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Summary of results

LCA comparison was developed for the following product groups:

• Single-family houses (raw construction): Comparison between blockhouse, timber-frame house and conventional brick house (all of approximately the same k-value);

• Simple large buildings:

• Window frames (lifetime 30 years): Comparison between wood, PVC and aluminium windows;

• Flooring materials: Comparison between wood flooring, PVC flooring, linoleum and parquets of different types;

Single-family houses (raw construction)

Three different house types of approximately the same heat transition coefficient (k-value) are compared: timber-frame house, blockhouse and conventional brick house. The analysis is conducted for two cases, Case A: No thermal utilization of waste wood and Case B: Thermal utilization of waste wood.

Case A: No thermal utilization of waste wood

In this case, the potential of energy to be generated by thermal utilization of waste wood is neglected. The potentials of the impact categories on global warming, acidification, eutrophication and photochemical ozone creation are calculated on the basis of energy consumed for production of building materials and construction of the single-family houses concerned. The results obtained can be summarized as follows:

• The house with the lowest share of wood-based building materials (brick house) shows the most unfavourable impact assessment results in comparison with the other two house types.

• Despite the highest amount of wood and wood-based materials, the blockhouse seems to be environmentally less favourable than the timber-frame house.

Case B: Thermal utilization of waste wood

At the end of life cycle, the CO2-neutral waste wood substitutes the fossil fuels as biomass for energy generation. The analysis of the environmental impact is based on the net energy consumption which is the difference between the energy input and the energy generated by the thermal utilization of renewable waste. The results obtained lead to the following conclusions:

• The real environmental impacts of the three house types are in this case notably lower than in Case A.

• The blockhouse is environmentally the most favourable family house followed by the timber-frame house and the brick house.

Simple large buildings

Comparison between two three-storey buildings

Two buildings are compared, Building 1 consisting of 1 000 tonnes of wood and 60 tonnes of steel and Building 2 only of steel. Two cases are analysed, Case A: Total energy consumption excluding the thermal utilization of waste wood and Case B: Net energy consumption including the thermal utilization of waste wood.

Case A: Total energy consumption

The total energy inputs for Building 1 and Building 2 are 5 460 GJ and 17 000 GJ, respectively. Even without thermal utilization of waste wood, the wood building shows significant advantages which indicates the dominance of wood as an environmentally sound building material. The results obtained show that compared to Building 1 the environmental burdens caused by Building 2 are more than three times higher.

Case B: Net energy consumption

At the end of life cycle, the waste wood from Building 1 is considered as a CO2-neutral energy source which provides an additional 7 290 GJ of energy and replaces fossil energy of the same amount. The substitution of fossil fuel results in the reduction of the corresponding amount of emissions in the atmosphere. Therefore, in Table 9, the figures for impact potentials have negative values and show the importance of timber as an environmentally sound building material. The energy input for Building 2, however, remains at the high level of 17 000 GJ.

Comparison between sheds made of wood (nailplate structure), steel and concrete
(shell only)

Similar to the previous example, two cases are analysed, Case A: Total energy consumption and Case B: Net energy consumption.

Case A: Total energy consumption

The energy input amounts to 5 328 GJ, 6 577 GJ and 8 003 GJ for the sheds from wood, steel and concrete, respectively. The thermal utilization of waste wood is not taken into consideration. The results obtained show that:

• compared with other sheds, the wood shed is the most favourable building due to the low emissions and the resulting impact potentials;

• steel and concrete sheds are placed second and third/last;

• for the three buildings, the operation phase of 20 years requires most of the energy consumed. Furthermore, the differences between the three shed types are relatively small, e.g. the global warming potential (GWP) of the wood shed is 7 percent smaller than that of the steel shed and 12 percent smaller than that of the concrete shed; and

• major differences are found in the production phase of the sheds concerned.

Case B: Net energy consumption

After the operation phase of 20 years the waste wood is utilized as fuel and at least 3 400 GJ of energy are produced. Thus, for the wood shed the energy consumption and the relating environmental impact potentials are reduced. For the other shed types, however, there is no reduction of energy input and the corresponding environmental impact potentials.

The comparison between sheds made of different building materials (wood, steel and concrete) was carried out on the basis of the sum of the net energy consumption for production, transport, operation and demolition. The results obtained for the environmental impact potentials are much more in favour of wood as building material.

Window frames

The window frames have a lifetime of 30 years and are made of three different materials: wood, polyvinyl chloride (PVC) and aluminium.

The results achieved lead to the following conclusions:

• For all impact categories concerned the environmental burden of wooden windows is the lowest.

• Regarding the wooden window, waste wood can replace fossil fuel so that the environmental impact is reduced.

• Acidification potential (AP) of the wooden window is only from 40 percent to 47 percent of that of aluminium and PVC windows.

• Concerning the eutrophication potential (EP) and the photochemical ozone creation potential (POCP), the results for the wooden window are around two-thirds of that for other windows.

The following are differences in the impact potentials for various modules.

• Concerning the global warming, the lifetime impact of windows is significantly high and due to the periodical treatment with paint, lacquer or other chemicals, the wooden window results in having the highest impact followed by PVC and aluminium. However, when the entire life cycle is considered, the wooden window is the most favourable product and the PVC and aluminium windows are placed second and third, respectively.

• With regards to AP and EP, the effect resulting from window transport is almost the same for aluminium and PVC as frame material and considerably higher than for the wooden window. In the case of POCP, the transport effect is again for the wooden window the lowest followed by aluminium and PVC windows.

• From the viewpoint of frame material, the wooden window shows the lowest AP, EP and POCP. Aluminium and PVC are alternately placed second and third.

• Concerning the environmental impact of lifetime, AP, EP and POCP are for the three window types almost the same. However, the wooden window shows a slightly higher potentials than the other window types.

Flooring materials

The analysis of flooring materials includes the ecological comparison between wood, PVC and linoleum as well as the comparison between three parquet types.

Comparison between wood, PVC and linoleum flooring

The methods applied by Εsa Jφnsson (1995) to carry out the initial study on flooring materials differ from the LCA method. Therefore, the original study provided the data for LCI while the impact assessment was conducted according to ISO 14042 within the framework of this study.

The analysis includes the importance of wood as substitute for fossil fuels as well as the environmental impacts of different flooring materials. The results obtained lead to the following conclusions:

• Pinewood as flooring material consumes the lowest amount of energy (electricity and fossil) followed by linoleum and PVC.

• Burning wood at the end of life cycle has no negative effects because the CO2 released was removed from the atmosphere by photosynthesis.

• Non-renewable materials as components of linoleum and PVC cause negative effects due to the additional CO2 released to the atmosphere.

• Besides the CO2-neutrality, the renewable waste can substitute equivalent amount of fossil fuels leading to the reduction of CO2 in the surrounding atmosphere.

• PVC shows the highest GWP (4.2 kg/m²) which is 2.5 times more than that of linoleum (1.6 kg/m²), while the effect of wood is very small (0.42 kg/m²) and can be more or less neglected.

• With regard to AP, PVC again shows the worst record followed by wood and linoleum, and the fact that wood shows higher potential than linoleum might be related to the incineration process.

• The ecologically most unfavourable result for wood flooring is the relatively high EP, whereas PVC flooring shows the lowest EP. Concerning POCP, however, wood as flooring material is the best, whereas PVC and linoleum are placed second and last, respectively.

Comparison between parquets of different types

The parquet types investigated are "mosaic solid parquet, glued", "two-layer prefabricated parquet, glued" and " three-layer prefabricated parquet, glued". The results show:

• As expected, the increasing energy consumption leads to the increase of impact potentials. The mosaic solid parquet is specified as the most environmentally sound flooring.

• Increase of renewable energy results in an overproportional reduction of environmental impacts.

• For the two-layer and three-layer prefabricated parquet, the consumption of non-renewable energy and the resulting impact potentials are almost the same. These can be reduced by increasing renewable and decreasing non-renewable energy.

• Attention should also be paid to the environmental effects caused by renewable energy. Between mosaic solid parquet and two-layer prefabricated parquet the differences of GWP, AP and EP are smaller than between the two-layer and three-layer prefabricated parquet.

• Regarding POCP the renewable energy is less favourable than non-renewable energy. However, the absolute values are too small and might not have a serious effect.

Main reasons for wood substitution

Despite the favourable environmental aspects, wood is still facing strong substitution by synthetics and other materials. For example, for production of certain products (windows, coating materials for furniture) synthetics are dominating. The reasons for this phenomenon are:

• Regulations and standards often direct the decision in a certain way. This can hardly be influenced by the customer. Examples for such an obstacle are the fire hazard regulations in many countries, which prohibit or restrict the use of wood in many building types.

• Technical superiority is very important when it comes to decision-making. Customers tend to chose the technically best and most durable solution whenever the costs for this solution are still reasonable.

• Wood products and product systems must be cost-effective and competitive. Higher prices for wood products compared to competing products can only be justified if there are other features, such as very positive image, aesthetics, technical superiority (e.g. better insulation properties), which are rated high by the customers.

• The knowledge on the advantages of using wood in constructions is rather limited. This is not only the case for architects, also the end users often do not know enough about wood. This limited knowledge often leads to the wrong utilization of wood and consequently to problems which negatively affect the image of wood.

• Many environmentalists still believe that trees should stay in the forest in order to preserve nature. Certainly, environmental preservation is an important task, but there are environmentally sound forest management systems which secure sustainable utilization of forests without endangering nature.

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