Can’t blow this off 

New Air Barrier Requirements
in Vermont

Vermont’s 2020 Commercial Building Energy Standards (CBES) has been in effect since last September. In addition to many minor modifications to the code, there are also several notable changes related to the air tightness of the building.

These code changes are relatively easy to incorporate into the project — unless they are ignored during design and/or construction. BVH is here to help architects and builders save time, money and major aggravation.

In this four-part series we will highlight the new code requirements and strategies to meet them.

Part 1 provides a general overview of the changes. In Parts 2, 3 and 4, we’ll look at the blower door compliance path, the commissioning compliance path and multi-family compartmentalization testing.

Part 1: General Introduction to the New Air Tightness Requirements in the Code

The Vermont Commercial Energy Code, also called the Commercial Building Energy Standards (CBES), has been updated, effective September 1, 2020. Like all code updates, there are some changes. In this first post, we will cover the overall requirements for the air barrier in the commercial code:  

New commercial buildings must meet a whole-building air tightness standard of 0.30 CFM/sf at 75 pascals (0.30 inches water gauge). This standard must be verified by a blower door test on the building (C402.4.1.1). 

For apartment buildings, condominiums, and other multi-unit residential construction there is a further requirement that at least 10% of the units be individually blower door tested to a target of 0.35 CFM/sf at 75 pascals (C402.4.2).  This test shows that the units are sufficiently compartmentalized, or independent of each other, in terms of air movement.

There is an alternate path in the code to whole-building blower door testing – this requires commissioning of the building envelope during construction (C402.4.1.2). However, there is no alternate path to blower door testing individual units in multi-unit residential buildings – this is a requirement.

Anticipated properly, these are not difficult provisions to meet but they can be daunting if they are not considered early in the project.

Guidelines for architects:

  1. In the specifications, we recommend referencing the CBES whole building air tightness requirement of 0.30 CFM/sf at 75 pascals (0.3 inch water gauge) as verified by blower door testing per ASTM E779 (C402.4.1.1). We also recommend referencing the CBES alternate path to the blower door test, air barrier commissioning in subsection C402.4.1.2. Make it clear in the specifications which path to compliance is required for the project; or, you may specify that both paths are required. Additionally, make it clear who is responsible to contract the testing and/or commissioning firm – this will be the owner, the architect, or the construction manager.  If the building is multi-unit residential, the specifications will also need to reference the unit target of 0.35 CFM/sf at 75 pascals (C402.4.2). The most logical place is to add this language is in the air barrier or weather barrier section of the project specifications. 
  • There is a certificate and affidavit that must be completed and signed by the designer and the general contractor to show compliance with the code.  It is easy to miss because the code itself does not mention this form.  Find it here: scroll down find “2020 CBES Certificate and Affidavits”.

  • If air barrier commissioning is the compliance path, the architect has to provide evidence of commissioning by an approved agency (C402.4.1.2). Get the commissioning provider involved early, during schematic design if possible.  If you decide to make commissioning the responsibility of the construction manager, make sure this is clearly stated in the specifications.  It is in the owner’s best interest that these code provisions are understood by all parties as early as possible in the project.          

Guidelines for general contractors and construction managers:

  1. Most importantly, be aware of the new code provisions and how they apply to your project. Even if they are not described in the project specifications, they must be met. Find out immediately if your firm is to contract the testing and/or commissioning services and if not, who is providing them.

  2. If commissioning is to be provided by others, encourage the owner or architect to contract the services as soon as possible. The commissioning/testing agent can be a great resource to help the building meet the air barrier target. Having the agent involved early in construction increases the chances that these provisions can be met without hassle and rework.

  3. Like the architect, the general contractor has to fill out a certificate and affidavit to show compliance with the code.  Find it here — scroll down to find the “2020 CBES Certificate and Affidavits”.


Are there stretch code requirements in the 2020 CBES?  

Although there was a stretch code in the prior version of the code, it has been removed in this version.

What about buildings that are renovated or refurbished?

The code is reasonable regarding what level of alternations or repairs trigger the code; however, you should consult subsections C503 and C504 to make sure. For example, just replacing the roof covering of an existing building does not require the building to meet the air barrier standards.  However, a full gut renovation or a change building use will likely trigger the air barrier provisions.

Historic buildings are not required to meet the code but a “Historic Building Exemption Report” must be submitted and approved (C501.6). 


Part 2: Taking the Blower Door Compliance Path

Part 3: Taking the Commissioning Compliance Path

Part 4:  Multi-Family Compartmentalization Testing

Should you have further questions or need any assistance about how to meet these code provisions in your project, please email or call Jon Haehnel, BVH’s Building Envelope Specialist at or 802-522-9713.