Zone Pressure Diagnostics

1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – August 2010 eere.energy.gov

Zone Pressure DiagnosticsWEATHERIZATION ENERGY AUDITOR SINGLE FAMILY

WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – August 2010


By attending this session, participants will:

• Gain an understanding of the powers and limitations of Zone Pressure Diagnostics (ZPD).

• Learn when it is best to use zone pressure diagnostics.

• Practice using ZPD charts.

Learning ObjectivesZONE PRESSURE DIAGNOSTICS


Necessary Equipment

Photos courtesy of the US Department of Energy

ZONE PRESSURE DIAGNOSTICS


Practical Applications

• Determine relative leakiness.– The higher the pressure the smaller the hole.

• Prioritize air sealing activities.– Quickly determine which are the leakiest surfaces.

• Evaluate completed air sealing measures.– Know if your crew does good work.



Pressure houseto attic = 37PaPressure attic toexterior must be 13Pa(50Pa – 37Pa = 13Pa)

Q: What doesthis tell us?

1850 CFM50

50Pa

37Pa

? Pa


Relative Leakiness


Ratio of Pressure to Leakage

Zone Pressures Relative Size of Leaks

Zone-House Zone-Out

12 38

25 25

37 13

41 9

45 5

48 2

49 1

Zone-House Zone-Out

2 1

1 1

1/2 1

1/3 1

1/4 1

1/8 1

1/13 1

TO

TO



Probing Cavities

What if we stick a probe into the first floor ceiling cavity and read 41Pa?

Let’s put a probe into the cellar.

What does25Pa mean?

50Pa

37Pa

25Pa

41Pa



Changing Pressures

If we open the cellar door to the house and put a probe into the attic we might find the attic 37Pa has dropped to 25Pa.

50Pa

25Pa

0Pa

The pressure between the house and basement will now be zero.

WHY?



Can We Size The Holes?

50Pa

25Pa

0Pa

Pressure is gradually reduced by each layer of wall or ceiling between inside and outside.

Collecting CFM50 and pressure across each configuration lets us calculate hole size in each surface.



1850 CFM50

50Pa

2200 CFM50

25Pa

25Pa

50Pa

0Pa

50PaBasement door closed

Basement door open


Here is what we know


Open A Door – Zone To Main Body

25Pa 1850 2200 350

350 2.76 966 97 sq”

350 2.76 966 97 sq”

350 1.76 616 CFM50



What Do The Results Mean?

H/Z 350 x 2.76 = 966 CFM50 = 96.6 sq” of hole in the floor

Z/O 350 x 2.76 = 966 CFM50 = 96.6 sq” hole in basement walls

T/P 350 x 1.76 = 616 CFM50 is attributable to the path

50Pa

50Pa



Open A Door – Zone To OutsideZONE PRESSURE DIAGNOSTICS


At 1850 CFM50, house to attic pressure = 37Pa.Open attic hatch enough to create at least 6Pa change.

Bring the blower door back to 50Pa.CFM50 is now 2500

House to attic pressure is now 20Pa.

50Pa

20Pa


No Door on the Zone?


Flow Method: Hole – Zone To House #1ZONE PRESSURE DIAGNOSTICS


Flow Method: Hole – Zone To House #2

185037Pa

250020Pa

6501.36

884



Flow Method: Hole – Zone To OutsideZONE PRESSURE DIAGNOSTICS


Of 1850 CFM50:

Through attic: ≈ 900

Through basement ≈ 600

Walls (remainder) ≈ 350

50Pa


What Did We Learn Overall?


How about a garage?Any space that will accept a probe can be checked for pressure.ZPD requires being able to change the pressure over the surface to determine hole size.

48Pa

50Pa

2Pa


Checking Air Sealing


• Not great for excessively leaky buildings.

• ZPD requires being able to change the pressure over the tested surface to determine hole size.

• Not great in windy conditions.

• Time consuming.

LimitationsZONE PRESSURE DIAGNOSTICS


Practice!



40Pa 2050 2550 500

500

500

500




40Pa 2050 2550 500

500

500

500

0.63 315 31.5 sq”

1.54 770 77 sq”

0.54 270 CFM50



Flow Method: Hole – Zone To House

120045Pa

185018Pa

650



Flow Method: Hole – Zone To House

120045Pa

185018Pa

6500.43

280



• ZPD can help you determine the relative leakiness of a home, prioritize air sealing activities, and evaluate completed air sealing measures.

• ZPD requires a computer or charts to do the calculations.

• The calculations can be time consuming, so use ZPD only when needed to prioritize or verify critical air sealing activities.

• ZPD does not work well in extremely leaky homes or when it’s very windy.

• ZPD requires being able to change the pressure over the tested surface to determine hole size.

SummaryZONE PRESSURE DIAGNOSTICS

Documents

Zone Pressure Diagnostics