Guidebook for Energy Efficiency in Municipalities

Insulation of ceilings, walls and floors is a more significant factor for smaller buildings with
low internal heat loads than for large multi-storey buildings. For example, consider two
buildings, one five storeys high and the other only single-storey, both with 1000 square
metres of floor area per storey:
the five-storey building has around 0.9 square metres of external surface per square
metre of floor area;
the single-storey building has 2.5 square metres of external surface area per square
metre of floor area.
Energy flows through the roof, walls and floor are therefore a much larger proportion of
total energy flows for the smaller building.
To summarise, under extreme conditions, an energy-efficient building envelope always
reduces energy consumption and energy charges for peak demand. The smaller the
building and/or the lower the internal heat loads, the more energy insulation will save.
Since most municipal buildings have long lives and relatively long occupancy hours, and
aim to provide a high standard of comfort, it makes sense to incorporate a high standard
of insulation into all these buildings.
For existing buildings, it may be difficult to retrofit insulation into walls, but it is usually
possible to insulate ceilings and under exposed floors (such as floors above car parks).
Air leaks
Air leaking at the rate of only 100 litres per second (about the rate of air removed by a
domestic exhaust fan) creates a cooling or heating load of up to 2 kW under extreme
climatic conditions. In a building housing 250 people, entry of outside air at twice the
required rate could add up to 50 kW to the cooling or heating load—a substantial waste of
energy, costing up to €3 per hour.
Problem areas and strategies to address them include:
Ensure doors are closed where feasible; use self-closing doors, fit heavy plastic strips
to limit air flow, or install windbreaks or airlocks at entrances.
Large amounts of air-conditioned air may be removed by exhaust fans, particularly
where a building includes a commercial kitchen (such as for Meals on Wheels). In
such a situation, outside air could be ducted into the area near the exhaust fan,
providing an alternative source of air for the fan and preventing it removing airconditioned
air.
Gaps around doors and windows, and cracks in the building fabric can be weather
stripped or sealed. Often there are serious air leaks around doors and hatches to unair-conditioned
areas; these depressurise the building and allow cold draughts to
cause discomfort for staff near doors and windows.
Open fireplaces and heater flues are large sources of air leaks in some municipal
buildings converted from residential use. Open fireplaces can be blocked off or fitted
with dampers. Not much can be done about existing heater flues, but new heaters can
be chosen that isolate combustion air from the indoor air, so (warmed) indoor air is
not lost.
Evaporative coolers installed for summer cooling can allow large quantities of warm
air to escape in winter; they should be fitted with automatic louvres to seal them
closed when not in operation.
Further information
ES Guides (CRES)
ENERGY SAVINGS THROUGH THERMAL INSULATION