Take a walk through a building constructed 50, 75, or 125 years ago, and you’ll notice something: It’s almost certainly drafty.
Older buildings were built with very different building envelope strategies than today’s high-performance structures. Air leaked around windows and doors. Wall assemblies had more natural airflow. Insulation levels were modest compared to modern standards. From an energy-efficiency perspective, those buildings leave a lot to be desired.
Yet many of them have survived decades (or centuries) of rain, snow, humidity, and changing seasons with relatively few moisture-related failures.
Now compare that to a modern building.
Today’s commercial and residential buildings are tighter, better insulated, and more energy efficient. That’s a good thing. Occupants enjoy greater comfort, lower energy costs, and improved indoor environmental quality.
But those same advancements have also changed one of the most important aspects of building performance: Modern buildings don’t dry like they used to.
Why Older Buildings Were More Forgiving with Moisture
Historically, buildings unintentionally managed moisture through air leakage.
No one would recommend going back to leaky buildings because air infiltration wastes energy, reduces comfort, and makes environmental control nearly impossible. However, those leaks did provide one unintended benefit: They allowed wall assemblies to dry.
When moisture found its way behind siding, masonry veneers, stucco, or cladding systems, airflow often helped remove that moisture before it caused significant damage.
Today’s buildings don’t have that luxury.
High-Performance Buildings Require Better Moisture Management
Modern building codes continue to push for higher-performing structures through:
- Improved insulation
- Continuous air barriers
- Better windows and doors
- Reduced air infiltration
- More efficient HVAC systems
Together, these improvements create buildings that are significantly more energy efficient. They also create tighter assemblies that control conditioned air more effectively but require intentional strategies for managing moisture.
When water enters a modern wall assembly, it often has fewer opportunities to escape naturally. But that doesn’t mean moisture problems are inevitable. It simply means moisture management must be intentional.
Water Management, Not Water Elimination
One of the fundamental principles of building science is that moisture management begins with accepting the reality that every building is exposed to:
- Wind-driven rain
- Bulk water intrusion
- Vapor diffusion
- Humidity
- Condensation
- Construction moisture
Moisture is part of a building’s environment, and while exterior cladding serves as the first line of defense, no assembly should rely on a single layer to prevent every instance of water intrusion.
Instead, durable wall systems incorporate multiple layers of protection, including drainage and ventilation, to help move moisture back out of the assembly before it can affect long-term performance.
Modern architects and builders design for drainage and drying.
Why the Building Envelope Must Work as a System
Years ago, individual products received most of the attention but building science has shifted toward systems thinking.
A wall assembly isn’t just siding. Or just a weather-resistive barrier. Or just insulation.
Every component works together to manage heat, air, and moisture.
A high-performing building envelope may include:
- Exterior cladding
- Weather-resistive barriers (WRBs)
- Drainage planes
- Ventilation cavities
- Flashing systems
- Air barriers
- Insulation
- Sealants
- Interior vapor control strategies
If one layer underperforms, the entire assembly can be affected.
Drainage Is No Longer Optional
Water management begins with one simple principle: Give water a way out.
Drainage cavities and rainscreen systems create space between the exterior cladding and the wall assembly. Instead of allowing moisture to remain trapped against the structure, these systems provide a path for water to drain away from sensitive materials.
This simple concept can help reduce prolonged moisture exposure and support more durable wall assemblies over the life of the building.
Whether the project is commercial or residential, drainage has become one of the defining characteristics of durable construction.
Why Ventilation Matters in Modern Wall Assemblies
Removing liquid water is only part of the equation.
Moisture also exists as vapor and ventilated wall assemblies promote airflow behind exterior cladding, helping moisture evaporate more efficiently.
The combination is powerful: Drainage + Ventilation = Better Drying
And better drying contributes to better long-term performance. That’s one reason rainscreen design has become increasingly common across a wide range of building types and climate zones.
Better Buildings Require Better Building Science
As energy codes evolve, so does the importance of understanding moisture movement and designers, architects, contractors, and building owners must think beyond simply selecting materials. The focus has shifted toward understanding how those materials interact as a complete system.
Questions now include:
- Where will water go if it gets behind the cladding?
- How will the assembly dry?
- Is ventilation incorporated into the design?
- Are transitions and penetrations properly detailed?
- Will the wall continue to perform years after construction?
These are building science questions, not just product questions.
Durability and Efficiency Go Hand in Hand
Energy efficiency and durability should never compete. In fact, they depend on one another.
A highly efficient building that traps moisture may experience premature deterioration, reduced performance, or costly repairs. Likewise, a durable building that wastes energy falls short of today’s expectations.
The most successful projects balance both priorities through thoughtful building envelope design.
Frequently Asked Questions About Building Envelope Moisture Management
Why don’t modern buildings dry like older buildings?
Modern buildings are designed to be more energy efficient with tighter air barriers, improved insulation, and reduced air leakage. While this improves performance, it also means moisture that enters a wall assembly has fewer opportunities to escape naturally.
What is the purpose of a rainscreen system?
A rainscreen system creates a drainage and ventilation cavity behind exterior cladding. This space allows water to drain away and promotes drying by encouraging airflow behind the cladding.
Why is ventilation important in wall assemblies?
Ventilation helps remove moisture vapor from wall assemblies by allowing airflow behind exterior cladding. Combined with drainage, it helps reduce the risk of prolonged moisture exposure.
Can building envelopes completely prevent moisture intrusion?
No building envelope system can prevent every instance of moisture intrusion. Instead, modern building science focuses on managing moisture by providing multiple layers of protection, including drainage, ventilation, flashing, and proper detailing.
Looking Ahead
Construction has changed dramatically over the past hundred years.
Buildings are tighter. Materials are more advanced. Energy codes are more demanding. Occupant expectations continue to rise.
These are all positive developments, but they require a different mindset than the one used generations ago.
Instead of assuming buildings will dry themselves naturally, today’s projects must be designed to actively manage moisture. That means providing pathways for drainage, creating opportunities for ventilation, and understanding how complete assemblies work together.
Because while buildings may not dry like they used to, they can perform better than ever when moisture management is built into the design from the very beginning.
At Keene Building Products, we believe the future of construction isn’t about relying on a single product, it’s about designing complete building envelope systems that work together. Through intentional drainage, ventilation, and moisture management strategies, today’s buildings can achieve the durability, efficiency, and long-term performance owners, architects, and contractors expect.
