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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 Whole House Ventilation Table Exhaust-Only Ventilation Supply-Only Ventilation Forced-Air Supply Ventilation Multiport Supply 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 ® Home & Site Map 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 how and why to use supply-only ventilation 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. 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. Supply-Only Fresh Air Ventilation System Design & FeaturesAs reported in Best Practices Guide to Residential Construction: While not widely used, supply-only systems have distinct advantages over exhaust systems. The incoming air is easily filtered and can be directed to bedrooms and main living areas. The slight positive pressure helps guard against radon, backdrafting, and other problems associated with negative pressures. In cold climates, however, delivering nontempered air can lead to uncomfortable drafts. Also, forcing moist, interior air out through gaps in the building shell could contribute to condensation problems in building cavities and between prime and storm windows. In airtight homes in very cold climates, supply-only systems have reportedly iced up keyholes to entry doors as exfiltrating warm, moist air came in contact with the cold metal. Adding a single exhaust fan wired to operate whenever the supply fan switches on can alleviate these problems. Below we discuss two types of supply-only building ventilation approaches, followed by a discussion of Balanced Ventilation designs.
Forced-Air Supply Ventilation Piggybacks on Existing HVAC SystemA multiport forced air home ventilation system piggybacks on the ductwork of a central heating or cooling system by running an intake duct from outside into the return ductwork. The screened intake has a motorized damper that is timed to open when ventilation is needed, blending fresh air into the HVAC system and slightly pressurizing the house. A special controller is needed to control the damper and fan, activating the damper whenever ventilation is needed and activating the fan whenever the air handler has not run for a set period of time, typically 20 minutes. Several manufacturers, including Lipidex Corporation, Tjernlund, and Honeywell, make controllers for this application. One manufacturer, American Aldes, offers a packaged system for warm, humid climates: the DHV-100V, which dehumidifies and filters incoming air and integrates with the home’s central air-conditioning system. This approach is relatively inexpensive since it uses existing ductwork, and it provides good distribution of fresh air. The chief drawback is that ventilation is required at regular intervals, often when the HVAC system is not operating. At those times, the controller will switch on the air handler, which is typically noisy and inefficient, making this the most expensive system to operate. Also, delivering untempered outside air through the duct system can cause discomfort in very hot or cold weather. And if the return ducts are not well sealed, they can pull contaminants from attic or basement spaces into the ventilation system. The operating costs can be cut in half by replacing the standard air-handler blower with an efficient, variable- speed fan with an integrated control motor (ICM). The fan would work on high speed for heating and cooling and continuous low speed for ventilation-only, cutting operating costs in half. However, the damper adjustment that provides the right amount of ventilation air at 500 cfm Laboratory (LBNL) as the optimal system for tract homes will produce too little when run at 100 cfm. Either the based on first cost, operating costs, air distribution, and the setting has to be changed seasonally or a compromise level potential health and safety benefits of positive pressures. found. It is also easy to filter and, if necessary, to dehumidify the incoming air (Figure 7-4 below). Multiport Supply House Ventilation System to Improve Indoor Air Quality
Although the least common type of ventilation system, the multiport supply system was identified in a recent study by Lawrence Berkeley National Laboratory (LBNL) as the optimal system for tract homes based on first cost, operating costs, air distribution, and the potential health and safety benefits of positive pressures. It is also easy to filter and, if necessary, to dehumidify the incoming air. See our figure at left for details about a multi-port fresh air supply whole house ventilation system. Though not widely used, supply-only ventilation has several advantages: incoming air can be easily filtered and distributed to the rooms where it is needed, and positive pressures help guard against backdrafting and radon entry. Illustration Source: Recommended Ventilation Strategies for Energy-Efficient Production Homes, 1998, by Judy A. Roberson, et al., Lawrence Berkeley National Laboratory, appearing in the text cited above. While few packaged systems are currently available, one manufacturer, Tamarack Technologies, offers a unit with a replaceable filter and an efficient variable-speed fan that provides 90 cfm of ventilation through one 3-inch and three 2-inch ducts. Since these systems pressurize the house, the LBNL study recommends that, in cold climates, the supply fan be balanced by a single-port exhaust fan, which could also serve as a bathroom fan. In this type of system, a central fan, typically in the attic or basement, draws in outside air through a filter and delivers it through ducts to bedrooms and main living areas. The supply ductwork should be in conditioned space or insulated and sealed airtight. Supply grilles should be placed high on the wall away from beds, chairs, or other places where drafts could cause discomfort. Since these systems pressurize the house, the LBNL study recommends that, in cold climates, the supply fan be balanced by a single-port exhaust fan, which could also serve as a bathroom fan. In this type of system, a central fan, typically in the attic or basement, draws in outside air through a filter and delivers it through ducts to bedrooms and main living areas. The supply ductwork should be in conditioned space or insulated and sealed airtight. Supply grilles should be placed high on the wall away from beds, chairs, or other places where drafts could cause discomfort. -- Adapted with permission from Best Practices Guide to Residential Construction. Share this Article
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