HVAC system operation in residential buildings during a pandemic

Professor Chandra Sekhar, PhDFellow ASHRAE, ISIAQDepartment of Building,

School of Design and EnvironmentNational University of Singapore, Singapore

ASHRAE Webinar for Emerging Economies:Managing COVID-19 and HVAC in Buildings for Emerging Economies

18 June 2020

Infection control pyramid adapted from US Centers for Disease Control (CDC)

CDC. HIERARCHY OF CONTROLS. Centers for Disease Control and Prevention; 2015

Elimination

Engineering Controls

Administrative Controls

PPE

To physically remove the

pathogen

To separate the people

and pathogen

To instruct people what

to do

To use masks, gowns, gloves

etc.

VENTILATION(Outdoor Air)

Quality

Quantity (L/s)

Room air distribution (Ventilation

effectiveness)

Dilution of indoor contaminants

0

500

1,000

1,500

2,000

2,500

3,000

3,5001:

06…

1:28

…1:

50…

2:12

…2:

34…

2:56

…3:

18…

3:40

…4:

02…

4:24

…4:

46…

5:08

…5:

30…

5:52

…6:

14…

6:36

…6:

58…

7:20

…7:

42…

8:04

…8:

26…

8:48

…9:

10…

9:32

…9:

54…

10:1

6…10

:38…

11:0

0…11

:22…

11:4

4…12

:06…

12:2

8…12

:50…

13:1

2…13

:34…

13:5

6…14

:18…

14:4

0…15

:02…

15:2

4…15

:46…

16:0

8…16

:30…

16:5

2…17

:14…

17:3

6…

CO2

Conc

entr

atio

n (p

pm)

TimeSensor 1 Sensor 2 Sensor 4 Sensor 6 Sensor 7

AOvernight CO2 Build-up

1 personBedroom door closed

ECO2 Decay

Bedroom UnoccupiedBedroom door fully open

HCO2 Decay

Bedroom UnoccupiedBedroom door fully openBathroom exhaust - ON

Kitchen Hood - ON

Residual CO2 monitoringHouse Unoccupied

Bedroom door fully openBathroom exhaust - OFF

Kitchen Hood - OFF

CCO2 DecayBedroom

UnoccupiedBedroom door

closed

Bedroom CO2 measurements

Temperate Climate – Heating Season – Natural VentilationSemi-detached House with two levels – Trickle vents on windows and doors

- Bedrooms on upper level

Window airing

PAPER 1: Chandra Sekhar, Mariya Bivolarova, Mizuho Akimoto and Pawel Wargocki, 2020 – Journal Article under review

ACR < 0.1 h-1

ACR ≅ 0.3 h-1

ACR ≅ 1.0 h-1

“B”

“C”

P1

Exha

ust

Fan

Window

Multi-Split system Fan Coil Unit

6.36 m

2.90 m

1.73

m

3.15

m

“A” “B”

“C”

Bed-HeadBuilt-in wardrobe

Built-in W

ard-robe (floor-to-ceiling)

1.08

m

Master Bed-room in a condominium apartment (8th Storey)5

Tropical Climate – Split-System AC unitHigh-Rise Residential Apartment

18:00 06:0000:00

500

1000

1500

2000

2500

3000

3500

4 Adults (Experiment Phase)

Exhaust fan switched on

CO

2C

once

ntra

tion

Leve

l (pp

m)

Time

2 Adults, 1 Child – SleepingPeriod during night

CO2 concentration during measurement and night-time sleeping periods

6 Tropical Climate – Split-System AC unitHigh-Rise Residential Apartment

ACH1.96 (Exh Fan ON)0.32 (Exh Fan OFF)

PAPER 2: Sekhar, S. C. (2004). Enhancement of ventilation performance of a residential split-system air-conditioning unit. ENERGY AND BUILDINGS, 36(3), 273-279.

0102030405060708090

100

<47 47-93 93-139 140-186 186-232 232-279 279-325 325-372 372-418 418-465

Dw

ellin

g Ve

ntila

tion

rate

(L/s

)

Dwelling Floor Area (m2)

Dwelling Unit

1 Bedroom 2 Bedrooms 3 Bedrooms 4 Bedrooms 5 Bedrooms

Ventilation requirements for whole dwellings – ANSI/ASHRAE Standard 62.2 (2019)

PAPER 3: S.C.Sekhar, Mizuho Akimoto, Xiaojun Fan, Mariya Bivolarova, Chenxi Liao, Li Lan and Pawel Wargocki 2020. Bedroom Ventilation and Sleep – A Review (article under preparation)

0

200

400

600

800

1000

1200

1400

1600

Cat I Cat II Cat II I Cat IV

Desig

n ∆C

O2

-ppm

abo

ve o

utdo

ors

Building Category

Living rooms Bedrooms

Design CO2 levels in living rooms and bedrooms - EN 16798-1:2019

PAPER 3

Design extraction air flow rates by room and building type - EN 16798-1:2019

PAPER 3

0

5

10

15

20

25

30

35

40

45

1 room 2 rooms 3 rooms 4 rooms 5 and more rooms

Desig

n Ex

trac

tion

-L/s

Number of rooms in dwelling

Kitchen Bathroom/Shower Other Wet areas Toilets - 1 in dwelling Toilets - 2 or more in dwelling

[14][29][15][28][19][17][3][21][30][1][22][2]0

1000

2000

3000

4000

5000

6000

[5] [26] [22] [2] [17] [27] [24](**)(**)(**) (**)

(M)

Mean (M) Min of mean

CO

2 Con

cent

rati

on (

ppm

)

Literature (NV)

1350 780

EN 16798-1(2019)

(**)

Max of all measurements Max of mean

Min of all measurements

Heating SeasonCooling Season

(M)

Reported CO2 values in the literature for NV bedrooms across heating and cooling seasons

PAPER 3

[1] [20] [17] [19] [30] [15] [22] [2] [3] [14]0

1000

2000

3000

4000

5000

6000

[22] [20] [2] [17] [26](**)(**) (**) (**) (**)

(M)

CO2 C

once

ntra

tion

(ppm

)

Literature (MV)

Cooling Season Heating Season

Max of all measurements Max of mean Mean (M)

Min of all measurements Min of mean

1350 780

EN 16798-1(2019)

(M)

Reported CO2 values in the literature for MV bedrooms across heating and cooling seasons

PAPER 3

[21][15] [8] [13][17][12][14][22][23]0

1

2

3

4

5

[26][11][13] [8] [22] [7] [17][24][23](**) (**)(**)

(M)

(M)

(M)

(M)

(M)

Air

chan

ge ra

te (h

-1)

Literature (NV)

Cooling Season Heating SeasonASHRAE 62.2(2019), Dwelling (bedroom)*

EN 16798-1(2019), dwelling

5.69

EN 16798-1(2019), bedroom

Max of all measurements Max of mean Mean (M)

Min of all measurements Min of mean

1.22.02.9

(M)

0.7 0.2 0.7 0.5 0.4

Reported ACH values in the literature for NV bedrooms across heating and cooling seasons

PAPER 3

[15] [14] [8] [13] [17] [22] [19] [23]

0

1

2

3

4

5

[26] [11] [7] [13] [8] [22] [17] [23](**)(**) (**)

(M)

(M)

Air

change r

ate

(h

-1)

Literature (MV)

Cooling Season Heating Season

Max of all measurements Max of mean

Mean (M)

Min of all measurements Min of mean

1.22.02.9

EN 16798-1(2019), bedroom

EN 16798-1(2019), dwelling

ASHRAE 62.2(2019), Dwelling (bedroom)*

4.4

(M)

(M)(M)

(M) 0.7 0.2 0.7 0.5 0.4

Reported ACH values in the literature for MV bedrooms across heating and cooling seasons

PAPER 3

[10] [8] [13] [22] [38]0

1

2

3

4

5

[35] [8] [10] [37] [7] [11] [38] [22] [13] [40] [39]

(M)

(M)

Mean (M)A

ir ch

ange

rate

in w

hole

dw

ellin

g (h

-1)

Literature (NV)

Heating SeasonCooling Season

ASHRAE 62.2 (2019), dwelling (bedroom)*

EN 16798-1(2019), dwelling

0.7 0.2 0.7 0.5 0.4

Reported ACH values in the literature for whole dwelling across heating and cooling seasons - NV

PAPER 3

Reported ACH values in the literature for whole dwelling across heating and cooling seasons - MV

[8] [13] [22] [38]0

1

2

3

4

5

[35] [8] [7] [37] [11] [38] [22] [13] [40] [39]

(M)

Air

chan

ge ra

te in

who

le d

wel

ling

(h-1)

Literature (MV)

Cooling Season Heating Season

Mean (M) EN 16798-1(2019), dwellingASHRAE 62.2 (2019), dwelling (bedroom)*

(M)

0.7 0.2 0.7 0.5 0.4

PAPER 3

https://www.ashrae.org/technical-resources/residences-faq

RESIDENCES FAQ

https://www.ashrae.org/technical-resources/residentialnew#general

RESIDENTIAL IAQ GUIDE

17

Principles of ventilation

Ventilation in Residential Buildings – Field Data –Temperate and Tropical climate examples

Ventilation in Residential Buildings – A Review of literature

COVID 19 Guidance – ASHRAE – RESIDENTIAL IAQ GUIDE

COVID 19 Guidance – ASHRAE – RESIDENCES FAQ

18

19

Professor Chandra Sekharbdgscs@nus.edu.sg