Sharp JX-9400 Technical Information PDF herunterladen (Seite 83)

ﬂow rates at each pressure using the method described in section ‘Determining

the leakage coeﬃcients’, below.

Components that can usually be sealed include: chimneys, ﬂues; ventilation

openings, external doors (other than the one used to mount the pressurization

fan), wooden ground ﬂoors or roof, cracks between walls and ﬂoors, pipe and

cable entry or exit points, and any other obvious cracks and opening s (f or

example, gaps between a window frame and the wall into which it is ﬁxed).

The last air leakage test in this process gives a measure of the background air

leakage, i.e. the remaining air leakage not sealed during the previous tests. It is

quite common for this to constitute more than half of the overall air leakage,

even where all of the most obvious air leakage paths have been sealed.

When all the components required have been sealed and air leakage tests

carried out, the pressurization fan can be reversed and the air leakage tests

repeated as the components are progressively unsealed in the reverse order to

that in which they were sealed.

Best results are usually obtained by seali ng groups of components (for

example, all openable windows in the dwelling) because the leakage through

an individual component (for example, a single openable window) can be too

small for the pressurization fan to resolve.

Multi-zone fan pressurization method

The technique can be extended to multi-zone pressurization, aiming to assess

the air permeability of not only the envelope of an object (for example, a

building) but also of its internal partitions (Fu

rbringer and Roulet, 1991).

The building zones are represented by nodes of a network linked by partitions.

One of the zones is the outdoor air. To assess the coeﬃcients of all partitions

requires the measurement of many inter-zone airﬂow rates and pressure diﬀer-

entials. An appropriate design of the experiment aiming to assess the required

coeﬃcients, and only these, will considerably reduce the work required.

For example, two fans and a control system allow assessment of the leakages

of many parts of a building. To avoid the tedious wor k of sealing with plastic

foil all building parts that should not be measured, the airﬂows through these

parts are inhibited by maintaining a zero pressure diﬀerence across them.

The measuring fan with its ﬂowmeter equipment is installed in a wall or

door of the room containing the element to be measured. Another larger fan

is installed in a door or a window of the building (or the dwelling) containing

the room (see Figure 4.3).

In order to get the leakage characteristics for a given element, the pressure

in the room should be varied step by step from 10 Pa up to 60 or 70 Pa. The

guarding pressure should be varied simultaneously to maintain a zero average

pressure diﬀerence between the room and the building. This pressure diﬀer-

ence actually varies between 1 and þ1 Pa. A ﬁt through several measurements

provides the airﬂow rate corresponding to a zero pressure diﬀerence.

Several experiments are necessary to measure the other walls of the room

by simply opening or closing various doors and windows. When a set of

62 Ventilation and Airﬂow in Buildings

1 2 ... 78 79 80 81 82 83 84 85 86 87 88 ... 210 211

Kommentare zu diesen Handbüchern

Keine Kommentare

Sharp JX-9400 Technical Information Seite 83

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Drucken & Scannen Sharp JX-9400