Ventilation Requirements for EV in Multi-Family and Mixed-Use Construction

By Anthony Basden, PE, LEED AP BD+C
It’s been over a year since California’s Air Resources Board approved a rule requiring 100% of cars and light trucks in California to have zero emissions by 2035. Since then, Maryland, Massachusetts, New Jersey, Oregon, and Washington have adopted similar rules prohibiting gas-powered vehicles in 2035.

About the Expert:

Anthony Basden, PE, LEED AP BD+C, is an electrical project designer/manager responsible for the design of electrical power systems, lighting, fire protection systems, and audio/visual and data systems. His design work has included infrastructure for charging stations at commercial and residential developments in Washington and California.

As a result, building codes are changing to reflect this and similar rules. The 2022 CalGreen code, effective January 1, 2023, requires new construction multifamily projects to install electric vehicle charging stations, or Electric Vehicle Supply Equipment (EVSE). Washington Administrative Code (WAC) 51-50-0429, effective July 1, 2023, will require 10% of all parking spaces in R-2 occupancies (multifamily construction) to be equipped with an EV charging station.

A recent project of Ayres needed to meet the new WAC requirement. After the appropriate calculations, we determined that the project required 136 40-amp circuit breakers (32 amp load) for each 208V single phase electric vehicle charging station. 33 EVSEs will need to be installed in the underground parking structure of the project.

That seems like a lot, and it is. It’s a very heavy electrical load, but the purpose of this article is not about the electrical load presented. It’s about the required coordination between the electrical and mechanical engineers to adequately size the HVAC systems.

New Regulations for EV Charging Stations

Previous code cycles required provisions and capacity in the electrical system for future electric vehicle installations. We dutifully complied with capacity and conduit provision requirements in the applicable codes at the dismay of the owners.

The construction industry as a whole did not address that many EVSEs being installed in an enclosed space. This is partially because some didn’t believe that many electric vehicle charging stations would ever be installed, and, more practically, few multifamily projects consist of parking structures that are completely enclosed. It is more expensive to enclose a parking structure because building codes require mechanical exhaust.

In the most complicated multi-family and mixed used projects, as in the one Ayres is engineering, the parking structure is underground to make the ground level accessible to restaurant tenants.

So, what’s the concern to electrical engineers when it comes to ventilation?

The electrical code contains information on mechanical ventilation for EVSE in article 625.52(B). At first blush, one might think that it applies to every installation because of its wording. A careful review of 625.52(B) reveals two things:

  1. Only EVSE listed as requiring indoor ventilation requires ventilation. In our experience, no EVSE currently bears this listing. To be fair, the listing for “use without ventilation” described in 625.52(A) is not present on equipment cut sheets either. This may be a situation where the listing information simply hasn’t made it to the cut sheets yet because it hasn’t caused a problem. In similar situations, if the listing like this is not present, we typically assume additional equipment is not required.
  2. 625.52(B)(4) requires the ventilation be interlocked with the EVSE. This is typical for other installations utilizing battery charging. However, this interlocking is typical of lead acid battery installations, not Lithium-Ion battery charging. When charging, lead acid batteries vent hydrogen and create a class 1 division 1 explosion hazard by article 500 of the electric code. Lithium-Ion batteries do not create this hazard since they do not produce hydrogen in their charge cycle. In our experience, no EVSE has the capability to interlock with ventilation. So, ventilation is not required.

So, what? It still doesn’t affect electrical engineers. Except….

There is one thing that every electrical circuit produces when power flows – heat.

Electrical and Mechanical Coordination Challenges

When electrical engineers specify dry type transformers in our electrical rooms, we do our equipment and our mechanical engineers a solid by providing the heat rejected to the space so they can size the HVAC systems accordingly. It is the same case for electric vehicles in an enclosed parking structure. We owe our mechanical engineers heat rejection information.

In our project’s case, we can calculate the heat rejection as follows:

  • Power delivered to EVSEs = Number of EVSEs x Voltage x Current
  • Power delivered to EVSEs = 136 EVSEs x 208V x 32 A
  • Power delivered to EVSEs = 905 kW

That’s the electrical usage of a large department store in a space 1/5 the size. That’s not the heat rejection though – that’s power delivered to the EVSEs. Li-Ion batteries are approximately 90% efficient. So, 10% of the power delivered is rejected as heat. So, the heat rejection is:

  • Heat rejection = Power delivered to EVSEs x (1 – Efficiency)
  • Heat rejection = 905 kW x (1 – 0.9)
  • Heat rejection = 90.5 kW

That is the information electrical engineers are required to provide our mechanical counterparts.

Now, to the engineering coordination point of this discussion. 90.5 kW represents the entire heat rejection capacity of the batteries charging. How much of that maximum value would be used to size adequate ventilation? Is it the actual installed EVSEs at 22.0 kW (33 / 136 x 90.5 kW)? Is it the full value? Is it some portion of the actual installed EVSEs?

A hint to the answers is contained in the electrical code article 625.41. It regards EVSEs as a continuous load, and the only demand that can be taken at the service is to limit the maximum load to that of a load management system installed. In other words, if your project like many others do not have a load management system installed, the mechanical engineer must make a choice to address the full heat rejected for that which will be installed, or the full heat rejected of the entire electrical capacity.

Since engineers typically don’t play “what if” games when it comes to permit documents (our designs are complete at permit), my suspicion is the industry will land on the heat rejected for that which will be installed, or 22.0 kW. Remember earlier that some didn’t believe the EVSEs would make use of the code required provisions in the previous code cycles? That belief still applies to the capacity and provision requirements. If there is no rule to provide ventilation for the entire capacity of EVSEs on the electric service, we, as an industry, will do what we have been trained to do in the previous code cycle. In other words, we won’t address something that isn’t there.

Future Implications

Some multifamily projects are on a 15-year recapitalization cycle. That means a significant remodel to the building will not happen for 15 years after it’s built. So, in the case of Washington, a project permitted on July 2, 2023, and given a certificate of occupancy in July 2025 will not have a major remodel until 2040 or later. When Washington’s car dealerships are only selling zero emissions vehicles in 2035, this project will have only 10% of its parking spaces with EVSEs installed. It’s anyone’s guess as to how many internal combustion engines will still be on the road by then, but the need for EV will far outpace the EVSEs installed in this project at the end of its capitalization cycle.

Do you have questions or comments? Reach out to Anthony Basden or one of our many MEP experts for more information.


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