How Warehouse Design is Evolving | Henderson Engineers How Warehouse Design is Evolving | Henderson Engineers

How Warehouse Design is Evolving

The warehouse and distribution industry has been evolving in recent years. With shifts in consumer behavior and the growing prevalence of one- or two-day shipping and same-day pick-up, online ordering has taken hold as the preferred shopping method for many. Fulfilling these online orders has necessitated expanded and more advanced warehousing for many of our partners. Since 2018, Henderson Engineers has been involved with the design of more than 250 million square feet of warehouse facilities – almost half of which has been completed in just the last eight months. As leaders in both retail and grocery design, we were well aware of the changing paradigm, but the COVID-19 pandemic and associated “stay at home” orders shifted things into high gear as online ordering became the only option for many.

It’s not just the need for warehouse space that’s climbing though; the sophistication of these spaces that were once just big empty “boxes” has reached new levels of efficiency and automation. The ways in which warehouses are being utilized is steadily changing, and as such, so are the building systems that bring them to life. The mechanical, electrical, plumbing, refrigeration, fire protection, and technology infrastructure in these dynamic buildings has become more complex than ever before. Below are some of the key points made by our experts in the August 26th webinar, Warehouse Building Systems Design: Designing Today for the Needs of Tomorrow.

Changing Needs

In the past, warehouses existed primarily to serve other warehouses or retail/grocery stores. While this is still the case for many, we have seen significant growth in direct-to-customer warehouses or warehouses that are serving as fulfillment centers. This shift has created high demand for both locations and square footage. However, existing warehouses in desired city centers often are not built for the modern needs of most of our clients, so many tenant improvements need to be made.

When planning for a new warehouse, regardless of whether you’re repurposing an existing space or building a ground-up facility, engaging a building systems engineer early in the design process can lead to extensive savings. Having a thorough understanding of what it will take to meet the owner/tenant’s needs and requirements is crucial to ensuring the proper infrastructure exists. We’ve also often seen that the landlord/developer is willing to share in the cost of the upgrades if the client knows what their needs may be at the time of the build out or handover.

Site Validation

Often our first involvement as the engineer is a site validation. For this, our team goes through a vetting process for the property or existing structure and can help in a go/no-go process, including reviewing the landlord letter and providing rough order of magnitude (ROM) costs.  During this process, the goal is to get a realistic and complete picture of the existing systems and how they compare to the needs of our clients.

Refrigeration/Cold Storage

One of the biggest changes, and arguably one of the most impactful, in the warehouse and distribution industry is the vast increase in the need for refrigerated or cold storage. Unlike standardized mechanical equipment like RTUs that you can order off the shelf, refrigeration systems are custom, individually designed for each site. The “right” refrigeration solution for a warehouse depends on a variety of factors.

  • Refrigerant type: Different refrigerant types (e.g. hydrofluorocarbons (HFCs), CO2, ammonia, etc.) each have their own set of considerations if chosen. Discussing the merits, drawbacks, and requirements of each can drive, or even dictate, the decisions related to refrigeration in a warehouse.
  • System type: You can either do a packaged system or a plant system. Packaged systems are assembled at the manufacturer’s facility and shipped to the site on a trailer. Plant systems, however, have the individual components shipped to the site and they are constructed by the contractor into your overall system.
  • Service availability: If you’re in a rural area with few other refrigerated systems/warehouses around, that could limit the availability of skilled technicians which will drive the type of refrigerant and system you choose.
  • Structural integrity: Refrigeration equipment is heavier than many people think, which means a well thought out space plan is key. Consider whether the roof can handle the weight of the equipment; even if the equipment is not roof-mounted, there are evaporators in the chilled spaces that are typically hung from joists and girders. Additionally, if you have a chilled space that is lower than 32 degrees Fahrenheit, like a protein box or freezer area, the roof cannot be used as the box lid. In those situations, an internal box lid that hangs, often supported from the joist and girders, must be used. In some cases, extra structural support may be required.
  • Plumbing concerns: Similar to mechanical equipment, evaporators have condensate discharge that has to go somewhere. In many existing buildings, sanitary inverts may only exist on one side of the building, which could mean having to tear up concrete or add a pump if the client wants to locate the refrigeration systems away from those inverts. For some systems, you also need a water for evaporative condensing or adiabatic units, consider whether or not there’s enough water supply for these purposes as well as the rest of the building systems, including fire protection.
  • Cold docks: Important to protecting the product cold chain, cold docks are different than ambient docks in that they need to be physically separated from the rest of the space with walls and other methods such as continuous pits and dock door packages specific for cold docks.
  • Durability: Forklifts are often in use in a warehouse so there’s a need to protect against forklifts damaging panels and other equipment, including evaporators if the product or pallet is extended up on the forklift. Anything on the floor such as drain covers need to be able to withstand the heavy forklift traffic going over it. Doors need to be able to withstand the operating temperatures in the space as well as frequent openings and near constant use.
  • Thermal Envelopes: Integrity of thermal envelope is critical. Things like columns, doors so people can go in and out, refrigerant pipes, fire protection pipes, and so on can break the thermal continuity. To mitigate this risk, we take great care in detailing how the continuity is broken and applying our broad knowledge of insulated products available with an understanding of how building codes are applied to refrigerated spaces. Just as important as the walls and roof, is the floor. In chilled spaces that will be below freezing, it’s important to protect the floor from the cooling and warming of the soil underneath. A heated floor slab can be added with either a glycol underfloor warming system or just electric heat in smaller spaces.
  • Vapor barrier: Vapor is water, and in cold storage facilities, water is ice, and ice means damage. A properly designed vapor barrier, coupled with the thermal envelope, protects your building and your systems.
  • System location: If you can’t locate the equipment on the roof, there are two remaining options – inside the building or outside the building. Locating refrigeration equipment inside decreases available warehouse storage space for product and requires an exterior location for the condenser. However, opting to locate all equipment outside of the building requires augmented security such as fences, gates, and bollards to protect against both vandals and accidental damage from trucks.
  • Electrical load: The electrical load in a warehouse that includes refrigerated equipment can be anywhere from five to ten times that of a standard warehouse, which equates to one or two additional electrical services. It also means talking about generators. If electrical service goes down, depending on the duration and current ambient conditions, there is likely some product loss – and depending on the size of the refrigerated space, that can mean tens of thousands of dollars lost. Incorporating back-up generators to electrical services feeding the refrigeration equipment can help mitigate this risk.
  • Ambient HVAC: The air around refrigerated areas needs to be to be conditioned air primarily to address humidity control. When people and product pass through doors from ambient to chilled environments, it’s critical that humidity is controlled to prevent icing over the coils and equipment.


Historically most warehouses were by and large unconditioned buildings, ventilated by a few exhaust and air moving fans. Many of the newer warehouses we are designing include HVAC to address the employee comfort and protect product integrity, especially if the warehouse includes food storage. As a bare minimum we look for louvers and fans in existing buildings.

  • Air conditioning: Many existing warehouse buildings were not set up to have any air conditioning. So, adding air conditioning for employee comfort and humidity control for cold storage adds a lot of capacity that was not originally intended.
  • Air movement: In large volumes of space, like a warehouse, racks can block air movement. To address this, we may perform a computational fluid dynamics analysis to ensure the air flows throughout the building.
  • Address vehicle impact: As many warehouses are now being used as fulfillment centers, this means instead of only having trucks pick up or drop off at a dock door, delivery drivers are now coming into the sites. In some cases, this means the fulfillment drivers are driving into the building or through drive-through canopies to load their vehicles. This creates a new set of design challenges as the mechanical system needs to be able to process the vehicle emissions and CO2 created, address the added heat from the vehicles, and account for the outside air infiltration coming into the building.
  • Heat from technology: Just as the sophistication in warehouses has increased, so has the added heat loads from sortation, conveyance, robotics, and assorted other types of equipment/technology inside of the building. This addition has rendered the “tons/square foot” rule of thumb calculation almost obsolete.
  • Infection Control: The current coronavirus pandemic has brought infection control technologies to the forefront of many building systems conversations. While every situation is unique and requires a tailored conversation, many of our clients have taken steps such as increased filtration, installing UV lights within air handling units, and upping the number of air changes (especially in smaller spaces like offices and break areas).


  • Service size: With the addition of refrigeration and mechanical equipment, as well as increased automation in warehouses, the electrical service size can increase immensely. If a utility upgrade is required, coordinating that early on can be an important piece in getting your project complete in a timely matter.
  • Lighting levels: As building heights go up, it also requires us to have higher powered lighting. Most of our clients are looking for higher foot candle levels so that their employees are able to quickly read what’s on the sides of boxes in order to easily pick product for distribution.
  • Generators: As we touched on in the refrigeration section, generators can be crucial to preventing product loss. However, it’s not just product loss that is a concern. For many warehouse and distribution centers that are focused on rapid delivery and operating 24 hours a day, a power failure could have a negative impact on the customer experience as well. When considering adding a generator, there are a few options to examine. The type of back up will depend on the needs of the building. For facilities with cold storage, often a full back up is worth the cost, in the case of a single failure, preventing product loss could pay for the system. With those, you have automatic transfer switches to run them seamlessly in case of a power outage. A secondary generator option would be a partial backup in which case you would only do emergency or critical systems. For example, if the building includes cold storage, the client may just back up the refrigeration or products that are more expensive. The third thing we see are quick connects. This is the case when there isn’t space for a generator inside the warehouse. Quick connects rely on an outside service to get their power back up. So, when power goes down, they can call the outside service, they come and quick connect to the system, and that gets the facility back up and running.


  • Service size and pressure: The first thing we look at regarding plumbing is the available service and pressure for water and gas; looking at where the systems enter and determining if we need a domestic pump. For gas, the same thing, knowing this helps determine how pipes are sized throughout the space.
  • Sanitary inverts: The biggest thing with sanitary is knowing what your inverts are, which means how far down under the ground the sanitary pipe connects into the city system. So, when you use a break room sink or a bathroom set on the other side of the building, the sanitary line has to slope down across the site. We’ve had plenty of projects where we’ve had to add lift pump or a new sanitary line across or outside the building. Knowing where your invert is and how deep it is in the actual ground will determine if modifications are necessary.
  • Multi-story buildings: Knowing how to coordinate plumbing through multiple floors is important, especially if it’s a warehouse on an upper floor with a tenant underneath. These situations require increased coordination with other owners/tenants.
  • Drains: In warehouses that handle food delivery, preparation areas, and commercial kitchens that require drains and grease interceptors, which require an added level of coordination beyond the sanitary conversation. Condensate coming off of refrigerated equipment also needs to be considered, looking at whether that will need to be pumped away or if there will be drains for it.


At Henderson, we may not be experts in automated logistics, but we are experts in understanding how they impact buildings and providing the services and infrastructure that are necessary for success.

  • Excellent connectivity: As the warehouse industry moves toward a “faster, better, stronger” mentality with automated systems and robots, excellent connectivity be it hard-wired or Wi-Fi is critical to success in these highly complex environments.
  • System placement: We focus primarily on the location of IDFs (intermediate distribution frames), which are technology cabinets that include network switches for the various devices like Wi-Fi, IP enabled security cameras, data connectivity, etc., as well as the pathways that connect the central point, known as an MDF (main distribution frame) with those IDFs. This pathway also needs to be protected just like other systems, like fire protection, that are critical to the building’s operations.
  • Charging: Recently, especially in last mile delivery warehouses and distribution centers, we’ve seen that these facilities are supporting local delivery vehicles. For some of our clients who have goals to become carbon neutral or net zero, that means these trucks or vehicles are electric or hybrid and require charging. Buildings that use robotics also may require charging inside the building, so it’s important to identify where this space will be and how they will be charged.
  • Infection control: Many existing technologies, such as IP enabled security cameras, can include temperature sensing to limit access to individuals who may have a fever. We can also use access control technology to create dedicated entrances and exits to limit cross contamination during shift changes.

Fire Protection

Fire continues to plague the storage industry. Large loss fires (and explosions) in warehouses and bulk retail facilities generally result from fire protection that is not matched to either the commodity (the product that burns) or the storage configuration (what the product sits on such as racks and shelves). In many cases, if the fire protection and life safety systems aren’t complete, matched to the client’s installation, and all components aren’t properly (and regularly) tested and maintained, the facility will not be allowed to operate.

  • Sprinkler system: Avoid “ordinary hazard” sprinkler systems if you have the option, in favor of early suppression fast response (ESFR) sprinklers. ESFR sprinklers are not a one-size-fits-all solution and even with ESFR, it’s often not enough to just “be a sprinklered building” when it comes to controlling a warehouse fire. “Install per NFPA 13” isn’t enough because many of the desired warehouse scenarios aren’t in the code book yet.
  • Frequent challenges: There are several common issues that we see in warehouse and distribution facilities that we can help our clients address.
    • Storage type – Most ESFR protected warehouses are designed for carton storage but many clients, especially those with automated warehouses, opt for plastic totes which are a more combustible product.
    • Product storage – When products are placed tightly together on racks that the configuration becomes a solid shelf rack, in-rack sprinklers are required.
    • Product type – ESFR sprinklers aren’t rated for everything; for example, they cannot be used on combustible liquids fires. In these cases, we must use specific protection methods from NFPA or insurance standards. We may also use performance-based design where we do a full-scale test to confirm that a protection scheme will work.
    • Rack configuration – In these large facilities, racking configurations often create dead end, which can make the make it difficult to meet the maximum allowable travel distance to exits allowed by model building codes. To address this, we can use computational fluid dynamics (CFD) to model how a fire will travel and how long it will take for a deadly smoke layer to form and compare it to the time it takes to egress to keep people safe.
    • Water supply – A very strong water supply is crucial to fire protection systems in warehouses. Often that means that we are installing a fire pump, or two, and in some cases a water storage tank to create redundancy for important facilities
  • Automated facilities: Clients are increasingly dependent on automated storage facilities which is creating new challenges for fire protection, like thinking about how to deal with robots that can spread a fire without any idea that it’s happening. On some of our recent projects we have incorporated aspirating smoke detection systems, which can detect a fire before it starts, combined with the automated storage systems to stop the robots from moving and mitigate the risk of a total loss by giving the sprinkler system a chance to work by keeping the fire from spreading so quickly.
  • Full-scale fire test: Technology is changing faster than the codes and standards can keep up with, but the industry is doing the best it can. In some cases, though, a full-scale fire test might be the only solution available for an untested storage configuration.

Engaging an Engineer

As the industry continues to evolve, the simple stuff is no longer simple when it comes to building systems in warehouse and distribution facilities. Which is why it can be important to bring engineering into the conversation early in the design process. If you have questions in regard to anything discussed in this article, or to discuss your warehouse needs, contact our warehouse practice director, Justin Harvey, today.

Written By

Sector Practice Manager

Written By

Grocery & Distribution Sector Executive

Written By

Technology Technical Director

Written By

Fire & Life Safety Technical Director

Written By

Grocery & Distribution Sector Cold Storage Practice Director | Distribution Center Practice Director


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