Reflective insulations (RIs) are currently being used in building envelope components (walls, roofs, windows, curtain walls and skylight dives). RIs use single- and multi-airspaces with at least one surface having low emittance. As the three modes of heat transfer (conduction, convection and radiation) occur in the airspace, its thermal performance depends on airspace dimensions and orientations, and temperatures and emittances of all surfaces bounding the airspace as well as heat flow direction through the airspace. The evaluations of airspace thermal performance are presently based on data from the U.S. National Bureau of Standards and represented in the ASHRAE Handbook-Fundamentals and ISO-6946. These evaluations, however, are limited to a few airspace configurations and do not account for all of the parameters that impact thermal performance.

In several studies, advanced and extensively validated 2D- and 3D-numerical models were used to assess the energy and moisture performance of building envelope components. This model simultaneously solves the Heat, Air and Moisture (HAM) equations for various building applications. For building components with reflective insulations and radiant barriers, the model was used to:

(a) Develop an innovative user-friendly evaluation and design tool called “Airspace Reflective Tool - ART” developed to evaluate enclosed airspaces for different building applications. ART addresses limitations in the currently available methods.

(b) Assess the energy performance of reflective insulations with air intrusion due to infiltration and wind washing for various air-changes per hour for walls, flat-roofs and sloped-roofs, with different heat- flow directions.

(c) Assess the energy performance of reflective insulations having multiple airspaces with quantitative evaluation of the effect of defects and cross airflow between the airspaces.

(d) Assess the energy performance of residential attics containing radiant barriers and various heat-flow directions.

The results obtained for case studies of the above items will be discussed.

The lecture will highlight two different themes: First, the lecture will discuss how to assess the service life of buildings and building components. Predictions of the real service life are complicated and have so far been achieved primarily by analyzing the technical status of the components, while several non-technical circumstances may in reality be decisive. The lecture will discuss these factors and introduce a debate on the relevance of the durability of building materials in light of the increased focus in the construction industry on sustainability, renovation and circularity. Second, the lecture will provide a refresher on the definitions of moisture buffers and modern related research, e.g. from the IEA EBC Annex 92 on Smart Materials. Furthermore, the lecture will discuss how and whether moisture buffering of building materials is beneficial and how we can elevate the analysis from the material level to the room level.