16469 Low Energy Building Design Conflict and Interaction in Environmental Engineering Design

16469 Low Energy Building Design Conflict and Interaction design is a complex task, especially in low energy buildings and where there are multiple design objectives in this situation there is rarely an “optimum” design solution –a good choice according to one criteria may be detrimental when judged against another (conflicting outcomes) effectively need to undertake multi-criteria analysis and select a “best” design option requires the generation and assessment of multiple design solutions

16469 Low Energy Building Design Conflict and Interaction Challenge: -generate alternative design solutions: to meet the design objectives while “optimizing” (one or more) performance criteria -need to appraise the different design options and decide on that which best matches the criteria – perhaps an iterative process

16469 Low Energy Building Design: Conflict and Interaction Targets: Design criteria can be usefully expressed in terms of targets – e.g. capital cost, energy consumption

16469 Low Energy Building Design: Conflict and Interaction There are many examples of conflicting outcomes between different design options: energy/comfort conflicts -reducing window size: may improve thermal comfort near the window, but will increase heating load in certain circumstances -increasing window size: may lower heating energy consumption but lead to overheating in summer -energy acoustic conflict -increased thermal mass: may reduce overheating problem but cause acoustic problems

16469 Low Energy Building Design: Conflict and Interaction How to choose between options? need evidence of how design options will perform – taking account of interactions –simulation need to find some mechanism of comparing and ranking options according to design criteria – need a method –subjective comparison (table of options) –PAM –iterative approaches

16469 Low Energy Building Design: Conflict and Interaction Subjective comparison: -take into account all design objectives -assess suitability of each design choice against objectives – usually use a matrix -present results via rank-ordering of design options (possibly after applying weighting factors to the evaluation results)

16469 Low Energy Building Design: Conflict and Interaction Example compare different design options to maximise solar gain and reduce heating load (3-good 2-average 1-bad) design option reduction in heating load reduction in lighting load timing of gain glare riskoverheatin g risk capital cost score south facing glazing south facing glazing plus shade trombe wall

16469 Low Energy Building Design: Conflict and Interaction Subjective comparison: -advantages: results are easy to understand results – through generating the data to support the assessment may be difficult -disadvantages: -results depend upon comparative criteria -danger of basing results on opinion rather than evidence -subjective – which criteria are more important? How to translate technical result to assessment score? -difficult to compare between very different design outcomes

16469 Low Energy Building Design: Conflict and Interaction Example – let’s compare different LEBD options for a householder trying to reduce their heat and electricity costs Get into a group of 3 or 4 and rank the following options based on your existing knowledge ….

16469 Low Energy Building Design: Conflict and Interaction design option reduction in heating/ HW costs reduction in electricity costs installatio n cost running costs carbon savings Score PV solar thermal collector micro-CHP double glazing cavity wall insulation loft insulation

16469 Low Energy Building Design: Conflict and Interaction design option reduction in heating/ HW costs reduction in electricity costs installatio n cost running costs carbon savings Score PV solar thermal collector micro- CHP double glazing cavity wall insulation loft insulation my scores …

16469 Low Energy Building Design: Conflict and Interaction previous example was very subjective … need to remove some of the guess work –need to provide technical evidence to back up scores –need to translate technical outcome to score or (weighting) –how can we do this where there may be a need to appraise many options modelling and simulation can play a role

16469 Low Energy Building Design: Conflict and Interaction The use of simulation for design option appraisal -virtual design: based on integrated computational tools -multi-factorial tools available: various demand and supply systems simulation tools -decision support: iterative appraisal techniques (building energy performance, occupant comfort, renewable supply potential, etc.) -easily interpreted display: enable designers to quickly identify impacts (PAM)

16469 Low Energy Building Design: Conflict and Interaction can apply modelling based - multi-criteria analysis at various levels –strategic – country or city level –individual building and at different levels of detail –appraisal of energy supply technologies (demand supply matching) –appraisal of system performance and different system design options in the following examples we have a computationally based more methodological (sometimes automated) approach

Digital cities predicted energy energy model database population energy/environment information overlaid on maps to support decision-makers at all levels support for decision-makers metered energy demand & supply database of actual & likely consumption consumption & emissions monitoring; city profiling & property classification; trend analysis & action planning government local authority institutions industry utilities and others database analysis city or region

Supply demand matching supply v. demand surplus or deficit auxiliary duty cycle goodness of fit combinatorial search demand scenario supply scenarios

Virtual design

filtering of data for perfomance appraisal

The Lighthouse Building in Glasgow total demand: 68 kWh/m 2.yr total RE supply: 98 kWh/m 2.yr PV: 0.7kW e PV hybrid: 0.8kW e & 1.5kW h DWT: 0.6kW e

16469 Low Energy Building Design: Conflict and Interaction model for use of simulation in multi-criteria design process: design options appraisal simulation literature review