Discuss US Green Building Council LEED-AP-Homes Exam Topic 7 Question 4

Envelope leakage is measured in air changes per hour (ACH) at what pressure differential?

A25 pascals

B50 pascals

C75 pascals

D100 pascals

Suggested Answer: B

The LEED for Homes Rating System (v4) requires blower door testing in the Energy and Atmosphere (EA) Credit: Air Infiltration to measure envelope leakage, expressed as air changes per hour (ACH) at a specific pressure differential.

According to the LEED Reference Guide for Homes Design and Construction (v4):

EA Credit: Air Infiltration (1--3 points)

Conduct a blower door test to measure envelope leakage in air changes per hour (ACH) at a pressure differential of 50 pascals (Pa). This standardizes the measurement of air tightness across projects.

Source: LEED Reference Guide for Homes Design and Construction, v4, Energy and Atmosphere Credit: Air Infiltration, p. 124.

The LEED v4.1 Residential BD+C rating system confirms:

EA Credit: Air Infiltration

Envelope leakage is measured using a blower door test at 50 pascals, reported as ACH50, to assess the airtightness of the building envelope.

Source: LEED v4.1 Residential BD+C, Credit Library, accessed via USGBC LEED Online.

The correct answer is 50 pascals (Option B), as this is the standard pressure differential for measuring ACH in LEED for Homes.

Why not the other options?

A . 25 pascals: This is not the standard pressure for ACH measurements in LEED or ENERGY STAR protocols.

C . 75 pascals: Higher pressures are not used, as 50 pascals is the industry standard for consistency.

D . 100 pascals: This is too high and not used in residential testing standards.

The LEED AP Homes Candidate Handbook emphasizes EA credits, including air infiltration testing, and references the LEED Reference Guide for Homes Design and Construction as a key resource. The exam is based on LEED v4, ensuring the relevance of the 50-pascal standard.

References:

LEED Reference Guide for Homes Design and Construction, v4, USGBC, Energy and Atmosphere Credit: Air Infiltration, p. 124.

LEED v4.1 Residential BD+C, USGBC LEED Credit Library, accessed via LEED Online (https://www.usgbc.org/credits).

LEED AP Homes Candidate Handbook, GBCI, October 2024, p. 12 (references study resources and exam scope based on LEED v4).

USGBC LEED for Homes Rating System (v4), available via USGBC website (https://www.usgbc.org/resources/leed-homes-design-and-construction-v4).

LEED v4.1 for Homes, USGBC, accessed via LEED Online, confirming ACH50 testing standard.

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19 comments · newest first

Olene 10 months ago

Wait, are we sure about that? Seems low.

France 10 months ago

I thought it was 50 pascals?

Teri 10 months ago

It's 25 pascals for sure!

Tayna 11 months ago

Definitely 25 pascals, that's standard.

Marsha 11 months ago

Agreed, 25 pascals is the norm in testing!

Lashon 11 months ago

I thought it was 100 pascals, but now I'm second-guessing myself after reviewing similar questions.

Emmett 11 months ago

I feel like it might be 75 pascals, but I can't recall the exact details from my notes.

Susy 11 months ago

I remember practicing a question like this, and I think it was 50 pascals.

Terina 12 months ago

I think envelope leakage is measured at 25 pascals, but I'm not entirely sure.

Velda 12 months ago

I remember the professor mentioning that envelope leakage is measured at a specific pressure differential, but I can't recall the exact value. I'll have to review my materials to refresh my memory on this topic.

Tommy 12 months ago

25 pascals? 50 pascals? I'm honestly not sure. I'll have to guess on this one and hope I get it right.

Henriette 1 year ago

Okay, let me think this through step-by-step. Envelope leakage is measured to determine air tightness, and the pressure differential is used to simulate real-world conditions. I believe the standard is 50 pascals, but I'll double-check my notes to be sure.

Herman 1 year ago

Hmm, I'm a bit unsure about this one. I remember learning about envelope leakage, but I can't recall the exact pressure differential. I'll have to think this through carefully.

Cristina 1 year ago

I'm pretty sure it's 50 pascals, that's the standard pressure differential used for envelope leakage testing.

Galen 1 year ago

Wait, isn't it 100 pascals? I recall seeing that in the building code somewhere. Gotta double-check that.

Goldie 1 year ago

Hmm, I'm not sure about that. Isn't it 75 pascals? I vaguely remember that from a building science course I took.

Tambra 1 year ago

I think it's B) 50 pascals.

Micaela 1 year ago

I think it's definitely 50 pascals. That's the standard pressure differential for envelope leakage testing, right?

Chuck 1 year ago

↳ replying to Micaela

I believe you are correct, 50 pascals is the standard pressure differential for envelope leakage testing.

US Green Building Council LEED-AP-Homes Exam - Topic 7 Question 4 Discussion