ME425/525: Advanced Topics in Building Science

Transcription

1 ME425/525: Advanced Topics in Building Science Indoor environmental quality for sustainable buildings: Lecture 4 Dr. Elliott T. Gall, Ph.D.

2 Questions? HW1 assigned today Individual submission, can work together Questions? Initial project selection due Monday

3 Climate change and indoor air Indoor air and climate change Changing outdoor air pollutants (e.g., higher ozone) Weatherization (lower AER) more on this later [ CO2] indoor [ CO2] outdoor E V [CO 2 ] outdoor rising at ~2 ppm/year Air exchange is decreasing to reduce building energy demand

4 Indoor CO 2 concentration (ppm) Steady-state mass balance Increasing air-tightness increasing the importance of indoor sources! For V = 60 m 3 E = 40 g/h E = 80 g/h E = 160 mg/h 1 person 2 person 4 person CO ] outdoor [ 2 [ 2 Q CO ] indoor E Q Air exchange rate (h-1) [ CO2] indoor [ CO2] outdoor E V What is the lowest indoor CO 2 concentration possible in a typical indoor environment? For E > 0, what happens as λ?

5 Indoor CO 2 concentration (ppm) Steady-state mass balance 9000 Increasing volume is mathematically equivalent to decreasing emissions V = 60 V = 120 V = 30 CO ] outdoor [ 2 [ 2 Q CO ] indoor E Q Air exchange rate (h -1 ) [ CO2] indoor [ CO2] outdoor E V

6 Mass-balance + exposure models A re-analysis of the National Morbidity, Mortality and Air Pollutions Study Funded by HEI Health effects institute A general association between air pollutants and mortality Limitations Other air pollutants Only for those near death? Improvements Look across different regions where air pollutants are varied Account for personal exposures with what data was available

7 Mass-balance + exposure models NMMAPS researchers note general absence of measured exposure data precludes making firm conclusions as to specific effects of errors Would need an extensive (and expensive monitoring campaign to validate a model of exposure in all of these locations! Mass-balance models can help bridge the gap!

8 Mass-balance principles applied to buildings enable development of new knowledge. IEQ in action Highly respected journal, fully open-access, funded by NIH. Mass balance from the paper: Where does this come from? See derivation

9 Research is a team effort Klepeis et al., 2001 the NHAPS (National Human Activity Pattern Study), funded by the EPA thousands of activity diaries collected by phone calls

10 Critically evaluate research (methods) x is fraction of time that cooling occurs for: 1) Via open windows (homes w/o AC) 2) Via AC (homes w/ AC) y fraction of residences with air conditioning So what does this assumption imply?

11 Know the literature! Persily et al. 2010, Indoor Air modeled air exchange rates using a multi-zone model (CONTAM) with parameters specific for 19 cities in the US, representative of different climactic conditions

12 Summarized from studies conducted in controlled lab environments to field environments Know the literature!

13 - ln((c t -C o )/(C t -C o ) in ) Know the literature! y = x R² = 0.94 Illustrative first-order process this data is from a decay test conducted in a chamber where a constant stream of ozone is injected A k vd s V Time (s) We will talk about this more in week 3

14 Put it all together Differences in ozone mortality across cities (each number in the plot is a different city in the US), are partially explained by differences in outdoor-indoor transport and indoor pollutant dynamics! Chen et al. 2012, Environmental Health Perspectives

15 Research is a team effort Can t consider IEQ issues in isolation. All three methods we discussed on day 1 are mentioned here: 1) Ventilation 2) Filtration 3) Source removal

16 Indoor CO 2 concentration (ppm) Dynamic mass balance Period with emissions occuring Emissions off, decay of pollutant With no air cleaning With air cleaning Time after initial occupancy condition (h) We will discuss air cleaning next week!