Stop Throwing Fancy Materials at Bad Design
Design Before Execution
In building science discussions, a common theme emerges. Despite our extensive knowledge of building behavior, many projects rely on thick walls, triple-layered components, and complex systems to compensate for inefficient designs from the outset. This issue was central to a BS and Beer chat with Mark Rosenbaum, a seasoned expert in optimizing buildings of all sizes. His key message was consistent: If the form and glass do not align with physics, no product lineup can truly save the building. He supported this with real-world projects rather than theoretical concepts.
Two Houses, One Lesson
Mark began with two current houses that appear equally well-designed on paper. House A is situated on a compact urban lot near Boston. The narrow lot, close neighbors, and street aesthetics demand a fitting design. The house comprises two units, maximizing housing on a single foundation. Its simple shape, compact walls around conditioned space, and modest window sizes meet a strict state energy code, slightly exceeding it without being groundbreaking. Mark describes it as “code plus” rather than a deep energy experiment.
House B, on the other hand, is located on a spacious rural site. The architect prioritizes low-carbon materials and high-performance assemblies. The house features thick, super-insulated walls, triple-glazed, double low-emissivity windows, and a mix of bio-based products. Its form stretches into an H shape with glassy connectors, a sunken gallery, and a large porch, making it a showcase for high-performance design.
Contrary to assumptions, the rural house is not the clear winner in terms of energy and carbon efficiency. Mark compared key metrics:
Total enclosure area per square foot of floor area
Glass area per square foot of floor area
Design heat loss per square foot
The rural house has about fifty percent more exterior surface per square foot of space and more than twice the glass per floor area. Both homes have similar south-facing glass proportions, but the rural house's design creates more surface area and uses more glass overall. Consequently, it experiences higher heating and cooling loads, despite its impressive insulation and window specifications. Over a decade, considering embodied carbon in the extra assemblies, Mark suspects the modest urban house would likely outperform.
This comparison highlights a simple truth: When a building sprawls and incorporates excessive glass, even high-performance materials cannot compensate for unnecessarily large loads.
Bright Interiors Without Excessive Glass
Designers often fear that reducing glass will result in dark, cramped rooms. Mark presented an older project to demonstrate how layout can significantly enhance lighting. Decades ago, he designed a traditional Vermont farmhouse for an owner with numerous reference photos. The house has a straightforward shape and roughly thirteen percent glass relative to floor area, a modest figure. Over half of this glass faces south.
On paper, the window ratio seems conservative, yet the interior remains bright and comfortable. This effect is achieved by strategically placing glass. Everyday rooms, such as the kitchen and main living spaces, are located on the south side, benefiting from consistent daylight. Service spaces and less-used rooms occupy the north side, where smaller openings suffice.
This example illustrates a fundamental principle: A light-filled house with minimal glass is possible by positioning windows strategically and aligning main rooms accordingly. This approach saves energy, reduces window costs, and prevents future comfort issues.
Packed Buildings, Airflow, and Humidity
The discussion shifted to larger buildings, where loads are influenced by occupancy and ventilation rather than just wall conduction. Mark discussed a classroom building at Vermont Law School accommodating several hundred students across multiple rooms. Compared to a house, the square footage per person is significantly lower, making body heat and fresh air requirements dominant factors.
The design team placed classrooms on the north side to ensure consistent daylight without excessive solar gains. Circulation and service spaces were positioned on the south side, where more exposure was beneficial. The enclosure uses high-performance panels and triple-glazed windows, keeping basic heat loss and gain manageable.
With enclosure loads minimized, ventilation became the primary focus. Instead of using individual fan coils under each window, the team implemented central energy recovery ventilation and integrated heating and cooling into the ventilation air. Each classroom received a simple control with a clear “push for ventilation” message and a small green light indicating outdoor air flow. Occupancy sensors adjust settings when rooms are empty.
To prevent common humidity issues at part load, they used chilled water coils that maintain part of the coil cold even when temperature loads are low. This approach controls moisture during mild weather when many systems would allow humidity to rise.
These solutions relied on straightforward assessments of key factors when rooms are densely occupied and air must carry the load.
Simple Metrics for Accountability
Throughout the discussion, Mark emphasized a few basic metrics that help keep projects grounded:
Enclosure area compared to floor area, revealing the compactness of the form
Glass area compared to floor area, along with the orientation of the glass
Concrete and steel per square foot, which significantly impact embodied carbon and cost in large buildings
For projects connected to central plants, he also closely monitors peak heating and cooling demand, as reducing this peak can prevent costly expansions, even if annual energy usage remains similar.
These metrics do not dictate the building's appearance but ensure the design aligns with performance goals.
Final Pour
By the end of the conversation, a clear theme emerged: Great buildings begin with solid fundamentals, not extravagant measures. Efficient shapes, strategically placed glass, and mechanical systems sized for actual loads, rather than assumptions, are key. Layouts that allow structure, ducts, and pipes to work together, rather than compete, are essential.
While low-carbon materials, high-efficiency heat pumps, effective controls, and thoughtful certification programs are important, they are most effective when built upon a design that respects physics rather than trying to compensate for it.
When planning your next project, consider this simple question: Is the form, glass, and basic system concept aligned with the climate, or are you relying on products to compensate later? Keeping this question in mind from the initial sketch to the final details increases the likelihood of creating a building that is comfortable, efficient, and environmentally responsible throughout its lifespan.