Site selection is the critical first step in any new commercial real estate development. Thorough due diligence during the programming process is imperative so that the site’s infrastructure meets or exceeds an owner’s requirements and expectations. In most instances, an architect may assist the broker in the selection by reviewing multiple buildings and spaces from an architectural standpoint, while the engineer gets involved only after a site has been selected. Given today’s ventilation, cooling, and power requirements associated with technology-intensive clients such as trading firms, hospitals, financial institutions, and other mission critical facilities, it is imperative that design engineers be involved from day one — when the owner is prospecting buildings.
The occupant density and equipment heat gain associated with today’s high tech facilities is much higher than that of a typical office space. Due to the higher heat dissipation, the base building air conditioning system is usually not adequate for technology-intensive firms, and supplemental cooling is often required. It is important that the cooling requirements be identified in the development program and communicated to the building representatives. The building staff can then verify if their infrastructure is capable of supporting the tenant’s needs. It is equally important to be cognizant of future requirements as day one occupancy and equipment is often a fraction of the desired ultimate build out. Buildings that cannot meet the current needs or will require major upgrades in the future can potentially be eliminated upfront.
As mentioned, the occupant density and equipment heat gain associated with technology-intensive spaces is higher than that of a typical office. On some of the high-density trading floors, power density can exceed 30 Watts/sq ft. Coupled with 24/7 operation, the annual cost of operation can be significant and should be evaluated during the programming phase.
Mechanical water and airside systems as well as electrical systems capacity will be most critical and should be evaluated by an MEP engineer during site selection. While the electrical costs can be similar for buildings in the same region, the cost of other utilities remains at the discretion of building management and, therefore, can vary significantly. This includes chilled water, condenser water, after-hours HVAC, standby generator power, and more.
Most buildings offer the tenant the ability to tie into the base building chilled water (CHW) or condenser water (CW) systems for supplemental cooling units. It is important that the riser sizes and nearest tie-in point be evaluated. It can be cost prohibitive if piping has to be routed over long spans or new taps into the existing riser are required. Some buildings do not have a water system for tenant use or the system might not be available at certain times of the year. In that case, supplemental cooling would require space for heat rejection equipment.
The temperature of heat transfer fluid (chilled water or condenser water) being provided by the building is also important. If the building incorporates temperature reset schedules, the system needs to be designed for the worst-case water temperature. For buildings utilizing a centralized pumping system, the minimum differential pressure (DP) anticipated at the risers should be calculated. If the anticipated DP seems inadequate, secondary distribution pumps may be needed. This affects space planning as the pumps may require mechanical equipment, thereby using valuable floor space.
The supply air temperature being provided by the building is an important factor. If the building incorporates temperature reset schedules, the design needs to be based on the worst-case air temperature. The supply air temperature has a direct bearing on the sizing of ductwork, terminal units, and possibly supplemental cooling units. The airflow available from the base building systems should also be considered. While that data might not be available during the programming phase, the base building infrastructure can still be reviewed to determine the feasibility of delivering the required airflow to the tenant space.
Any special exhaust requirements such as battery exhaust or kitchen and potential tie-in or discharge locations should be evaluated. It can be cost prohibitive if ductwork has to be routed over long spans.
The existing electrical infrastructure and the method of delivering power to the tenant should be analyzed. If the switchboard is located on a different floor, riser space needs to be identified for routing of conduits to the tenant floor. Major upgrades to the existing electrical system need to be identified upfront as utility transformers, switchgears, and switchboards can potentially have long lead times and could impact the project schedule.
Electrical equipment that needs to be located within the tenant space such as distribution switchboards, the UPS system, transformers, and panels all affect space planning as the electrical rooms use valuable floor space and may have expensive structural implications. Electrical equipment can impose high loads on the existing structure and the need and potential of reinforcement should be evaluated by the structural engineer during the programming phase. Many technology intensive spaces require continuous uptime and standby generator components such as louvers, remote radiators, fuel storage tank, sound attenuators, location of flue and radiator exhaust, and location of fill system and therefore should also be analyzed during site selection. Some sites might impose major restrictions on the generator location due to noise and flue exhaust issues.
EXISTING DATA REVEALS TRUE CONDITIONS
It can be extremely useful if building automation system (BAS) data related to base building infrastructure is available for review. The BAS trends will indicate the frequency and duration of downtime experienced by the site in the past. They can also help verify building claims regarding system setpoints (air temperature, water temperature, differential pressure, static pressure, etc.).
Surveying the infrastructure will also be beneficial. Condition and robustness of existing equipment, extent of BAS, and potential for expansion are important factors as they affect the uptime and resiliency of the building systems and therefore, the tenant equipment. If the client is relying on the building for critical power and cooling, an uptime threat analysis should be performed to identify single points of failure in the base building systems. Categorized as high, medium, or low based on their impact on business continuity, these threats can be an important parameter when comparing buildings.
WHEN EXISTING CONDITIONS CALL FOR DEDICATED SYSTEMS
The engineer can calculate the anticipated annual operating cost based on client requirements in the form of a life-cycle cost analysis, which will help in making economically sound site selection decisions. If the total cost of utilities anticipated over the duration of the lease is cost prohibitive, it might be viable to install a dedicated HVAC system, standby generators, or supplemental cooling systems, which are owned and operated exclusively by the tenant.
Operation of a dedicated HVAC and supplemental cooling system during off-peak hours as well as economizer mode can significantly reduce the operating costs. While the same principle applies to base building systems, the unit cost of utility ($/Ton-hr, $/Ton, $/hr, etc.) is typically fixed by the base building and savings are not passed over to tenants. A dedicated infrastructure will increase the project space and budget requirements. However, the increase in capital expenses could potentially be offset by a reduction in operational expenses over the duration of tenancy.
Employing dedicated systems also alleviates many issues associated with utilizing base building infrastructure while offering a build-to-suit opportunity, or the ability to tailor the infrastructure to meet the tenant’s specific requirements and criteria. The system can be designed to be scalable, such that a portion of the infrastructure, which is adequate to satisfy day one requirements, is initially installed. The remainder can be installed in phases down the road when specific thresholds come up.
FINAL SITE SELECTION
The engineer can be a valuable asset to the site selection process, reviewing existing infrastructure, space planning for mechanical and electrical rooms, interviewing facility operators, commenting on MEP lease requirements, identifying scope, establishing project requirements, performing economic and life-cycle cost analysis, and setting expectations — services that will provide both the advice and the peace of mind building owners and operators seek.
|Frequently missed items in site selection
1. Airside and waterside temperature reset: Some buildings
might reset the air and waterside temperature setpoints
seasonally. This can lead to undersized equipment or a shortage
of cooling provided by the building. Ask the building engineer if
the base building mechanical system utilizes a reset schedule.
2. Static pressure anticipated at the air riser: Some older systems
do not provide adequate static pressure at the riser and long
runs of ductwork may need to be oversized to deliver the design
3. Differential pressure anticipated at the water riser: Some
buildings require tenants to install pumps to circulate water on
each floor because the building pumps are not sized to distribute
water to the floor. Check to see if this will be required for your
tenant build out.
4. Riser space for electrical feeders/conduits: Adequate riser
space will be required to bring conduits/feeders from the
building’s electrical room to tenant space. If not, it will be hard to
install electrical requirements. This will be critical when the tenant
requires a generator.
5. New plumbing installations: If you plan on installing new
plumbing work, which will take up real estate in the ceiling below,
make sure the space can accommodate that. Be aware of any
“no-fly” zones for plumbing.
6. Fire/life safety considerations: Make sure the building’s fire/life
safety infrastructure is up to code or up to your standards. Not all
legacy buildings are fully sprinklered.