Intelligent Environments

INTELLIGENT BUILDING ENCLOSURE AS ENERGY AND INFORMATION MEDIATOR

Intelligent Building Enclosure

as Energy and Information Mediator

Ardeshir Mahdavi and Khee Poh Lam

One essential aspect of building activity may be interpreted as defining

boundaries between 'inside' and 'outside'. The notion of the building as

a protective shell or a climate modifier emphasizes this utilitarian view. 1

In fact, building enclosures define physically the interface between the

(principally) non-controllable outdoor space and the (commonly) controlled

indoor space. This control aspect implies that the building enclosure handles

environmental factors as a selective and flexible 'filter'.

Traditionally, this filtering function has often been seen to be limited to

the domain of matter/energy flows. Solar radiation and mechanical waves

(sound, vibration) are typical examples of energetic impact, whereas air and

water impact involve mass transfer. The informatory aspect of the underlying

environmental relationships has often been either neglected or insufficiently

addressed. However, the informatory aspect of the building enclosure is by

no means limited to the variations of information flux as a result of the

material-energetic filtering effect. Building enclosures also mark the extension

of architectural artifacts (elements of the built environment) both in the

spatial and 'programmatic' sense. They thus define structures that can be

recognized, attributed, referenced and viewed in relation to other components

of the environment. Enclosures not only modify the informatory flux relevant

to building occupants but act simultaneously as sources of information for

observers and/or visitors.

This multi-fold functionality and the related, complex pattern of

concurrent formal and functional requirements explain why the realization of

high-quality enclosure systems has always been regarded as a critical and

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demanding challenge for building designers. At the same time, it implies

the necessity of a conceptual framework for an integrative approach to the

design and evaluation of building enclosure systems. 2 Based on human

ecological terminology and studies in building physics, this contribution

deals particularly with the informatory aspect of building enclosures as a

'mediator' between building inhabitants and environmental factors. To

demonstrate the wide pertinence of this concept, different strategic levels

of information processing have been considered. The topics discussed here

include (in increasing order of the dominance of the informatory aspect) the

importance of energy distribution patterns for the hygro-thermal evaluation

of building components, the role of information processing considerations in

the definition of acoustic performance requirements of building envelopes,

the importance of flexible control strategies to assure adequate degrees of

freedom in the determination of indoor climate, and the significance of the

communicative function of building enclosures.

Hygro-Thermal Evaluation of Building Components

Architectural heat transfer computation has relied traditionally on the

concept of U-value, which may be regarded as a single energetic specifier in

terms of its dimensional reference (conductive thermal energy flux) and the

related quantitative/scalar nature. The concept of U-value is based on the

notion of 'uniform' one-dimensional heat transfer across the boundaries of

planar building components. This concept cannot be applied to describe

the thermal behavior of building components which involve more complex

distribution patterns of thermal energy (higher 'structural complexity')

and thus require a higher level of information processing in terms of the

description of the phenomena involved. 3 Numerous studies have shown that

the assessment of this higher degree of complexity is necessary if significant

indicators of the hygro-thermal behavior of building components, such as

the minimum indoor surface temperature (important for the evaluation

of surface condensation risk) need to be accurately predicted (Heindl et al.,

1987; Mahdavi 1993a; Mahdavi and Mathew, 1992; Panzhauser et al., 1990;

Panzhauser and Mahdavi, 1989).

Illustrating this point are the results of a study of a significant number

of constructions that are typical in residential and light commercial buildings

in North America (Mahdavi and Mathew, 1992; Mahdavi et al., 1992).

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