Condo Living

January 24, 2025 Published by Golden Horseshoe Chapter - By Kevin Shaw, Smit Patel, Greg Allan

Impact Assessment of Electric Vehicle Parking in Underground Garages

From the Volume 22, Winter 2025 issue of the CCI GHC Condo News Magazine

Introduction

With the continuing move towards a lower-carbon society and the proliferation of electric vehicles, our communities need to start assessing the potential impacts of these changes on our built environment.

One of these is the potential impact of the significantly heavier weight of electric vehicles compared to gasoline powered ones. Can our garage parking structures accommodate the additional weight of electric vehicles while ensuring structural safety and integrity.

Another is to determine whether current fire protection designs can accommodate the potential risks associated with electrical vehicles while ensuring the life and safety of owners and their vehicles.

Vehicle Weight Analysis

To evaluate the impact of adding electric vehicles to a parking garage, we need to compare the weights of typical gasoline-powered internal combustion engine (ICE) vehicles with electric vehicles (EVs) across different categories: a small sedan, a medium sedan, an SUV, and a truck. These categories were chosen to represent a range of vehicle sizes and types commonly found in parking garages.

From the comparison shown in Table 1, we can observe that EVs tend to weigh significantly more than their ICE counterparts. This difference is mainly due to the heavy battery packs used in EVs. However, even with the heavier weight, most of the common EVs found on the market today still fall within a 4000 kg limit.

Assessing the Existing Structure

In order to properly assess the capacity of an existing structure, the original base building structural drawings need to be reviewed to verify the design parameters. For parking garage structures with 200mm thick reinforced concrete slabs with 110mm thick drops, the typical design live load would be in the range of 2.4 kPa. This corresponds to Ontario Building Code (OBC) requirements for garages supporting vehicles weighing up to 4000 kg in gross weight.

Special Conditions

While most of today’s electric vehicles fall within the 4000 kg limit, there are existing exceptions such as the GMC Hummer EV, which has an operational weight of 4,300+ kg. This is heavy vehicle that could exceed the design weight limit of a typical garage structure although still not likely to pose a structural concern.

Conclusions

When comparing electric vehicle weights with those limits implied and stated in the OBC, existing underground parking garage structures are likely to be capable of supporting current models of electric vehicles however this should be assessed on a case-by-case basis before entire garages are filled with EV’s.

Parking Garage Fire Protection

Fire protection systems for most parking garages within buildings consist of full sprinkler protection in addition to fire hose cabinets on all levels. The spacing of sprinklers should be consistent with the NFPA requirements for parking areas to be designed to Ordinary Hazard Group 1 requirements. Under NFPA requirements, dry piping systems must deliver water to the most remote sprinkler head within 60 seconds of sprinkler activation.

“Dry” sprinkler systems consist of piping that is empty of water and pressurized with air under normal conditions. This system is often provided in parking garages that are unheated to prevent freezing of water in the sprinkler piping. In a Dry system, water is introduced into the piping system at the sprinkler room when a sprinkler head is activated. The piping fills with water until water reaches the open sprinkler. Depending on the location of the activated sprinkler, this filling delay can take up to 60 seconds. It is important to note that the inherent delay associated with dry sprinkler systems is problematic with respect to EV’s where early detection and suppression is recommended.

Fire Hazards in Parking Garages

To evaluate the impact of adding electric vehicles to the parking garage, we need to compare the differences between car sizes, fuel type, and fire ignition sources of typical gasoline-powered internal combustion engine (ICE) vehicles with electric vehicles (EV).

Table 1: Comparison of average weights of ICE vehicles versus EVs

Vehicle Type	ICE	EV
Small Sedan	Honda Civic – 1365 kg	Tesla Model 3 – 1850 kg
Medium Sedan	Toyota Camry – 1570 kg	Tesla Model S – 2240 kg
SUV	Chevy Equinox – 1570 kg	Chevy Equinox EV – 2200 kg
Truck	Ford F-150 – 2300 kg	Ford F-150 Lightning – 3000 kg

Table 2: Comparison of average sizes of ICE and EV

Vehicle Class	ICE (mm x mm x mm)	EV (mm x mm x mm)
Small Sedan	4,547 x 1,801 x 1,415	4,694 x 1,849 x 1,431
Medium Sedan	4,915 x 1,840 x 1,445	5,021 x 1,987 x 1,431
SUV	4,695 x 1,940 x 1,680	4,714 x 1,882 x 1,613
Truck	5,311 x 2,029 x 1,910	5,683 x 2,032 x 1,796

From Table 1, we can observe that EVs and ICEs are similar in size when comparing vehicles within the same vehicle class. However, when comparing the average size of vehicles from 2013 to 2023 the average length and width of vehicles are 12.24%, and 17.24% larger respectively. As such vehicles have been increasing in size due to modern design and not by fuel type. This is important to note as an increase in vehicle size would increase vehicle density within the parking garage increasing the likelihood of fire spreading from vehicle to vehicle.

Similarly, modern vehicles have an increased usage of plastics and combustible materials when compared to older models. As per the 2020 FPRF report, this change has been significant to the heat release rate (HRR) and it has contributed to increasing the ability for fire to spread from vehicle to vehicle.

Comparing fuel types for ICE and EV testing performed within the 2020 FPRF report determined that the HRR between the types were similar. If the ignition source does not affect the battery of an EV, prevention methods for ICEs will function for EVs as well. That is, there is no real change to the HRR for the vehicle itself, but there is significant change to the fuel systems.

If the ignition source is from the battery of an EV or it reaches and ignites the battery, then thermal runaway would occur. This is a particular concern for battery fires as these are self-sustaining and can cause re-ignition by overheating neighboring battery cells. Battery fires also burn at a much higher HRR when compared to ICEs fires causing them to rapidly spread from vehicle to vehicle.

It is important to consider the size of batteries within EVs and how they are expected to change over time.

Figure 1: EV Battery Sizing/Capacities as a Function of Time

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Greg Allan, P.Eng., is the Studio Manager for Mechanical Engineering at NORR. Greg has over 25 years of experience in mechanical engineering and oversees all the staff and projects within the Mechanical Department.

Smit Patel, P.Eng., is a Structural Engineer with NORR. Smit has over 8 years of experience in executing structural engineering projects across a variety of sectors including residential, commercial and institutional properties.

Kevin Shaw is a Principal with Cion - Engineers and Building Scientists and is responsible for all operational aspects of Cion’s building science services. Kevin has over 25 years of experience in building evaluation and rehabilitation. Kevin holds his LCCI designation with CCI and is an active member of the Business Partners Committee of the Golden Horseshoe Chapter.