Energy use in hospitals is generally driven by internal heat gains, such as equipment loads and high code-required ventilation air change rates, and 24/7 operation. However, a high performance building envelope can still play a critical role in not only reducing the energy consumption and peak heating and cooling load of a hospital, but also ensure the thermal comfort and well-being of its occupants.

Technical Description

Background

The building envelope represents an essential boundary between the exterior environment and interior conditioned space. It must effectively control and respond to the environmental loads to maintain environmental separation and ensure desired indoor environment to the occupants.

According to a Fact sheet, developed by U.S. Department of Energy’s Hospital Energy Alliance, the building envelope, made up of all areas that interface between a building’s interior and exterior, is a major factor in determining how much energy will be needed to satisfy the building’s heating and cooling demands and maintain occupant comfort.

The major components of a building envelope include:

• Roof: The roof is the top covering of a building, providing protection against weather conditions such as rain, snow, wind, and sunlight. Common roofing materials include asphalt shingles, metal, slate, tile, and membranes for flat roofs.
• Walls: Walls are vertical structures that enclose and support the building. They can be made from various materials, such as wood, masonry, concrete, and steel. Walls provide structural support, insulation, and resistance to heat, air, and moisture.
• Windows: Windows are openings in the building envelope that allow natural light and ventilation into the interior spaces. They can also provide views and aesthetic appeal. Windows consist of glass panes set in frames, and their performance is influenced by factors like glazing type, frame material, and sealing.
• Doors: Doors are movable barriers that provide access and security to the building. They can be made from a variety of materials, such as wood, metal, glass, or composite materials. Like windows, doors must be properly sealed and insulated to maintain the integrity of the building envelope.
• Foundation: The foundation supports the entire building structure and transfers loads from the building to the ground. Common foundation types include slab-on-grade, crawl space, and full basement. The foundation also helps to prevent moisture infiltration and provides thermal insulation.

Design considerations and best practices

Retrofitting the building envelope should focus on the following design considerations to help achieve decarbonizing a hospital building:

High performance building envelope:

Improve the thermal performance of the building envelope by upgrading insulation, air sealing, and fenestration systems. This will reduce heating and cooling loads, leading to lower energy consumption and GHG emissions.

High performance opaque surfaces (wall/roof/slab/exposed floor) :

Increase the insulation levels in the walls, roof, and floors of the building envelope. Select insulation materials with high R-values (thermal resistance) to minimize heat transfer through conduction. Common insulation materials include fiberglass, mineral wool, cellulose, and foam boards or spray foam. Identify and minimize thermal bridges, which are areas where heat can transfer more easily due to differences in material conductivity or a lack of insulation. This can be achieved by using continuous insulation, thermally broken structural elements, or insulating materials at junctions and connections. Seal gaps, cracks, and penetrations in the building envelope to prevent uncontrolled air infiltration and exfiltration. This can be done using weatherstripping, caulking, spray foam, or other air sealing materials. Proper air sealing not only reduces heat transfer but also helps maintain indoor air quality and reduce moisture-related issues.

High performance glazing:

Replace existing windows with high-performance, energy-efficient glazing that minimizes heat transfer, reduces solar heat gain, and allows for adequate daylighting. This will help decrease the building's reliance on artificial lighting and HVAC systems.

Other than replacing the existing glazing with higher performance glass or replacing the entire fenestration with better product, adding a window film to improve its thermal performance could be an effective cheaper alternative.

Window films are composed of a polyester substrate to which a special scratch resistant coating is applied on one side, with a mounting adhesive layer and protective release liner applied to the other side.

Another product that has gain a lot of traction recently is Dynamic Glazing. Glazing systems that have the ability to reversibly change their performance properties, including U-factor, solar heat gain coefficient (SHGC), and/or visible transmittance (VT) based on desired condition. Based on a recent research by The Center for Healthcare Design, healthcare facilities are increasingly embracing dynamic glass to benefit patients. Another white paper has been published by one manufacturer demonstrating significant energy saving could be achieved by installing dynamic glass.

Cool roofs and green roofs:

Install cool roofing materials that reflect more sunlight and absorb less heat than traditional roofing materials, or consider green roofs that provide natural insulation, absorb rainwater, and help reduce the urban heat island effect. Both options contribute to reducing the building's cooling load and energy consumption.

Carbon-neutral materials:

Choose low-carbon, environmentally-friendly materials for the building envelope retrofit. Consider the embodied carbon of materials, as well as their durability, recyclability, and potential for reuse.

Renewable energy integration:

Integrate renewable energy sources, such as solar photovoltaic (PV) panels or solar thermal systems, on the building envelope to generate clean electricity or heat, offsetting the building's energy demand and reducing its carbon footprint.

How does this decarbonize?

Improving the building envelope performance helps decarbonize a hospital building in several ways.

By enhancing the thermal performance of the building envelope, hospitals can minimize heat loss or gain, which reduces the demand for heating and cooling. This leads to lower energy consumption and associated greenhouse gas (GHG) emissions.

A high performance building envelope reduces the load on heating, ventilation, and air conditioning (HVAC) systems, allowing for more efficient operation and potentially downsizing equipment if the existing equipment is coming to end-of-life.

A high performance building envelope will also help facilitate the transition to electrification of heating and cooling systems, reducing the reliance on fossil fuels and lowering the building's direct GHG emissions.

Implementation

Barriers: Codes

There are no code barriers to implementing an upgraded building envelope. In fact, the T24-2019 Energy Code, which took effect in January 2020, requires that any altered components of the building envelope must meet the Mandatory requirements for insulation per Section 120.7 and either meet the Prescriptive requirements per Section 141.0(b), shown below in Table 2, or comply using the Performance approach. Designers and builders may choose between meeting the insulation requirements (R-value) or assembly U-factors for compliance.

Table 1: Mandatory U-factor Requirements for Alterations per Section 141.0

Barrier: Financial

Retrofitting a building envelope can be expensive, requiring substantial initial investments in materials, labor, and professional services. Hospitals, which often have tight budgets and competing priorities, may find it difficult to allocate funds for such projects. In addition, Hospitals may struggle to secure financing for retrofit projects due to limited funding sources, strict lending criteria, or a lack of awareness of available financial incentives and programs.

Barrier: Disruption to operation

Hospitals are critical facilities that must maintain continuous operations to serve patients and communities. Retrofitting the building envelope can cause disruptions to these operations, which may be difficult to manage and mitigate.

Barrier: Technology

There are no technology barriers to implementing an upgraded building envelope as a lot of the technology has been developed for upgrading the building envelope more easily and economically.

• Continuous Insulation : Zip-sheathing CI ZIP System R-sheathing offers all-in-one structural panel with built-in exterior insulation. Featuring integrated moisture, air and thermal protection.
• Window films: IWFA international window film association website has a list of manufacturers that are members of the IWFA and follow its guidelines and principles as approved by the IWFA board of directors.
• Dynamic glazing: Dynamic Glazing is currently available in a variety of pane sizes and shapes, with numerous control and power options to choose from. As with all windows, electrochromic windows is able to cope with a variety of environmental conditions and temperature ranges. Many manufacturers now state that they are durable for up to 30 years.

Strategy

Overcoming the barriers to upgrading the building envelope of a hospital requires a combination of strategic planning, financial management, stakeholder engagement, and effective communication. First of all, develop a detailed plan that addresses the technical, financial, regulatory, and operational aspects of the building envelope upgrade. Secondly, Research and pursue available financial incentives, grants, or rebates that can help offset the costs of the building envelope upgrade. Thirdly, Involve key stakeholders, including hospital administrators, staff, patients, and community members, throughout the planning and implementation process. Engage them in discussions about the benefits of the building envelope upgrade, address their concerns, and keep them informed about the project's progress.

Financial analysis

The cost effectiveness of a certain building envelope efficiency measures (EEMS) or a bundle of EEMs for healthcare will depend on a number of factors including project size, existing conditions, technology selected, etc. Some of the low cost solutions like high performance window film result in a quick payback less than 2 years for an older healthcare facility, whereas higher cost technologies like dynamic glazing carry paybacks of 20+ years.

Funding is often the primary barrier to the implementation of retrofit projects in healthcare facilities. To overcome this barrier, financial decision-makers need reliable cost and energy savings analysis by building an energy model to evaluate the cost effectiveness and risk of a project.

In addition, consumers can find financial incentives and assistance for energy efficient and renewable energy products and improvements in the form of rebates, tax credits, or financing programs.

Business case

Healthcare institutions are coming to sustainability much later than other sectors like education or office. However, the urgency of building decarbonization pushes energy efficiency improvement on healthcare facility to an unprecedented level. An overwhelming majority of healthcare facilities have committed to reducing their impact on the environment through better energy consumption.

As mentioned above, a high performance building envelope can not only reduce the energy consumption of a hospital but also ensure the thermal comfort and well-being of its occupants, which can play a huge role in the decision making process. These valuable non energy benefits complement significantly to the direct cost reduction benefits. Non Energy benefits may in fact be dominant project drivers in situations where energy costs are less important to the bottom line. For example, daylighting not only cuts energy use, but can be beneficial to patients. These benefits are hard to quantify and are often omitted from financial analysis, but should be considered in the business case because they support the overall healthcare mission.

Building envelope retrofit analysis of an outpatient facility in San Francisco, CA

A building envelope retrofit analysis was conducted for an outpatient facility in San Francisco, CA. Constructed in 1970s, the facility has 9 stories with a total area of 220,000 sf. The window to wall ratio of the building is approximately 70%. The glass is all single glazed with a gray tint film added. The analysis is to quantify the energy/carbon emission saving by replacing the existing single glazed window with T24-2019 compliant insulated glass unit, which has significantly better thermal performance. The table below summarizes the properties of the two window systems.

The results show that the IGU could significantly reduce the cooling load by 28% and reduce the heating load by 46%. The overall carbon emission savings on HVAC systems operation are 35%.

Energy saving from better building envelope design

Ringgold County Hospital in Mount Ayr, Iowa recently replaced old structures with a new 62,000-square-foot, 16-bed facility. Situated on a 22-acre site, the new facility offers inpatient and outpatient care that includes clinical services, emergency, surgery, a lab, diagnostic imaging, and physical therapy. Compared to an ASHRAE 90.1-2004 code-compliant baseline building, the annual energy savings is 188,399 kWh of electricity consumption and 23,060 therms of natural gas consumption.

The thermal performance of the building envelope are as follow:

• Walls are made of a precast concrete panel system with an integral core of R-21 insulation.
• The floor slab is insulated with R-21 insulation, which is extended 7 to 10 feet across the building’s perimeter and down into its foundation.
• It has an ENERGY STAR-qualified cool roof with R-30 insulation and a coating of white flexible thermoplastic polyolefin membrane that has a solar reflectance of 0.79 and a thermal emittance of 0.85.
• Windows have double-pane glazing with a U-value of 0.29 and solar heat-gain coefficient of 0.42.
• Building envelope case study

Envelope retrofit using window films

Loewenstein Hospital Rehabilitation Center in Tel Aviv, Israel is a 9-story 1970’s Hospital building, the total square foot of retrofit area is around 48,000sf. A 9 mil Silver 20 SolarZone Safe film manufactured by Hanita coating was used for this retrofit. The energy savings were beyond expectations, cutting an estimated 3,578 mmBtu from the annual HVAC costs, a savings of nearly 20%. In fact, the total energy savings gave the security upgrade a remarkable payback period of less than two years.

Window film case study