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UCL Institute for Environmental Design and Engineering


Blogs from UCL IEDE Staff and Students


Energy performance gap assessment and Post Occupancy Evaluation of UCL Cruciform Library / Main outcomes

By ucqbvko, on 12 November 2015

This update includes the main results of my dissertation research regarding UCL Cruciform Library. The most important outcomes of the methodology used, including hygrothermal monitoring, occupant comfort surveys, dynamic thermal modelling and Carbon Buzz are presented.

After the monitoring period (6-20/7/2015), the results extracted from the Hobo data loggers were analysed. The most important findings are summarized below:


Hygrothermal monitoring plan

the average internal temperature in the majority of spaces (excluding computer clusters – average of 24 degrees Celcius) fluctuates between 21 and 22 degrees Celcius, really close to the external one (average of 18.9 degrees Celcius).

the average internal relative humidity in the majority of spaces fluctuates between 51 and 55%, falling inside the acceptable range of 40-70% according to CIBSE Guide A (2006).


Average temperature (degrees Celcius) recorded in each space of Cruciform hub


Average relative humidity (%) recorded in each space of Cruciform Hub

Regarding the BUS survey that was conducted during the week 20-27/7/2015 (sample of 56 students), the most important issues are summarized below:

  1. internal low temperatures
  2. natural ventilation not existent at present
  3. need for more working spaces, personal computers and facilities for practicing
  4. some spaces (mainly the entrance) are noisy
  5. lack of natural lighting

Average of students’ answers regarding 6 areas of interest (Scale 1-7)


Average of students’ answers regarding comfort during summer (Scale 1-7)

Dynamic thermal modelling (IES VE software) / Design energy performance

The model was simulated on IES VE software, trying to make it as similar as possible to what the designers had proposed.

Meter readings _ Data obtained from Carbon Culture Platform / Actual energy performance

The actual energy consumption of the library was calculated using data from Carbon Culture Platform resulting in a value of 765.3 MWh.

Estimation of the performance gap

As demonstrated in the graph below, the actual energy performance is 59% higher than the estimated one.


Estimation of the performance gap


IES VE model

Performance gap factor (actual energy use / design energy use) : 2.49


CARBON BUZZ Platform – Comparison to CIBSE TM46 benchmarks

Carbon Buzz is a collaborative research platform that was launched by the Royal Institute of British Architects (RIBA) in collaboration with the Chartered Institution of Building Services Engineers (CIBSE) in 2008 (http://www.carbonbuzz.org/), enabling designers to compare calculated and real energy use for their buildings. This initiative emerged from the need to manage CO2 emissions from buildings.


Data obtained from Carbon buzz platform


Actual and design data compared to CIBSE TM46 benchmarks


Performance gap factor change for some case studies examined

Next update….

Conclusions of the research

Recommendations to UCL Estates

Further research

Vasiliki Kontopoulou

Supervisor: Anna Mavrogianni

In collaboration with

UCL Estates: Joanna Marshall – Cook

Green UCL: Alex Green


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