Fenestration-Shading, The Human Factor And Energy Efficient Buildings

Despina K. Serghides

Architect/Department of Civil Engineering, School of Engineering & Technology
Cyprus University of Technology
Tel: 357-25002542, 25002724, Fax: 357-25002769,

Email: D. K.Serghides@cytanet. com. cy
Abstract

In previous research on energy efficiency in buildings has found that it is possible to achieve comfort conditions, for the Mediterranean climate, without the need for mechanical energy for heating and cooling in houses, through the use of compact shape and the optimization of insulation, internal mass and fenestration design.

However, it became clear in the work that a more sophisticated analysis of buildings and user behaviour was necessary and this forms the concern of this paper.

From building simulations and analysis of results in previous research on fenestration, it was found that the human element is instrumental in changing some of the assumed building characteristics by such simple acts as opening or closing shutters of doors and windows. It was also found that the effects of the behaviour of the building and the users must be considered interdependently as it is the combined effect that is important.

In this study, the relative thermal effects of the parameter of the use of shutters for shading, in various combinations in computer simulations, is to be considered to understand the qualitative behaviour of the building fabric in use. Also the possibility of introducing automatic shading controls is investigated. This leads to the optimal choice between different design alternatives based on flexibility, operational ease, and potential thermal efficiency.

As an integral part of the planning process, strategies are recommended which, by reducing the operational constraints currently imposed upon buildings, secure an optimized, performance for energy efficient houses in Mediterranean.

Keywords: Shading, shutters, human factor, energy efficient buildings

1. Introduction

In previous studies on fenestration [1, 2-4] it has been concluded that the provision of shading devices is a very important fenestration parameter to combat overheating in the dwelling in the summer period.

It was also found that winter solar gains through fenestration reduce considerably (11%) fuel consumption for heating. The optimized fenestration shading strategies are summed up as follows:

Summer: Shading between 07.00-19.00 hours.

Winter: Unobstructed solar access between 07.00-17.00hrs

However the introduction of manually operating shutters in order to provide summer solar control in occupied (usual practice in Mediterranean) may result in large energy penalties when misused by the occupants in either season to cause:

In Summer : Overheating when the shutters are left open during the day.

In Winter: Solar losses by sun blinding when shutters are left closed.

In this chapter the misuse of shutters, in both seasons (winter and summer), and the effect on indoor temperature in free running buildings are examined through computer simulation with thermal analysis program “Quick” [2]. This is done in series of combinations of sun control on fenestration for the “Zero Energy House” derived in previous research [1].

2. Approach

This section presents and discusses the results obtained from building simulations of the “Zero Energy House” which have specific profiles of fenestration shading as their only variable and are modeled under free running conditions. The tested shading profiles are specified and outlined having as basis possible occupancy interference with the shading design objectives of the “Zero Energy House”. These may range from maximum solar admission to total exclusion of direct radiation as a source of heat, depending on the season (winter or summer). Thus the simulations of shading combinations are classified for the two seasons as follows:

A. Winter. In this series of simulations the effect of window shutters left closed during the day, contrary to the optimised fenestration winter strategy, and consequently the drop of indoor temperature is examined. The orientation of shaded windows is as follows:

a) All unshaded

b) North windows shaded

c) North and West windows shaded

d) North, West and half of South window area shaded

e) All Shaded

B. Summer. In this series of simulations the effect of window shutters, left open during the day, contrary to the optimised fenestration summer strategy, on indoor temperature rise is examined.

The orientation of windows left unshaded is as follows:

a) All Shaded

b) Half area South fenestration unshaded

c) All South windows unshaded

d) South and West windows unshaded

e) All Unshaded

The outline of window shading profiles of the building simulations and the effect on indoor temperature is tabulated in tables 1 and 2 and illustrated on figures 1-4. The discussion of the results follows the same order of the simulations as presented in the ranges for the two seasons as stated above (2. A. Winter and B. Summer). The calculations from each simulation is analyzed in terms of its own entity and invites remarks derived from comparisons with the calculations from simulations of the other shading profiles. All simulations are also analyzed on the basis of comparing results of each shading profile with the optimized design strategy for that range (All unshaded – for winter and All Shaded – for summer).

The performance of the parameters is analyzed in the following clauses and their efficiency is compared with each other and with the optimized strategy for the winter and summer season. The effect of the parameters on the indoor temperature as well as the deviation from comfort conditions are assessed both in winter and summer (tables 1, 2, figures 1-4). Particular shading patterns which appear problematic are identified in summaries for each season. Finally design strategies are recommended which by reducing the operational constraints of manually operated shading devices secure optimum performance of fenestration for the “Zero Energy House” in Cyprus.

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