1

Energy & Indoor Environmental evaluation of a student residence in Ireland - Results

and lessons learnt after two years monitoring

Hernandez, Patxi1; Lennon, Donal

2; Brophy, Vivienne

3

1 TECNALIA Research & Innovation, Derio, Spain

2 UCD Earth Institute, Dublin , Ireland

3 UCD School of Architecture, Dublin , Ireland

Abstract: This paper analyses the results of the monitoring during 2012 & 2013 of the first student

residences to be constructed to Passivhaus standard in Ireland. The monitoring program included

whole building energy performance and detailed energy and indoor environment parameters for 16

studio-bedrooms. Equipment electricity with circa 450 kWh per year per student is the highest energy

use, followed by hot water with 420 kWh per year, heating with circa 380kWh and lighting with 90

kWh per year. Indoor environment conditions such as temperature and CO2 concentration present a

very large variation between the users, showing the importance and variability of the personal

behavior. Potential improvements on the energy performance should focus on engagement of building

users on energy efficient behavior, as technological aspects on the building are well implemente and

personal plug-in equipment and hot water use represent around 65% of the final energy use.

Keywords: Student accommodation, passive house, occupant behavior, monitoring, energy

performance

Introduction

Heating has traditionally been the major energy use in Ireland, despite the temperate maritime

climate. In 2011, about 69% of the final energy use in Irish housing stock was to provide

space heating, with an average of about 15,000kWh final energy use per standardized

household of 4 persons for heating. Water heating at 16% of the final energy use is the second

largest energy load, followed by plug-in equipment, lighting and cooking [1,2].

The progressive implementation of more stringent building regulations has gone a long way

towards tackleing this issue of building energy performance, particularly through better

insulation standards and more efficient heating appliances. A typical house of 100 square

meters complying with 2008 Building Regulations Part L TDG Conservation of Fuel and

Energy could have as low as 40 kWh per square meter per year, however there is still room

for further reduction of the heating demand.

This paper presents the results of an energy monitoring program during 2012 and 2013 of a

student residence built to PassivHaus Standard, further lowering space heating demand with

the objective to reach values of 15 kWh per square meter per year.

Description of the building

Roebuck Hall 2 is the most recent addition to the student accommodation complexes on the

Belfield Campus of University College Dublin, Ireland´s largest university. The building was

2

completed in 2010, and comprises twelve apartments over six floors. Eleven of the apartments

comprise twelve individual rooms, a communal kitchen, a recreation room and two dedicated

study areas. Apartment 2 on the ground floor consists of three individual living spaces plus a

kitchen and recreation space with wheel chair access. Each of the individual rooms contains a

modular bathroom unit of wet room arrangement, a wardrobe/ storage area and a

living/sleeping area with bed, desk and chair.

These units are the principal living areas for students throughout the year. UCD students have

sole access during the academic year. During the months of June, July and August apartments

are rented or leased to foreign exchange students or participants on foreign language courses

in Dublin. Thus the building is occupied almost constantly all year round.

The building is constructed of GGBS concrete cross-wall, stair core and floor structure, with

lightweight unitized metal-framed external wall panels to all student rooms, which create an

airtight façade. All concrete walls are insulated externally with foil-faced and taped PIR

boards and with external laminated cladding boards. The student rooms have triple-glazed

windows, foam sealed and taped under panels. While openable, they have an interlock

control, closing off the local heating circuit when the window is opened. The project makes

extensive use of renewable or recycled materials, such as acetic-acid modified timber,

recycled sorghum strand board, water-based paints, linoleum floor finishes and GGBS cement

based concrete.

Heat recovery ventilation is provided through two central rooftop heat-wheel air handling

units. Domestic hot water demand is partially supplied by two drain-back flat plate solar

water heating systems on the roof. Rainwater is harvested from the building roof and used for

toilet flushing.

Figure 1. Roebuck Student Residence.

3

Monitoring Strategy

Fitting of sensors within the building to perform the monitoring was carried during the

construction stages. The measurement instrumentation installed allows the examination of

energy consumption and comfort levels at both individual room and whole building levels.

A total of sixteen individual rooms within the twelve apartments were selected and

instrumented in order to monitor the various energy loads and indoor air quality. These rooms

were selected on the basis of their position and aspect within the building envelope. This

approach was adopted to allow the researchers to assess the impact of room location within a

building envelope on energy consumption for that room, for example, its location along a

corridor or the impact of direct and indirect solar gains, the number of outside walls or the

affects of height above ground.

Each of the monitored rooms is fitted with a ceiling-mounted sensor to measure relative

humidity, ambient temperature and carbon dioxide. Space heating loads are monitored using a

flow meter and two temperature sensors installed in the heating circuit next to the radiator

located behind the headboard. Energy required to provide domestic hot water to each room is

measured using a flow meter and a temperature sensor installed in the hot water service

located in the riser next to the room. The low temperature is measured by a sensor installed in

the cold water supply to the clorifier located in the plant room at roof level. Plug-in

equipment and lighting loads are measured in the corresponding electrical supply panels.

Data from each room is logged every 5 min on a data logger connected to the Ethernet

network and located in the services riser next to the room.

Monitoring results and discussion

Figure 2 shows typical results output for a sample room for a cold winter week. It can be seen

how internal temperature is quite stable between 19 and 21ºC, heating use is fairly constant at

about 200W, and how water use is concentrated in few hours of the week.

Figure 3 shows similar results for a summer week, showing internal temperatures between 21

and 23 degrees for that particular room.

Figure 2. A winter week for one studio-bedroom. Figure 3. A summer week for one studio-bedroom.

4

Figure 4 shows the different end-uses in kWh per year for the monitored rooms, with the

average consumption indicated. It can be observed that, the main energy load is plug-in

equipment with 450 kWh per year , quite different to what can be observed in typical housing,

followed by hot water demand, with 450 and 420kWh per year in each case for each studio-

bedroom. Space heating is only the third largest energy load at around 380kWh per year,

which corresponds to circa 25 kWh per square meter per year. The lighting load is

approximately 90 kWh per year per studio-bedroom. The large variability between the users

can already be observed in figure 4. Although the variability applies to all the energy uses, it

is particularly noticeable in the heating and hot water use where individual habits, preferences

and behavior can account for large differences on the final energy consumption across the

individual studio bedrooms.

Figure 4. Average yearly energy use in each of the monitored apartment for the different end-

uses.

Observing the montly energy use for a year (2013), consumption is at the lowest value during

the summer months, and particularly during July. The graph also shows how hot water is the

largest energy demand for most months during 2013, followed closely by plug-in equipment

energy, which is the main electrical use. This trend changes in the winter months when space

heating is generally the energy demand as would be expected.

0

200

400

600

800

1000

1200

1400

Hot Water Load (kWh) Space Heating(kWh) Lighting Electricity (kWh) Equipment Electricity (kWh)

kW

h /

ye

ar

1_03 1_06 1_09 4_04 4_057_01 7_03 7_06 7_09 8_068_07 11_01 11_03 11_06 11_0812_06 AVERAGE

5

Figure 5. Average monthly energy consumption for the monitored studio-bedrooms during

2013

Similar trends can be observed between the final energy uses for hot water, lighting and

electricity. Taking into account the influence of the outdoor environment on these final energy

uses is generally small; it could be argued that the trends on these results can be used as an

indication of occupancy during the different months, for example, students may be on

vacation or remote field work, leaving the studio-bedrooms vacant for a number of days

during these months.

For space heating demand, the correlation with the occupancy rate also exists, but the

influence of the outdoor environment needs also to be taken into account. In Figure 6 it can be

observed there are lower heating energy use values during the summer months, which can be

partly explained with the observation of average outdoor and indoor temperatures. It is

obvious that heating during summer is scarcely used as indoor temperature can already be

maintained at comfortable levels without the need of space heating.

6

Figure 6. Average heating use and measured indoor and outdoor temperature during 2013.

Indoor temperatures have been maintained generally at comfortable levels throughout the

monitored bedrooms for the two years. Despite some increase in temperature during daytime

in summer, the number of hours over 28 ºC were not more than 1% of annual hours in any of

the monitored studio-bedrooms, and temperature during nightime were generally reduced

depending on the individual operation of the bedroom windows.

Conclusions

Overall energy use in the monitored student residence shows the building performs well as a

low energy building, with a total energy use of circa 36 kWh of electricity per square meter

per year, and circa 53 kWh of thermal energy per square meter per year. These values are

considerably lower than good practive values for similar buildings using the CIBSE

benchmarks [3], which are set to 45 kWh of electricity and 200 kWh of thermal energy.

The monitored heating demand is much lower than comparable buildings in Ireland, at just 25

kWh per square meter per year. However, the real performance does not match the design

goal of 15 kWh per square meter, likely due to students’ preferences and behavior in

operating the heating sytem and window opening. To ensure a correct operation of the

heating, emphasis has to be put on the introductory briefing to new students moving into the

residence.

The results also show that, in contrast to the typical building energy consumption in Ireland

and due to the large reduction in heating energy requirement, electricity use for plug-in

equipment is the largest energy load, consuming about 450 kWh per year. This is followed by

the hot water demand at about 420 kWh per year. In view of these results it is important to

note that there are currently few technical measures that can be applied to further reduce

building energy load from a building design perspective, as they depend mostly on the

preferences and habits of the building occupant. Potential measures are in the case of this

7

building, to engage the students in energy saving behavior through student competitions or

gamification experiences [4]. Simple measures such as displaying energy use information in

real time can also lead to energy savings in university student accommodation [5].

Acknowledgements

We would like to thank the Sustainable Energy Authotity of Ireland (SEAI) for funding the

UCD Energy Research Group in carrying out this monitoring program.

We would also like to acknowledge the support of UCD Earth Institute throughout this

project.

References

[1] Sustainable Energy Authority Ireland (2013)- Energy in the Residential Sector - 2013

Report

[2] ODYSSEE (2014). Unit consumption per dwelling by end uses: space heating, water

heating, cooking. The Odyssee database is available at http://www.odyssee-indicators.org/.

[3] The Chartered Institution of Building Ser-vices Engineers. (2008). CIBSE - TM 46 -

Energy Benchmarks.

[4] Brewer, R. S., Lee, G. E., Xu, Y., Desiato, C., Katchuck, M., & Johnson, P. M. (2011,

May). Lights Off. Game On. The Kukui Cup: A Dorm Energy Competition. In Proceedings of

the CHI 2011 Workshop Gamification: Using Game Design Elements in Non-Game Contexts.

[5] Chiang, T., Mevlevioglu, G., Natarajan, S., Padget, J., & Walker, I. (2014). Inducing

[sub] conscious energy behaviour through visually displayed energy information: A case

study in university accommodation. Energy and Buildings 70, 507-515.