Lifecycle analysis

4.3.1 Approach

Within the system boundaries, energy consumed for the production, renewal and disposal of materials were considered. The underground parking was excluded from the system boundaries. In the calculation of primary energy for electricity used by the technical systems of the house, the mix of Swiss electricity production were assumed. Household appliance electricity was excluded.

Table 4.3.1 shows selected basic parameters of the house. The data on the amount and type of materials used in the building was collected from construction plans and submission documents.

For the amorphous silicone photovoltaic panels (Unisolar, triple thin-film cells), the inventory material properties are only roughly estimated. In order to give an impression of the influence of this uncertainty in the inventory, the calculations were also carried out for a PV system with crystalline PV panels of similar peak power according to data from Frischknecht et al (1996).

Table 4.3.1 Basic parameters

Parameter

Description

Unit

Value

Building volume

4900 m3 heated;

m3

7700

2800 m3 unheated

Floor area

Net heated floor area

m2

1233

Solar collector

36 m2 vacuum tube collector, DHW and space heating

KWh/a

17,340

PV system

Amorphous triple-cell modules (16.2 kWp)

KWh/a

15,000

Space heat demand

Covered to 60 per cent through environmental + solar heat

kWh/a

10,790

Heat for domestic

Covered to 82 per cent through environmental + solar heat

kWh/a

28,900

hot water (DHW)

Electricity, heat pump

Air-water heat pump for space heating and DHW

kWh/a

9420

Electricity, other

Electricity used for ventilation and pumps

kWh/a

5580

Note: Data refer to the design values of the entire apartment building.

Note: Data refer to the design values of the entire apartment building.

4.3.2 Results

All results refer to the m2 net heated 'carpet area' and year (building life span: 80 years). For comparison, a reference building is considered: a two-storey row house without a cellar made of brick walls with polystyrene insulation. The six units each have 120 m2 net carpet area. The heat demand of 65 kWh/m2a (DHW: 25 kWh/m2a) is met with a conventional gas furnace.

4.3.3 Life cycles of the building assessed with Eco-indicator 99

In Figure 4.3.3, the impact of construction, renewal, disposal, transportation and operation on the total cycle is shown. The weighting method Eco-indicator 99 (hierarchist) was used. The most important conclusions derived from Figure 4.3.3 are the following:

• The total impact over the life cycle for Sunny Woods is only 37 per cent (design value) or 44 per cent (measured value) that of the reference building.

Different types of PV systems influence the total impact by about 10 per cent.

The impact of the material used for renewal over the building's lifetime is similar to the impact of the initial building construction.

The disposal of construction materials is driven by the concrete used. The disposal of the materials during periodical building renovations is less important.

If no PV system were built, the electricity mix used for the building operation would amount to about 20 per cent of the total impact of the house. The impact of the electricity need by the heat pump with the Swiss electricity mix (high amount of hydro energy and low share of fossil fuels) is nearly offset by the output of the PV system. For the European electricity mix (Union for the Coordination of Transmission of Electricity, or UCTE), the house with a PV system clearly has an advantage and reduces the total impact by 25 per cent. In this case, the impact payback time for the amorphous PV cells would be four years.

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.2 Bird's eye view

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.3 Life-cycle phases, Eco-indicator 99 H/A

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.2 Bird's eye view

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.3 Life-cycle phases, Eco-indicator 99 H/A

4.3.4 Building components assessed with Eco-indicator 99

In Figure 4.3.4, the impact of the different material groups over the life cycle was analysed using the Eco-indicator 99 method (hierarchist).

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.4 Building components, Eco-indicator 99 H/A

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.5 Living room, middle attic apartment

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.5 Living room, middle attic apartment

The following can be observed from Sunny Woods (see Figure 4.3.4):

• The insulating materials constitute only 5 per cent of the total impact of the building.

• The massive building materials amount to 33 per cent of the total impact of the building. This impact is primarily caused by the cellar and the cement cover of the floors.

• The heating and ventilation system makes up only 5 per cent of the total impact of the building (construction and renewal, excluding the solar and PV system).

• The thermal solar collector amounts to about 6 per cent of the total impact of the building (construction and renewal, including pipes, heat exchanger and storage tank).

• The amorphous-cell PV system leads to about 6 per cent of the total impact of the building (construction and renewal, including parts for roof mounting). Using the inventory of the crystalline-cell PV system as a 'worst' case scenario, this impact share rises to 16 per cent.

Within the other building materials (47 per cent of the total impact), an important share (19 per cent of the total impact) is caused by the windows, which have a higher impact due to the triple glazing with krypton filling.

4.3.5 Influence of the building components: Assessment with cumulative energy demand (CED)

Larger differences appear in the cumulative energy demand (CED) of non-renewable energy, as shown in Figure 4.3.6.

S 80

S 80

□ Energy use for operation

■ HVAC components, solar collector, PV

□ Other building materials

□ Insulation of envelope

□ Massive building materials

_

_

_

_

_

Calculation variant

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.6 Nonrenewable cumulative energy demand of building components

Source: Beat Kämpfen, Zürich, www.kaempfen.com

Figure 4.3.7 Living room, west attic apartment

Calculation variant

The cumulative energy demand on non-renewable energy over the life cycle of Sunny Woods ranges from 27 per cent (design value) to 53 per cent (using measured energy data) of the CED of the reference building. The installation of the PV system is favourable because it minimizes the amount of non-renewable energy. The sensitivity of the inventory data used for the PV system is higher than in the calculation with Eco indicator 99 (>20 per cent of total impact). The polycrystalline PV cells data of Frankl (2002) result in a CED that is 68 per cent lower than the CED using the data in the calculations. The high difference between the design value and measured value is caused by a much higher heating demand, mainly due to an inadequate functioning of the shading devices.

The results are similar to the results from Eco-indicator 99 for the impact share of the different building components. Here, the insulation share is 7 per cent and the massive building materials 23 per cent of the total impact. The PV system amounts to 8 per cent, the solar system to 5 per cent and the other heating, ventilating and air conditioning (HVAC) components to 6 per cent of the total nonrenewable CED of the building.

In addition to the non-renewable energy, the following renewable energy is used over the life cycle of the building with amorphous PV cells (design values):

• hydro power for electricity: 2.1 kWh/(m2a); and

In total, the share of renewable energy makes up 35 per cent of the total energy. The main part of the energy in biomass is used for construction.

4.3.6 Life-cycle analysis conclusions

The construction, renewal and disposal of the Passivhaus Sunny Woods have a very low impact over the life cycle of the building compared to a reference building in the same climate. To a large extent, this is a result of the low energy level needed for the operation of the building. The thick insulation results in a 5 per cent to 7 per cent negative impact for embodied energy compared to the resulting large energy savings.

The output of the large PV roof offsets the energy for heating and DHW. Due to the uncertainty within the inventories for the PV cells, a clear conclusion here is, however, difficult. The impact

reduction (18 per cent to 49 per cent) compared to an operation of the building is clear if the UCTE electricity mix is used in the calculations. If the electricity mix contains a high amount of hydro power (40 per cent for the Swiss mix), the result depends on the cell type (embodied energy; quality of the inventory) and the assessment method used. Using CED for the assessment, the building with a PV system shows, in all cases, the best result (24 per cent to 40 per cent lower than without the PV system).

Sunny Woods demonstrates the low life cycle of a building's minimized losses and high solar gains. Ecological optimization of such buildings is difficult and may negatively affect fire safety, acoustics or the space concept.

The excellent energy performance could still be improved. Heating hot water uses three times more primary energy than does space heating. If the building is seen in a wider context, the impact of the inhabitants' mobility is important since the total annual impact of the building equals only about 5800 km driven with a passenger car per apartment (Eco-indicator 99 H/A).

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