Detailed simulation of the indoor environment to aid ventilation system design in low energy houses

  • Maria Del Carmen Bocanegra-Yanez

Student thesis: Doctoral Thesis

Abstract

According to the International Energy Agency, buildings represent over one-third of total final energy consumption. Thus, a more sustainable future begins with low energy buildings which must combine comfort and function using passive systems and new evolving technologies. Policies to reduce building energy consumption and carbon emissions have been developed worldwide during the last decades. As a consequence, Building Regulations and Standards require more insulated and air tight buildings which may lead to indoor environment issues when the ventilation system is not designed appropriately or it is not used as designed. Poor Indoor Air Quality (IAQ) in low energy buildings is a concern, not only as a result of reduced ventilation rates, but also due to the increased number of materials used in modern building construction. These materials, together with cleaning products and occupants’ activities, emit pollutants to the indoor environment and can lead to health problems.Detailed building modelling and simulation can provide an indication of building performance and furthermore, it can be used to assess indoor environment issues. This research is focused on the variability of overheating risk and poor IAQ at different locations in the building at different times. The impact that different pollutant sources and ventilation strategies has on the distribution of thermal comfort levels and IAQ in low-energy houses has been assessed through a modelling study using the detailed thermal simulation program, ESP-r. CO2 is commonly used as a proxy for IAQ, but a novelty of this research is the integrated analysis of distribution for other pollutants, specifically formaldehyde, PM2.5, PM10 and nitrogen dioxide. A model was created based on monitored data from a Passivhaus development in Scotland.Acceptance criteria for calibrating the model were defined, addressing the current absence of specific guidelines for model calibration based on the monitored indoor environment. Then, a review of current literature of indoor pollutants was undertaken and source emission models were implemented in ESP-r making use of the available published literature, with release rates as a function of the prevailing temperature and humidity. Different scenarios were defined to investigate specific design questions and common ventilation issues regarding the indoor environmental quality (IEQ). Ventilation regimes included natural ventilation, mechanical ventilation and mechanical ventilation with heat recovery options. These scenarios were compared in terms of energy demand, plus temporal and spatial variation of indoor environment metrics (thermal comfort and IAQ).The general conclusion arising from the analysis is that, contrary to the usual assumption of even distribution of the indoor environmental conditions, there can be significant variations in the internal distribution. Important factors are number and location of occupants and the movement of air within the building. The results demonstrate that detailed modelling and simulation can predict IEQ issues and help to design ventilation strategies in low energy houses. Although this study was focused on climate representative of conditions in Scotland, similar variations would be expected in other climates.
Date of Award1 Oct 2017
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde & BRE Trust
Supervisor (Supervisor)Nicolas Kelly (Supervisor)

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