Moisture brings durability and air quality problems with it, and myriad green products are designed to manage it and keep it out. Given the variety of products available, we look for those that meet key performance standards and that make sense in a whole building assembly—such as vapor-permeable weather-resistive barriers that not only prevent moisture from entering the building envelope but also allow drying when the envelope gets wet.
Before specifying efficient heating and cooling equipment, it’s important to do what we can to reduce heating and cooling loads. Insulation is one of the key products to consider here, but because there are so many insulation products on the market, we look for additional benefits. Examples include cellulose insulation with recycled content, mineral wool insulation with no flame retardants, and fiberglass insulation with no formaldehyde binders. Other products in this area are high-performance windows and glazings, products that contribute to building airtight envelopes, products that reduce thermal bridging, and window-retrofit products.
With products in this area under constant development, we are always refining our approach. For example, as we have learned about insulation products with hazardous flame retardants and blowing agents that have high global warming potential, we have removed those products from GreenSpec, pending manufacturing changes. We encourage building professionals to pressure manufacturers for those changes through specification language and purchasing decisions.
Once we’ve considered low-emitting products and those that prevent moisture problems, we also consider green ventilation products, filters, radon mitigation equipment, and other equipment and devices that help to remove pollutants or introduce fresh air. Because ventilation equipment is standard, we only recognize products that are particularly efficient or quiet or which have other benefits, such as heat recovery.
Cyclonic Air Scrubbing Technology, Inc. manufactures air pollution emission control units (ECUs) with contaminant removal rates for grease, smoke, odors, and VOCs of 90% - 99.7%. The ECUs use water bath air scrubbing technology, low-pressure-drop Airguard HEPA filters (approximately MERV 18), carbon cell filters, and a catalyst medium. Replacement frequency for filters and catalyst depends on pollutant concentrations (averaging every 4 - 6 months according to the manufacturer). Two models are available in a variety of sizes. The Maxium is a rooftop unit designed for solid fuel cooking with heavy grease and high VOC concentrations. The Low Boy model is designed for gas or electric kitchens with lighter oils and works in above-ceiling and sidewall exhaust discharge situations. The Low Boy optional air recirculation package allows for 80% recirculated air applications and reduces A/C, makeup air, and exhaust fan loads. With the demand ventilation control option, C.A.S.T. air scrubbers can reduce utility costs by 60%, according to the manufacturer.
Dust, mold spores, volatile organic compounds (VOCs), hazardous airborne pollutants, and other contaminants can accumulate indoors, creating health problems for occupants and affecting the performance of other HVAC equipment. Filtering out contaminants is challenging, however, since different filtration methods are required to reduce particulates and gases across a variety of building types, ventilation systems, and end uses.
The most common mechanical filters use membranes to trap airborne particles, and include panel, pleated, box, and other varieties. ASHRAE 52.2 Test Procedure for filters measures particle size efficiency (PSE) at 0.3–1.0 micrometers (E1), 1.0–3.0 micrometers (E2), and 3.0–10.0 (E3) micrometers, to create an overall minimum efficiency reporting value (MERV). MERV ratings are based on a scale from 1 to 16, with 1 capturing <20% of E3 particles and 16 capturing 95% of all particles. High-efficiency particulate air (HEPA) filters must remove 99.97% of particles >0.3 micrometers.
Simple filters may be enough to protect HVAC equipment from contamination and damage, but disposable filters with MERV ratings between 8 and 13 are most often used to capture contaminants found in residential and commercial buildings. HEPA and higher MERV filters are usually used in hospitals, laboratories, and other applications that require control of pathogens or other contaminants. A balance has to be maintained between adequate filtration and ventilation, however, as higher MERV filters typically create a pressure drop that forces the HVAC equipment to work harder and requires additional energy.
Electrostatic precipitators can also be effective and have less pressure drop. In these systems, air passes through an ionizer where the particles are charged; the particles then attach to other particles and fall to the ground, attach to objects in the room, either to a charged filter (which is recommended). Electrostatic precipitators sometimes produce a small amount of ozone, but should not be confused with ozone generators, which can cause indoor air quality problems and should be avoided.
Filtering gases, such as VOCs, vehicle exhaust, and cooking odors, requires an adsorbant filter media, typically activated carbon. While not often used in residential applications, they are used as part of pollution control devices for restaurants in many urban areas.
UV lights alone or in combination with a catalyst in photocatalytic oxidation (PCO) systems can be effective for breaking down VOCs and other contaminants into less harmful forms, but most ducted UV systems are limited in applicability by cost, maintenance requirements, and limited air exchanges.
GreenSpec lists a variety of equipment, filters, and pre-filters that remove particulates and contaminants, minimize pressure drop, or reduce pollution from operations. Products include MERV 13 or higher filters from major manufacturers as well as proven technologies that remove harmful or nuisance gasses, and those that protect HVAC equipment from contaminants. GreenSpec does not list products that produce ozone, either using an ozone generator or as a byproduct of other systems, because of indoor and outdoor air quality problems associated with ozone.
Ratings and Commentary