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    • BPI WRITTEN EXAM >
      • Section 1 Building Science Fundamentals >
        • 1a. Basic Terms & Definitions >
          • 1. Airflow in Buildings
          • 2. Equipment Efficiencies
          • 3. Power and Energy
          • 4. Effective Leakage Area
          • 5. Area Weighted R-Value
          • 6. Baseload / Seasonal Energy Use
          • 7. Driving Forces (Including Natural and Mechanical)
          • 8. Behavior of Radiation
          • 9. Thermal Resistance / Transmittance: R and U Values
          • 10. Latent / Sensible Heat
          • 11. Total Equivalent Length
          • 12. Dehumidification / Humidification
          • 13. Convert Pressure Units
          • 14. Thermal Bridges
          • 15. Pressure Boundary
          • 16. Stack Effect
          • 17. Exfiltration and Infiltration
          • 18. Natural / Mechanical Ventilation
          • 19. Net Free Area
          • 20. Input & Output Capacity
          • 21. Peak Electrical Demand
          • 22. Permeability and Perm Rating
          • 23. Standby Loss
          • 24. IAQ (indoor air quality): Moisture, CO, Dust
        • 1b. Principals of Energy, Air & Moisture Thermodynamics >
          • 1. Thermodynamics: Conduction, Convection, Radiation, ΔT
          • 2. Factors That Affect Insulation Performance
          • 3. BPI certification online with BPI practice exams and study guides.
          • 4. Heat Gain / Loss
          • 5. Power and Energy
          • 6. Moisture Transport Mechanisms
          • 7. Identify Areas of Highest Relative Humidity
          • 8. Principles of Combustion
        • 1c. Combustion Safety >
          • 1. Combustion Analysis
          • 2. Carbon Monoxide (CO) Testing
          • 3. Combustion Appliance Venting, Draft, Combustion Air & Sizing
          • 4. Understand Combustion Safety Issues
      • Section 2 Buildings and Their Systems >
        • 2a. Building Components >
          • 1. Identify basic duct configurations and components
          • 2. Identify Basic Hydronic Distribution Configurations and Components
          • 3. Identify Basic Structural Components of Residential Construction
          • 4. Thermal Boundaries and Insulation Applications
          • 5. Basic Electrical Components and Safety Considerations
          • 6. Basic Fuel Delivery Systems and Safety Considerations
          • 7. Basic bulk water management components (drainage plumbing gutters sumps etc)
          • 8. Vapor barriers/retarders
          • 9. Radiant Barrier Principles and Installations
          • 10. Understand Fenestration Types and Efficiencies
          • 11. Understand Issues Involved With Basements, Crawlspaces, Slabs, Attics, Attached Garages, Interstitial Cavities, and Bypasses
          • 12. Understand Issues Involved With Ventilation Equipment
          • 13. Understand Basic Heating / Cooling Equipment Components Controls and Operation
          • 14. Understand Basic DHW Equipment Components Controls and Operation
          • 15. Identify Common Mechanical Safety Controls
          • 16. Identify Insulation Types and R-Values
          • 17. Understand Various Mechanical Ventilation Equipment and Strategies: Spot, ERV, HRV
        • 2b. Conservation Strategies >
          • 1. Appropriate Insulation Applications and Installation Based On Existing Conditions
          • 2. Opportunity for ENERGY STAR Lighting and Appliances
          • 3. Identify Duct Sealing Opportunities and Applications
          • 4. Understand Importance of Air Leakage Control and Remediation Procedures
          • 5. Blower Door-Guided Air Sealing Techniques
          • 6. Water Conservation Devices and Strategies
          • 7. Domestic Hot Water (DHW) Conservation Strategies
          • 8. Heating & Cooling Efficiency Applications
          • 9. Proper Use of Modeling to Determine Heating and Cooling Equipment Sizing and Appropriate Energy
          • 10. Understand the Use of Utility History Analysis in Conservation Strategies
          • 11. Appropriate Applications For Sealed Crawlspaces Basements and Attics
          • 12. Identify / Understand High Density Cellulose
          • 13. Appropriate Applications for Fenestration Upgrades Including Modification or Replacement
        • 2c. Comprehensive Building Assessment Process >
          • 1. Determine Areas of Customer Complaints / Concerns in Interview
          • 2. Understand / Recognize Need For Conducting Appropriate Diagnostic Procedures
          • 3. Interaction Between Mechanical Systems, Envelope Systems and Occupant Behavior
        • 2d. Design Considerations >
          • 1. Appropriate Insulation Applications Based On Existing Conditions
          • 2. Understand Fire Codes as Necessary to Apply Home Performance in a Code-Approved Manner
          • 3. Understand / Recognize Building Locations Where Opportunities for Retrofit Materials
          • 4. Understand Climate Specific Concerns
          • 5. Understand Indoor Environment Considerations for the Environmentally Sensitive
          • 6. Understand Impact of Building Orientation, Landscape Drainage, and Grading
          • 7. Opportunity Potential Renewable Energy Applications: Geothermal, Photovoltaic, Wind
          • 8. Understand Impact of Shading on Heating / Cooling Loads
          • 9. Awareness for Solar Gain Reduction / Solar Gain Opportunities
          • 10. Understand Need for Modeling Various Options For Efficiency Upgrades
      • Section 3 Measurement & Verification of Building Performance >
        • Section 3a Measurement & Verification of Building Performance >
          • 1. Air Leakage Test Results
          • 2. Understand Building Shell / Envelope Leakage
          • 3. Apply Fundamental Construction Mathematics and Unit Conversions
          • 4. Calculate Building Tightness Levels (Minimum Ventilation Requirements)
          • 5. Calculate Heating Degree Days and Cooling Degree Days
          • 6. Identify Proper Appliance and Combustion Appliance Venting
          • 7. Ventilation calculations and strategies
          • 8. Proper methods for identifying / testing fuel leaks
          • 9. Blower door setup, accurate measurement and interpretation of results
          • 10. Combustion Appliance Zone (CAZ): depressurization, spillage, draft, Carbon Monoxide (ambient and flue)
          • 11. Carbon Monoxide (CO) evaluation: ambient
          • 12. Proper applications and use of temperature measuring devices
          • 13. Pressure pan and room to room pressure diagnostics
          • 14. Recognize contributing factors to comfort problems
          • 15. Inspect for areas containing moisture or bulk water in undesirable locations
          • 16. Understand and inspect for basic electric safety (e.g. frayed wires, open boxes, etc)
      • Section 4 BPI National Standards & Project Specifications >
        • 1. Understand applicability content and intent of BPI National Standards – Do no harm, make buildings more healthy, comfortable, durable and energy efficient
        • 2. Recognize need for a professional local/state/national codes evaluation
        • 3. Be able to specify appropriate materials and processes needed for building performance projects
      • Section 5 Analyzing Buildings Systems >
        • 1. Recognize need for air sealing measures and their impact on other building systems
        • 2. Recognize need for mechanical equipment improvements
        • 3. Understand blower door use for identifying critical air sealing areas
        • 4. Apply blower door test results and Building Tightness Limit (minimum ventilation requirements) in development of improvement strategies
        • 5. Using combustion analysis and safety testing results to develop appropriate recommendations
        • 6. Determine appropriate method for assessing wall insulation levels
        • 7. Equipment control strategies for maximizing occupant comfort and minimizing energy consumption
      • Section 6 Conduct and Communications >
        • 6a. Conservation strategies
        • 6b. Personal Safety & Work Practices >
          • 1. Locations in which to identify indoor air quality issues
          • 2. Material Safety Data Sheets
          • 3. Isolation procedures for household pollutants
          • 4. Practice building science within your limits of professional competency
          • 5. Precautions when working around chemical biological and other potential hazards
          • 6. Understand role and responsibilities of the building analyst professional
    • BPI FIELD EXAM >
      • How To Put The House Under Worst Case & CAZ
      • What's What? Pa, CFM, CFM50, CAZ, Draft, Room Pressure
      • What To Know In The Attic
      • What To Know In The House
    • BLOWER DOOR TEST >
      • Manometer Setup
    • BPI BUILDING ANALYST STANDARDS >
      • BPI Standards Decoded
  • ESSENTIALS
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    • AUDITOR TO CREW COMMUNICATION
    • COMMON AUDITOR / CREW MISTAKES
    • RUN LIKE HELL
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BPI Field Exam - Worst Case and CAZ

How To Put The House Under Worst Case Conditions

Why worst case?  Worse case conditions try to set the house up to fail so if something bad is potentially going to happen (CO getting into the home), we want it to happen while we are there so we can notify the homeowners and fix the source of the problem.

Note: even in all electric homes, if there is an attached garage, there IS a potential to bring CO into the home.  Don't believe it or have a homeowner that doesn't believe it?  Try leaving a car running in a closed garage and leave your CO meter in the adjacent or bonus room while the house is under worst case conditions and watch the CO meter start to raise.  Yes there is a real danger of CO poisoning and you never want to have it happen under your watch.

Doors closed, doors open, what's the deal?!

Worse case conditions used to be having all the exhaust fans and AHU on (think of all the exhaust fans like a little blower door depressurizing or sucking the air out of the house) and interior doors closed.  That is not the case anymore.  


For worst case conditions in a CAZ, we want the HIGHEST NEGATIVE NUMBER, remember we want the house to fail while we are there.  So we are going to use all the fans (AHU, dryer, bathroom exhaust fans, laundry room exhaust fan and kitchen exhaust fan if it goes outside) to help us create a negative... the highest negative number possible, then do our combustion tests.


We need to test different scenarios with the doors open or closed to see its effect on the house pressure (by watching your manometer).  If opening an interior door makes your pressure reading more negative, leave the door open.  If opening an interior door makes the CAZ worst case more positive, that is working against our worst case goal (the highest negative number possible, -10 Pa is better than -2 Pa for worst case), so leave the door closed.  We need to go around the house and open and close all the interior doors to see their effect on the worst case reading.  


Start with all the interior doors shut and windows and exterior doors closed.  Turn on all exhaust fans, AHU and dryer.  Now it's time to check each door.  Open an interior door, then go back to your manometer and check it's reading, if it's more negative, leave it open, if it's more positive, go and close it.  Then go to the next interior door and open it, go back to your manometer and check the pressure reading (in Pa, not CFM), if it's more negative leave it open, if it's more positive, go and close it.  Got the hang of it?


You also need to check the affect of the AHU on your worst case.  This can be done at the same time as your dominant duct leakage.  Dominant duct leakage is done right after you get a baseline reading with all the interior doors open, exterior doors and windows shut, all exhaust fans off and ONLY the AHU on (use high speed if new dual speed AHU).  So in other words, only the AHU is on.  If you get a negative dominant duct reading (more leakage on the supply), that's is good for our worst case, so leave the AHU on during worst case conditions.  If you get a positive dominant duct reading (more leakage on the return), that is working against our worst case, so shut the AHU off for your worst case test. 


Or you can simply turn the AHU off before or after your interior door check and check your manometer, if the pressure goes down (more negative), leave the AHU on, if the pressure goes up (more positive), shut the AHU off for your worst case conditions.

Accounting for the Baseline

We want a true worst case by not accounting for the baseline.  You can do this by:

  1. Take a baseline and then take into account the baseline.  How do you do this?  If your baseline is positive, pretend it is negative and add it to your worst case number.  This will make the worst case number you found (after all the exhaust fans are on, AHU on or off and you have tested the affect of opening and closing the doors) MORE NEGATIVE.  For example, if your baseline is +.0.7 Pa, worst case is -1.0 Pa, your true worst case is (-1.0 + -0.7) -1.7 Pa.  You do this because worst case IS NOT TAKEN WITH RESPECT TO THE OUTSIDE, it is just concerned with conditions inside the house.       
  2. If your baseline is negative, then compare the baseline to your worst case and pick the more negative number as your worst case.  For example, you get a baseline of -2.1 Pa and worst case of -1.2 Pa... your worst case would be -2.1 Pa (-2.1 is more negative than -1.2 Pa. If your baseline is -0.5 Pa and worst case is -1.2 Pa, your worst case would be -1.2 Pa.

Now once you have the house under worst case conditions, you are ready to get your CAZ pressure readings, draft and CO tests done!

How to Find Your CAZ

We need to test and check if conditions in the home can create backdrafting, spillage or flame rollout. CAZ pressures may overcome the draft pressure needed to safely exhaust hot water tanks and furnaces. To create worst case conditions, we should turn on every device that can create a negative pressure in the house and then measure the negative pressure created where the combustion appliance is located and compare that pressure to the outside (aka WRT outside).

How to fix a failed CAZ

Recommend:

  1. Room pressure relief
  2. Replace appliance with power-vented or sealed combustion unit
  3. Switch out to an electric appliance
  4. Isolate the CAZ (build a space with dedicate outside air)

Also always recommend installing UL-2034 rated CO detectors in homes with attached garages, inside the CAZ, separate detectors for each floor located 3-6 feet off the ground.

Next Section

Quick Links

1. BPI Written Exam
2. BPI Field Exam

3. Blower Door Test 
4. BPI Standards
The main topics of the BPI BA exam are listed out below.  Click on a link that interests you, or you need some brushing up on to learn more on each subject.

1. Building Science Fundamentals
1a. Basic terms and definitions
1b. Principals of energy, air & moisture
1c. Combustion science

2. Buildings and Their Systems
2a. Building components
2b. Conservation strategies
2c. Comprehensive building assessment process
2d. Design considerations

3. Measurement and Verification of Building Performance
3a. Applied diagnostics and troubleshooting

4. BPI National Standards and Project Specifications
4a. Comprehensive building assessment

5. Analyzing Buildings Systems
5a. Comprehensive building assessment
5b. Appliances and lighting

6. Conduct and communications
6a. Conservation strategies
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