October 6, 2026
The expanded Cadillac showroom is designed to strengthen the customer experience and improve vehicle flow through the building.
Rendering of Miller Brothers Cadillac showroom expansion in Ellicott City, Maryland
A showroom addition of roughly 6,000 square feet does not sound like the kind of project that would collide with one of the most significant energy code changes Howard County has adopted in years. Miller Brothers Cadillac’s expansion did exactly that, and the project team’s approach is worth the attention of any owner planning even a modest addition under the 2024 International Energy Conservation Code (IECC).
For nearly a century, family-owned Miller Brothers has served drivers in Ellicott City, Maryland. Its latest investment is an expanded Cadillac showroom designed to strengthen the customer experience and improve vehicle flow through the building. Arium AE is providing architecture and MEP engineering services for the addition and renovation, working alongside Wilhelm Builders. The project encloses a covered exterior display area to create a larger interior showroom. It adds a new vehicle delivery entrance, giving customers a more spacious and polished setting for one of the most memorable moments of the buying experience: taking delivery of a new car.
That is the part clients see. The part that determined whether the project could be built as designed happened in the engineering.
The renewable energy requirement holding up the permit
When Howard County adopted the International Energy Conservation Code (IECC) 2024, it changed how additions must account for renewable energy. Under the Renewable Energy Systems code (Section C502.3.8), an addition must comply with the energy efficiency requirements (Section C405.15) for the addition alone. Where a project includes no on-site renewable energy systems, the owner must procure that renewable energy in another way. Just as important for the schedule: the county will not release the building permit until that renewable energy agreement is in hand.
The renewable energy requirements do not apply to the full 6,000-square-foot project, only to the 1,392-square-foot addition. Arium used COMcheck energy modeling to establish the project requirements. Because the addition is in climate zone 4A with an off-site renewable energy factor of 1.35, it established an annual renewable energy requirement of 21,141 kWh.
Here is the part that surprises owners. 21,141 kWh is a small amount of renewable energy, and buying it is relatively inexpensive. That sounds like good news, and on price it is. The problem is the paperwork. A purchase that small isn’t worth the administrative effort for most renewable energy certificate (REC) sellers, who would rather transact at volume. So, the owner lands in an unusual bind: a low-cost permit condition that is hard to satisfy not because of money, but because few sellers will bother to do the deal, and the permit cannot be released until one does.
This is where Arium’s relationships did the work that engineering alone could not. Rather than leaving the owner to cold call REC brokers, Arium reached out through its network and connected Miller Brothers with a seller willing to handle a purchase this small and turn the paperwork around quickly. With the agreement documented through a letter of intent to procure the off-site renewable energy, the permit condition was cleared, and the project kept moving.
It is a small line item that could have quietly stalled the schedule. Knowing the requirement was coming, quantifying it early, and having the right people to call is what kept it from becoming a delay.
Where to put a demonstration EV charger
Evolving electric vehicle requirements also shaped the design. Miller Brothers hoped to install a demonstration charger inside the showroom so customers could see how the technology works up close. To manage costs, the team chose to place an additional exterior charger elsewhere on the site instead. The exterior location remains fully accessible for customer demonstrations while avoiding the added construction and fire protection measures an interior charger would require, keeping the showroom simpler and more economical to build.
Reinsulating without reroofing
The existing roof created a second constraint. Adding another roofing layer to meet current energy performance would have interfered with drainage and added weight, potentially triggering costly structural reinforcement on a building that was never designed to carry the additional load. Rather than reroof, Arium specified a lighter closed-cell spray foam insulation system that brought the addition up to current energy requirements while limiting added construction and cost.
Coordinating with a specialty exterior skin
The showroom’s sculptural metal panel facade is a special Cadillac-branded system. Arium designed the waterproof building enclosure behind the finish panel system. The two function as a single assembly, requiring close coordination between Arium’s enclosure design and the special skin so the envelope stays continuous and weathertight, and the finished branded exterior installs cleanly over a substrate built to receive it.
Why this matters for your next addition
The code changes that complicated this project are not unique to Miller Brothers. Any owner in Howard County contemplating an addition will meet the same IECC 2024 requirements, including the renewable energy provisions that apply to the addition alone under Section C502.3.8, and the smaller the project, the more easily those requirements can throw it off course. The difference between a code change that stalls a project and one that is managed usually comes down to how early the right engineering questions get asked.
Arium AE brings architecture and MEP engineering together and pairs that technical work with the practical relationships needed to clarify the requirements that surface along the way. If you are planning an addition or renovation and want to understand how current energy codes and building codes will affect it, and how to keep them from delaying your permit, we would welcome the conversation.
Please reach out to us at 410-730-2300 or through our contact form.
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