Change is seldom easy. It’s common to become set in our ways, and once we’ve mastered a skill, we want to use that expertise again and again.
Building codes and construction methods have generally stayed the same over the years, with modifications coming gradually. Energy codes, on the other hand, have changed from the moment they were first introduced and will continue to evolve well into the future. Addressing these codes as they grow means adapting our design and construction practices. It’s an ongoing challenge for everyone in the building industry, including self-storage developers; but meeting energy requirements can bring benefits to a project.
The International Code Council introduced the first edition of the International Energy Conservation Code in 1998. The code is reviewed, updated and reissued on a three-year cycle.
Twenty-one years ago, it was understood that the introduction of energy-conservation elements and methods would take time to infiltrate the building culture, and that more stringent measures would gradually be introduced with each cycle. Each new version usually increases insulation levels, tightens air-sealing, and calls for more efficient lighting and mechanical systems.
Building design must be adapted to accommodate the changing requirements while preventing unintended side effects—most significantly, condensation and humidity. New, energy-efficient approaches to design and construction are typically refined through trial and error. The codes respond to these new methods and continue to evolve.
Each state, and sometimes an individual municipality, determines which version of the code to adopt and how often to update it. Some opt to amend the code in response to local building practices, while a few choose not to have an energy code at all. A new building constructed a year after an existing, identical structure on an adjacent lot may have very different energy requirements.
Today’s self-storage buildings are designed differently than in the past, and the way we build them tomorrow will be different still. Following are some ways in which they’re likely to progress.
The three main components of the building envelope, which separates the interior conditioned space from the exterior environment, are the walls, roof and floor. The envelope keeps out water (rain and snow), controls temperature (keeps out heat and cold), limits air movement (leaks and drafts), and minimizes vapor penetration (dampness and humidity).
Portions of the envelope may be a single material (such as an insulated metal panel) or several (metal siding, insulation, vapor barrier, caulk, etc.). There’s no one approach that works best for all conditions, so each building needs to specifically address the unique site conditions and applicable codes.
Let’s consider a simple, single-story metal building in the winter. On a metal building, the structure and exterior surfaces are metal, while the floor is concrete—both of which are highly conductive materials. Heat travels through the walls because the interior liner panels conduct heat through the studs. The studs pass the heat to the exterior siding, which loses it to the winter air.
When stud spaces are filled with insulation, the metal frame conducts the heat around it, and the building still gets cold. This is called thermal bridging, and the basic solution for controlling thermal loss is to “break” or interrupt these paths. The less metal-to-metal connection you have, the slower the heat loss.
Reducing Heat Loss
Batt insulation is typically used since it’s relatively inexpensive and easy to handle. Batts hold still air in their fibers and are most effective at full thickness. If they’re compressed, they hold less air and lose insulation value.
Walls. For metal buildings, batts are typically attached to the top plate of the metal wall framing and draped to the ground. The exterior metal panels are then screwed through the insulation into the metal studs. This compresses the batt at the studs, which reduces its effectiveness. Though there’s some reduction in thermal bridging, it isn’t much, and the insulation winds up not being very effective. In some cases, a second layer of insulation is installed from the inside, covering the metal girts and providing some reduction in thermal bridging.
Rigid insulation doesn’t compress, so when it’s installed between the metal siding and studs, the only metal-to-metal connections are through the screws. This reduces thermal bridging. As the energy code evolves, we can expect to see more rigid insulation required to provide continuous insulation around the building envelope.
Roofs. For sloping roofs on a metal building, metal girts generally run side to side. Batt insulation is laid over the girts and the roof panels installed, oriented from ridge to the eave. The panels are attached to the girts, compressing the insulation and reducing its effectiveness.
To reduce thermal bridging here, the roof system can be modified to include rigid-insulation spacer blocks between the metal framing and the roof panels. The blocks lift the roof above the metal frame, allowing an additional layer of batt insulation, with the only metal-to-metal contact from “hi-lift” clips that attach the roof to the framing. However, once the roof is lifted, it’s no longer directly supported by the girts, and the roof panels need to be upgraded to standing seam.
Floor. Any concrete surfaces exposed to the exterior will be sources of heat loss and need to be minimized. This is typically done with rigid insulation, either installed on the outside of foundation walls or beneath the building slab for a certain distance. Because rigid insulation isn’t structural, it can’t interfere with the bearing of the slabs and foundation. This makes it difficult to install and thermally isolate the interior slab from the exterior.
Connections. An equally critical consideration is how to connect the roof system to the walls and the walls to the floor, so the building envelope is sealed. Air and vapor barriers, as well as the insulation, need to be continuous, as the control of moisture becomes extremely important. Any gap that lets in air or moisture will impact the building’s energy performance.
When warm, moist air comes in contact with a cool surface, it can condense and cause water to form inside the building. It’s not unusual to have condensation running down an uninsulated wall or puddling on a cold concrete floor. It can bead on pipes, ducts or the underside of a metal roof, causing “rain.” Controlling air flow through the building envelope helps control condensation. This is important to the long-term integrity of the building, as water can cause steel framing to rust.
As energy codes strengthen, self-storage developers may complain the additional requirements increase costs without adding any rentable area. However, when properly constructed to code, a facility is more durable and benefits from a more stable indoor environment. This means lower operating costs and fewer moisture issues.
When properties are sold, energy costs are often factored as part of the value assessment. A self-storage facility with high energy costs will also have high operating costs, which lowers property value at the time of sale.
The importance of an energy-efficient building can’t be dismissed. While your goal may be to minimize construction costs, this may be shortsighted, as future buildings developed by competitors will be required to be more energy-efficient. Installing energy-conservation measures during development is the easiest and most cost-efficient approach. The more robust the envelope is, the more integrity the structure will have and the longer the building will hold its value.
David Wytmar is president of Groundwork Ltd., a Chicago-based architectural, planning and engineering firm that’s served the self-storage industry for 25 years. He’s a licensed architect and building-science practitioner with LEED (Leadership in Energy and Environmental Design) accreditation. He has expertise in architectural design, production and coordination, from feasibility study through contract administration. For more information, visit www.groundworkltd.com.