Performance Assessment of the Overall Building Envelope Thermal Performance-Building Envelope Performance(BEP)Metric

Today,to describe the thermal performance of the building envelope and its components we use a variation of metrics;such as,R-value,ACH(air exchange rate per hour),SHGC(solar heat gain coefficient)of windows,U-factor etc.None of these performance indicators is meant to represent the overall thermal performance.In this paper,such a metric is introduced,the BEP(building envelope performance)value.Unlike the thermal resistance,typically expressed as an R-value,the BEP-value considers additional elements of heat transfer that affect the energy demand of the building because of exterior and interior(solar)thermal loads:conductive and radiant heat transfer,and air infiltration.To demonstrate BEP’s utility,validation studies were carried out by comparing the BEP-value to theoretical results using whole building energy simulation tools such as EnergyPlus and WUFI Plus.Results show that BEP calculations are comparable to calculations made using these simulation tools and that unlike other similar metrics,the BEP-value accounts for all heat transfer mechanisms that are relevant for the overall energy performance of the building envelope.The BEP-value thus allows comparing envelopes of buildings with different use types in a fair and realistic manner.

WARMING ISSUES ASSOCIATED WITH THE LONG TERM SIMUL ATION OF HOUSING USING CFD ANALYSIS

The determination of internal building air temperature has an impact on the design and performance of a building in measuring thermal comfort and heating and cooling loads.There is software to assist with measuring internal building air tem-perature such as Autodesk CFD simulation.However,the use of Autodesk CFD simulation for the analysis appears to have an issue with simulations extending over a long term(i.e.months or years)as the internal air temperature in a building keeps rising with time.This paper addresses the challenges encountered using CFD simu-lation in the modelling of a building for long term performance.A new method to overcome the issue of the progressive rising of internal air temperature using two external air boundaries,one for the external volume(sky boundary)and the other surrounding the building,is suggested in the paper.

THE INFLUENCE OF THERMAL RESISTANCE AND THERMAL MASS ON THE SEASONAL PERFORMANCE OF WALLING SYSTEMS IN AUSTRALIA

This paper describes an experimental investigation of the thermal performance of four Australian domestic walling systems(cavity brick,insulated cavity brick,insulated brick veneer and insulated reverse brick veneer)having various combinations of thermal insulation and of thermal mass location within the wall.This experimental analysis extends further the previous studies of the benefits of thermal mass on the overall thermal performance of building enclosures(Gregory et al.2008,Luo at al.2008,Alashaary et al.2009).The comparison is based on the time required to maintain thermal comfort for free-floating internal conditions.The results clearly show that internal comfort levels are influenced by both the thermal resistance of the walls as well as the extent and location of the thermal mass,with neither parameter being the sole predictor.The best thermal performance is therefore obtained by an appropriate combination of thermal mass and resistance,rather than focussing on the overall wall thermal resistance(R-value)alone.A new approach of density temperature plots for comparison of temperature variation is also used in the assessment of module thermal performance.

A concept of capillary active,dynamic insulation integrated with heating,cooling and ventilation,air conditioning system

When a historic façade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation,one needs to use interior thermal insulation systems.Interior thermal insulation systems are less effective than the exterior systems and will not reduce the effect of thermal bridges.Yet they may be successfully used and,in many instances,are recommended as a complement to the exterior insulation.This paper presents one of these cases.It is focused on the most successful applications of capillary active,dynamic interior thermal insulation.This happens when such insulation is integrated with heating,cooling and ventilation,air conditioning(HVAC)system.Starting with a pioneering work of the Technical University in Dresden in development of capillary active interior insulations,we propose a next generation,namely,a bio-fiber thermal insulation.When completing the review,this paper proposes a concept of a joint research project to be undertaken by partners from the US(where improvement of indoor climate in exposed coastal areas is needed),China(indoor climate in non-air conditioned concrete buildings is an issue),and Germany(where the bio-fiber technology has been developed).