Sitios de interacción del sustrato en la reducción de CoI y CoII

An important measure of the applicability of the star rating to the actual energy used for heating and cooling relates to the actual quality of the insulation installation, and the amount of air leakage within the home. Many jurisdictions in the EU already require thermographic and air leakage testing of all new buildings. Eleven of the homes in south-east Queensland and two of the Townsville homes (plus two display homes in Townsville) were subject to thermal imaging and air infiltration tests.

Thermal imaging was conducted according to EnergyLeaks Quickscan EL 1 utilising a FLIR E50bx camera. Air leakage testing was conducted using a Retrotec 2000 fan, and in accordance with the following standards:

• ATTMA TS1 Issue 2 – Measuring Air Permeability of Building Envelopes

• BS EN13829:2001 Thermal Performance of Buildings

• BINDT – Quality Procedures and Explanatory Notes for Air Tightness Testing In general, conducting these tests revealed poor levels of housing documentation.

Many occupants did not have copies of their house plans (building documents) despite all homes being relatively new (generally less than six years old), and only three households could provide a copy of the energy rating certificate for the house or provide information on the expected thermal performance of the house (e.g. the star rating). All of the 15 houses subjected to thermography had issues that would make them non-compliant (minor to serious) with the current building regulations and impact negatively on the thermal performance of the building. Common issues included:

• Poor perimeter coverage (typically 300–600 mm around perimeter of internal ceilings), with particularly poor coverage in the corners of hip roof designs.

(Note: BCA requires that all insulation covers at least 40% of the external wall top plate to give the desired thermal coverage to suit the dwelling) (Figure 5.7a and b)

• Patchy (or absent) ceiling coverage in general (Figure 5.7 c and d)

• Entry hallways, utility rooms (e.g. bathrooms, toilets, laundry) and bulkheads often not insulated correctly (Note: BCA requires bulkheads to be insulated as per ceilings) (Figure 5.7 e)

• Poor insulation around downlights, exhaust fans, manhole covers (Figure 5.7f)

• Doors and windows are weak spots thermally (Figure 5.7g and h)

• Poor/absent insulation of adjoining garages (with shared roof space with living areas)

A Framework for Adaptation of Australian Households to Heat Waves 169

Fig (a): poor perimeter coverage Fig (b): poor perimeter coverage

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Fig (c): patchy ceiling coverage l Fig (d): patchy ceiling coverage

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Fig (e): poor bulkhead insulation Fig (f): absent draft stopper on vent

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Fig (g): heat leakage around window frame Fig (h): door leakage points

Figure 5.7: Typical thermal images showing gaps or missing insulation, and air leakage around doors and windows

Two of the homes revealed extensive and serious non-compliance issues that required house owners to seek restitution from the relevant builders (Figure 5.8).

170 A Framework for Adaptation of Australian Households to Heat Waves

Figure 5.8: Missing insulation as well as large air gaps around insulation, representing serious breaches of BCA regulations

Overall, these results show a significant inconsistency between expected and actual insulation installs. Consequently, without any quality control measures it is unreasonable to assume that the thermal resistance of roof spaces are as currently assumed.

5.12 Conclusions

The majority of homes in Australia have cooling equipment and this trend is likely to continue over time. In hot dry climates such as Adelaide, Perth and Melbourne, evaporative cooling is an effective and low cost provider of thermal comfort during heat waves. However, nationally, the dominant form of cooling equipment is reverse cycle air conditioning either as single split systems or ducted whole-of-house systems.

Currently MEPS does not consider the performance of the whole of system efficiency in the case of ducted systems or the efficiency of evaporative systems. The separation of ducting thermal performance, which is in the BCA, and MEPS, has resulted in new systems being installed with ducting that is inferior to current regulations. In addition, no quality control assessment of ducting, can result in significant air leakage dramatically increasing energy consumption, particularly during peak periods.

Currently, no consideration is given to the peak demand of inverter air conditioners, which can be significantly greater than the name plate due to its ‘hidden’ capacity.

NatHERS accredited software tools such as AccuRate, are very comprehensive and powerful building thermal models. Heat flow through the roof represents the dominant building load in peak summer. Assumed performance of insulated roof in these thermal models is unreliable, and research has shown that the thermal resistance or R value of the roofing system can be as low as half that of the R value of the bulk insulation.

Analysis has shown that the increase in heating and cooling required by the building between the assumed and the potentially likely thermal resistance of the roof system was on average 34% across Australia. The application of roof heat flow reduction measures such as applying a high TSR roof and the use of foil in combination with the likely performance of insulation is able to deliver significant savings, reducing annual air conditioning electricity consumption by 18% on average across Australia. This saving directly translates to reduction in running costs.

The sizing of air conditioners is currently unregulated. Calculation of the design load considering the issues relating to ducting and heat flows through the roof identified how these factors are increasing the sizes of installed air conditioners. In addition to the natural bias of retailers to oversize air conditioners, larger systems are being installed in more energy-efficient homes, adding to the peak power demand problem.

AccuRate was used to identify the potential of reflective roofing with a high TSR and foils, operating in conjunction with bulk insulation on peak reduction in air conditioning

A Framework for Adaptation of Australian Households to Heat Waves 171 demand. Significant reductions were identified and the estimated impact reduction in total peak power demand was identified.

The impact of adaptive comfort which complements demand side management of air conditioning was shown to be able to dramatically reduce electricity consumption for cooling by over 60%, as well significantly reducing peak power demand.

The future climate is likely to move all mainland cities into cooling dominated demand.

Based on future TMY, the electricity usage for heating and cooling in Hobart is predicted to decrease over time. In all mainland cities, electricity usage is expected to increase with Sydney and Brisbane experiencing the most dramatic increases. All mainland cities can expect increased electricity costs.

With the onset of climate change, peak power demand will increase at higher rates than currently anticipated, particularly in Brisbane and Sydney. Furthermore, the usage levels of electrical infrastructure will skew away from winter which may affect electricity prices such that electricity savings during winter heating may not directly translate to equivalent cost savings. Consequently in all locations studied, apart from Hobart, electricity prices are expected to increase due to climate change. The measures to reduce peak power demand presented herein can reduce these trends.

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