Insulation the technical risks

The use of high levels of insulation brings with it some risks. Some problems relate to the presence of moisture within the building insulation-

square framed work insulation-

square framed work insulation-

seal-

aluminium-rail

24 cm lime stone wait

6 mm glass-

transparent Insulation Venetian blind-

insulation-

seal-

aluminium-rail

24 cm lime stone wait

6 mm glass-

transparent Insulation Venetian blind-

25 mm air gap-

insulation-

insulation-

seal-

square framed work-

6 mm glas&

Figure 6.5

Transparent/translucent insulation wall insulation-

insulation-

seal-

square framed work-

construction which, because the temperature gradient has been changed by the presence of insulation, condenses into water. This can lead to several difficulties such as rotting, rusting or other degradation of components, and in addition can pose a safety risk if it comes into contact with electrical circuitry. Some insulation materials absorb moisture, and when wet, their insulating effect is very much reduced. Cavity insulation should be treated with a water repellent.

If substantial variations exist between the insulation levels of different parts of the building fabric, this creates weak links, which then become the main cold bridges or 'thermal bridges'. It is on the inner surfaces of such cold bridges that condensation will occur. The answer is to ensure continuity of insulation. The problem mainly occurs at the junction between main structural components, for example:

• at the junction of roof and wall;

• around windows and doors, particularly frames and lintels;

• around apertures for building services - electrical, water, drainage, etc.;

• at positions where structural framing elements connect with roofs, walls and floors.

When considering floors, the majority of the heat loss occurs at its exposed edges. Particular attention must therefore be paid to ensuring adequate and correctly designed insulation details at floor edges.

The use of vapour barriers becomes more important as insulation levels rise, since it is the appropriate construction and positioning of such layers that reduces condensation risk. It is advisable to carry out a technical assessment of the condensation risk if this is suspected of being a problem. It is even more important to design components correctly and ensure that the construction is carried out according to the specification. A large proportion of the reported faults associated with condensation are attributable to poor workmanship. As stated earlier, as a general principle, vapour barriers should always be on the warm side of the insulation, otherwise they will actually cause condensation.

Chapter Seven

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