1. Objectives Blower door and duct bluster measurements - Theory and lab
IGERT: Indoor Environmental Science & Engineering

2. Infiltration/Leakage Measurements (Calibrated Fans)
Flow going through fan is calibrated to pressure rise across fan
If you measure pressure, than you know flow
Requires very smooth inlet and outlet conditions
Often have to restrict flow to get measurable pressure signal for low flows
Examples:
Blower door and Duct Blaster 2

3. Fan Pressurization
In 1970s, smoke evacuation fans used to find air leakage
Install blower door
Use fan to create artificial pressure difference between inside and outside
Use smoke stick (or cigarette, etc.) to visualize flow patterns.
Seal leaks

6. Quantitative Blower Door
How many points should you measure?
How can you estimate uncertainty?

7. Test Data 1000 ft2 house, 10 ft high ceilings Two-point test
1688 CFM at 51 Pa
1048 CFM at 24.5 Pa
What is ACH50 (λ50), C?

8. Answers
λ50= 1 ACH
C = CFM/Pan
n = 0.65

9. Reporting blower door data
Flow (or air exchange rate) at a given pressure
Equivalent Leakage Area
What are dimensions of c?

10. Comment Blower doors do not measure air exchange rate
Why not?
What do they measure?

11. Blower Door Misc. All windows and doors to outside closed HVAC off
Why? What about buffer spaces?
HVAC off
Hard to do on windy days
Watch out for buckling linoleum floors and fireplaces
Flow direction change/ring change can be discontinuous
Remember to record before and after reference pressures with fan covered 11

12. More Blower Door Tests Measure component leakage Series leakage paths
What fraction of leakage is due to a certain component?
Tape off component and repeat test
What are issues with this approach?
Series leakage paths
Air leaks to attic and then to crawlspace and then to outside

13. Residential Component Leakage
Range
Average
Walls
18-50%
35%
Ceilings
3-30 13
Windows/Doors
6-22 15
Fireplaces
0-30 12
HVAC
3-28 18
Other Vents
2-12 5

14. Duct Leakage
Responsible for enormous energy losses (20-30% is not uncommon)
Comfort
Outdoor air pollution
Contaminant spread

15. Duct Leakage Excluding registers, grills, diffusers
Ducts leak to the inside
Ducts leak to the outside (mostly an American problem)
Ducts leak on the supply (positive pressure) side
Ducts leak on the return (negative pressure) side
What are we concerned from the perspective of:
Energy?, Indoor air quality? Comfort?

16. Duct Leakage Method 1 Blower door subtraction
Two successive blower door tests
Normal
With duct registers sealed (with tape)
Difference is total duct leakage
Is this supply, return, or total?
Is this inside, outside, or both?
Problems and limitations?

17. Duct Leakage Method II Duct pressurization Tape registers
Use Duct Blaster (calibrated fan) to do a “blower door” test of the ducts
Is this supply, return, or total?
Is this inside, outside, or both?
Problems and limitations?

19. Duct Pressurization Test Extension
How do you measure exterior leakage?
How do you measure supply and return leakage separately?
How do you measure duct leakage at operating conditions?

21. Reporting Duct Leakage
Are we interested in absolute amount of leakage or relative?
If relative, relative to what?
ASHRAE Standard 152 defines:
αs supply leakage fraction
αr return leakage fraction 21

22. Air Handler Flow Measurement
Often need to know flow through air handler
Historically many methods, all problematic:
Non-uniformity of flow (i.e., very turbulent)
True Flow Plate
Specialized type of orifice
Replaces filter
Gives air handler flow
Pressure correction 22

23. Other Duct Leakage Testing Methods
Nulling test
Measures duct leakage at operating conditions
Also measure air handler flow
Very intensive to set-up and also sensitive to wind
Delta-Q test
Only uses a blower door and does not require taping registers
But mathematically problematic

24. Nulling Test
Step 1: Install Duct Blaster fan in doorway to building, turn on air handler and zero* out any pressure imbalance
What does the flow through the fan equal?
Why is this test sensitive to wind?
Under what conditions will this test fail? 24

25. Nulling Test (cont.)
Step 2: Second Duct Blaster is installed in HVAC system, return side sealed off, air handler fan turned on, and air flow rate is adjusted to match supply plenum pressure under normal conditions
Step 3: Step 1 is repeated
What is flow through Duct Blaster installed in door this time? 25

26. Summary of Nulling test
Use a Duct Blaster as envelope fan to “null out” change in envelope pressure caused by unbalanced duct leakage
First with normal operation –unbalanced leakage
Second with return isolated and a Duct Blaster assisting the AH fan so there is no return leakage –supply leakage
Difference is return leakage
Measures leakage directly –thought to be accurate
Very sensitive to wind

27. General Comments about Fan Tests
Buildings are complicated, go slowly and methodically
Practice/experience are key
Practical matters (HVAC turned on, someone stepped on a tube, wind, etc.) are very important
Cardboard and tape are useful research tools/skills