reset bangladesh - post occupancy technical evaluation

Post Occupancy Evaluation Data Analysis Report

Resilient Rural Housingin South West Bangladesh

December 2012

AcknowledgementsThis project was funded by the Department for International Development under contract number 2210082. It was delivered in the village of Boro Kupot, Satkhira district, south west Bangladesh, with the help and support of the local community, in association with field partners Practical Action Bangladesh, DHARA, the Self-Help Promotion Network, Plastic Buddha/People's Voice Community Video and Risal Ahmed. RESET Development is very grateful to all partners and particularly the inhabitants of Boro Kupot for their involvement in this project.

CreditsAuthorStefano Palmerini

Design & layoutMarianna Magklara

Published by RESET Development16 Hoxton Square, N1 6NT, Londonemail: [email protected]: www.reset-development.org

Charity No 1137511Company No 07144369

Prototype housing designsJA Architects, Bangladesh

Risal Ahmed, Bangladesh Photographs

The Self-HelpPromotionNetwork

DHARACommunity based training & development

Table of contents

1. Introduction ..........................................5

1.1 Aim of the project ...........................5

1.2 Methodology ....................................5

2. Location and material of the four prototype houses ............................ 7

2.1 Location ..............................................7

2.2 Materials .............................................7

3.Climate ..................................................10

4. Results ..................................................11

4.1 The upper space ............................11

4.2 The living space .............................12

4.3 The coldest period .......................14

4.4 The hottest period ........................15

4.5 The outdoor space .......................16

5. Discussion and conclusion .................19

6. Recommendations ..............................23

Bibliography ............................................24

Appendix .................................................25


Fig. 1: Golpata leaf roof performs better overall than the other roof types

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1. 1 Aim of the project

The aim and scope of the research is to investigate thermal and humidity performance of four prototype houses in the Province of Satkhira, Bangladesh, built between April and July 2011.

The significance of the research depends on the understanding of the thermal performance of different materials used in the construction of the four prototype houses in the context of a region which has been repeatedly exposed to seasonal flooding. This research produces a comparison of thermal data with the aim of producing useful recommendations in adopting appropriate design strategies for sustainable housing solutions.

This research indicates that the golpata leaf roof prototype house is performing better overall than the others, showing lowest maximum ambient air temperature values in the living space during the hot period of the summer.

Further to this, this research aims to champion post occupancy evaluation as a routine process as part of disaster response and reconstruction building programmes. The insights that developed from this research could provide information needed to support informed decision making for future building programmes.

1. 2 Methodology

In the original draft of the project, four data loggers were to be deployed in each prototype house, as illustrated in following diagram.

Data loggers were actually installed in the four prototype houses for collection of air temperature and relative humidity data in only three zones, namely upper area (n#1), indoor living space (n#3) and outdoor of the house under the porch (n#2). Data loggers’ installation and monitoring was carried out by Khulna University in collaboration with the lead field partner Practical Action Bangladesh.

Relative humidity and ambient air temperature data were recorded at 2 hourly intervals. The data was downloaded every month, with exceptional cases in which data was collected after three months due to the absence of residents. Data collection spanned from 20th September 2011 up to 5th of May 2012.

A weather station was also installed in order to record meteorological data. However, because of technical problems in the field, data could not be collected. Monthly average temperature data is based on data from the Meteorological Department of Bangladesh.

Data collected from data loggers deployed in the four prototype houses has been exported into Excel Worksheets by using the licensed version TempIT pro software. Data analysis and graphs were then produced by Microsoft Excel Software.

This report presents a comparative study in order to judge the thermal performance of the four prototype houses during the four seasons, particularly with respect to the thermal comfort temperature range. Thermal performance evaluation is made with daily maximum and minimum ambient air temperatures – the daily maximum ambient air temperature is the highest value

1 Introduction

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for day time and daily minimum is the lowest value for night time ambient air temperature.

The performance evaluation is made on the basis of temperature difference between the four prototype houses both in the indoor living space and upper area as well as the outdoor area, relative to the thermal comfort range. The thermal comfort range in Bangladesh differs from the summer season to the winter season, being 24°C to 32°C during the summer and 17°C to 24°C during the winter. In this study we will consider the summer comfort range as mentioned above, nonetheless, we will think of the winter comfort range spanning 17°C to 32°C . The reason we consider ambient air temperature values above 24 still comfortable during the winter is because we assume that house occupants can adopt behavioural adaptationstrategies to keep themselves comfortable when ambient air temperatures rise during the winter, such as removing heavy layers of clothing or opening the windows.

One limitation to the data analysis will be that, since data is collected only every two hours from the data loggers, this might not represent the real maximum and minimum ambient air temperature of the monitored days. Indeed, the maximum and minimum peaks may have happened in between two consequent measurements and not been recorded. However, data collected is still indicative of ambient air temperature trends in the four monitored prototype houses, and is valid for the comparison of the four houses’ performance.

Fig. 2: Original drawing: Jalal Ahmad, J A Architect, for RESET Development and Practical Action Bangladesh

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2. 1 Location

The four prototype houses, A, B, C and D, are located in Boro Kupot village, in the upazilla of Shyamnagar, Satkhira district, Bangladesh.

Satkhira is a district in south-western Bangladesh and is part of Khulna Division. Satkhira District has an area of 3858.33 km².

It is bordered to the north by Jessore District, on the south by the Bay of Bengal, to the east by Khulna District, and to the west by 24 Pargana District of West Bengal, India.

The following image shows the exact location on a SPOT satellite image, taken on March 2010.

2.2 Materials

The four prototype houses are constructed from different combinations of materials, as illustrated in the following table and pictures.

2 Location and materials of the 4 prototype houses

Fig. 3: Location of Shyamnagar, Bangladesh

Fig. 4: Aerial view of the four prototype houses (Practical Action Bangladesh, 2012)

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Fig. 5a: View of Prototype AFig 5b: External sensor under the shade of extended roof of the houseFig 5c: Thermal Data Logger position in the upper space Fig. 5d: Placement of sensor in the indoor living space

Prototype house A is covered by a corrugated metal roof, whilst walls are made up of a wooden frame and a plain red metal sheet. The house is surrounded by little vegetation and one single tree, which might provide some shade during the day.

Prototype house B is covered by a corrugated metal sheet roof, whilst walls

were designed to be compressed earth bricks. The reason the bricks haven't been used remains unknown. We do not have any picture of the external sensor, because, at the time pictures were taken, the external data logger had gone missing. Indeed, the resident of the house left for a couple of months, leaving the place unattended from approximately October 2011 to January 2012.

Fig. 6a: View of Prototype BFig. 6b: Placement of sensor in the indoor living spaceFig. 6c: Thermal Data Logger position in the upper space

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Prototype house C is made up of a golpata leaf roof and wooden framed walls of bamboo mat. The walls have been painted black. The reason and the date they were painted is unknown. It may have been to present the building well, for decorative or status reasons. However, as black is known to absorb heat at a higher rate than a bright yellow colour, thermal performance of this prototype may have been affected.

Prototype house D is made up of a clay tile roof with wooden framed walls of bamboo mat. Also the walls of this house have been painted black, which may have had an effect over thermal performance.

Fig. 7a: View of Prototype C. Fig. 7b: Thermal Data Logger position in the upper space Fig. 7c: External sensor under the shade of extended roof of the house Fig. 7d: Placement of sensor in the indoor living space

Fig. 8a: View of Prototype D. Fig. 8b: Thermal Data Logger position in the upper space Fig. 8c: External sensor under the shade of extended roof of the house Fig. 8d: Placement of sensor in the indoor living space

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In this region of south-west Bangladesh, the annual average maximum ambient air temperature reaches 35.5°C (95.9°F), and the hottest month is usually April – June. The minimum average ambient air temperature is 12.5°C (54.5°F), usually occurring sometime in December. The annual rainfall is approximately 1710 mm (67 in).

The climate of Bangladesh, based on the widely used classification by Atkinson (Koenigsberger, 1973), presents several climatic variables, as shown in table 1.

2. Climate3 Climate

Table 1: Classification of the seasons and climatic variables in Bangladesh (Bangladesh Meteorological Department)

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4 Results

Annual maximum and minimum ambient air temperatures graphs were created for each of the three zones monitored in the houses, which are the upper zone under the roof (Figs. 8,9), the indoor living space at occupant level (approx 1.10 m from floor level) (Figs. 10,11) and the outdoor zone under the porch (Figs. 15,16).

4.1 The upper space

Maximum ambient air temperature values go above the upper threshold of the comfort temperature range of 32 ˚C in all of the four prototype houses. However, the intensity and duration varies significantly among them.

Prototype A maximum ambient air temperatures exceed the upper threshold of the comfort temperature range most of the year, reaching the highest values of 47 ˚C.

Prototype B maximum ambient air temperatures stay above the comfort range threshold most of the year, excluding the winter season (December to February).

Prototype C maximum ambient air temperatures stay within the comfort temperature range most of the year, with the exception of a few weeks in the months of March and April 2012.

Prototype D maximum ambient air temperatures reach values above the comfort temperature range during the entire month of October till the 15th of November 2011 and, again, from the 20th of February till the end of April (end of the recorded data). Maximum ambient air temperature values never drop below the lower indicative threshold of 17 ˚C. To sum up, A>B>D>C.

The different materials seem to absorb the heat with varying intensity. Corrugated roofs appear to absorb heat at the very highest rate, whilst the golpata leaf roof (Type C) seems to absorb heat at the lowest rate. Clay tile roof performance (Type D) is in between the golpata leaf and the corrugated materials.

With regards to the walls, we are able to compare only two different materials, that is, metal sheets and wooden framed bamboo mat. The metal sheet appeared to contribute hugely in absorbing heat, as we can infer by comparing the two prototype houses A and B. They both have same material roof, only differing in wall material composition.

Fig. 9: Annual maximum ambient air temperatures recorded in the upper space of the four prototype houses during the period October 2011 to April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The blue dotted line represents the minimum value of the comfort temperature range for the summer period, which is 24˚C. The red dotted line shows the maximum value of the comfort temperature range for both the summer and the winter period.

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The prototype A, corrugated roof and metal sheets walls, shows higher internal temperatures than prototype house B, with its corrugated roof and bamboo mat walls. However, minimum ambient air temperature trends are discussed in the following paragraphs.

Minimum temperatures stayed above the minimum comfort temperature of 24˚C during most of the summer period (March to October). Nevertheless, during the winter (December – February), ambient air temperatures in all four houses dropped below at some point the winter minimum comfort temperature of 17˚C. There don’t seem to be remarkable differences among the four prototype houses with regards to their minimum ambient air temperature values. This indicates that these different materials might not have much difference in their capacity to retain heat over night.

4.2 The living space

The following two graphs illustrate the situation in the living space, which best represents the living thermal condition for the residents of the houses.

The maximum ambient air temperature values follow the same trend already seen in the upper area. Nevertheless, differences in temperature seem to be smaller than in those recorded in the upper space.

Prototype A shows the highest ambient air temperature values, reaching 42˚C in April 2012, with temperature values above the comfort zone most of the year, exception made for the winter time (December to February). Prototype B maximum ambient air temperature values stay above the comfort zone during the month of October 2011 and again from March 2012 on.

Fig. 10: Annual minimum ambient air temperatures recorded in the upper space of the four prototype houses during the period October 2011 to April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The blue dotted line represents the minimum value of the comfort temperature range for the summer period, which is 24˚C.

Fig. 11: Annual maximum ambient air temperatures recorded in the indoor space of the four prototype houses during the period October 2011 to April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The blue dotted line represents the minimum value of the comfort temperature range for the summer period, which is 24˚C. The red dotted line shows the maximum value of the comfort temperature range for both the summer and the winter period, which is 32 ˚C.

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Prototype C maximum ambient air temperature values stay within the comfort zone from the second half of October 2011 till the second half of March 2012, reaching the highest temperature of 37˚C in April 2012. Prototype D maximum ambient air temperature values are quite similar to those of Prototype C, but they reach higher values during the hot period, rising up to 39˚C in April 2012. To sum up A>B>D>C.

Prototype A shows the highest temperature, indicating that corrugated roof and metal sheet walling materials appear to offer the highest rate of heat absorption in the indoor living space. This is particularly evident in the first five months of the monitored period October 2011 to February 2012. During the same period, prototype houses C and D show the same ambient air temperature values most of the time. They are the houses which seem to perform the best thermally wise, which could mean that the bamboo mat walls are actually a better material for allowing the living space to breathe and avoiding the overheating of the houses.

Prototype B shows a lower ambient air temperature than prototype A, but still higher than C and D. It seems that in this case the bamboo mat walls still allow the house to reduce overheating caused by the corrugated roof, but performance still remains poor. However, from March to April 2012, data seems to get more homogeneous and prototype houses A, B and D ambient air temperature values and trend either overlap or show small differences most of the time during these months.

Prototype C continues to perform better than the others, with ambient air temperature values considerably lower than the other prototypes. Such differences might be due to residents’ use of the living space, such as opening and closing of doors and windows at different time during the day and the night, as well as use of fans or other electrical appliances to cool the house during the daytime.

Minimum ambient air temperatures stayed above the minimum comfort temperature of 24˚C during most of the summer period (March to October). Nevertheless, during the winter (December – February), ambient air temperatures dropped below the minimum comfort temperature of 17˚C. There don’t seem to be remarkable differences among the four prototype houses with regards to their minimum ambient air temperature values. These values do not present sensitive differences if compared to those recorded by other sensors in the upper space and the outdoor space. This information appears to confirm that none of the material used differs in term of capacity of retaining temperature during the night time.

Fig. 12: Annual minimum ambient air temperatures recorded in the indoor space of the four prototype houses during the period October 2011 to April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The blue dotted line represents the minimum value of the comfort temperature range for the summer period, which is 24˚C.

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4.3 The coldest period

Further graphs show in more detail the daily ambient air temperature variation during one of the coldest periods of winter 2011.

Ambient air temperatures fall below the winter minimum comfort threshold of 17˚C for 12 days in a row, from 15th - 26th December 2011.

The following table shows the difference between the winter minimum comfort temperature of 17˚C and the ambient air temperature values recorded in the four prototype houses during two of the coldest days of the winter. The minimum ambient air temperature is recorded in the prototype B (14.08˚C). The highest ambient air temperature is recorded in the prototype A (25.12˚C). Negative values show temperatures falling below the thermal comfort zone.

Nine negative measurements were recorded for prototype D, indicating that the house

was cold for a period of about 18 hours on the 22nd of December 2011; prototype B for 16 hours; prototype C for 14 hours and prototype A for only 12 hours.

These values indicate that thermal comfort is not achieved during the coldest period in the winter. The houses get quite cold from 7PM to 11AM. The reason prototype A is cold for the fewest hours is due to its capacity to absorb heat quicker. This may also cause the house to get hotter quicker in the morning. In the evening, we observe that prototype A stays warmer for a longer period before its ambient air temperature drops to the minimum values, which are comparable to those of the other prototypes. This phenomenon is interesting and appears to give more information about the thermal behaviour of the four prototype houses.

Fig. 13: This graph shows daily ambient air temperature values of the four prototype houses recorded in the indoor living space during the period December 10 to December 31 of 2011. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The red dotted line shows the maximum value of the comfort temperature range for both the summer and the winter period, which is 32 ˚C.

Table 2: The table shows the ambient air temperature values recorded in the four prototype houses from midnight of the 21st of December to midnight of the 22nd of December 2012. The values were recorded every two hours. The blue colour underlines values below the ambient air temperature comfort range of 17 ˚C. Values in orange are above the temperature comfort range of 17 ˚C. Minimum values were recorded in the prototype house B. Highest modulation values are recorded in the prototypes A and B.

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Fig.14: This graph shows daily ambient air temperature values of the four prototype houses recorded in the indoor living space during the period 10-31 December 2011. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the temperature values recorded in the prototype house D. The red dotted line shows the maximum value of the comfort temperature range of 32 ˚C.

Apparently, the metal sheet walls along with the corrugated roof tend to absorb more heat during the day and, than, release it during the night. This may keep the house warmer for a few hours longer than in the other prototypes.

If we were to consider only maximum ambient air temperature values, we would observe the following relationship between the four prototypes, where A>B>D=C. However, if we focus on the length of the period in which ambient air temperatures drop below the comfort range, we observe that prototype D is the coldest during most of the day, followed by prototype B, and the relationship could be rewritten this way, D<B<C<A. However, this is based on assessment of thermal data only, without information on patterns of occupancy or activity, or other factors which might affect the ambient air temperatures in the house, such as heating, cooking etc.

4.4 The hottest period

This graph shows more into details the daily ambient air temperature variation during one of the hottest period of the summer of 2012.

Ambient air temperatures start overtaking the summer maximum comfort threshold of 32 ˚C from the 10th of April 2012.

In the following table are reported the difference between the summer maximum comfort temperature of 32 ˚C and the ambient air temperature values recorded in the four prototype houses during April 22nd, which has been the hottest day of the observation period.

Negative values show ambient air temperatures falling within the thermal comfort zone, whilst positive values show ambient air temperature falling over the temperature comfort zone threshold of 32 ˚C. The highest maximum ambient air temperature is recorded in the prototype A (41.1 ˚C). The lowest maximum ambient air temperature is recorded in the prototype C (37.08 ˚C). The golpata leaf roof prototype seems to perform better than the other prototype houses during the hot period.

Furthermore, five positive measurements in a row have been recorded for the prototype C, indicating that the house had been overheated for a period of about 10 hours on the 22nd of April 2012, whilst the overheating for the prototype A,B and D lasted for 12 hours.

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The golpata leaf roof prototype records the lowest maximum ambient air temperature values and its ambient air temperature stays above the comfort range for the shortest period of time during the day. On the basis of these observations, golpata leaf roof prototype thermal performance seems to perform better than the other prototype houses; nevertheless it doesn’t succeed in keeping ambient air temperatures within the comfort zone. In the following graph, it is possible to visualize what has just been mentioned in the above paragraph.

4.5 The outdoor space

The ambient air temperature values in the outdoor space are shown in the following graphs.

Table 3: The table shows the ambient air temperature values recorded in the four prototype houses from midnight of the 22st of April to midnight of the 23nd of April 2012. The values were recorded every two hours. The dark yellow colour underlines values above the ambient air temperature comfort range of 32 ˚C. Values in light yellow are within the temperature comfort range. The lowest maximum values were recorded in the prototype house C. Highest modulation values are recorded in the prototypes A and D.

Fig. 15: This graph shows daily ambient air temperature values of the four prototype houses recorded in the indoor living space during the 22nd and 23rd of April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The red dotted line shows the maximum value of the comfort temperature range of 32 ˚C.


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Maximum ambient air temperature values of prototype A are considerably above the comfort limit of 32˚C for most of the period of observation. They drop within the comfort range only for few days during the winter. These values are remarkably higher than other ambient air temperature values recorded in prototype houses C and D, especially in the first 3 months of the observation period, where differences account for up to 10 degrees.

From January 2012 these differences start to decrease considerably. During the month of April we can actually see that the hottest ambient air temperatures are recorded in the prototype house D. The reasons of these changes in temperature differences among the four prototype houses are not clear. However, occupancy activities might have had an impact in changing thermal response of the prototype house, such as modification or adaptation of the building, which we might not be aware of.

Ambient air temperature values of prototypes C and D stay within the comfort range from November to the second half of February. Nevertheless, prototype D shows the lowest ambient air temperature values during the first 5 months October to February. Then, they get higher than those of prototype C, from March to April. Eventually, they overtake those of prototype A during the month of April. Data from prototype B is missing, because the sensor was removed at the beginning of the observation period, the cause of which is not known. The minimum ambient air temperature for the same period and deployment point are shown in the following graph.

In this graph, we observe prototype house C showing the highest ambient air temperature values during most of the period of observation, with special regard to the period October to December, where ambient air temperature difference can reach a few degree Celsius. These values do not differ much from those previously observed in the other deployment points.


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Fig. 18: Prototype house B situated between the road through the village of Shyamnagar and the river

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The aim of this analysis is to compare thermal performance of four prototype houses made of different combination of materials. There were limitations to the analysis, as discussed further on, given that no data could be gathered regarding occupancy levels and activities (cooking, heating, etc). Also, although this data was to be included, external ambient temperature data was not collected due to a failure in the local weather station.

Therefore, inevitably, assumptions have had to be made, but these are also described in the section on limitations of the research.

Thermal performance evaluation is made with daily maximum and minimum ambient air temperatures – the daily maximum temperature is the highest value for day time and daily minimum is the lowest value for night time temperature. The table below summarises the key findings for each prototype:

5 Discussion and Conclusions

Table 4: Summary of key findings for each prototype

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It can be observed from the table above that, in this study, the main weaknesses in terms of the prototypes’ thermal performance are issues of:

high maximum ambient air temperature values during the hot season, with variation depending on the building, and

low minimum ambient air temperature values during the coldest period of the winter

This indicates a possible direct relationship to external air ambient air temperatures without much modulation, especially in the cooler periods.

Different materials appeared to behave in very different ways with regards to their capability to absorb and release the heat. The two corrugated sheet metal roofs (Types A & B) appear to absorb heat at the very highest rate, whilst the golpata leaf roof (Type C) seems to absorb heat at the lowest rate. Clay tile roof performance (Type D) is in between the golpata leaf roof and the corrugated sheet metal.

With regards to the walls, the bamboo mat walls actually appear to a better material for allowing the living space to breathe and avoiding the overheating of the houses during the hot season, as we could observe comparing the thermal performance of both corrugated sheet metal roof prototypes A and B.

During the hot season, the golpata leaf roof (Type C) records the lowest maximum ambient air temperature values and its ambient air temperature stays above the comfort range for the shortest period of time during the day. On the basis of these observations, the thermal performance of the golpata leaf roof appears to be better than the other prototype houses.

During the winter, there seem to be no

considerable differences in minimum ambient air temperatures between the four prototype houses. In fact, the houses have been designed to maximise air flow in order to answer the need for ventilation during the hot months of the year, and therefore fail to keep the living zone warm during the winter nights, with ambient air temperatures dropping below the comfort range of 17 ˚C, sometimes reaching minimum values of 13-14˚C for up to 8 hours overnight.

However, the colder internal ambient air temperatures at night were for a period of approximately 2-3 weeks, whereas the warmer season lasts for approximately 8 months a year, in which case one could conclude that overheating may be more of an issue than being too cool. This does not however preclude good design that can do both, and further investigation into the inclusion of thermal mass and/or other materials in housing would be beneficial, to understand how winter performance could be improved. This may also have beneficial consequences for overheating in summer.

Research limitations

The main limitation of this study is due to the absence of external ambient air temperature data from the weather station. This made it impossible to compare internal ambient air temperature data from the monitored houses to local external ambient air temperatures, in order to assess with more precision their level of performance (eg ability to modulate external temperatures).

Further limitations come from the positioning of the data loggers inside the houses. The data loggers were placed very close to the surface of walls and roofs. They therefore may not have reflected exactly the internal ambient air temperatures perceived by the occupants. They may have been affected either by proximity to metal components of the buildings such as sheet metal walls, wood, each with different

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thermic behaviour, and also given that the surface temperature of a material can often be several degrees different to ambient air temperature.

Lastly, since data was only collected every two hours from the data loggers, the actual maximum and minimum ambient air temperature peaks may have occurred in between two consequent measurements and not been recorded, adding a limitation to the data. Data could have been collected over shorter periods, but would have necessitated more frequent visits to download and also generated a huge quantity of very specific data, which was not considered necessary in order to gain an overall picture of the prototypes’ performance.

It is also worth mentioning that a certain degree of uncertainty of this analysis comes from lack of information on levels of occupancy and the activities carried out by the occupants during the monitoring period, such as:

opening and closing doors and windows at different times of the day and night, or other adaptive means to cool the house

cooking or other activities that may have increased internal ambient air temperatures

any structural modifications or adaptation of the buildings which may have modified their thermal response (such as Types C and D which were painted black at some point during the monitoring period)

the effect of the orientation of the houses and their exposure to direct sunlight

the impacts of shading such as nearby trees or vegetation

Given the limitations mentioned, certain assumptions were made.

The thermal comfort range of minimum 17 ˚C (in winter) to maximum 32 ˚C (in summer) was accepted (sources: Practical Action Bangladesh and Ahmed & Rashid)

Even though actual minimum and maximum internal ambient air temperature events may have occurred at times between data intervals, the data gathered were accepted for the purposes of this analysis

It was assumed that measurements were taken at identical times, although this was not in fact the case, as the resetting of the data loggers each month after downloading occurred at different times between the four houses. This may have had a minor impact on the comparative data

It was assumed that changes in temperature are the result of construction materials performance, although they may in fact have been as a result of occupant behaviour, or at least influenced by this. However, as discussed, it is not possible to understand how this may have affected the data, without further information on occupant levels and activities

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Fig. 19: The thermal performance of the golpata leaf roof appears to be better than the other prototype houses.

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Design and construction

Comments on this research (operational)

As previously discussed in the limitations of this research, it would have been beneficial to ensure that:

Data loggers should be placed in comparative position with regards to the orientation of the house and their proximity to the wall and roof surfaces with more attention paid to ensure external loggers couldn’t be easily removed

Data loggers should be timed to gather data exactly at the same time in both all the prototype houses and the weather station

External weather data should be gathered and downloaded monthly Information on occupant behaviour and levels of occupancy should be collected and documented

Further research (strategic)

Opportunities to improve understanding through further research, such as:

Explore potential for the reduction of summer overheating, through the introduction of thermal mass in walls, eg clay and lime plasters and renders

Principles of approach

Above and beyond the immediate technical data, other more fundamental issues can also affect research programmes such as this and are the subject of study elsewhere in this report.

They can include issues such as:

Ensuring that all partners have a shared understanding of the purposes of the research

Involvement of occupants and local community in the project (ownership)

Good quality, regular and mutual communication between occupants, community, project partners and researchers

Research projects inevitably have their limitations. However, to maximise the effectiveness of research, it is essential to be really clear about the intended aims and outcomes of the research from the start. This is so as to help design an effective research programme, with appropriate methods and methodologies, means of data collection and analysis, and an understanding of how the research will be applied in practical terms, and by whom. This assumes in turn an understanding of the core values of communication, ownership and inclusion. This can be challenging, but is essential if research projects are to be realistic and useful to those whom they are designed to serve.

6 Recommendations

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Fig. 20: At the end of the rainy season, Satkhira district, 2009

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ASPIRE User Manual - A Sustainability Poverty and Infrastructure Routine for Evaluation. ICE R & D, Engineers Against Poverty, Arup.

Da Silva, J. (2010) Lessons from Aceh. Practical Action Publishing, Rugby.

Da Silva, J., Brunel International Lecture: Shifting Agendas - From Response to Resilience – the role of the engineer in disaster risk reduction. Institution of Civil Engineers, London.

Ferretti, S. (2009) Evaluation of the Disaster Response Programme (Cyclone SIDR). Action Aid, Johannesburg.

Ferris, E. & Petz, D. (2011) A year of living dangerously: a review of natural disasters in 2010. The Brookings Institute: London.

Flinn, B. and Beresford, P. (2009) Post-Sidr Family Shelter Reconstruction. DFID.

Koenigsberger, O. H. et al (1973) Manual of Tropical Housing and Building Design, Part I. Orient Longman, Andhra Pradesh.

Sriraman, V. (2008) Cyclone SIDR 2007 BRAC’s Rehabilitation Programme funded by Oxfam Novib and Oxfam America: Monitoring of Shelter project. RedR India.

UNDP (2008) Lessons Learnt Workshop on Sidr 2007 Emergency and Early Recovery Response. UNDP, DMB.

UNDP Bangladesh (2009) Post-Cyclone Sidr Family Shelter Construction in Bangladesh – Documentation of Plans and Processes. UNDP Shelter Working Group Bangladesh 2007-2009. UNDP Bangladesh, Dhaka.

UNISDR (2011) Hyogo Framework for Action 2005-2015: Mid-term review 2010-2011. UNISDR, Geneva.

Bibliography

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Websites

Bangladesh Meteorological Department http://www.bmd.gov.bd

Engineers Against Povertyhttp://www.engineersagainstpoverty.org/major_initiatives/aspire.cfm

REDR – Register of Engineers for Disaster Reliefwww.redr.org

Practical Action Bangladeshwww.practicalaction.org.bd

UNDP Bangladeshwww.undp.org.bd

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Appendix

Fig. 9: Annual maximum ambient air temperatures recorded in the upper space of the four prototype houses during the period October 2011 to April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The blue dotted line represents the minimum value of the comfort temperature range for the summer period, which is 24˚C. The red dotted line shows the maximum value of the comfort temperature range for both the summer and the winter period.

Fig. 10: Annual minimum ambient air temperatures recorded in the upper space of the four prototype houses during the period October 2011 to April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The blue dotted line represents the minimum value of the comfort temperature range for the summer period, which is 24˚C.

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Fig. 11: Annual maximum ambient air temperatures recorded in the indoor space of the four prototype houses during the period October 2011 to April 2012. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The blue dotted line represents the minimum value of the comfort temperature range for the summer period, which is 24˚C. The red dotted line shows the maximum value of the comfort temperature range for both the summer and the winter period, which is 32 ˚C.


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Fig. 13: This graph shows daily ambient air temperature values of the four prototype houses recorded in the indoor living space during the period December 10 to December 31 of 2011. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the ambient air temperature values recorded in the prototype house D. The purple dotted line represents the minimum value of the comfort temperature range for the winter period, which is 17 ˚C. The red dotted line shows the maximum value of the comfort temperature range for both the summer and the winter period, which is 32 ˚C.

Fig.14: This graph shows daily ambient air temperature values of the four prototype houses recorded in the indoor living space during the period 10-31 December 2011. The red line shows the ambient air temperature values recorded in the prototype house A. The blue line shows the ambient air temperature values recorded in the prototype house B. The green line shows the ambient air temperature values recorded in the prototype house C. The yellow line shows the temperature values recorded in the prototype house D. The red dotted line shows the maximum value of the comfort temperature range of 32 ˚C.

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reset bangladesh - post occupancy technical evaluation

Documents

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