Building science is the science and technology-driven collection of knowledge to provide better indoor environmental quality (IEQ), energy-efficient built environments, and occupant comfort and satisfaction. Building physics, architectural science, and applied physics are terms used for the knowledge domain that overlaps with building science. In building science, the methods used in natural and hard sciences are widely applied, which may include controlled and quasi-experiments, randomized control, physical measurements, remote sensing, and simulations. On the other hand, methods from social and soft sciences, such as case study, interviews & focus group, observational method, surveys, and experience sampling, are also widely used in building science to understand occupant satisfaction, comfort, and experiences by acquiring qualitative data. One of the recent trends in building science is a combination of the two different methods. For instance, it is widely known that occupants' thermal sensation and comfort may vary depending on their sex, age, emotion, experiences, etc. even in the same indoor environment. Despite the advancement in data extraction and collection technology in building science, objective measurements alone can hardly represent occupants' state of mind such as comfort and preference. Therefore, researchers are trying to measure both physical contexts and understand human responses to figure out complex interrelationships.

Building science traditionally includes the study of indoor thermal environment, indoor acoustic environment, indoor light environment, indoor air quality, durability, moisture damage, and building resource use, including energy and building material use. These areas are studied in terms of physical principles, relationship to building occupant health, comfort, and productivity, and how they can be controlled by the building envelope and electrical and mechanical systems. The National Institute of Building Sciences (NIBS) additionally includes the areas of building information modeling, building commissioning, fire protection engineering, seismic design and resilient design within its scope.

One of the applications of building science is to provide predictive capability to optimize the building performance and sustainability of new and existing buildings, understand or prevent building failures, and guide the design of new techniques and technologies.

During the architectural design process, building science knowledge is used to inform design decisions to optimize building performance. Design decisions can be made based on knowledge of building science principles and established guidelines, such as the NIBS Whole Building Design Guide (WBDG) and the collection of ASHRAE Standards related to building science.

Computational tools can be used during design to simulate building performance based on input information about the designed building envelope, lighting system, and mechanical system. Models can be used to predict operational energy use, solar heat and radiation distribution, air flow, and other physical phenomena within the building. These tools are valuable for evaluating a design and ensuring it will perform within an acceptable range before construction begins. Many of the available computational tools analyze building performance goals and perform design optimization. The accuracy of the models is influenced by the modeler's knowledge of building science principles and by the amount of validation performed for the specific program.

When existing buildings are being evaluated, measurements and computational tools can be used to evaluate performance based on measured existing conditions. An array of in-field testing equipment can be used to measure temperature, moisture, sound levels, air pollutants, or other criteria. Standardized procedures for taking these measurements are provided in the Performance Measurement Protocols for Commercial Buildings. For example, thermal infrared (IR) imaging devices can be used to measure temperatures of building components while the building is in use. These measurements can be used to evaluate how the mechanical system is operating and if there are areas of anomalous heat gain or heat loss through the building envelope.

Measurements of conditions in existing buildings are used as part of post occupancy evaluations. Post occupancy evaluations may also include surveys of building occupants to gather data on occupant satisfaction and well-being and to gather qualitative data on building performance that may not have been captured by measurement devices.

Many aspects of building science are the responsibility of the architect (in Canada, many architectural firms employ an architectural technologist for this purpose), often in collaboration with the engineering disciplines that have evolved to handle 'non-building envelope' building science concerns: Civil engineering, Structural engineering, Earthquake engineering, Geotechnical engineering, Mechanical engineering, Electrical engineering, Acoustic engineering, & fire code engineering. Even the interior designer will inevitably generate a few building science issues.