ASHRAE Journal - April 2021 - 57

COLUMN IEQ APPLICATIONS

FIGURE 1 Summary of the available studies examining the effect of bedroom ventilation (IAQ) on sleep quality.

5,000
Objective Sleep Quality Assessment
Subjective Sleep Quality Assessment
Higher Ventilation Condition
Lower Ventilation Condition

Mean CO2 Concentration (ppm)

4,000

3,000

2,000

Lower % of Deep Sleep
Reduced Self-Reported SQ1

1,000

1,0042
500

Lower SE
Increased % of Wakefulness
Lower Scores of EOA5
Lower Sleep Satisfaction
Increased Snoring
Lower SE3
Increased NOA
Increased NOA4
2,012
Lower Depth of Sleep
1,654

Lower SE
Longer SL6
Reduced Next-Day Performance7
More Sleepy
Less Able to Concentrate Next Day
2,585

Longer SL
Decreased SWS8
Reduced Self-Reported SQ
3,000

2,395

1,150
717

601

672

Mishra, et al.

Liao, et al.

Zhang, et al.

835

660

800

0
Xiong, et al.

Strøm-Tejsen, et al.

Xu, et al.

LOCATION

Australia

Netherlands

Belgium

China

Denmark

China

SAMPLE SIZE (AGE)

48 (20 - 44 yr)

18 (21 - 27 yr)

27 (20 - 33 yr)

104 (20 - 20 yr)

14 (20 - 30 yr)

16 (20 - 30 yr)

12 (23 - 25 yr)

VENTILATION SYSTEM 9

VENUE

Apartment

Dormitory

Chamber

Autumn

Heating Season

Cooling Season

Actigraphy

PSG

SEASON

Cooling Season

Heating Season

Spring

Spring and
Autumn

SLEEP QUALITY
ASSESSMENT

Actigraphy10

Actigraphy

Actigraphy, PSG11

Actigraphy

1 - SQ: sleep quality; 2 - the mean CO2 concentration with a single occupant is adopted; 3 - SE: sleep efﬁciency; 4 - NOA: number of awakenings; 5 - EOA: ease of awakenings;
6 - SL: sleep onset latency; 7 - next-day performance: next-day performance of a logical thinking task; 8 - SWS: slow wave sleep; 9 - NV: natural ventilation, MV: mechanical
ventilation; 10 - Actigraphy: a wrist-worn sleep tracker, 11- PSG: Polysomnography

and subjective sleep quality assessments are given in
red and black text, respectively, inside the ﬁgure. The
assessments are connected to a speciﬁc CO2 concentration, which can be read on the y-axis of the ﬁgure.
Laverge and Janssens4 examined whether window
opening would affect bedroom IAQ and sleep quality.
The measured peak CO2 concentration was between
3,000 ppm and 4,500 ppm (air change rate between
0.2 h-1 and 0.3 h-1) with windows closed and between
1,000 ppm and 2,500 ppm (air change rate between 0.4
h-1 and 1.0 h-1) with windows open. Window opening
reduced the number of awakenings during the night
and improved the subjectively assessed restfulness
and lightness of sleep, while sleep efﬁciency increased
slightly with the window closed, most probably due to
external noise disturbance in the open window condition, as the authors of the next study concluded. For this
reason, and because only peak concentrations of CO2
were recorded, we have omitted this study from Figure 1.
Strøm-Tejsen, et al.,5 investigated the effect of

bedroom IAQ on sleep quality in two experiments. In
one of them, sleep quality was measured when windows
were open or closed. In the other, windows remained
closed, while an inaudible fan was turned on/off and
supplied just enough outdoor air to keep the CO2 concentration below 900 ppm or was idled. The average
CO2 concentration was 2,585 ppm with the window
closed and 660 ppm with the window open; the air
change rates were 0.17 h-1 and 1.8 h-1, respectively. In
the second experiment, the mean CO2 concentration
was 2,395 ppm without ventilation and 835 ppm with
ventilation; the air change rates were 0.24 h-1 and 1.1 h-1,
respectively. They reported that sleep onset latency
increased (i.e., it took longer to fall asleep), sleep efﬁciency was reduced and next-day performance on a test
requiring concentration was reduced when the outdoor
air supply rate was lower.
Mishra, et al.,6 modiﬁed the ventilation rate in bedrooms by keeping doors and windows to bedrooms
either open or closed. The average CO2 concentration
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