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.
With energy-consuming equipment, such as water heaters and refrigerators, we have good data on energy consumption and can set clear standards accordingly. In some product categories—clothes washers, for example—Energy Star standards were adopted because those standards provide a high enough threshold to represent just the very top segment of the product market (less than 10%). In other product categories—e.g., refrigerators and dishwashers—we set a higher threshold than ENERGY STAR: for example, exceeding those standards by 10% or 20%. With lighting and lighting control equipment, certain generic products qualify, such as compact fluorescent lamps and occupancy/daylighting controls, while in other categories only a subset of products qualify. In some cases, products that meet the energy efficiency requirements are excluded, because of evidence of poor performance or durability. Microturbines are included here because of the potential for cogeneration (combined heat and power) that they offer.
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.
The Novus 300 HRV, from Zehnder America, is a high-efficiency, Passivhaus-certified heat-recovery ventilator (HRV). Based on HVI test methods, it achieves an ASEF of 94%–96% and an SRE of 90%–91%, making it the highest performing HRV in the HVI Certified Products Database. The efficiency is thanks in part to an ECM motor. The Novus 300 can move up to 177 cfm, and comes standard with a MERV 7/8 filter, but an optional MERV 13 filter is available. An optional humidity heat exchanger is also available. The Novus 300 comes with a two-year warranty.
Heat-recovery ventilators (HRVs) and energy-recovery ventilators (ERVs) are mechanical air-exchange systems that can capture up to 90% of the heat content from stale indoor air being exchanged for fresh outside air. These products work by passing the air streams through a heat-exchange core, generally made with multiple aluminum or plastic plates.
HRVs and ERVs capture heat from the outgoing air during heating season to warm the incoming air. During the cooling season, warmer incoming air is cooled, minimizing air conditioning loads. ERVs also provide humidity conditioning using a desiccant wheel or plates made of a permeable material; these help retain indoor moisture during the heating season and exclude it during the cooling season. Most systems are balanced: the same volume of air is exhausted and taken in.
The efficiency of the heat exchange is dependent on both the equipment and the climate. While there are no Energy Star standards for HRVs and ERVs in the U.S., Energy Star standards are in place in Canada for residential units with a capacity of no greater than 500 cfm. These products must have a minimum "sensible heat-recovery efficiency" (SRE) at 32°F (0°C) of 65% and a minimum SRE at –13°F (–25°C) of 60%. The "fan efficacy" for models with SREs below 75% must be at least 1.2 cfm per watt (0.57 L/s/W) and for models with SREs of 75% or higher the fan efficacy must be at least 0.8 cfm per watt (0.38 L/s/W).
ERVs are a necessity in most commercial buildings. Though not appropriate for areas where contaminants are present, such as medical laboratories or kitchens, ASHRAE 90.1-2007 requires ERVs in certain climate zones for buildings with air exchanges equal to or greater than 5,000 cfm; ASHRAE 90.1-2010 increases requirements across most zones.
GreenSpec lists manufacturers of commercial packaged ERVs that meet Air-Conditioning, Heating, and Refrigeration Institute (AHRI) requirements, and residential models that have earned Canadian Energy Star certification, with exceptions for high-performing products that clearly meet those specifications but haven't yet earned certification.
EAc1: Optimize Energy Performance
EAc1.3: Optimize Energy Performance—HVAC
EAp2: Minimum Energy Performance
EAp2: Minimum Energy Efficiency Performance
EQc7.1: Thermal Comfort—Design
EQc7.2: Thermal Comfort—Verification
EQp1: Minimum IAQ Performance
IEQc1.3: IAQ Best Management Practices—Increased Ventilation
IEQc2.3: Occupant Comfort—Thermal Comfort Monitoring
IEQc7: Thermal Comfort—Design
IEQc7.1: Thermal Comfort—Design
IEQp1: Minimum IAQ Performance
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