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Whole House Ventilation Design Guide InspectAPedia®  -     Key strategies for whole house ventilation & Fresh Air Intake How to choose the size & type of whole house ventilation system Table comparing different house ventilation systems Removing or keeping out indoor contaminants Best methods for cleaning & filtering indoor air

Here we discuss how to design, buy, and use a whole house ventilation system 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. See VENTILATION in BUILDINGS for our full list of building ventilation articles.

© Copyright 2009 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.

Whole House Ventilation Strategies for Improving Indoor Air Quality

There are a number of strategies for providing whole-house ventilation, which vary in cost, complexity, and effectiveness. All strategies, however, can be categorized as either exhaust-only, supply-only, or balanced (Below we provide Table 7-1 - Whole House Ventilation Strategies).

Guide to Sizing House Ventilation Systems - How Many CFM of Vent Fan Capacity are Needed?

As detailed in Best Practices Guide to Residential Construction:

ASHRAE Standard 62-1989 recommends a minimum ventilation rate in houses of 15 cfm per person, or .35 air changes per hour (ACH), whichever is greater. Based on the ACH method, a three-bedroom house of 1,500 sq ft with 8 ft ceilings would require:

(1,500 x 8) x .85
x .35 / 60 = 60 cfm

Multiplying the volume by .85 accounts for partitions and exterior wall thickness.

Using the per person method and assuming two people in the master bedroom and one in each other bedroom, the rate is also 60 cfm.

The revised ASHRAE standard 62.2, released in 2003, uses the formula of 7.5 cfm per person (based on the number of bedrooms plus one) plus an factor of .01 cfm for each square foot of house area. For example, based on the new ASHRAE standard, the same three-bedroom, 1,500-square-foot house would require:

(7.5 x 4) / (1,500 x .01) = 45 cfm.

As these calculations show, a low ventilation rate is adequate if run on a continuous basis. A higher continuous rate would be advisable for a home with higher-than-average moisture levels or pollutant sources such as smoking. Intermittent ventilation can also work as long as the total daily ventilation rate is equivalent, but is most effective when the system is timed to operate when people are home breathing air and generating pollutants.

A two-speed or variable-speed fan provides flexibility, allowing the ventilation rate to be raised when needed, for example when painting a room or during a party. More important than the precise number of cubic feet per minute, however, is a well-designed system that is quiet, reliable, and low- maintenance, ensuring it will actually be used.

TABLE 7-1 Whole House Ventilation Strategies

Installation Tips for Whole House Ventilation Systems

Whole-house ventilation systems should be installed by people familiar with the equipment. Since they normally operate at 100 to 200 cfm rather than the much larger fans found in air handlers, they are less forgiving of errors. Numerous field studies have found heat-recovery ventilators performing poorly due to installation errors and poor maintenance.

For good performance with whole-house ventilation systems, follow these general guidelines:

• Size the whole house ventilation system correctly. Oversizing will increase heating and cooling costs.
• Choose quiet, efficient fans in the house ventilation equipment
• Keep HVAC or ventilation duct runs as short and straight as possible.
• Locate fresh air intakes away from pollution sources such as cars, pesticides, and outlets from HVAC equipment or exhaust fans.
• Seal all ducts and insulate where required. Examples: Insulate intake ducts that run though a hot attic or exhaust ducts that pass through a cold, unheated space.
• Integrate spot ventilation in bathrooms or provide separately.
• Use separate spot ventilation in kitchens due to grease.
• Place supply registers high on walls and away from beds, sofas, chairs, and other places likely to cause occupant discomfort.
• Keep controls as simple and automatic as possible.
• Educate homeowners about the system and maintenance requirements.

-- Adapted with permission from Best Practices Guide to Residential Construction.

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Technical Reviewers & References

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• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
• InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Additional technical contributors & reference sources for this article are listed below.

Use links just below or 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.

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
ACTION GUIDE - WHAT TO DO ABOUT INDOOR 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
    Guide to Sizing House Ventilation
  Whole House Ventilation Table
    Installation of Whole House Ventilation
  Exhaust-Only Ventilation
  Single-Port Exhaust Venting
  Multiport Exhaust Venting
    Ventilating Heat-Pump Systems
  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
INDOOR AIR QUALITY METHODS COMPARED
LEAD POISONING HAZARDS GUIDE
MOISTURE CONTROL in BUILDINGS
MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD
VAPOR BARRIERS & AIR SEALING at BAND JOISTS
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VAPOR BARRIERS & HOUSEWRAP
VAPOR CONDENSATION & BUILDING SHEATHING
VENTILATION in BUILDINGS
  Air Bypass Leaks, Thermal Tracking
  ATTIC CONDENSATION CAUSE & CURE
  BATHROOM VENTILATION
  Blocked Soffit Intake Vents
  BRICK VENEER WALL INSULATION
  CATHEDRAL CEILING INSULATION
  CRAWL SPACE VENTING & Dryout Procedures
  Heat Tapes: Use on Roofs for Ice
  Inspect Attics for Moisture or Mold
  Inspect Basements for Moisture or Mold
  Inspect Building Exterior for Moisture Problems
  Inspect the Ridge Vent System from the Attic
  Inspect the Soffit Vent System from the Attic
  BLOWER DOORS & AIR INFILTRATION
  HEAT LOSS: How to Calculate Heat Loss in a Building
  HOUSEWRAP AIR & VAPOR BARRIERS
  HUMIDITY LEVEL TARGET
  ICE DAM PREVENTION
  MOISTURE CONTROL in BUILDINGS
  Crawl Space Ventilation
  MOISTURE CALCULATIONS
  MOISTURE PROBLEMS: CAUSE & CURE
  ROOF VENTILATION SPECIFICATIONS
  ROOF VENTING ENERGY SAVING DETAILS
  ROOF VENTING NEEDED?
  Soffit Ventilation
  HOUSEWRAP AIR & VAPOR BARRIERS
  WHOLE HOUSE VENTILATION Strategies

• "Minimizing Air Leakage in Log Homes" U.S. Department of Energy suggestions
• "Controlling Moisture in Log Homes" and the more general (but brief) DOE article series on moisture control:
  • "Moisture Control", U.S. DOE
  • "Moisture Control in Basements", U.S. DOE
  • "Crawl Space Moisture Control", U.S. DOE
  • "Slab-on-Grade Foundation Moisture and Air Leakage Control", U.S. DOE
  • "Moisture Control in Walls", U.S. DOE
• "Ventilation", U.S. DOE, describes the purpose of building ventilation and three basic ventilation strategies:
  • Natural house ventilation methods
  • Whole House Ventilation Methods, including exhaust ventilation methods, supply ventilation of buildings, balanced building ventilation, and energy recovery (heat exchanger) ventilation systems
  • Spot Ventilation in Buildings
• "Weather-Resistive Barriers", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
• "Vapor Barriers or Vapor Diffusion Retarders", U.S. DOE: how vapor barriers work, types of vapor diffusion barriers, installing vapor barrier

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Wiley.com and also at Amazon.com. See our book review of this publication.
• "Energy Savers: Whole-House Supply Ventilation Systems", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
• "Energy Savers: Whole-House Exhaust Ventilation Systems", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
• "Energy Savers: Ventilation", U.S. Department of Energy
• "Energy Savers: Natural Ventilation", U.S. Department of Energy
• "Energy Savers: Energy Recovery Ventilation Systems", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
• "Energy Savers: Detecting Air Leaks", U.S. Department of Energy
• "Energy Savers: Air Sealing", U.S. Department of Energy
• Basement Moisture Control, U.S. Department of Energy
• Crawl Space Moisture Control, U.S. Department of Energy
• Energy Recover Ventilation Systems for Buildings, U.S. Department of Energy
• Energy Savings Methods: Whole House Systems Approach, U.S. Department of Energy
• Log Homes: MInimizing Air Leakage in Log Homes, U.S. Department of Energy
• Log Homes: Controlling Moisture in Log Homes, U.S. Department of Energy
• Log Homes: Log Home Design, U.S. Department of Energy
• Moisture Control in Buildings, U.S. Department of Energy
• Moisture Control in Walls, U.S. Department of Energy
• Natural Ventilation for Buildings, U.S. Department of Energy
• R-Value of Wood, U.S. Department of Energy
• Spot Ventilation for houses, U.S. Department of Energy
• Slab on Grade Foundation Moisture and Air Leakage, U.S. Department of Energy
• Straw Bale Home Design, U.S. Department of Energy
• Vapor Barriers or Vapor Diffusion Retarders, U.S. Department of Energy
• Ventilation for energy efficient buildings, Purpose, Strategies, etc.,
• Whole House Ventilation Systems, U.S. Department of Energy
• Whole-House Balanced Ventilation Systems, U.S. Department of Energy
• Whole-House Exhaust Ventilation Systems, U.S. Department of Energy
• Whole-House Supply Ventilation Systems, U.S. Department of Energy
• ...

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