Building Envelope Design and Narrative Submittal
Pre-determining the Building Envelope Design Prior to Construction Eliminates Problems in the Field and Helps Avoid Pre-mature Failure at Critical Junctures
We provide building envelope design services for new construction and design build projects on a nationwide basis. On many of our USACE projects, this entails establishing the proper waterproofing details and air barrier installation procedures so the building air tightness tests can be successfully completed.
So what is a Building Envelope? The Building Envelope or Building Enclosure, is the physical separator between the interior and the exterior environments of a building. This, with the mechanical conditioning systems, serves as the outer shell to help maintain the indoor environment and facilitate the building’s climate control. Building envelope design is a specialized area of architectural and engineering practice that draws from all areas of building science and indoor climate control.
The many functions of the building envelope can be separated into three categories:
- Support: to resist and transfer mechanical loads
- Control: the flow of matter and energy of all types
- Finish: to meet human desires on the inside and outside
The control function is at the core of good performance, and in practice focuses on rain, air, heat, and vapor control. There are numerous strategies to control rain which includes perfect barriers, drained screens, and mass/storage systems. Control of air flow is important to 1) ensure indoor air quality, 2) conserve energy consumption, and 3) avoid condensation—and thus help ensure durability as well as comfort. Control of air movement includes 1) air flow through the enclosure (the assembly of materials that perform this function is termed the air barrier system), 2) components of the building envelope (interstitial) itself, and 3) in and out of the interior space—which can greatly affect building insulation performance. Hence, air control includes the control of wind-washing and convective loops.
The physical components of the envelope include the roof, walls, doors and windows. The dimensions, performance and compatibility of materials, fabrication process and details, their connections and interactions are the main factors that determine the effectiveness and durability of the building enclosure system.
Common measures of the effectiveness of a building envelope include 1) physical protection from weather and climate/comfort, 2) indoor air quality (hygiene and public health), and 3) durability and energy efficiency. To achieve these objectives, all building enclosure systems must include 1) a solid structure, 2) a drainage plane, 3) an air barrier, 4) a thermal barrier, and 4) may include a vapor barrier. Moisture control is essential in all climates, but cold climates and hot/humid climates are especially demanding.
The thermal envelope or heat flow control layer, is usually different than the building envelope. The difference can be illustrated by understanding that an insulated attic floor is the primary thermal control layer between the inside and the exterior of the building, while the entire roof—from the surface of the shingles to the interior paint finish on the ceiling—comprises the building envelope.
Building Envelope Thermography involves using an infrared camera to view temperature anomalies on the interior and exterior surfaces of the structure. Analysis of infrared images can be useful in identifying moisture issues from water intrusion, or internal condensation. Shown below is an example of an image within the scope of a residential infrared inspection in which a non-insulated HVAC plenum was located in a confined attic space. The humidity from the warm attic air condensed on the plenum and was damaging the ceiling and walls.
