Cardiff University : AHU - Low Energy Air Filter Case Study
Cardiff University - ASSL Building AHU LEAF Case Study
Cardiff University is well known for its Welsh School of Architecture and their study program into
the sustainable use of energy in buildings. The EU funded iSERV project forms part of the
university work in this area and the iSERV working group is tasked with constructing an European
wide database profiling building energy use. The focus of the project is to gather monitored data
on Heating, Ventilating and Air Conditioning systems energy use in buildings.
Air filtration was identified as a significant Energy Conservation Opportunity(ECO) and Camfil
building IAQ and HVAC energy consultant Peter Dyment was invited to sit on the project Steering
committee by Professor Ian Knight of Cardiff University, who is heading up the project team.
Camfil's Adrian Bell was already working with Keith Sims of the Estates department on the site to
improve HVAC plant efficiency. The work being done to optimize the air filters in the Arts and
Social Science Library building Air Handling Units demonstrated real energy savings. The results
are shown below and form the basis of this case study.
The ASSL building has two AHU systems of the same size and duty running side by side and a
trial was conducted on these AHU's using the existing air filters in one unit and in the other were
fitted Camfil Low Energy Air Filters (LEAF) with high performing micro-fibre glass HiFlo medium.
The variable speed drives on the AHU fan motors were locked into the same air volume flow rate
for each system and the monitored results can be seen above. After the first few months of the
test the results indicated that the South AHU was using less energy but investigation identified a
wiring fault on the motor was causing a faulty reading. This was corrected and the trial resumed. It
can be seen that the Low Energy Air Filters reduced the fan motor energy consumption by 21%
over the following period of the test. During the same period the particle stopping efficiency for the
filters was also tested and an improvement of 21% at 0.4 micron dia. size was achieved by the use
of Low Energy Air Filters from Camfil. These results giving a 21/21 improvement show that it is
possible to both reduce energy consumption and improve air cleaning efficiency. Other benefits
include reduced maintenance costs, reduced disposal costs, longer filter life due to a higher dust
holding capacity. The HiFlo micro fibre filter medium shows higher consistent life particle stopping.
Optimizing AHU air filters by used of Camfil Low Energy Air Filters is the first step in a logical
progression of measures to reduce energy use and other running costs in Air Handling Unit plant.
The payback time for improving air filters is short, typically only a few months.
Other actions such as checking filter mountings integrity for sealing, use of effective clean air
intake screens, cleaning of coils and other heat exchangers, checking and reducing damper and
duct leakage and their working condition can all give payback times of less than a year. After this
process use of variable speed drives is a key measure and to maximise the VSD savings a control
strategy that employs time clocking, zoning and demand led sensor parameters should be utilised.
Large building HVAC systems consume a huge share of the energy consumption in the UK and
around the rest of Europe it presents a major opportunity for energy efficiency savings with low
cost to implement and short payback times. These results were presented at the REHVA meeting.
Find out more and see further case studies. www.lowenergyairfilter.co.uk www.camfil.co.uk
www.keepthecityout.co.uk (The Cardiff University AHU trial report was produced by Adrian Bell)