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Mobile View ENERGY SAVINGS in BUILDINGS ENVIRONMENTAL HAZARDS GUIDE AIR POLLUTANTS, COMMON INDOOR ALLERGEN TESTS for BUILDINGS ALLERGENS in BUILDINGS, RECOGNIZING ALLERGY TESTS for PEOPLE ALLERGY TEST ACCURACY FLOODS IN BUILDINGS-priorities FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP MOLD: A COMPLETE GUIDE TO MOLD MOLD INFORMATION CENTER ACCURACY OF VARIOUS MOLD TEST METHODS ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD CLEARANCE INSPECTIONS - MOLD CLEANUP DO IT YOURSELF MOLD CLEANUP ENERGY SAVINGS in BUILDINGS ENERGY AUDIT - How to Use a Free One ENERGY SAVINGS MAXIMIZE RETURNS ON ENERGY SAVINGS PRIORITIES ENERGY SAVINGS RETROFIT CASE STUDY ENERGY SAVINGS RETROFIT LEAK SEALING GUIDE ENERGY SAVINGS RETROFIT OPTIONS ENERGY USE MONITORING FIND MOLD in BUILDINGS, HOW TO FUNGICIDAL SPRAY & SEALANT USE GUIDE HIDDEN MOLD, HOW TO FIND HUMIDITY CONTROL TO PREVENT MOLD INDOOR AIR QUALITY & HOUSE TIGHTNESS INDOOR AIR QUALITY IMPROVEMENT GUIDE Health Effects of Air Pollutants Common Indoor Air Pollutants Key Strategies for Improving Indoor Air Quality Whole House Ventilation Strategies Exhaust-Only Ventilation Supply-Only Ventilation Balanced Ventilation Heat Recovery Ventilation Energy Recovery Ventilators Air Filtering Strategies Particles in Indoor Air - Chart Quick Guide to Gases Air-Cleaner Types Particulate Air Cleaner Table Air Filter Effectiveness Real-World Effectiveness of Air Cleaners Finding & Reducing Air Pollutants Radon Hazards Formaldehyde Hazards Biological Pollutants Volatile Organic Compounds VOCs Pesticide Exposure Hazards Lead Exposure Hazards Asbestos Exposure Hazards Carpeting and Indoor Air Quality Combustion Appliance Contaminants Backdrafting Appliances Fireplace & Woodstove Contaminants INDOOR AIR HAZARDS TABLE INDOOR COMBUSTION PRODUCTS & IAQ ODORS, Smells, Gases in Buildings-Diagnosis & Cure INDOOR AIR QUALITY METHODS COMPARED LEAD POISONING HAZARDS GUIDE MILDEW in BUILDINGS ? MILDEW ERRORS - MOLD PHOTOS MILDEW REMOVAL & PREVENTION MOISTURE CONTROL in BUILDINGS MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD MOLD AGE - Old is the Mold? MOLD APPEARANCE - WHAT MOLD LOOKS LIKE MOLD APPEARANCE - STUFF THAT IS NOT MOLD MOLD ATLAS & PARTICLES INDEX MOLD BY MICROSCOPE MOLD CLASSES, HAZARD LEVELS MOLD CLEANERS - WHAT TO USE MOLD CLEANUP COMPANIES MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD MOLD CLEARANCE INSPECTIONS MOLD DETECTION & INSPECTION GUIDE MOLD DOCTOR? MOLD EXPERT, WHEN TO HIRE MOLD EXPOSURE RISK LEVELS MOLD EXPOSURE STANDARDS MOLD FAQ's MOLD FREQUENCY in BUILDINGS MOLD GROWTH on SURFACES MOLD INSPECTORS & MOLD TESTERS MOLD LEVEL REPORTS MOLD LEVELS IN BUILDINGS MOLD by MICROSCOPE MOLD ODORS, MUSTY SMELLS MOLD PREVENTION GUIDE MOLD RELATED ILLNESS GUIDE MOLD RELATED ILLNESS SYMPTOMS MOLD SPRAYS, SEALANTS, PAINTS MOLD STANDARDS MOLD TEST KITS MOLD TEST KITS for DIY MOLD TESTS MOLD TEST PROCEDURES MOLD TEST REASONS MOLD TESTING METHOD VALIDITY MOLD TESTING SERVICES NOISE / SOUND DIAGNOSIS & CURE ODORS, Smells, Gases in Buildings-Diagnosis & Cure RENTERS & TENANTS GUIDE TO MOLD SEWAGE BACKUP TEST & CLEANUP STAIN DIAGNOSIS TECHNICAL & LAB PROCEDURES THERMAL TRACKING TRAPPED MOLD BETWEEN WOOD SURFACES USING LIGHT TO FIND MOLD VENTILATION in BUILDINGS Air Bypass Leaks, Thermal Tracking ATTIC CONDENSATION CAUSE & CURE BATHROOM VENTILATION BLOWER DOORS & AIR INFILTRATION BRICK VENEER WALL INSULATION CATHEDRAL CEILING INSULATION CATHEDRAL CEILING VENTILATION CRAWL SPACE VENTING & Dryout Procedures HOUSEWRAP AIR & VAPOR BARRIERS HUMIDITY LEVEL TARGET ICE DAM PREVENTION MOISTURE CONTROL in BUILDINGS MOISTURE CALCULATIONS MOISTURE PROBLEMS: CAUSE & CURE ROOF VENTILATION SPECIFICATIONS ROOF VENTING ENERGY SAVING DETAILS ROOF VENTING NEEDED? VENTILATION DESIGN PROBLEMS & SOLUTIONS WHOLE HOUSE VENTILATION Strategies VINYL Siding or PLASTIC Window ODORS in Buildings VINYL CHLORIDE HEALTH INFO WATER ODORS More Information InspectAPedia Blog - News Updates Air Conditioning & Heat Pumps Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Privacy Policies Contact Us |
Here we discuss using balanced fresh air ventilation systems, heat recovery ventilators, and energy recovery ventilators to improve indoor air quality in homes. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. But many indoor contaminants are simply too small to see, or are not particles at all but rather gases or chemicals. See ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY for our full list of environmental hazard identification and remedy related to buildings © Copyright 2010 Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. Balanced Ventilation Air for Improving Indoor Air Quality
Balanced Ventilation System ControlsHRVs and ERVs are typically run continuously, but they also may be set to run 8 to 12 hours per day when people are at home. In addition, most have a high-speed mode that can be manually activated for spot ventilation of kitchens and bathroom. Some balanced ventilation systems also use dehumidistats to automatically turn on or increase ventilation when the air reaches a preset humidity level. Balanced Ventilation System DuctingWhile a dedicated ductwork system is the best approach for HRVs and ERVs, to save money they are often piggybacked onto the home’s HVAC ductwork. In one approach, the HRV or ERV draws exhaust air from the return ductwork and feeds fresh air into the furnace’s return plenum. In a slightly better arrangement, the HVAC ductwork is used only for supply, while the exhaust side picks up stale air in bathrooms, laundry, and kitchen. Neither approach distributes fresh air as well as a dedicated duct system. Also, since HRV/ERV fans operate at 100 to 200 cfm while air-handler fans are often sized at over 600 cfm, trying to integrate the controls, balance airflows, and provide the correct amount of ventilation air is challenging and rarely works well. The most common approach is to run the ventilation system only when the thermostat calls for heating or air-conditioning, providing too little ventilation. Heat-recovery efficiencies are also compromised, typically due to unbalanced airflows. Balanced Ventilation System MaintenanceOne drawback of HRVs and ERVs is that they require more maintenance than other ventilation systems. Numerous studies have found that many of these systems significantly under perform in the field due to both installation errors and poor maintenance. In addition to cleaning or changing intake, outtake, and internal filters, the homeowner or service person needs to clean the core once a year or more to prevent mold and bacteria growth. It is important to follow closely the manufacturer’s recommendations. Unless the homeowner enjoys the responsibility of HVAC maintenance, the work is best handled by a professional service company. Balanced Ventilation System Cost EffectivenessFor HRVs and ERVs to work properly and achieve the rated efficiencies, they must be installed correctly and balanced well, and the house must be very tight. Even so, the added cost over a basic ventilation system will be recouped only in the most extreme United States climates with the highest energy costs. However, in very cold or hot climates where mechanical ventilation is needed during most of the year, the added cost may be justified by the comfort of tempered, filtered ventilation air, the effectiveness of the distribution, and the lack of pressure-related problems. Heat Recovery Ventilation Systems - HRVsDefrost cycle for heat recovery ventilatorsIn cold climate applications, a defrost cycle is required. It usually switches on at about 20°F to keep frost from building up in the core as condensation from the exhaust stream begins to freeze. Systems either recirculate indoor air or preheat incoming air to prevent freeze-ups. Energy Recovery Ventilators - ERVs for Indoor Air VentilationEnergy-recovery ventilators are primarily used in air-conditioned homes in hot, humid climates. They are generally recommended for climates where the cooling load exceeds the heating load and where sustained freezing temperatures are rare. Sustained temperatures below 10°F can damage the permeable core material used in many ERVs. ERVs either use a dessicant-coated plastic wheel or a special “enthalpic” core material to move moisture (latent heat), as well as sensible heat, between the two air streams. In summer, incoming air is cooled and dehumidified. Since dehumidification is the biggest component of air-conditioning costs in humid climates, it is important to find a unit with a high TRE (total recovery efficiency) rating, indicating that it can transfer large amounts of moisture. To achieve the rated efficiencies, the units must be run at the recommended airflows. In cold weather, an ERV will tend to humidify the incoming air, since the moisture transfer is always toward the less humid air stream. This is rarely a problem, however, since the cold incoming air holds so little moisture to begin with that the net effect of the air exchange is to remove humidity from the house. -- Adapted with permission from Best Practices Guide to Residential Construction. ... Technical Reviewers & References
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