Combating overheating: mixed-mode conditioning for workplace comfort

Figures & data

Table 1. Description of the study buildings.

Building code	Aus1	Aus2	Aus3	Ind1	Ind2	Ind3	Ind4
Year of building completion/major refurbishment	2000	2004–05	2005–06	2012	2011	2009	Pre-2003
City	Sydney, Australia	Melbourne, Australia	Melbourne, Australia	New Delhi, India	Gurgaon, India	Ahmedabad, India	Ahmedabad, India
Latitude/longitude	–33.5/151.1	–37.5/144.6	–37.5/144.6	28.4/77.1	28.3/77.0	23.0/72.5	23.0/72.5
Climate classification under local building codes	Warm temperate	Mild temperate	Mild temperate	Composite	Composite	Hot dry	Hot dry
Year of post-occupancy study	2003	2006	2007	2012	2012	2012	2012
Building floor area (m^2)	2000	1215	9300	3600	2676	13,377	16,842
Number of floors in the building	4	4	9	5	2	2	8
Type of organization surveyed	Government/owner occupied	Corporate/owner occupied	Government/owner occupied	Non-governmental organization/owner occupied	Non-governmental organization/owner occupied	Government/owner occupied	Corporate/tenant
Total number of employees	120	30	540	75	90	More than 200	More than 200
Predominant layout of surveyed employees	Open plan	Open plan	Open plan	Open plan	Open plan	Open plan	Open plan
Environmental system description passive/active	Stack ventilation with operable louvres/Variable refrigerant volume (VRV) heating, ventilation and air-conditioning (HVAC) system	Stack ventilation with operable window/VRV, three-pipe gas heat pump HVAC system	Stack-driven displacement ventilation with under-floor air delivery (both modes) plus supplementary passive chilled-beam cooling	Natural ventilation through operable windows with ceiling fans/ducted HVAC system	Natural ventilation through operable windows with ceiling fans/displacement ventilation HVAC system	Natural ventilation through operable windows with ceiling fans/centralized evaporative cooling	Natural ventilation through operable windows/individual air-conditioning units (split, window and ceiling unit)
Changeover mixed mode as operated in the year prior to the survey	As conditions permit all year round	As conditions permit all year round	As conditions permit all year round	Seasonal: natural ventilation (NV) in Summer; air-conditioning in monsoon and heating in winter	As conditions permit all year round; typically cooling runs from March to September and heating during December–January	Seasonal: NV from November to March and evaporative cooling from April to October	As conditions permit all year round
Temperature regime as operated in the year prior to the survey	19–25°C	19–25°C	20–25°C	Varies – refer to Table 3 for observed mean operative temperature during the survey

Table 2. Summary of BUS study results.

Building code	Aus1			Aus2			Aus3			Ind1			Ind2			Ind3			Ind4
City	Sydney			Melbourne			Melbourne			New Delhi			Gurgaon			Ahmedabad			Ahmedabad
Number of responses	59.0			26.0			260.0			44.0			58.0			180.0			157.0
Benchmark dataset used for comparison	Australian			Australian			Australian			International			International			International			International
Year of survey	2003			2006			2007			2013			2013			2013			2013
Variable	Score	% Dissatisfied	Result	Score	% Dissatisfied	Result	Score	% Dissatisfied	Result	Score	% Dissatisfied	Result	Score	% Dissatisfied	Result	Score	% Dissatisfied	Result	Score	% Dissatisfied	Result
Temperature in summer – overall	3.2	58%	Worse	5.4	10%	Better	4.5	31%	Better	3.1	64%	Worse	5.4	12%	Better	2.5	76%	Worse	4.9	16%	Better
Temperature in summer – hot/cold	3.2	40%		3.7	5%		3.3	23%		2.8	49%		4.5	25%		2.0	69%		4.1	17%
% Rating too hot			33%			5%			21%			45%			2%			69%			9%
Air in summer – overall	3.1	66%	Worse	5.6	11%	Better	4.5	28%	Better	3.9	39%	No difference	5.4	7%	Better	3.2	55%	Worse	4.7	19%	Better
Temperature in the monsoon – overall										4.8	20%		5.4	4%		4.7	16%		4.9	8%
Temperature in the monsoon – hot/cold										4.2	13%		4.3	9%		4.1	7%		4.4	12%
% Rating too hot												5%			2%			5%			1%
Air in the monsoon – overall										4.7	12%		5.3	0%		4.5	15%		4.9	8%
Temperature in winter – overall	3.4	55%	Worse	4.4	31%	Better	4.7	26%	Better	4.3	15%	No difference	6.0	1%	Better	5.8	4%	Better	5.4	8%	Better
Temperature in winter – hot/cold	4.8	47%		5.1	38%		4.1	28%		5.5	48%		4.2	3%		4.4	9%		4.6	17%
% Rating too hot			9%			0%			12%			0%			2%			1%			1%
Air in winter overall	3.4	60%	Worse	4.4	40%	No difference	4.7	25%	Better	4.8	16%	No difference	5.7	5%	Better	5.3	6%	Better	5.1	5%	Better
Lighting – overall	5.1	14%	No difference	6.0	8%	Better	4.2	37%	No difference	6.0	0%	Better	6.2	0%	Better	5.8	5%	Better	5.5	10%	Better
Noise – overall	3.4	60%	Worse	5.1	15%	Better	4.2	38%	No difference	5.2	11%	Better	5.6	9%	Better	5.0	21%	Better	4.7	24%	Better
Comfort overall	3.6	46%	Worse	5.7	12%	Better	4.9	22%	Better	5.1	7%	No difference	5.6	1%	Better	4.7	16%	No difference	4.7	13%	No difference
Control over cooling	1.8	90%	Worse	2.4	73%	No difference	1.5	93%	Worse	2.6	65%	Worse	2.7	62%	No difference	2.5	73%	Worse	4.2	30%	No difference
% Rating control over cooling as important			46%			23%			13%			27%			34%			34%			22%
Control over heating	1.8	91%	Worse	2.4	73%	No difference	1.5	92%	Worse	2.5	67%	Worse	2.5	66%	Worse	1.1	97%	Worse	3.5	46%	No difference
% Rating control over heating as important			46%			19%			12%			23%			19%			8%			12%
Control over ventilation	2.0	86%	Worse	2.0	81%	Worse	1.9	83%	Worse	4.9	20%	Better	3.3	54%	No difference	3.9	41%	No difference	3.2	55%	No difference
% Rating control over ventilation as important			42%			15%			16%			34%			17%			12%			16%
Control over lighting	1.7	90%	Worse	4.0	42%	No difference	2.8	65%	Worse	5.8	5%	Better	4.4	31%	Better	4.6	28%	Better	4.0	33%	No difference
% Rating control over lighting as important			37%			15%			21%			41%			22%			2%			15%
Control over noise	1.9	89%	Worse	2.6	65%	No difference	1.9	85%	Worse	3.9	33%	No difference	3.4	47%	No difference	2.1	81%	Worse	3.0	60%	No difference
% Rating control over noise as important			34%			31%			17%			32%			26%			5%			15%
Effectiveness of response to requests for changes				4.8	27%					4.9	25%	Better	4.6	31%	Better	2.9	60%	Worse	4.5	24%	Better
Design	3.7	46%	Worse	6.3	4%	Better	5.5	7%	Better	5.8	2%	Better	6.4	0%	Better	4.4	29%	No difference	4.4	19%	No difference
Do facilities meet needs?	4.2	37%	No difference	5.9	8%	Better	5.2	10%	No difference	5.5	4%	Better	6.0	1%	Better	4.8	18%	No difference	5.1	9%	No difference
Health (perceived)	3.1	56%	Worse	4.7	4%	Better	4.6	21%	Better	4.7	6%	Better	5.1	2%	Better	4.7	13%	Better	4.6	14%	Better
Productivity (perceived)	–13.5	46%	Worse	6.0	4%	Better	5.5	11%	Better	2.8	36%	No difference	11.7	14%	Better	1.4	23%	No difference	8.5	19%	Better
Forgiveness	1.0			1.1			1.1			1.1			1.0			1.0			0.9

Each variable above is rated on a 7-point A type scale (1 is worst, 7 is best) with the exception of perceived productivity rated on a 9-point scale and Temperature Hot/Cold (4 is best, 1=Too Hot; 7=Too Cold).

% dissat refers to percentage of dissatisfied respondents. For variables on an A Type scale this refers to those rating as 1, 2 or 3 on the 7-point scale and for B type scale this refers to those rating 1, 2 or 6, 7. For the Temperature Hot/Cold variable, additional information as to only those voting 1, 2 (too hot) is also provided

Result indicates if the mean building score is significantly Better or Worse or No diff (No different) to the mean of the corresponding benchmark dataset for the year of study.

Forgiveness is a measure of tolerance and is calculated as Comfort Score/Average of scores for Temperature, Air, Noise, and Lighting. If this ratio is greater than 1, it means occupants are forgiving.

Table 3. Selected thermal comfort field study (TCS) survey results for Indian study buildings.

Building information						Field measurements and derived parameters									Field survey			Calculated indices			Adaptive measures
			Survey month in 2012	Respondent mode	Number of votes	Mean indoor air temperature (°C), avg_ta	Mean indoor radiant temperature (°C), avg_tr	Mean indoor relative humidity (%), avg_rh	Mean indoor airspeed (m/s), avg_vel_a	Mean metabolic activity (met), avg_met	Mean insulation chair + clothing (clo), avg_insul	30-Day outdoor running mean, tâ (°C)	7-Day outdoor running mean (°C), out7 day_ta	Mean indoor operative temperature (°C), avg_top	Mean ASHRAE thermal sensation vote (+3 hot; –3 cold), avg_ash	Thermal acceptability; % rating unacceptable, tsa_dissat%	Mean office comfort score/(1,7), avg_comf	PMV (+3 hot; –3 cold), avg_pmv	PPD (%), avg_ppd	Indicative results for neutral operative temperature (°C), Topneut (LR)	% Using ceiling or pedestal fans	% Opening windows (partially or fully open)
Ind1		Summer	June	NV	66	36.2	36.3	43%	0.5	1.2	0.8	38.8	40.6	36.2	1.7	65%	4.3	3.0	100%		100%	39%
		Monsoon	August	AC	45	26.9	27.3	62%	0.2	1.3	0.8	34.2	32.3	27.1	–0.1	4%	5.6	1.1	39%	28.2	53%	0%
		Winter	December	AC	52	17.9	17.7	52%	0.1	1.2	2.2	20.2	18.4	17.8	–1.0	54%	5.0	0.5	12%		0%	0%
Ind2		Summer	June	AC	55	26.1	26.4	43%	0.2	1.2	0.8	38.9	39.9	26.2	–0.1	13%	6.4	0.6	19%	27.4	69%	11%
		Monsoon	August	AC	62	25.2	25.6	60%	0.2	1.2	0.8	33.9	31.3	25.4	–0.1	5%	6.1	0.6	20%	26.1	37%	0%
		Winter	February	NV	64	24.1	23.6	38%	0.1	1.3	1.5	15.3	15.7	23.9	0.1	5%	6.0	0.9	24%	22.4	0%	8%
Ind3		Summer	May	AC	194	33.5	33.6	48%	0.5	1.1	1.0	35.5	32.9	33.6	1.6	65%	4.2	2.7	94%	27.9	98%	34%
		Monsoon	August	AC	170	29.8	29.7	74%	0.5	1.2	0.8	31.2	28.5	29.7	0.3	24%	4.9	1.7	64%	26.3	98%	62%
		Winter	Jane	NV	186	24.4	24.1	31%	0.1	1.2	1.1	22.0	21.8	24.3	–0.2	9%	5.2	0.5	14%	26.3	0%	23%
Ind4		Summer	May	AC	180	25.3	26.0	47%	0.1	1.2	1.1	35.6	32.9	25.6	–0.2	20%	5.6	0.9	24%	26.3	0%	0%
		Monsoon	July	NV	46	24.8	25.4	56%	0.1	1.3	0.8	31.7	28.9	25.1	–0.4	4%	5.3	0.7	17%		0%	0%
		Monsoon	July	AC	131	24.5	25.2	54%	0.1	1.2	0.8	31.7	28.9	24.8	–0.4	12%	5.4	0.5	14%	29.5	1%	0%
		Winter	January	NV	112	25.6	25.6	49%	0.1	1.2	1.1	22.1	21.0	25.6	–0.1	12%	4.9	0.9	25%	26.4	1%	0%
		Winter	January	AC	57	25.2	25.2	47%	0.1	1.2	0.9	22.1	21.0	25.2	–0.4	11%	5.3	0.6	18%	26.7	0%	0%

Note: AC = air-conditioning; NV = natural ventilation.

– Office occupants' response to thermal sensation avg_ash is recorded on a seven point ASHRAE thermal sensation scale (+3 hot; -3 cold)

– tsa_dissat% is the percentage of occupants rating ‘unacceptable’ for thermal acceptability on a binary scale (1 = unacceptable, 2 = acceptable)

– Office comfort (right here, right now) is rated on a 7-point A type scale (1 = uncomfortable to 7 = comfortable)

– The 7 day outdoor running mean air temperature out7day_ta and the 30-day outdoor running mean air temperature out30day_ta are derived from weather station data.

– The average Predicted Mean Vote avg_pmv and predicted percent dissatisfied avg_ppd for each cohort are calculated from field measurements.

– Neutral Operative Temperature Topneut (LR) is derived using linear regression on observed thermal sensation controlling for extrapolation outside observed range.

Figure 1. Cross-sectional views of the study buildings.

Figure 2. Scatter plot showing BUS ratings for ‘temperature in summer hot/cold’ versus ‘temperature in summer overall’.

Figure 3. Predicted cooling energy at different cooling set-points for Sydney and Melbourne (north) and Delhi and Ahmedabad (south).

Figure 4. Scatterplots showing the relationship between ratings for (a) perceived control over cooling and (b) effectiveness of response with ratings for temperature in summer overall.

Figure 5. Statistical correlation showing the strength of the relationship between ratings for (a) temperature in summer overall and comfort overall, (b) temperature in summer overall and perceived productivity, (c) comfort overall and perceived productivity, and (d) comfort overall and perceived health. (a–d) show the study buildings in the context of the wider BUS dataset. The regression line is for the whole set.

Figure 6. Layout plan showing zones of environmental control for Aus3.

Source: City of Melbourne, drawing © DesignInc.

Figure 7. Layout plan showing zones of environmental control for Ind1.

Source: Ashok B Lall Architects.