Procedures enabling to take into account the effect of adaptive building envelope elements in the calculation of the energy needs for heating, cooling, internal temperatures and sensible and latent heat loads for buildings.
ISO 52016-1:2017 contains a normative Annex G that provides already a framework for such calculation procedures. The aim of this new proposed standard is to work out calculation procedures instead of only a framework for the calculation.
Adaptive building envelope elements are (usually: transparent) elements in the building envelope with thermal and/or solar and/or visual properties that vary in time, either passively or due to an active control.
The aim of adaptive building envelope elements is to improve the energy performance and/or comfort in the building under varying outdoor conditions (weather, season), indoor conditions (e.g. internal heat gains) and user needs.
Examples of adaptive building envelopes are products or assemblies with one or more of the following features:
• movable blinds,
• controllable vents,
• switchable glazing,
• movable thermally insulating shutters,
• PV integrated glazing (leading to variable total (thermal) solar energy transmittance),
• double skin facades.
The input data for the calculation are the thermal, solar and visual properties of the building element for the different states (e.g. from open to closed, from dark to light and combinations of these); and in case of gradually varying properties: for a number of representative discrete states.
In order to be able to use these properties for energy and internal temperature calculations, the details of the (passive or active) control protocol are needed as input as well.
The thermal, solar and visual properties of the building element are the thermal transmittance (Uvalue), air permeability (L-value) and solar transmittance (g-value). Or, where needed, the properties per component: e.g. thermal resistances and air permeability per component, solar absorptance and solar and visual transmittance per component. It is assumed that the existing standards on glazing
(ISO/TC 160/SC 2, CEN/TC 129) and on building elements (especially the EPB standards recently revised under ISO/TC 163/SC 2 and CEN/TC 89) enable to obtain these input data in most cases.
No ready-to-use international standards exist for the assumptions on the control protocol. EN 15232-1 (and ISO 52120-1 in preparation) provides some guidance.
The output of this standard should also be usable to compare products and assemblies. Due to the interactive nature of adaptive building envelope elements, this may require the use of specific reference buildings and occupant patterns (similar as for current international standards on energy performance rating of glazings and windows).