The demands of mixed-use facilities
Mixed-use facilities require engineers to handle several complex components. Here, engineers with experience on such facilities offer advice on bringing successful execution into the mix.
Timothy Chatterton, PE, Project Manager, RMF Engineering, Selbyville, Del.
Kari Engen, PE, CxA, LEED AP, Senior Mechanical Engineer, WD Partners, Dublin, Ohio
Taner Tekin, PE, LEED AP, Project Manager, exp, Maitland, Fla.
John Torre, PE, LEED AP, Principal in Charge of Electrical Engineering Services, OLA Consulting Engineers, Hawthorne, N.Y.
Scott Vollmoeller, PE, LEED AP BD+C, Associate DBIA, Managing Principal, Glumac, Seattle
CSE: What's the No. 1 trend you see today in the design of mixed-use facilities (facilities that have a mixture of retail and residential units and may include offices, parking space, cultural space, or a variety of other needs)?
Timothy Chatterton: Recently, we have seen an increase in owners requesting variable refrigerant flow (VRF) systems. These types of systems are on the rise in the industry, in general. However, VRF systems do present their own unique challenge in a mixed-use project depending on how many stories a space has and how that space is being used. The biggest challenge when using VRF systems is that they require a separate system to provide outdoor air.
Kari Engen: Becoming more common is the use of a 1st-floor retail strip space, with residential on upper floors. This appears to create more of a community within a single building.
Taner Tekin: The most recent trend we have been seeing in mixed-use projects is the combination of hotel and condo with associated parking and retail spaces. Parking garages are commonly both underground and above ground to meet the number of parking spots required for the project. Office spaces are often thrown into the mix to increase the long-term profitability.
Scott Vollmoeller: What we're seeing is a push toward maximizing the amount of glazing along the major view corridors, creating amazing amenity spaces (rooftop gardens, comfortable "living room"-type lobbies, etc.) and selecting systems for enhanced energy efficiency to meet current energy codes.
CSE: What other trends should engineers be aware of for such projects in the near future (1 to 3 years)?
Tekin: Engineers should expect to see more projects that include building types with different occupancies. Fire separation and smoke management are some of the challenges engineers have to address when designing these projects. In addition, LEED certification is almost becoming a standard in modern building design, not only in the U.S. but in other countries as well.
Engen: The retail experience appears to be moving toward a shorter time frame for the in-store customer experience, so occupancies are more intermittent.
Vollmoeller: Ensuring systems (mechanical, envelope, shading, etc.) are designed to maximize efficiency in an effort to maximize glazing percentages.
CSE: Please describe a recent mixed-use facility project you've worked on—share details about the project including location, building type, systems engineered, team involved, etc.
Engen: The facility was located in a major metropolitan high-density urban location, with a restaurant in a 1st-floor tenant space and residential units on upper floors; the building was circa 1930s with brick façade; MEP systems included variable refrigerant flow HVAC.
Tekin: One of the recent projects that I worked on was a fairly large mixed-use development in South Florida. The complex spans the entire three city blocks with an 18-story hotel, two 17-story residential buildings, one 12-story office building, underground and above-ground parking garages, and retail spaces on the first 2 floors of each building. Total floor space of the project is close to 3 million sq ft. The underground parking garage is beneath the ground floor of the whole site including the streets that divide the city blocks. This required a detailed coordination between the plumbing systems and the structural design, especially in a geographical location where constructing anything below-ground is a challenging task.
CSE: Describe your experience working with the contractor, architect, owner, or other team members in creating a BIM model for such a project.
Vollmoeller: Our BIM experience was limited on this project. However, on other similar projects, we work directly within the architect's Revit model to develop a coordinated set of design documents for future use by the design-build subcontractors.
Engen: Generally in mixed-use buildings where tenant work is involved, the BIM model work is often segregated; the tenant BIM is a stand-alone kit-of-parts model and the remainder of the building is modeled as part of the shell. Architectural coordination is facilitated through the use of BIM. Opportunities are available for the owner to incorporate BIM into its building management structure; however, this is not yet common practice.
Tekin: Taking the size of the project site into account and the volume of the BIMs that the design team had to work with, it was very challenging to design our systems inside multiple models. Where architects and structural engineers could limit their work to one model at a time, we had systems serving multiple buildings and therefore had to reside in multiple models and travel between models.
CSE: Have you designed any such projects using the integrated project delivery (IPD) method?
Engen: With the advent of LEED v4, this method is more likely to be used. However, our firm has not had exposure to this method.
CSE: What unusual requirements do such projects have from an engineering standpoint?
Engen: The IPD model allows for and encourages more owner participation throughout the design process. During early stages, schematic designs for engineered systems tend to be more openly vetted between all team members. Such a process tends to result in more owner buy-in on systems design decisions. Owners have more confidence in how systems work because of the ongoing collaboration between the engineering team and the owner's representative.
Vollmoeller: Communication is paramount from all parties.