BPI Certification

Blower Door Testing Requirement Open to Interpretation

A look into how BPI IDL overlaps with other BPI Certifications and, more importantly, how BPI Building Analyst Certification takes building science further

Blower Door Testing Requirement Open to Interpretation

If you’ve browsed the list of BPI Certifications, you’re aware that several designations exist and cross-over on skills may cause you to question such things like Building Analyst vs. IDL. It can be difficult to determine which certification is right for your business. Specifically, blower door testing has grown in popularity due to the blower door testing requirement in many building codes across the country. And several of the BPI certifications address this skill set. So the question becomes, BPI Building Analyst vs. IDL – which do I need for blower door testing and code compliance?

Across the country, we’re seeing HVAC contractors and home performance professionals racing to get the BPI Infiltration & Duct Leakage Certification in an attempt to satisfy their local building code requirements for blower door testing and/or duct leakage testing.

What is BPI Infiltration & Duct Leakage?

The BPI Infiltration & Duct Leakage Certification (BPI IDL, for short) was created in 2014 by the Building Performance Institute (BPI), a nonprofit organization devoted to energy efficiency-related standards development.

BPI IDL is a certification that focuses exclusively on setting up and operating air leakage equipment, specifically blower door and duct blaster equipment.

Modern building codes are starting to include a blower door testing requirement for new homes constructed in many jurisdictions.

energy auditor addressing the blower door testing requirement

Other BPI Certifications Exist, However…

BPI has created workforce standards for a variety of home energy skill sets, resulting in professional certifications for the individuals who work in those roles.

Prior to 2014, the most popular BPI Certification was BPI Building Analyst, which is known as the whole-house energy auditor certification. BPI Building Analyst professionals are skilled at evaluating energy efficiency points throughout a home, using interior and exterior home inspection, doing blower door tests, and combustion safety.

Since 2014, there’s been some confusion about which BPI certification to pursue – should I get BPI Building Analyst or BPI IDL? Enter the Building Analyst vs. IDL debate.

As you can imagine, this answer largely depends on what you’re trying to achieve, but let’s dive into the differences between the two certifications quickly.

BPI Building Analyst vs. IDL: The Differences

In the BPI IDL course, you learn how to use the air leakage equipment to meet the blower door testing requirement.

BPI Building Analyst, on the other hand, focuses more on building science principles and the “house-as-a-system” approach to home energy auditing. This approach considers the house as an energy system with interdependent parts, each of which affects the performance of the entire system. It also takes the occupants, site, and local climate into consideration.

BPI CertificationsIDLBA
 Energy Code Compliantan Energy Auditor
Blower Door Tests



Duct Leakage Tests


Building Science Analysis 


Carbon Monoxide Tests 


Gas Leak Tests 


Combustion Safety Tests 


Energy Modeling 


BPI Building Analyst Focuses on the “Why”

What you’ll find when you research Building Analyst vs. IDL is that IDL shows you how to use the tools, but Building Analyst is going to teach you how to evaluate every single home – because literally, every home is so different.

Regardless of whether it’s a new construction project or an existing home retrofit, the “why” matters quite a bit.

Every home is designed a little bit differently. So a BPI Building Analyst professional has a keen understanding of why certain elements inside the home are acting as they are and how that impacts other elements in the home. BPI Building Analyst really gets into the why – why what you’re doing as a BPI IDL blower door technician actually matters.

types of houses

For this reason, building code officials may start to require the BPI Building Analyst Certification instead of, or in addition to, the BPI IDL Certification. They want a skilled workforce that can comprehend a wide variety of residential energy issues.

Putting It Into Practice

Because no two houses are exactly the same, a certified home energy auditor should be able to use his or her building science background to troubleshoot and brainstorm appropriate solutions.

The idea behind the Building Analyst is that you learn the science behind why different home elements matter (in the big picture) and how they interact with one another.

For example, in some cases, when doing a home energy audit, you might exclude the volume of a home’s attic, understanding how it affects the house and the impact it has on other elements in the home.

  • Is the attic an un-conditioned space that’s drawing in conditioned air?
  • Is it completely sealed and independent?
  • Or is it a conditioned space that should be included in the total house calculations?

It all depends on what you’re trying to measure, so you need to be well-versed in the overall building science to make those kinds of unique decisions.

Which BPI Certification Do You Need?

^ A question we are seeing more and more, as it relates to building code compliance!

As we mentioned before, many state building codes are starting to require blower door and/or duct leakage testing by a third party, certified professional. Beyond that, the building code typically does not go into any further detail about what’s required to satisfy this action item.

And because the state energy code is written using sometimes vague or broad language, it is open to interpretation by the building departments in each municipality.

This is the same in literally every state: it’s up to the local municipalities to set and enforce the rules (unless, on a rare occasion, the state forbids it). So that means neighboring municipalities can require two unique sets of rules. You have to be compliant wherever you are doing the work – whether that’s one jurisdiction or several.

Example of building code adoption by county in Missouri:

County building codes in Missouri

A municipality can also set a higher (or more strict) standard than the state! For example: Pennsylvania building code

Why the Building Code is Open to Interpretation

It’s been difficult for rule-making committees like BPI and the state level building codes to write good rules about home energy auditing. They’ve struggled over the last 20 years because every home is so different.

One thing we can say for a fact is that having a completely sealed building envelope is extremely important. But beyond that, there’s so much nuance in literally every home situation.

Having a one-size-fits-all approach can be difficult and even more difficult to write into code in a way that can be universally followed – and we haven’t even started talking about the specialized approaches you must have in different climate regions (homes in the Northeast vs. homes in Florida)!

For anyone who is particularly passionate about building science and state energy codes, you might consider volunteering either on the state level or at the BPI level to help write some of this code. It takes smart people in the field to be able to participate in that role. And especially if you’re the type of energy professional who desires uniformity, volunteering with these rule-making committees could be a good outlet and contribution to the industry.

It’s really hard to get uniformity – not just at the municipality level – but even in the interpretations of how to do some of the analysis.

To summarize…

  • every home is different
  • every climate has unique needs
  • no two municipalities will interpret the building code in the same way
  • building science will help you make informed decisions in any home

BPI is growing increasingly popular. Whether you currently work in a residential building trade or want to get into the energy efficiency industry, BPI Certification offers a strong skill set and nationally recognized certification for home energy auditing. With a BPI certification, you can add onto your existing business, offer code compliance testing services, and help homeowners reduce their energy use.

For more information, visit our New to BPI? Start Here section or call us at (800) 460-2575.

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About Lesley Baulding

Lesley has been passionately advocating for and working with green building and renewable energy since 2009. She has experience with LEED certification, home energy auditing, blower door testing, solar energy, and more. She holds many certifications, including LEED Green Associate and NABCEP Certification. Her work has won numerous awards over the past decade.