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With energy use in Buildings responsible for approximately
55% of the CO2 released into the atmosphere, and CO2 a major
contributor to global warming, the Department of Education
and Science (DES), out of a commitment to the development
of low energy educational buildings, have designed and constructed
two low energy schools, in Tullamore, county Offaly, and Raheen,
county Laois, to research the latest construction techniques
and systems that have a potential to meet these aims.
It is hoped that the lessons learned from the construction
and monitoring of these buildings will assist in reducing
the energy usage of future school designs.
Sustainable Energy Ireland has provided part funding of the
buildings’ additional energy saving features and the
costs of monitoring the buildings. A third school is at the
planning stage.
The
environmental impact of the Gaelscoil and Raheen school buildings
throughout their life will be a fraction of a traditional
building’s construction and the occupants will have
the knowledge that they are working within a building that
is responsive to the environment. Working in a low energy
building has additional benefits such as improved comfort
associated with the increased daylight levels and availability
of user controllable natural ventilation. These schools will
also provide an ideal opportunity for the students to learn
about the responsible building technologies that will shape
their future.
The Department of Education and Science’s Planning and
Building Unit team including Senior Architect Frank Lewis
and Senior Engineer John Dolan were keen that the objectives
for the completed schools were to provide quality educational
facilities appropriate to their users’ requirements.
The project not only encompasses low energy design, but also
involves providing feedback to the Department on the schools
and their systems’ operation, and creating the schools
as life learning tools, that enable the buildings to be active
learning resources for energy conservation and sustainability
for the pupils and teachers.
Through the use of advanced energy and daylight simulation
software, the design team were able to gain a better understanding
of how the buildings would react with their environments,
and understand how these reactions can be used to improve
the internal environment while minimising energy consumption
GAELSCOIL AN EISCIR RIADA, TULLAMORE, CO. OFFALY
Project
Brief
The brief for this building was to provide an eight-classroom
primary school using considerably less energy in its operation
than a traditional school, and showing an appreciation of
sustainability in its construction. The school is provided
with a detailed monitoring system that will provide information
vital to the understanding of energy and water use in school
buildings.
Program
The project is complete and in use. The building and its systems
will be monitored in detail over the following years.
Meeting the Brief
The design aimed to use less than 20% of the energy used by
a similar school built to current good practice standards,
and to generate zero CO2 in the operation of its services.
When low energy buildings are considered, it is normal to
look to improved thermal insulation levels, but there are
many other factors that effect energy usage—and in some
cases, even more dramatically than insulation levels.
For instance, heat loss due to unwanted air leakage from a
building (known as infiltration) is typically a major source
of energy wastage, particularly when unoccupied overnight.
Heat slowly leaks out and more energy is needed to bring the
building back up to temperature the following day. In addition
to heating the school during winter, energy is also used for
water heating and lighting the school.
While consideration of energy use during the school’s
operation was vital, some consideration was also given, both
to the energy used during the building’s construction
and to selecting materials that are responsive to the environment.
Passive Solar Architecture
The building plan was arranged with most of the windows facing
the sun early in the morning to allow maximum benefit to be
taken from the free heat provided by the sun.
Improved Insulation Levels
The thermal insulation levels specified were double those
required by the Building Regulations, to reduce the energy
escaping from the building fabric.
Reduced Infiltration Levels
Most buildings are constructed with insufficient consideration
given to stopping air leakage through the structure. This
building has had its air tightness tested by forcing air into
the school under pressure and measuring the leakage. Leakage
routes were also tracked using smoke tests.
Attention to Materials Selection
A lightweight timber frame structure was specified with attention
paid to the selection of materials to minimise the environmental
impact of construction.
Natural Ventilation
Particular attention was paid to ensuring that adequate natural
ventilation was available and Building Design Partnership
Consulting Engineers carried out detailed simulations to optimise
distribution of ventilation air within the classrooms.
Natural Day Light
If natural daylight is provided to all classrooms, then the
energy consuming lights can be turned off for most of the
year. Careful design of the windows, using advanced computer
calculation methods has insured that the correct daylight
levels are achieved.
Artificial lighting should not be required in classrooms for
at least 80% of the year during daylight hours. Advanced lighting
controls have also been used to make sure that lights will
not be left on when they are not required.
Rain Water Recovery System
Rainwater is collected from the roof of the building and used
for flushing toilets.
Monitoring
An advanced building management system has been installed
to gather information on the building performance and to assist
the occupants in adjusting the controls to ensure minimum
energy wastage.
Advanced Heating System
A ground source heat pump was selected as the heating system
for the building in order to minimize CO2 emissions. There
are a number of pipe loops laid beneath the ground outside
the building and water is passed through the pipes to a heat
pump. The heat pump moves heat from the ground into the building
and the ground effectively acts like a huge solar collector
for the building’s heating system.
An under floor heating system is combined with the heat pump
as it allows a low flow temperature from the heat pump. The
under floor heating system acts like a storage heater and
allows the heat pump to be operated during the night on night
rate electricity. In this case, the electricity to run the
heat pump and the rest of the building will be taken from
a group wind scheme, therefore generating no CO2 in the buildings
operation. The performance of the heating system will also
be carefully monitored.
Educational Life Learning tool
The project incorporates a touch screen display positioned
near the schools entrance that is linked to the BEMS and will
provide the children and visitors to the building with energy
and environmental information relating to the building. This
commission includes the development of a cartoon character
that is used on the screen to encourage the children to learn
about the building construction and its day-to-day energy
use. The touch screen system is also connected to the ICT
system and can provide BEMS information to any computer in
the school for classroom based project work.
Gaelscoil Project Team Members
Technical
Manager
Martin Heffernan
Department of Education and Science.
Architects
and Design Team Leader:
Frank Lewis
Pat Kelly
Department of Education and Science.
Senior
Engineer and Energy Project Manager:
John Dolan
Department of Education and Science.
Mechanical
and Electrical and Energy Consulting Engineers:
John Doyle and Chris Croly
Building Design Partnership
Quantity
Surveyor Engineers:
Stephen J Ahern
Structural
Engineers:
Ken McGauran
Nicholas O’Dwyer + Partners
Main
Contractor
Portcastle Builders
Mechanical
Sub Contractor
Glow Heating Ltd
Electrical
Sub Contractor
John Fletcher Ltd
Timber
Frame Sub contractor
ITEC Timber Frame
RAHEEN
NATIONAL SCHOOL, RAHEEN, COUNTY LAOIS.
Raheen
National School is a new three-classroom school near Portlaoise
designed with sustainability in mind. The building promotes
low energy use and good daylighting levels. The three classrooms
all face south, with all support spaces facing other orientations.
The building is taller to the south, with mono-pitched roofs
and ceilings to give high spaces and more standard ceiling
heights in support areas. The tilted ceilings face clerestory
and other south facing windows. Circulation spaces are also
principally lit by daylight from above.
The school is of timber frame construction, which made it
possible for thicker insulation to be used than in conventional
cavity wall constructions. The wall insulation is of cellulose
(recycled newspapers), which were sprayed into place once
the building was water-tight. Analysis examined the advantages
of a heavy structure against a light one, and the lightweight
structure was found to be more beneficial, mainly due to the
shorter usage hours and days of the school compared with other
institutional buildings. It was found to be better to allow
the school to heat up quickly, and benefit from solar gain
quickly, rather than have a heavy inner wall leaf which would
only help store the solar gain up until after the students
had left for the day. The lightweight structure also meant
that the school would be quick to respond to its heating system.
The walls have a U-value of 0.23 W/m2/K, well below the Regulations
Elemental Method figure of 0.45 W/m2/K. Likewise the roof
U-value is 0.15 W/m2/K, compared with 0.25 in the Regulations.
Glazing is double glazed, with a low emissivity coating.
Overy and Associates noted that in well-insulated buildings,
a large part of the heating energy will be used to heat air
entering the building due to infiltration. As part of the
projects’s architectural specifications, they recommended
that an air leakage rate be specified and a test performed
to verify the school’s air-tightness. An “air
leakage index” of 5 m3/hr/m2 at 50 Pascals pressure
was specified.
Pressure testing was executed, using specialist equipment
provided by Overy and Associates. The first test showed leakage
rates above the specified value. During the smoke test, the
building was filled with artificial smoke using a smoke generator,
and pressurised. The locations where smoke emanated from the
building demonstrated where the predominate air leakage paths
occurred. The subsequent pressure test met the intent of the
specifications.
Some feel a dichotomy exists in pressure testing schools.
On the one hand, a leaky school will waste energy. On the
other hand, a school requires permanent background ventilation
to reduce the risk of condensation. Overy and Associates argue
that no dichotomy exists. The permanent background ventilation
openings are provided in known amounts. The purpose of the
pressure test is to find unknown leakage paths and seal them.
Rainwater is collected from the roof for sanitation and filtered
before being stored in a purpose built storage tank. In dry
weather, the tank is allowed to become almost empty at which
point automatic controls maintain a minimum level of water
by topping up with mains water. The quantity of water delivered
to the toilets and the quantity of mains make-up water is
recorded hourly by a building management system linked to
the Department of Education and Science’s engineers
in Tullamore, Co Offaly. The results can ascertain the efficiency
of the collection system, and obtain insight into the quantity
of water used in toilets in national schools. The logic for
using rainwater in toilets is strong. By using it in toilets
the burden on both the local mains water delivery system and
storm sewage disposal system is reduced. A detailed simulation
of the rainwater collection system was carried out and a computer
model was developed for the project, which estimates hourly
demand and available rainwater through the school day. Simulations
were carried out for various tank sizes, and an optimum size
chosen.
Energy
A sophisticated dynamic thermal model of the school was created
using a computer program from Simulation Research Group of
Lawrence Berkeley National Laboratory in Berkeley, California.
Over 150 different permutations and combinations of building
and systems configurations were simulated, and capital and
running cost differences compared. From these, recommendations
were made. Many related to the architecture, with a view to
reducing the need for energy by passive solar heating, natural
lighting, and so on. Numerous constructions with different
insulation types were studied, including the impact of floor
carpeting. Building orientation was studied.
Heating
Before choosing a system, comparisons were carried out of
the different mechanical and electrical systems such as:
• oil fired space heating with radiators, versus ground
source heat pumps coupled with underfloor heating
• modular boilers using between 1 and 4 boilers
• heat pump water heating, versus centralised oil fired
domestic water heating, versus decentralised electric domestic
hot water heating
• studies on weather compensating controls
The
studies concluded that in the absence of natural gas, conventional
oil fired boilers with radiators would offer the lowest CO2
emissions. One boiler is used and it also heats the domestic
hot water.
Lighting
High fluorescent lighting is used throughout the school. All
linear lamps are equipped with electronic ballasts with dimmable
versions used where required. For exterior lighting, compact
fluorescent and high pressure sodium lamps are used.
Lighting controls
In order to reduce the level of artificial light when there
is sufficient natural light, automatic photocell-controlled
dimming and switching of luminaires has been installed. The
fittings near windows are fitted with dimmable electronic
ballasts whose output is controlled by a photocell mounted
on the ceiling. Separate light switches are provided for the
normal lights and the dimmed lights. Manual switching of lighting
in response to daylight was chosen, after several schemes
involving automatic variable dimming in response to daylight
were considered.
In the corridor and lobby, photocells are used to automatically
switch the lights on when the natural lighting level drops
below 150lux. The corridors are so well lit with skylights
that the lights will only come on during the very dullest
of days. Neon indicators are provided on the switches to serve
as a reminder to switch the circuits off at night.
In storerooms lights with integral infra-red presence detectors
are installed. No wall switch is provided for these lights,
making it impossible for them to be left on when the room
is unoccupied.
Exterior lights for safe entry and egress are switched on
by a photocell and off by a timer. This ensures that they
only come on when required at dusk but that they do not remain
on all night. Security lighting is provided by floodlights
with PIR sensors.
Roofing
Selection of materials was considered in relation to achieving
a balance between the ecological, energy efficiency and practical
function of a roofing material. The roof system, which was
also selected for the Gaelscoil, offered a lightweight green
roof option which enhanced the insulation performance of the
build-up, has a low embodied energy, contributes continuously
to the processing of CO2 gases through photosynthesis and
is used as a specific learning tool for the pupils through
supporting micro-ecosystems. The seddum blanket also offers
further facilities of contributing to rainwater attenuation
and providing external noise absorption.
Raheen
Project Team Members
Technical
Manager
Martin Heffernan
Department of Education and Science.
Architects and Design Team Leader:
Frank Lewis
Pat Kelly
Department of Education and Science.
Senior
Engineer
John Dolan
Department of Education and Science
Main
Contractor:
Frank Murray & Sons Ltd
Consulting
Engineers:
Muir Associates
Quantity
Surveyor:
Michael J Turley
Mechanical
and Electrical Engineers:
Paul Overy
Overy + Associates
Mechanical Subcontractor:
Anthony Brady Plumbing Ltd
Electrical
Subcontractor:
Clancy Contracts Ltd
Timber
Frame Sub contractor
Cedarland Ltd Cork |
