, overall health, and the concentration and length of exposure. (Source: EPA)
Strategies for Whole-House Mechanical Ventilation
A building's envelope is the foundation for a successful ventilation strategy. A tight enclosure that minimizes moisture and air leakage lays the groundwork for a good ventilation system and also provides better energy performance overall. This creates a healthy, durable, energy-conscious space. All energy-efficient homes—new and existing—require mechanical ventilation to maintain good IAQ. For mechanical whole-house ventilation, there are four basic systems.
- Exhaust ventilation. Exhaust ventilation removes pollutants at the source. An inexpensive and simple approach to ventilating a home, exhaust-only ventilation works by forcing air out of the home to depressurize the interior and gain make-up air through passive vents. Because this ventilation system only actively exhausts air, it is not recommended in hot or humid climates. Since any make-up air is gained passively, that air may be very humid, contain pollutants, or be too cold, leading to energy penalties for the home. Powerful exhaust systems, such as commercial-capacity range hoods, should be used cautiously with combustion appliances, as they can cause back drafting. (Source: Panasonic Ventilation2)
- Supply ventilation. Supply ventilation, another simple and inexpensive approach, uses a fan to pressurize a home, actively bringing outdoor air inside while squeezing out indoor air. Supply systems offer better control over pollutants in incoming air, as they only obtain outdoor air through specified vents. Pressurizing the house more readily forces out combustion gases and other pollutants. However, supply systems struggle with conditioning or removing moisture from incoming air, and can raise heating or cooling costs.
- Balanced ventilation. Balanced ventilation works by both actively exhausting polluted indoor air and actively drawing in fresh, outdoor air in a balanced, controlled ratio. Because the system uses more fans and ducts than either the supply or exhaust approaches, it is more costly. However, balanced ventilation is appropriate for all climate zones.
- Energy Recovery Ventilation (ERV). By coupling a balanced approach with an energy recovery or heat recovery ventilator (ERV or HRV), incoming air can be conditioned and dehumidified, saving on heating and cooling expenses for the home. A tight enclosure guards the interior of the home and guarantees that air is properly enclosed and controlled.
During the past several code cycles, mechanical ventilation requirements have been added to ensure adequate outside air is provided for ventilation whenever residences are occupied. Ideally, an airtight home designed with both continuous and intermittent ventilation will contribute to a healthy and comfortable living environment for the entire family.
Building Energy Codes and Standards (Residential & Commercial)
Yet another factor for builders and homeowners to consider when evaluating the indoor air quality in their homes are the applicable local and national building codes. The International Energy Conservation Code (IECC) and American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) currently address the energy efficiency requirements for the design, materials, and equipment used in nearly all new construction, additions, renovations, and construction techniques.
ASHRAE 62.2 is the standard most commonly referenced for home ventilation. The purpose of this standard is to specify minimum ventilation rates and other measures intended to provide IAQ that is acceptable to human occupants and that minimizes adverse health effects. However, complying with a building energy code is challenging for both builders and architects. If a code requires ASHRAE 62.2 compliance and a home fails to meet the ventilation standard, a builder is faced with expensive alterations to mechanical systems, fan capacities, and duct sizing.
Home Energy Ratings
The Home Energy Rating System (HERS) Index is the nationally recognized scoring system for measuring a home’s energy performance. Ratings are calculated at the end of the construction process by a certified Home Energy Rater using diagnostic equipment and performance modeling software. The rating takes into account variables such as a home’s airtightness, level of insulation, and type of heating and cooling system. The lower the number, the more energy efficient the home.
In fact, the goal is to have a Net Zero home, which means that your home’s energy consumption is equal to the energy it is able to produce. These energy-efficient homes are more affordable to maintain, more comfortable, and have a higher value compared to regular homes. Older homes often fall under the higher ratings due to issues such as old sagging insulation or tiny cracks and holes that have developed over time, compromising the performance and energy efficiency of the home.
The U.S. Department of Energy has determined that a typical resale home scores 130 on the HERS Index, while a standard new home is awarded a rating of 100.
- A home with a HERS Index Score of 70 is 30 precent more energy efficient than a standard new home.
- A home with a HERS Index Score of 130 is 30 percent less energy efficient than a standard new home.
However, balancing a low HERS score with a whole home ventilation approach is difficult. As a measure of how tightly built your home is, a HERS score will likely increase when ventilation strategies are employed. For manufacturers and builders, the challenge becomes how to meet air cycle requirements as cost effectively as possible. The best measure of this in ventilation is "cost per HERS point."
To find a whole-house system that not only meets stringent ASHRAE 62.2 and ENERGY STAR® Certified Homes 3.0 ventilation requirements, but also provides the lowest cost per HERS point, builders and manufacturers are beginning to partner with utilities and independent third-party service providers and organizations that offer programs and/or services that support customer efforts to reduce energy consumption and improve energy efficiency. Finding OEMs that design and engineer ventilation solutions with these complex variables in mind can help you navigate this cost/efficiency nexus.
Popular voluntary performance programs such as Leadership in Energy and Environmental Design (LEED)® for Homes, ENERGY STAR® Homes program, and the Zero Energy Ready Home, use IECC and ASHRAE as the foundation to create a healthy, high-performance home. LEED works for all buildings—from homes to corporate headquarters—at all phases of development. Projects pursuing LEED certification earn points across several areas that address sustainability issues. Based on the number of points achieved, a project then receives one of four LEED rating levels: Certified, Silver, Gold, and Platinum.3
EPA also offers special recognition to builders who commit to building 100 percent of their homes to meet ENERGY STAR® program requirements. ENERGY STAR® is a voluntary government program administered through the EPA. Its goal is to help people and businesses save money and protect the climate through energy efficiency. Each year, EPA and DOE honor organizations and businesses that have made outstanding contributions to protecting the environment through energy efficiency with their annual ENERGY STAR® Awards event.
The blue ENERGY STAR label was established to reduce greenhouse gas emissions and other pollutants caused by the inefficient use of energy and make it easy for consumers to identify and purchase energy-efficient products that offer savings on energy bills without sacrificing performance, features, and comfort.4 ENERGY STAR® partners agree to measure, track, and benchmark energy performance; develop and implement a plan to improve energy performance, adopt the ENERGY STAR® strategy; and educate staff and the public about their partnership and achievements with ENERGY STAR®.
As more building codes call for whole house ventilation, a new ventilation system makes it easier to create supply or balanced ventilation system in a single-family or multifamily home. However, it’s important to note any mechanical ventilation system will not reach its performance potential if components are poorly manufactured or installed improperly. System imbalances occur when components of the HVAC system are improperly adjusted or installed and can create pressure differences (too much circulating air creating a draft or too little, circulating air creating stagnancy).
Unfortunately, most ventilation fans are not living up to their cfm claims, which can lead to costly compliance failure issues, expensive call-backs, IAQ problems, increased construction defects and warranty work, painful litigation, and angry, vengeful buyers.
A recent testing by Lawrence Berkeley National Laboratory found that of all the bathroom fans they evaluated, 48 percent failed the required airflow standards outlined in ASHRAE 62.2.2013. Many builders going for ENERGY STAR have learned that fans rated at 50 cfm generally don’t cut it and have turned to installing fans rated at 110 cfm in all their homes. One case study of Habitat for Humanity houses that were going for certification in the ENERGY STAR new homes program tested nine fans, all rated at 110 cfm. Only five of these 110 cfm rated fans beat the 51 cfm mark. They achieved between 51-85 cfm, none coming close to the 110 cfm rating. And the four fans that failed? Their exhaust flow rates were 30, 45, and 46 cfm.
So how does a ventilation fan help solve consumer desires? Home buyers want energy efficiency; 90 percent of home buyers list ENERGY STAR appliances as part of their most wanted features list, and 88 percent say the same about an ENERGY STAR rating for the whole home. Smart builders have listened. In 2015, 190,180 new homes in the United States were HERS rated, more than 38 percent of all new homes sold, which is a 30 percent increase over 2014. What's more, home buyers on average will pay an additional $10,732 up front to save $1,000 a year in utilities.
Whole-house mechanical ventilation is on the rise, driven by advances in building design, building codes, and an ever-more-discerning consumer base that recognize the importance of a healthy home environment. Since 2008, single-family detached homes with whole-house ventilation systems have grown from 9 percent to 27 percent of all new home construction, according to the 2015 Annual Builder Practices Survey conducted by Home Innovation Research Labs. Due to states' adoption of the 2012 International Building Code, more homes will be requiring mechanical ventilation, which will help alleviate moisture issues and maintain healthy indoor environmental quality for home owners.
Builders nationwide are seeking to lower their homes' HERS scores to meet ASHRAE 62.2 and ENERGY STAR® Certified Home 3.0 ventilation requirements. In an era with so many factors for builders and homeowners to consider, it's important to work with partners that understand all of these moving pieces and can help you find the best solution for your unique circumstance. Understanding how mechanical ventilation systems are evaluated and knowing their performance characteristics helps building and construction professionals find the right solution for their project needs. There are solutions that builders and contractors are working on that manufacturers haven't even seen yet. As new technologies arise and new public hazards are identified, working with manufacturers to come up with new products is a trend that will grow in the years to come. "Building tight and ventilating right" remains the recipe, both for a healthy home and a successful homebuilder.
This article originally appeared in the September 2017 issue of Occupational Health & Safety.