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Introduction

Evaluation of the Impact of Retrofitting a Mid-terrace 1950 ’ s House in Dublin on Indoor Air Quality. Introduction. The housing stock consists of dwellings which have been built with no particular care about ventilation, Indoor Air Quality (IAQ) or energy efficiency.

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Introduction

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  1. Evaluation of the Impact of Retrofitting a Mid-terrace 1950’s House in Dublin on Indoor Air Quality

  2. Introduction • The housing stock consists of dwellings which have been built with no particular care about ventilation, Indoor Air Quality (IAQ) or energy efficiency. • Several retrofit programmes to make homes more air tight. What about IAQ? • Principles of the study: • Start from a real case (house, weather…) and check hypotheses; • Use simulations to avoid the impact of local environment; • Study various air tightness to simulate various retrofit measures; • Simulate different ventilation approaches, including those not in the book but widely spread; • Look at the major IAQ criteria (Moisture and CO2) and at the impact of each measure on ventilation heat losses.

  3. Occupation scenario Dwelling description Ventilation system Weather conditions SIREN software Indoor Air Quality Energy losses Implementation • SIREN software: • From French equivalent to BRE; • Assessment of IAQ and energy efficiency; • Proven track record

  4. Working Hypotheses and Constraints • Weather data: Dublin, common design year format, with heating season from 1st October to 21st May. • House positioning: in order to limit the impact of a given house position, the exposure of the house is changed every week, over 4 cardinal directions • Dwelling description: mid-terrace house built in 1950’s in Ballyfermot, Dublin, described in the AVASH study under n° 29. BEDROOM 2 BEDROOM 3 HALL DINING ROOM LIVING ROOM KITCHEN BEDROOM 1 BATHROOM

  5. Working Hypotheses and Constraints • Number of occupants: based on the number of bedrooms in the dwelling, it has been decided to consider a couple with two children. • Water vapour generation: cooking, showers, clothes washing and drying were included. All parameters depend on the number of occupants. Only the mother has lunch at home during the week. • Activity scenarios: room occupancy and activity is described for each occupant, with a 30 minute step. Human metabolic water vapour and CO2 generation are modelled for awake and asleep periods

  6. Working Hypotheses and Constraints • Permeability: • Case A: n50 at 10 ACH before retrofit measures, corresponding to TGD L(2007) or  AVASH house without wet plastered masonry walls; • Case B: n50 at 7.8 ACH, corresponding to the AVASH house with wet plastered masonry walls before retrofit measures or Case A after standard retrofit measures; • Case C: n50 at 5 ACH, which is a key figure in new TGD F (2009). This can also be Case A with deep retrofit measures and Case B with standard retrofit measures; • Case D: n50 at 3 ACH, which corresponds to Best Practice. This can also be Case B with deep retrofit measures.

  7. Working Hypotheses and Constraints • Ventilation components: for each room the ventilation component exposure and airflow rate are described. We ran simulations to assess the IAQ and energy performance in 20 cases:

  8. Results – Indoor Air Quality Relative Humidity and Moisture • Good indicator for wet rooms. • SIREN directly computes the number of hours with RH higher than 75% for the various rooms and cumulates it over the simulation period. • Moreover, hourly rates in each room are available. From them, moving averages per wet room can be calculated, so as to confirm compliance with England and Wales Part F2010 criteria: no more than 85% RH over a day, 75% RH over a week and 65% RH over a month.

  9. Results – Indoor Air Quality

  10. Results – Indoor Air Quality

  11. Results – Indoor Air Quality CO2 Exposure • Good indicator for dry rooms. • During the assessment of the systems, SIREN characterises CO2 exposure as follow: CO2 concentrations over 2,000 ppm are aggregated over the heating season, and they are expressed in ppm.h. The recommended exposure threshold for that period is 500,000 ppm.h of CO2.

  12. Results – Indoor Air Quality

  13. Results – Airflow Rates and Energy Savings • SIREN calculates various airflows: - average cross ventilation, - average mechanical ventilation, - average equivalent cross ventilation, - average equivalent mechanical ventilation. • Ventilation heat loss equivalent total airflow rate: the constant airflow rate which would yield to the same total heat loss over the heating season.

  14. Results – Airflow Rates and Energy Savings Ventilation Heat Loss Equivalent Total Airflow Rate • Example with MVHR: in Case D, the average cross ventilation is 73 m3/h and average mechanical ventilation is 75 m3/h, so a total of 148 m3/h. This is what is actually extracted on average from the dwelling. Because part of the heat loss is recovered, the ventilation heat loss equivalent total airflow rate is only 90 m3/h. • The average airflow is useful to compare constant systems (MEV) with intermittent systems (Intermittent Fans) and modulating systems (DC MEV), whereas the equivalent airflow is useful to compare those systems with ventilation with heat recovery (MVHR).

  15. Results – Airflow Rates and Energy Savings

  16. Results – Airflow Rates and Energy Savings

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