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per day), ventilation strategies have a minor inﬂuence on heating energy demand.

The air may be either heated by coils in the supply air or by radiators in the room.

The energy use for heating does not change signiﬁcantly in all climates.

The tightness of the building envelope has a large inﬂuence, up to a factor of

two, on the heating energy need. When high inﬁltration occurs, humidity is also

reduced in winter.

Cooling

Cold ceilings are more eﬀective than air conditioning. For the same airﬂow rate

and same comfort conditions, more energy was required for cooling using air

conditioning than with the hydronic cooling ceiling.

Lowering the set point for cooling from 268Cto248C causes an augmenta-

tion of the cooling demand of the zones by a factor of three to eight, depending

on the geographic location.

A droplet catcher downwind of a cooling coil has a negligible eﬀect on

energy demand, but may be essential to avoid humidifying downstream ﬁlters

or acoustic dampers, cha nging them to biotopes.

Filters

Using a two-stage ﬁlter system instead of an old F7 ﬁlter leads to an increase

in electric power use for fans of 10–15 per cent, depending on the pressure

diﬀerence over the sy stem.

Again, depending on the pressure diﬀerence over the system, earlier

replacement of a ﬁlter results in a decrease in fan power consumption by 2–3

per cent.

Humidiﬁcation

In the northern (Oslo) and central locations (London and Zu

rich), humidi-

fying the supply air at 30 per cent minimum relative humidity requires about

20–25 per cent more energy fo r ventilation than without humidi ﬁcation. In

the southern climate (Rome), the increase is only 3 per cent, mainly because

humidiﬁcation is seldom required. In all climates, humidifying the supply air

at 30 per cent increases the total heating energy need by 5–10 per cent, while

this need almost doubles if the relative humidity is set at 50 per cent.

Heat recovery

Without heat recovery, the heating energy use for ventilation is 70–140 per cent

more than with medium eﬃciency (50 per cent) heat recovery.

Heat recovery with high eﬃciency (75 per cent) – such as those achieved by

well-installed rotating heat exchangers in airtight buildings – leads to a reduc-

tion of the heating energ y demand for ventilation by about 30 per cent,

compared to medium eﬃciency (50 per cent) heat recovery. That means that

the 3 per cent reduction in eﬃciency caused by installing a purging sector in

106 Ventilation and Airﬂow in Buildings

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Sharp JX-9400 Technical Information Seite 127