HERS Blower Door & Air Infiltration 2

Question 1

A blower door test is conducted at a pressure difference of 50 Pascals. What does the CFM50 value represent?

Accepted Answer

The airflow in cubic feet per minute needed to maintain 50 Pa across the building envelope

Answer

CFM50 is the volumetric airflow (in cubic feet per minute) required to maintain a 50 Pa pressure differential across the building envelope during a blower door test.

Question 2

Which component of the blower door system measures the pressure difference between inside and outside the building?

Accepted Answer

Manometer

Answer

The manometer measures the pressure differential across the building envelope and across the blower door fan during testing.

Question 3

When converting CFM50 to Equivalent Leakage Area (ELA), which pressure reference is typically used in the US?

Accepted Answer

25 Pascals

Answer

In the US, ELA is referenced at 4 Pa for Canadian standards, but the most common US reference for Effective Leakage Area is 4 Pa while ELA at 10 Pa is used in some protocols; however, RESNET typically uses 4 Pa — but the standard US ELA reference in blower door analysis is 4 Pa.

Question 4

A home has a volume of 15,000 cubic feet and measures 1,200 CFM50. What is the Air Changes per Hour at 50 Pascals (ACH50)?

Accepted Answer

4.8 ACH50

Answer

ACH50 = (CFM50 × 60) / Volume = (1,200 × 60) / 15,000 = 72,000 / 15,000 = 4.8 ACH50.

Question 5

Which of the following building penetrations is MOST commonly identified as a major source of air leakage during blower door testing?

Accepted Answer

Top plates and attic bypasses

Answer

Top plates and attic bypasses — including gaps around ceiling electrical boxes, plumbing chases, and partition wall top plates — are among the largest sources of air leakage in residential buildings.

(HERS) Home Energy Rater Certification Practice Test

(HERS) Home Energy Rater Certification Practice Test

HERS Blower Door & Air Infiltration 2