Technical Analysis. Building Green and Healthy IEQ. Introduction. Green Standards and Indoor Environmental Quality

Transcription

1 Technical Analysis Building Green and Healthy IEQ Mark Misner CIE, CMI, CMRC Introduction The new green generation is upon us. From manufacturers and architects to builders and homeowners, everyone is talking about green. Building to green standards has become increasingly common and a larger percentage of new construction is following the green path. Striving for maximum construction and operating efficiencies has become the new normal. However, there are a lot of unanswered questions associated with what building green delivers for homeowners and building owners. Green certified buildings are intended to represent the pinnacle of energy and resource efficiency. There is also an implied benefit that green certified structures provide a healthier indoor environment for building occupants. In fact, most green programs discuss the benefits of using low urea formaldehyde (UF) and VOC emitting building and finishing materials as well as high performance HVAC systems to improve indoor environmental quality (IEQ). Therefore, public perception is green is healthier; but is it really? The reality is that indoor environmental investigators are finding that green certified structures are suffering many of the same indoor environmental problems associated with traditional built structures. Of course this comes a quite a shock to a property owner who paid a premium to build green and expected a healthy indoor environment. Therefore, it is important to understand green design specifications, the sources for poor indoor air quality and steps that can be taken to promote healthy indoor environments. Green Standards and Indoor Environmental Quality There are presently over 28 green building standards utilized in the building industry. All green building standards embrace the same building concepts including: Site Design and Efficiency Energy and Thermal Efficiency Resource Efficiency and Sustainable Materials Use Water Efficiency and Conservation Indoor Environmental Quality The Indoor Environmental Quality section for most green building codes include: Combustion Venting Humidity Control Ventilation Construction Contamination Control Radon Mitigation Car Emission Control Low VOC Furnishing and Finishes HVAC Air Filtration Green Standards and Healthy IEQ Page 1 of 5

2 Common Indoor Environmental Stressors Indoor environmental quality (IEQ) is a measure of the health of our indoor environment. IEQ encompasses air quality, environmental comfort and the health of building occupants. Structures that are comparatively free of indoor pollutants, known as stressors, are deemed healthier than those structures with biologic or chemical contamination. Therefore, the presence or absence of stressors is the best gauge to assess overall IEQ. The following table identifies the most common indoor stressors and their sources: Stressor Type Biologic & Allergenic VOCs & mvocs Toxins Ozone Radon Gas CO & CO 2 Common Sources Mold, bacteria, pets, dust mites, plants, pests and outdoor sources. Building and finishing materials, furniture and fixtures, cleaners and chemicals, air fresheners, candles, pesticides, sewer gas, personal care products and biologic sources. Biologic toxins, plant toxins, chemicals and pesticides. Ionic air cleaners, electrostatic air filters, office equipment, germicidal UV lights and electrical equipment. Natural radioactive sources found in soil. Ventless fireplaces, gas appliances, chimney/flu backdraft and cars. As the table above indicates, there are two sources for indoor environmental stressors: 1. Stressors that are generated from building materials and natural sources. 2. Stressors that are introduced and/or generated by building occupants. By far, the most significant source for indoor stressors is generated by building occupant activities. While low UF and low VOC building materials may reduce a portion of the total VOC load, building occupants produce and introduce the most significant range and density of VOCs, biologic contaminants, chemical contaminants and toxins. Therefore, promoting healthy indoor environments through the use of low emitting building and finished materials may have no significant influence on IEQ. Simply stated, there little return on investment. Energy Efficiency and Indoor Stressors Extreme energy efficiency is the cornerstone of green construction. Achieving maximum energy efficiency includes using local supplied materials, recycled materials, efficient appliances and maximum thermal efficiency. To attain the highest level of insulation performance, every conceivable air infiltration point must be sealed and high R-value insulation must be used - this can be traditional bat insulation, ridged insulation panels and/or the use of expanding foam insulation. As buildings become more air tight, they become more isolated from and unaffected by the outdoor environment. In the past, traditional built structures breathed in that they had some air exchange with the outdoor environment. This is measured by the number of natural air changes per hour (ACH) a structure possesses. A typical residential structure built in the 1970's and 1980's has an ACH performance of 1.75 to 2.5 air changes per hour. Green Standards and Healthy IEQ Page 2 of 5

3 Every cubic foot of outdoor air that leaks into the structure must be conditioned by the HVAC system. Outdoor air entering the structure requires energy to be conditioned - heated, cooledand dehumidified. By reducing the number of ACH, energy is saved. Today, the average green built residential structure can easily achieve an ACH number of 0.3 air changes per hour. So we have moved from homes that achieve a full air exchange every 30 minutes to homes that do not achieve a full air exchange in three and a half days. While the reduction in ACH provides attractive energy savings, the loss of natural ventilation allows common indoor stressors to accumulate. In the past, stressors were diluted through natural ventilation. However, the benefits of dilution are lost in low ACH structures. As building occupants introduce chemical and biologic stressors into low ACH environments, exposure thresholds can reach levels that begin to impact occupant comfort and health. Without design elements and careful attention to stressor concentration, green certified structures are not healthy by default. Indoor Stressors and Occupant Health As indoor stressors accumulate, exposure risks for building occupants increase. While short term exposure (acute exposure) to poor IEQ can be an annoyance, long term exposure (chronic exposure) can lead to illness. In the late 1970's health care professionals began witnessing an alarming trend in both acute and chronic illness attributed to indoor stressor exposure. Two new terms were coined to indoor exposure reactions: 1. Sick Building Syndrome - Acute, nonspecific complaints that quickly subside when removed from the indoor stressor. 2. Building Related Illnesses - Chronic disease directly related to stressor exposure. Typically requires intervening medical treatment. As building occupants introduce chemical and biologic stressors into low ACH environments, exposure levels that would otherwise be diluted over time are allowed to linger and magnify. Without design elements and careful attention to the potential for stressor concentration, green certified structures can suffer from poor indoor environmental conditions. Steps To Protect IEQ As demand increases for green certified structures, builders must take into account the unique building science conditions associated with high energy efficient construction. If green construction only improves energy efficient but not indoor environmental quality, what has been accomplished? Fortunately, there are several steps in building design and construction that net significant benefits towards a healthy indoor environment. These are relatively low cost methods that promote and protect IEQ. The following list is not intended as a design specification, but rather best practices and standard of care. Green Standards and Healthy IEQ Page 3 of 5

4 Ventilation: The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has established ventilation guidelines for low rise residential structures. The ASHRAE 62.2 standard calls for whole house mechanical ventilation systems to assist in the dilution of stressor buildup. By installing one or more Energy Recovery Ventilation fans, balanced ventilation can be restored in low ACH structures. HVAC Manual J, Test and Balance: While Manual J/D calculations are common today, many times the installed system does not perform to the calculation. Many factors from true equipment performance, actual structural thermal performance, to variances in installation can lead to this divergence. Therefore, it is important to Test and Balance the system after installation to ensure maximum performance. Issues like short cycling can lead to ineffective moisture control and this leads to a whole host of environmental and building science issues. Moisture Mitigation: Bulk water intrusion and sustained relative humidity are the leading causes for not only structural damage but also for the presence and proliferation of biologic stressors in the indoor environment. Moisture not only enters structures through a number of pathways but is also created through occupant activities. Moisture is created in structures by occupants through breathing, perspiring, cooking, running water, showering, laundry, washing dishes and watering plants. The Department of Energy estimates that the average family of four can create as much as six gallons of water vapor per day. Therefore it is important not only to keep moisture from entering the structure but to take steps to control the buildup of moisture from within the structure. Controlling interior moisture buildup can be addressed through ERV units, proper sizing of HVAC systems and by the use of dehumidification systems. Moisture mitigation includes: Sub-Slab Depressurization Systems/Radon Mitigation Systems Vapor Proofing Monolithic Foundation Slabs Crawlspace Encapsulation and Environmental Control Drainage, Waterproofing and Capillary Protection for Below-Grade Walls Window, Door and Roof Flashing French Drains and Positive Drainage From Foundation Proper Sized Guttering and Drainage Systems Integral HVAC Dehumidification Systems Relative Humidity Data Logging Mold and Biologic Control: Virtually every construction site possesses some level of mold contamination. Too often, mold contaminated building materials are walled in without any consideration on its impact on air quality or the potential for future structural damage should amplification occur. This occurs as ambient spores settle on building materials and germinate with sufficient moisture. Historically, job site mold contamination was accepted by builders and posed no significant issue. However, with the advent of highly insulated exterior walls employing low PERM rated building materials, sustained wall cavity humidity can quickly lead to hidden mold growth. Green Standards and Healthy IEQ Page 4 of 5

5 The simple solution to job site mold contamination is to have a fungal evaluation performed by a certified inspector just prior to installing exterior wall insulation and exterior wall closure. Remediate resident fungal contamination on building surfaces. After biologic decontamination, an EPA registered bonded antimicrobial treatment like Biostat-500 should be used to protect building surfaces from future biologic growth. It is especially important to use a bonded antimicrobial treatment for all insulated wall and ceiling cavities, bathrooms, laundry rooms, kitchen areas and plumbing chases. Air Purification, Odor and VOC Mitigation Air purification encompass several processes today in the indoor environment. The primary air filtration technology employed in virtually every HVAC system today is particulate filtration. Indoor particulates can include dust, mold spores, pet dander, smoke and biologic contaminants. However, gas phase contaminants like odors and volatile chemistries cannot be filtered or absorbed in a cost effective manner. While many air purification gadgets have been introduced over the years to address indoor odors and volatile chemicals, most provide no measurable benefits or create other IEQ problems. However, in the 1990's photocatalytic superoxide generators were introduced that provided effective odor and VOC reduction for residential HVAC systems. Current generation superoxide generators provide cost effective odor and VOC control in the residential and commercial environment. After extensive testing, the systems are effective and do not create other undesirable byproducts like ozone or toxic compounds. Annual Inspections Most unoccupied green certified structures will pass the typical battery of IEQ tests. However, occupancy begets a new IEQ dynamics by adding stressors that are not present in an unoccupied structure. Every indoor environment is unique. Therefore, there is no one size fits all solution and no magic bullet. Achieving a healthy indoor environment requires a synergistic solution. Periodic post-occupancy inspections is the most effective method to ensure IEQ design elements are performing to specification. Conclusion Building green is the new normal and with it, comes new building science challenges that must be addressed. While the default impression may be that Green is healthy, the reality is that a healthy indoor environment is not a guarantee. Builders must include new design elements in addition to the standard green design specifications to achieve long term indoor environmental health and comfort. By incorporating IEQ design elements into Green construction projects, building owners and occupants will enjoy all the benefits associated with building Green. Sources: Department of Energy, Energy Efficiency and Renewable Energy DOE/CE EPA Green Building Strategy (November 2008) National Institute for Occupational Safety and Health Building Air Quality Action Plan Fisk, William J Health and Productivity Gains from Better Indoor Environments Green Standards and Healthy IEQ Page 5 of 5