ME425/525: Advanced Topics in Building Science

Indoor environmental quality for sustainable buildings: Lecture 2

Dr. Elliott T. Gall, Ph.D.

Questions from first class?

• Syllabus?

• Course expectations?

• Grading rubric?

• Potential project ideas?• A few thoughts…

Parameterizations drive new knowledge

4/4/2017 12

Lots of promise and misinformation…

Abbas et al. 2017, Building and Environment. PSU MME Ph.D. Candidate

Redacted!

But we do the math… for a 600 ft2 apartment

Ind

oo

r o

zon

e re

mo

val e

ffec

tive

nes

s (-

)

Plant surface area/volume ratio (m-1)

0.16

0.12

0.08

0.04

0.0

0.01 0.1

4 plants, ~2% removal

14 plants, ~5% removal

Potential term projects

Literature review on topic of your interest:• Some examples: IAQ considerations in green building standards?

Potential term projects

A blast from the past…• IAQ in the developing world

Ask me about experimental work if you are interested in making measurements!

NECC Pool Natatorium

• Northeast Community Center –NE 38th & Sandy, Portland

• Former YMCA Building • 1923 Construction• Heated Pool• Chlorination for Disinfectant• Heat Recovery System Mounted

on Roof

Air Quality Problems

• High Humidity

• High Level of Chloramine Vapor

Inadequate Ventilation?

Poor Air Circulation?

Other?

SupplyReturn

Potential term projects

For 100 µg/m3 target indoor level:As k increases from 1-10 /hPercentile: 96.6% - 100% below

For 40 µg/m3 level:As k increases from 1-10 /hPercentile: 57%-92% below

From Morrison et al., 2010, Atm. Env.

“For our primary analysis, we chose an indoor target of 20 ppb, which is twice the incremental increase shown to be associated with a 0.3% increase in mortality.”

Student modeling projects – IAQ in naturally ventilated homes• Contributed to a conference presentation at ASHRAE

Potential term projects

Other ideas?• Research a class of air pollutant

• VOCs, SVOCs, Radon• A type of monitoring approach

• Low-cost sensors• Mass spectrometry

• Smart buildings and indoor air quality• State of indoor air quality regulations

Research tools

• Library is a great resource- Go talk to them

• Web of science, Google Scholar, SCIhttp://guides.library.pdx.edu/az.php

• The CAT offers guidance for installing a VPN- So you can work download peer-reviewed articles

from any computerhttps://cat.pdx.edu/windows/maseeh-college-pptp-vpn.html

A sea of information…

Reference management tools can help, Zotero is free, open-source and what I use, others exist (EndNOte, Mendeley)

Automatic bibliography creation!

And sea level is rising…

The “art” of reading scientific literature….

Fundamental principles of air

Components, units, concentrations and mixing ratios

Components of air

“Other” %

CO2 0.04+ (400 ppm)

Neon 0.0018% (18 ppm)

Helium 0.0005%

Methane 0.0002%

Krypton 0.0001%

Hydrogen 0.00006%

Pollutant ~0.00001%

When we discuss air pollutants, we are typically referring to pollutants at very dilute magnitudes! Hence – be wary of the

“low-cost” sensor

A note on units

Concentration: Amount (moles, #, mass) per unit volume

• Variant with respect to pressure and temperature• However, in indoor air, pressure and temperature changes occur over relatively small

ranges, perhaps on the order of 10 Pa• Concentration and mixing ratios are both used in IAP field

• Often mixing ratios are referred to as “concentrations”

Number concentration• # of molecules/m3 (usually for reactive pollutants)• # of particles/m3 (particulate matter pollutants)• # of cells of CFUs/m3 (biological pollutants)

Mass concentration• ng/m3 (SVOCs, metals, low concentrations)• µg/m3 (VOCs, PM, Ozone)• mg/m3 (CO2, industrial environments)

A note on units

The SI unit for the amount of a substance is the mole (mol).• Note, this relates to the # of atoms or molecules according to _____ ?• Don’t confuse units of mole, mol, molecules

• And don’t abbreviate molecules!

Mixing ratios: Ratio of the amount of the substance in a given volume to the total

amount of all constituents in that volume (including water vapor, not condensed water)

𝑚𝑖𝑥𝑖𝑛𝑔 𝑟𝑎𝑡𝑖𝑜, 𝐶 =𝑐𝑖

𝑐𝑡𝑜𝑡𝑎𝑙

Molar concentration of compound i

Total molar concentration of air

𝑐𝑡𝑜𝑡𝑎𝑙 =𝑁

𝑉=

𝑝

𝑅𝑇 What is this equation?

𝐶 =𝑐𝑖

𝑝/𝑅𝑇=𝑝𝑖/𝑅𝑇

𝑝/𝑅𝑇=𝑝𝑖𝑝

So mole fraction is equal to pressure fraction. Why is this useful?

A note on units

Board work: mole frac, volume frac, pressure frac

Ideal gas law

• All gases in air act as an ideal gas:

pV = nRT

• What we refer to as “air” is really a combination of gases all following this relationship

• R = 8.314 pa m3 /mol /K; 0.0821 atm L /mol /K

𝑅𝑇

𝑉=

𝐿 𝑎𝑡𝑚𝑚𝑜𝑙 𝐾

𝐾

𝐿=

𝑎𝑡𝑚

𝑚𝑜𝑙

Daltons Law of partial pressure

Ideal gas law

Back to our original ideal gas law!

Properties of Air

Determine: 1) The molecular weight of air2) The density of air at STP (25 deg C, 1 atm)

Properties of Air

Determine: 1) The molecular weight of dry air?

2) The density of air at STP (25 deg C, 1 atm)?

Practice

Board work: 2 examples – conversion between molar and mass fraction and why do clouds float?

Exposure pathways

By what routes drives exposure?

Our focus, but…

• Ingestion• Water• Food• Hand-to-mouth

• Inhalation • Dermal uptake• Ocular/eyes

Not only inhalation for air pollution

Weschler and Nazaroff, 2013, EST

We are exposed to some air pollutants through our skin

Exposure models

Time-concentration model of exposure:

𝐸 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒 = න0

𝑡

𝐶 𝑡 𝑑𝑡

Not a uniformly accepted definition:

• Conceptually, exposure is a function of two things:

o the location of a target of interest (usually a person) at a

particular time: f(x,y,z,t)

o The level (i.e., concentration) of the pollutant: f(x,y,z,t)

Units are Concentration × time [=] ppb-h or µg m-3 h

So, can look at a particular “event”

• Assume 18 µg m-3 of PM2.5 in this classroom, we’re all here for

100 minutes. We’re exposed to 30 µg m-3 h

Exposure models

Summing over all “events”

𝐸 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒 =

𝑖=1

𝑛

න0

𝑡

𝐶 𝑡 𝑑𝑡

Units are still concentration × time [=] ppb-h or µg m-3 h

Think through your day… how would you go about getting this sort of

data?

• Where people spend their time

• How long at each location

• Pollutant level in each location for each duration

Seems like a fools errand…. More on that in a moment

Exposure models

Typically use time-averaged data, by necessity as measurements

don’t report continuous streams (1 min, 5 min resolution usually at

best)

l

j

m

i

iiinkjjokk tCtCEx1 1

,,

Exposure [=] µg m-3 h

1. Outdoor air quality data

Outdoor pollutant

concentration,

where k is PM2.5 or PM10,

[=] µg m-3

2. Activity pattern data

Time spent in

microenvironment i or j

[=] h

3. Indoor concentrations

Indoor pollutant concentration,

(from indoor/outdoor ratios)

[=] µg m-3

Inhalation Dose

Inhalation dose: accounts for amount crossing contact boundary

• Function of three things: 1) concentration, 2) duration of

exposure, and 3) breathing rate

• Inhalation dose is the amount ingested due to breathing

𝐷𝑜𝑠𝑒 =

𝑖=1

𝑛

න0

𝑡𝑖

𝐶𝑖 𝑡 × 𝑄𝑏,𝑖(𝑡)𝑑𝑡

Where:Dose = inhalation dose (mass or number of pollutant)Ci is the concentration of a pollutant in environment i (e.g., µg/m3, #/m3)Qb is the breathing rate in environment I (e.g., m3/h)

𝐷𝑜𝑠𝑒 =

𝑖=1

𝑛

න0

𝑡𝑖ഥ𝐶𝑖 × 𝑄𝑏,𝑖 × ∆𝑡

Inhalation Dose

Links with tox. data

Some toxicological terminology

Reference dose: Determined from animal studies

Slope factor: determined from dose-response curves

In order to obtain any carcinogenic response in

animal studies, high doses are typically used.

Hence, these must be extrapolated down to low

doses (a big source of uncertainty!)

dosed with varying amounts of the substance in question, and the largest

dose at which no effects are observed is identified. This dose level is called

the "No observable adverse effect level," or NOAEL. To account for the fact

that humans may be more or less sensitive than the test animal, a 10-fold

uncertainty factor is usually applied to the NOAEL.

[mg/(kg-day)]

[%]

Scales of indoor exposures

• Several ways of quantifying the scope of indoor exposures:• In relative spatiotermporal terms:

• To total exposure• To another exposure

• Relative to the amount of emitted pollutant• Intake fraction

Relative exposure

• Recall our exposure definition:

𝐸𝑥 =

𝑖=1

𝑛

ഥ𝐶𝑖 × ∆𝑡𝑖

• Relative contribution of a single microenvironment

𝑅𝐸𝑥 =ഥ𝐶𝑗 × ∆𝑡𝑗

σ𝑖=1𝑛 ഥ𝐶𝑖 × ∆𝑡𝑖

• Comparison of two microenvironments

𝑅𝐸𝑥 =𝐶1 × ∆𝑡1

𝐶2 × ∆𝑡2

Relative exposure

• Comparison indoor-outdoor exposure for ozone (an “outdoor” air pollutant)

Intake fraction

• Ratio of intake to emissions.o What should be of greater concern?

o A 1 kg emission from a source 50 miles away?o A 0.01 kg emission into your home?

• Intake fraction helps contextualize these two emissions

Intake fraction

slide from Stephens, B., IIT, BERG

Intake fraction

36

Exposure study in Singapore

respiratory tract infections1

cardiovascular disease2

asthma3

Investigate ambient PM10 and PM2.5 exposure in Singapore:

credit: retail-is-detail.com

• Rapid development

credit: telegraph.co.uk

• Distinct activity patterns • Episodic haze events

credit: greenworkspro.com

Ambient particulate matter (PM) pollution:

Ranked 11th risk factor for DALYs in SE Asia (9th globally)4

1Schwartz (1994) Environmental Research 64: 36-52; 2Dominici et al. (2006) The Journal of the American Medical

Association 295 (10): 1127-1134; 3Li et al (2003) Clinical Immunology 109 (3): 250-265; 4Lim et al. (2012) The

Lancet 380:2224-2260

37

1. PM2.5

2. PM10

• Spatially resolved

- 6 regions across Singapore

• Accounts for demographics

- Age stratified

- Gender stratified

• Accounts for 11 microenvironments

- From indoor/outdoor ratios

Exposure model

Of outdoor origin only

Goal: Assess exposure to ambient air pollution in Singapore

1. Both indoor and outdoor exposures to PM of ambient origin

2. Identify vulnerable regions

3. Identify vulnerable subpopulations

Approach: Construct exposure model to address:

Jurong

West

Clementi

Yishun

BedokNovena

Ang

Mo Kio

P09

P31

P03

P20

P24

P28

N

*

*** *

*Field study sampling locations

38

Exposure model formulation

Time-concentration model of exposure:

l

j

m

i

iiinkjjokk tCtCEx1 1

,,

Exposure [=] µg m-3 h

1. Outdoor air quality data

Outdoor pollutant

concentration,

where k is PM2.5 or PM10,

[=] µg m-3

2. Activity pattern data

Time spent in

microenvironment i or j

[=] h

3. Indoor concentrations

Indoor pollutant concentration,

(from indoor/outdoor ratios)

[=] µg m-3

39

Field study: Indoor/outdoor ratios

credit: thesingaporepromise.sg

Apartments and student housing:Example site layout (Site 1):

5 total sites: • 3 at Nanyang Technological University, 1 in north-central, 1 central

• Rooms with windows & split air-con systems

• Built between 1988 and 2012

• High floor (8th and above)

Fan WindowsMonitoring equipment Air-conditioner

Hostel at Nanyang Technological University

Undergraduate research project! Contributed to conference proceeding, published paper

40

Field study methods

Two modes of ventilation: • Natural ventilation (NV) – windows open and fans on

• Air-conditioned (AC) – windows closed, fans off, air-conditioning on

Continuous monitoring of indoor and outdoor PM:• Two TSI aerotraks, in indoor and outdoor space

• Co-located for correction factor (weekly)

• From 13:00 – 19:00 (no occupancy)

• Convert number to mass concentration (assumed ρ = 1.2 g/cc)

• We report PM2.5 and PM10

Also measured indoor/outdoor:• Ozone

• Temperature

• Airspeed

• Relative humidity

• CO2

41

Field study: time series

Example time series data (Site 4):

PM2.5 PM10

Calculated time-averaged (1-h) indoor and outdoor concentrations• Error bars are larger of instrument error or variability (std. dev.) across 1 hour

• These data are used to determine site averages, I/O ratio for each hour

5

10

15

20 Indoor-NV

Outdoor-NV

0

20

40

60

80Indoor-NVOutdoor-NV

5

10

15

20

13:00 14:00 15:00 16:00 17:00 18:00Time of day

Indoor-AC

Outdoor-AC

0

20

40

60

80

13:00 14:00 15:00 16:00 17:00 18:00Time of day

Indoor-ACOutdoor-AC

PM

2.5

concentr

ation (

µg m

-3)

PM

10

concentr

ation (

µg m

-3)

42

Field study: Indoor/outdoor ratios

0

0.2

0.4

0.6

0.8

1

1.2

1 2 3 4 5 Avg

Ind

oo

r/o

utd

oo

r P

M2.

5 r

atio

(-)

Field site

NV AC

0

0.2

0.4

0.6

0.8

1

1.2

1 2 3 4 5 Avg

Ind

oo

r/o

utd

oo

r P

M10

rat

io (

-)

Field site

NV AC

PM2.5 PM10

• Across all sites, average I/O ratios are slightly reduced with AC

PM2.5 = 0.74 (NV) and 0.60 (AC)

PM10 = 0.67 (NV) and 0.31 (AC)

• Split AC system performs better for PM10 removal than PM2.5

• Error bars are propagated from concentration averages

43

Indoor environments drive exposure

Exposure in the home dominates • especially under natural ventilation conditions,

Gall et al. 2015, Building and Environment

44

Model inputs: I/O ratios

Estimates of I/O ratios input to model:

• Values from field study (home)

• Values from literature (other

environments)

• Higher concentrations in NV

• Office work more protective

- construction assumed outdoors

- transport/storage assumed

equal to enclosed commute

• Naturally ventilated schools:

- high indoor/outdoor ratio

PM2.5 PM10

Home*

Air-con 0.60 0.31

NV 0.74 0.67

Work

Office 0.46 0.35

Construction 1 1

Manufacturing 0.72 0.55

Transportation/Storage 0.82 0.74

Commute

Open commute 1 1

Enclosed commute 0.82 0.74

School

NV 0.72 0.55

ACMV 0.20 0.15

Outdoor 1 1

*Average values from field study across five sites

in Singapore. Other I/O ratios taken from literature

45

Time-activity patterns

0

5

10

15

20

25

M F M F M F M F M F M F M F M F M F M F M F M F M F M F

0 - 4 5 - 9 10 - 14 15 - 19 20 - 24 25 - 29 30 - 34 35 - 39 40 - 44 45 - 49 50 - 54 55 - 59 60 - 64 65 & Over

Av

erag

e ti

me

du

rati

on (

h d

-1)

Work Commute School Home Outdoors Other

Age

Gender

• Work – S’pore Dept. of Stats: General Household Survey

• Commute - S’pore Dept. of Stats: Population and household characteristics

• School – S’pore Ministry of Education: School hours and activities

• Home – Exposure study in Hong Kong Chau et al. (2002) Environment International 27:617-630

• Outdoors – Ibid/Myopia in children in Singapore Rose et al. (2008) Ophthalmology 126:527-530

Data compiled from Singapore government surveys and literature:

46

Time-activity patterns

NHAPS: National Human Activity Pattern Survey

• Collected from 1992-1994, a 2-yaer phone survey of 9400 people in the US

47

Time-activity patterns

Very expensive and difficult to collect – but critical for understanding exposure.• What better ways do we now have to collect this data?

48

Exposure: Microenvironments

Importance of naturally ventilated environments:

• 67% of PM2.5 exposure

• 76% of PM10 exposure

PM2.5 exposure contribution: PM10 exposure contribution:

5%

5%< 1%

2%

1%

< 1%

4%

23%

58%

outdoors

work-office

work-const.

work-manu.

work-trans/storage

commute-enclosed

commute-open

school-ACMV

school-NV

home-AC

home-NV

5%

5%< 1%

2%

1%

< 1%

4%

23%

58%

5%

5%< 1%

2%1%

< 1%

3%

13%

68%

Next time

• Start on reactor models

• General transport equation (3-D advection/diffusion

equation)

• But most analyses will be zero-D or 1-D in this class

• First scenario of indoor environment