Calibración de la protección 27H

Within the modules strong air leaks were found coming through the various sockets (Figures 7.4 and 7.5). No other leaks were detected, including around the windows or at the junctions between walls, floors and ceilings.

Figure 7.4 (left): Air leakage path through sockets in modules: Loughborough case study Figure 7.5 (right): Architect’s plan drawing marked to indicate the location of sockets in bedroom and

kitchen modules [Architect 2, 2006]

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Air leaks were also detected along the full length of the corridor at floor and ceiling level where the corridor and modules interface (Figures 7.6 and 7.7).

Figure 7.6 (left): Air leakage paths along corridor ceiling indicated in red Figure 7.7 (right): Air leakage paths along the corridor floor indicated in red

Along the corridors, the leaks were strongest at ground level around the door frames where two modules interface (Figures 7.8 and 7.9).

Figure 7.8 (left): Air leakage paths around module door frames and corridor floor

Figure 7.9 (right): Corresponding IR thermal image showing corridor floor and module door frames

In the IR thermographic images of the external facade interesting variations in apparent temperature were seen, corresponding to the vertical party wall junctions between modules (Figures 7.10 to 7.13). These patterns are indicative of hot plumes of air rising in the cavity and hitting the outer leaf of the wall, and suggest that hot air is escaping from inside the building at these locations. The plumes vary in their occurrence and intensity, and were not observed at every party wall junction between modules, which suggests a variation in the quality of the construction in these areas, with some junctions performing better than others.

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Figure 7.10 (left): IR thermal image of modular walls with windows with brick cladding, plumes marked Figure 7.11 (right): Corresponding photograph showing position of lintels and masonry support system

Figure 7.12 (left): IR thermal image of brick and timber clad wall, plumes marked Figure 7.13 (right): Corresponding photograph of brick and timber clad wall

Analysis of the generic and project specific documentation obtained from (which included documents from contractors) found no mention of an air barrier, and no drawings detailing its design, its location within the external envelope, or how continuity should be achieved across the envelope. Some buildings may have an air barrier, if other members of the design team (such as the principal contractor or architect) ensured it was designed and constructed. However, the failure to find any mention or drawing of air barriers in any documents suggests that its design may typically have been overlooked, and that many (or perhaps all) buildings contained no intentionally designed air barrier, including the Loughborough and London case studies.

Air barriers can be provided by dry lining, such as within each module, if the joints and penetrations are correctly sealed. This explains why few leaks were detected within the modules under depressurisation with the blower door kit. However, at the party wall junctions between modules, there are no materials that can act as an air barrier. There is a

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Insulation

75mm

100mm

25mm air gap at the party wall junction between modules; at each end of these junctions are voids measuring 100mm by 175mm (Figures 7.14 and 7.15). The externally facing voids are filled with rock wool insulation before being covered with rigid insulation and cladding. The internally facing voids are simply covered with two layers of plasterboard, which form the corridor walls. No evidence was found of any further measures taken to seal the party walls junction between modules.

Figure 7.14: Air gap at party wall junction between modules

[ 2012]

Figure 7.15: Plan drawings detailing the party wall junction between modules

The insulation used externally cannot act as an air barrier, and while the dry lining used internally could, the detailing is not sufficient to achieve this (and would actually be quite difficult to achieve even with concerted effort, furthermore it would not be the preferred location for the air barrier [DCLG, 2007]). This means that air can exchange between the internal and external environments via the party wall junction between modules (Figure 7.16). This conclusion is supported by the location of air leaks detected during depressurisation with the blower door kit, which were through the sockets in module walls and along the corridor floor and ceiling where it interfaces with the modules, (Figure 7.17).

Figure 7.16 (left): Plan drawing of modules showing air leakage paths through cavities in the party walls Figure 7.17 (right): Plan drawing of modules showing air leakage paths under depressurisation

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This conclusion is also supported by the IR thermographic images that show plumes of hot air at the wall junctions between modules.

The insulation, if correctly fitted may slow the transfer of air, but any gaps in the insulation act as thermal bypasses, which create routes of minimal resistance for the air to escape (Figure 7.19). That plumes were evident at only some junctions,

.

Figure 7.19: Section drawing of the party wall junction showing thermal bypasses

Party wall cavity between modules Corridor Stone wool insulation Rigid insulation Brick cladding Air cavity

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7.2.2 Curtain Walling

During depressurisation with the blower door kit large quantities of air were found leaking through the interface between the curtain walling and the corridor, both horizontally and vertically (Figures 7.20 and 7.21).

Figure 7.20 (left): Air leakage paths shown in in red around bottom of curtain walling Figure 7.21 (right): Air leakage paths shown in red around top of curtain walling

The strongest air leak was at the interface with the floor (Figures 7.22 and 7.23). The curtain walling is connected to the corridor with a wooden frame, but there was no evidence of any seals between them, so air can pass freely into and out of the flat at this interface.

Figure 7.22 (left): photo of curtain walling indicating location of spot on IR thermal images Figure 7.23 (right): IR thermal image of curtain walling showing main leakage path

The detailed section drawings of the curtain walling show a design that is weak in terms of thermal performance (Figures 7.24 and 7.25). The curtain walling is in-line with the external cladding and there is a large gap between the curtain walling frame and the corridor end panels that leads directly into the cavity in the external wall, this gap has basically just been boxed in with a wooden frame. The drawings show no sealing around the wooden frame and no evidence of an air barrier, which would stop the exchange of air with between the internal environment and the cavity in the wall. It is also likely that air can exchange between the corridors on different storeys via the unsealed wooden frames.

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Figure 7.24 (left): Section drawing of curtain walling interface with corridor [Architect 2, 2006] Figure 7.25 (right): Plan drawing of interface between curtain walling, module and cladding, edited to

show module wall layers and steel [Architect 2, 2006]

The IR thermal images taken externally of the curtain walling appear to agree, that there is air movement between the internal environment and the cavity wall around the curtain walling. The apparent temperature distribution around the curtain walling is irregular, particularly at the junctions between floor and ceiling, and this indicates that hot air is escaping from the internal environment in these areas (Figures 7.26 to 7.29).

Figure 7.26 (left): IR thermal image of curtain walling – irregular temperature indicates air leakage Figure 7.27 (right): Corresponding photograph of curtain walling in render clad wall

Figure 7.28 (left): IR thermal image of curtain walling – irregular temperature indicates air leakage Figure 7.29 (right): Corresponding photograph of curtain walling in render and brick clad wall

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7.2.3 Airtightness Discussion

By combining data from multiple methods, air leakage routes were identified at the party wall junction between modules and at curtain walling where it interfaces with modules and cladding. It was determined that there is no continuous air barrier in the external envelope, individual modules have good airtightness due to the dry-lining that comprises the internal surfaces (with the exception of air leaks through the plug sockets), but the spaces between the modules are not airtight. informed that they had pressure tested individual modules (but they did not provide the data), indicating they had clearly thought about airtightness, but it appears only at the modular level, and not between modules or in panelised corridors. Within construction projects, acted as a sub-contractor, supplying offsite modules and corridor panels, they explicitly stated that they had no responsibility for the airtightness of whole buildings. However, were well placed to devise standard solutions between modules and where corridors interface with external walls. Based on the data from multiple sources it seems likely that airtightness between modules and in corridors was either overlooked altogether, or there was the misconception that the performance achieved by individual modules translated to the whole structure. There may also be other weak areas in the external envelope, such as at interfaces with the ground and roof, but this cannot be determined with confidence with the data available. The correct design and construction of the air barrier is essential if energy use is to be minimised within buildings, possible solutions are discussed in Section 7.9 Recommendations.