Changing perceptions of hospital design: why façade performance matters
A blog on usglassmag.com by Helen Sanders
This month, I sat down virtually with my good friend Stacey Hooper, partner and healthcare market leader at NBBJ in Los Angeles, to discuss sustainable façade design with a healthcare twist. We talked about best-practice façade design in hospitals and why, contrary to common belief, façade performance matters.
Why does Façade Performance Matter in Hospitals?
The biggest misconception in hospital design, and something Stacey sees many people still holding on to, is that the façade thermal and solar control performance doesn’t matter because internal loads drive HVAC system design.
Hospitals have high internal loads driven primarily by the air-exchange requirements and the heat generated from hospital equipment and people.
In Stacey’s experience, this position has proven to be antiquated. The envelope matters significantly.
This is not just because of the oversized impact of the façade design on perimeter thermal and visual comfort, but also because of the impact on sizing of the mechanical systems, which is often considered relative to overall building loads.
Often, hospitals are divided into the podium level, where the high-load procedural programming, such as operating rooms, is found, and a more highly glazed tower, where the patient rooms are located. The key to realizing the façade’s impact is evaluating the performance of the envelope relative to the dedicated mechanical systems serving these distinct programmatic functions. Architecture and engineering teams can misinterpret overall building performance and draw the wrong conclusion, which is that changes in envelope performance do not move the needle on overall energy use intensity.
However, the relative impact of the envelope becomes much clearer once these areas are not conflated. If not separated, the significant cost-saving impact of increasing the envelope performance on the patient room tower is often missed.
Stacey relayed a recent project example; when considering the two systems separately, the MEP engineer reported that using a better envelope on the patient tower could result in $10 million of upfront cost savings from reducing mechanical systems! This shows how important it is to decouple the building’s podium from the bed tower floors and consider them as separate systems when assessing the upfront cost of the mechanical system.
What is Your Patient-Focused Design Approach?
Patient rooms are typically located at the perimeter because daylight access and views of nature are a known link to faster healing, reduced pain and improved well-being. Stacey considers the bed tower design in a similar way to the perimeter of an office building, with a 10-foot depth of influence from the façade.
Achieving the comfort needed is challenging, especially because of the higher air changes. This is where the performance of the façade, and particularly the fenestration, is critical. Complex daylight, glare and thermal comfort simulations are done by the most sophisticated design teams to optimize the façade design.
Typically, Stacey completes a sun study and then designs the façade to minimize direct beam sunlight and glare in the first 10 to 15 feet of the building perimeter to deliver thermal and visual comfort.
She always recommends doing a thermal comfort study, but it normally isn’t part of the full-service architectural contract. In some cases, clients do not prioritize these studies as they don’t believe it will influence decision-making. Given the budget constraints of the current market (from federal funding cuts and construction inflation), hospital owners are doing their best to make their budgets stretch and make the best overall decisions. In California, the additional cost of seismic compliance adds yet more construction cost viability challenges.
These cost challenges drive an emphasis on upfront costs and, to some extent, payback on energy cost savings. Stacey notes that it is the architects’ responsibility to help their clients connect the dots between façade performance, dollars saved and optimized patient experience. Sometimes, this is done through full-scale mockups as well as, or instead of, simulated thermal comfort studies.
One of the most important outcomes is delivering patient agency, such as the ability to control their environment from the bed. Automatically controlled shades or blinds are often value-engineered out of the design, so this moves the priority to passive design for limiting annual sunlight impact.
Delivering quality views of nature is key to the patient’s healing experience, so avoiding situations where manual shades are drawn much of the day is serious. Stacey will often assess façade designs by doing “shades down” studies to estimate the amount of time the shades will likely be down and blocking the view throughout the year.
The focus on delivering patient comfort and maintaining views often leads to more sophisticated glazing strategies, with careful transparent fenestration placement and different coating, frit and shading treatments on upper clerestory glazing versus vision glazing. In some cases, two shades may be used, one to deliver privacy and one for solar control.
Speed of Construction Pushes Unitization
For hospital owners, a major driver is speed to market. Depending on the scale of the project, owners can face extreme escalation costs up to $10 million per month of delay. This significant schedule penalty, overlaid on the already tight budgets, drives unitized wall systems. Unitized curtainwall used to be a premium, but now it is a risk-mitigation strategy.
However, for unitized curtainwall systems, designers must now navigate their thermal inefficiencies, especially around spandrel design. This is becoming more challenging in jurisdictions like Massachusetts, where thermal bridges must be accounted for and mitigated.
While spandrel can be packed with insulation, an alternative strategy NBBJ uses involves large two- to three-story panels with glass reinforced fiber cement (GFRC) for the opaque areas alongside punched opening windows. In California’s Loma Linda University Medical Center (figure 2), these panels were three stories high and provided high-speed installation, as well as good thermal performance.
Mega panel systems are becoming more prominent in building design, especially where energy codes are more stringent, because of the high thermal performance achievable and the positive impact on project cost, schedule and quality. A good summary of the considerations for mega panel systems has been created by Christopher Grey at Simpson Gumpertz & Heger (SGH).
According to SGH, mega panel systems are “large, shop-fabricated sections of façade that incorporate several building elements and material types.” They are a threat to regular unitized curtainwall systems and have the potential to supplant them in jurisdictions with more stringent energy codes, if spandrel thermal performance is not sufficiently improved.
Improved spandrel designs have been developed (see here and here) to serve the British Columbia market. Wider availability of solutions will be necessary to compete against mega panel systems.
Competing Challenges
Hospital façade design is driven by many seemingly competing factors: speed and cost of construction, operational energy performance and the ability to deliver patient comfort, agency and healing experience. Stacey concludes, “I think this is the beauty of understanding all the factors; once you do, it helps get alignment around what could be competing factors. It’s our job to make it all sing and achieve excellence across all the variables.”
It is important to debunk the myth that the envelope’s performance is not important in hospitals. High thermal and solar control performance reduces upfront mechanical system cost and operational energy use, as well as delivering environments conducive to patient well-being and healing. When balancing the variables, a well-designed façade can save construction time and cost, while also delivering the desired high-performance.