Untreated Timber Claddings

If a timber fapade is left untreated, after a couple of years it will oxidize and develop an even grey tone (Figure 18.1).The process requires that it is evenly exposed to rain; roof overhangs and protruding flashings create a 'rain shadow' and in some cases areas where water drips, resulting in uneven colouring. On the other hand, this can be avoided by choosing different materials for surfaces that are not exposed, or else by treating the wall with iron vitriol (see page 404).

An untreated timbercladding will haveapproximatelythesamelifetimeasonethatis painted (Godal, 1994). At the same time, one saves work, expense and the environmental affects arising from cleaning and repainting. In addition, the untreated cladding will befully biodegradable and ready for energy recovery without the need for special smoke filtering.

The most relevant justification for painting a house is aesthetic. Exceptions are internal surfaces such as floors, mouldings and other details where treatment with oils and waxes will ease cleaning and reduce wear. Colour can also be used to lighten interiors and reduce the need for artificial lighting. Of importance here is wood panelling which, with the exception of aspen, lime and the sapwood of ash, will darken with time. Special paints are used for protection against rust, as flame retardants, as internal vapour barriers, to protect against radon emissions from radioactive building materials, to prevent emissions of volatile formaldehyde from chipboard, etc.

Ordinary paints consist of binders, pigments and solvents. The binder is the 'body' of the paint, helps the coat of paint to retain its structure, and binds it to the surface to which it is applied. The pigment gives the paint colour, but also plays a role in its consistency, ease of application, drying ability, durability and hardness. The solvent dissolves the paint to make it usable at normal room temperature and gives ease of penetration in to the surface material. In addition, it is possible to add fillers. Some paints also need a proportion of additional additives in order to fulfil technical and aesthetic requirements; for example, fungicides, drying agents, softeners, etc.

Dispersion paint contains particles so small that they are kept suspended in water - this is known as a 'colloidal solution'. Emulsion paint is a dispersion paint consisting of finely divided oil made soluble in water by adding an emulsifying agent, usually a protein. Lazure is paint with less pigment, used when the structure of the material needs to remain visible. Lazure painting can be achieved by using a larger proportion of solvent in the paint. Varnish is a paint without pigment, while stain, in its classic sense, is a paint with no binder, where the pigment is absorbed directly into the surface. Stain is nowadays often referred to as lazure. The terms used here are the classical definitions. Wax and soap are also included in this chapter. They have nothing to do with painting, but are widely used in the treatment of wood surfaces, and do have some effect on its appearance. They also saturate the wood so that dirt and moisture cannot get into it.

18.1

Unpainted and naturally grey timber cladding In a harsh climate on the Norwegian coast. Gaia Lista, 2004.

18.1

Unpainted and naturally grey timber cladding In a harsh climate on the Norwegian coast. Gaia Lista, 2004.

The necessary qualities of paint, varnish, stain and wax are that they must:

• bind well to the surface

• be elastic so that they can tolerate movement in the building.

Table 18.1 Types of surface treatments

Type/binder1

Solvent

Primary additives2

Exterior use

Interior use

Cement paints

Water

Possibly dispersing agents

x

x

Lime paints

Water

x

x

Silicate paints

Water

Possibly dispersing agents

x

x

Acrylate paints/varnishes

Water and/or organic solvents

Fungicides, softeners, drying agents, dispersion agents, film-forming agents, etc.

x

x

Alkyd oil paints/varnishes Organic solvents Fungicides, drying agents, x x dispersing agents, skin preventers, etc.

Alkyd oil paints/varnishes Organic solvents Fungicides, drying agents, x x dispersing agents, skin preventers, etc.

Epoxy paints/varnishes

Organic solvents

Fungicides; softeners, etc.

x

x

Polyurethane paints/varnishes

Organic solvents

Softeners etc.

x

x

Polyvinylacetate PVAC paints

Water and organic solvents

Softeners3, fungicides4; drying agents; dispersion agents; filmformings agents, etc.

x

x

Collagene glue paints

Water

Possibly fungicides4

x

Casein paints

Water

Possibly fungicides4

x

Linseed oil paints Organic solvents Drying agents; fungicides4 x x

Linseed oil paints Organic solvents Drying agents; fungicides4 x x

Emulsions of linseed oil Water Possibly fungicides4 x x with animal glues, starch, etc.

Emulsions of linseed oil Water Possibly fungicides4 x x with animal glues, starch, etc.

Wood tar

Organic solvents

Possibly fungicides4

x

Natural resin varnishes

Organic solvents

x

x

Starch paint

Water

Possibly fungicides4

x

Cellulose varnishes

Organic solvents

x

x

Cellulose paste paints

Water

Possibly fungicides4

x

Chemical stain

Water

Reactive substances

x

x

Water stain

Water

x

x

Beeswax

Organic solvents

x

Green soap

Water

x

1 Combining binders is possible; for example polyurethane/acrylates.

2 Excluding pigments.

3 A co-polymer of PVAC and acrylates do not need additional softeners.

4 When exposed to moisture.

1 Combining binders is possible; for example polyurethane/acrylates.

2 Excluding pigments.

3 A co-polymer of PVAC and acrylates do not need additional softeners.

4 When exposed to moisture.

Special conditions are often required by the materials and components to be treated, and in relation to their position in a building (Table 18.4). Especially important are factors such as diffusivity to moisture, sensitivity to water and mould growth, resistance to wear, sensitivity to light and the risk of emissions. There is a big difference between interior and exterior treatment in this respect.

Of all building materials, surface treatments are those that are renewed most often. The accumulated environmental loads through

Table 18.2 Synthetic paints and varnishes and essential hazardous substances that may be found in production and/or in finished products

CO

Product

Û.

Acrylate paints/varnishes

Acrylonitrile2; acrylic acid2; xylene2; isothiazolinone; folpet; bronopol; phthalates; styrene3; methyl metacrylate

Alkyd oil paints/varnishes

Xylene2; toluene2; nonylphenol; zinc; folpet; methyl ethyl ketone

Epoxy paints/varnishes

Epichlorohydrin; bisphenol A; amines2; xylene2; toluene2; butanol2; methyl isobutyl ketone2; phthalates2; nonylphenol

Polyurethane paints/varnishes

Isocyanates2;chlorinated hydrocarbons; amines2; toluene2; xylene2

Polyvinylacetate paints

Phthalates2; isothiazolinone; folpet; bronopol

See 'Risk potential' in Table 2.5.

1 Additional substances may well occur. Production of basic ingredients are not included.

2 Risk of emissions from treated surface.

3 In paints for exterior use.

See 'Risk potential' in Table 2.5.

1 Additional substances may well occur. Production of basic ingredients are not included.

2 Risk of emissions from treated surface.

3 In paints for exterior use.

a building's lifetime can therefore be considerable even though the effect of each single treatment may be small (Table 18.3).

Many products for surface treatment are based on raw materials from plants, while other are based on fossil oils. Pigments are usually mineral-based.

The energy consumption in production varies a great deal from product to product and is to a great extent dependent on the choice of pigments and solvents. As a rule of thumb, the surface treatments and their renewal will amount to about 1 to 2% of the total material-related energy requirement of a conventional building over a 50 year period (Baumann etal., 1994).

Table 18.3 Essential environmental qualities of surface treatments

Qualities

Exterior treatment

Interior treatment

As product

Production from renewable resources

x

x

Low emissions of greenhouse gases and other pollutants in the production phase

x

x

Minimal use of organic solvents and other toxic additives

x

x

Low emissions of organic substances when applied and afterwards

(x)

x

High durability

x

x

High biodegradability as waste

x

x

As part of the treated material

Maintains the moisture buffer capacity of the underlayer

x

Maintains the surface temperature of the underlayer1

x

Maintains the electrostatic properties of the underlayer

x

Maintains the recycling value of the treated material2

x

x

Notes: X: of primary relevance.

1 Most important when used on timber flooring.

2 Re-use, material recycling and energy recovery.

Notes: X: of primary relevance.

1 Most important when used on timber flooring.

2 Re-use, material recycling and energy recovery.

Table 18.4 Utility of some low impact paints on mineral materials

Substrate

Lime paint

Silicate paint

Collagen glue paint

Casein paint

Concrete

X

X

Plasterboards

X

X1

Lime plaster

X

X1

X1

Lime sandstone

X

X

X

X

Sandstone/quartzite

X

X

Vitrified bricks

X

Low-/Well-fired bricks

X

X

Loam plasters

X

X

X

Ref.: Ziesemann, 1998. 1 Subcoating is most often necessary.

Ref.: Ziesemann, 1998. 1 Subcoating is most often necessary.

In the Scandinavian Products Register for chemical products, there are 11 800 registered paints and varnishes that contain harmful substances. A wide range of pollutants are emitted from the industry. The surface treatments will comprise of a considerable part of the total materials-related emissions of the building. Organic solvents in particular must be included here; they have been estimated to be responsible for about 20% of the hydrocarbon pollution in the atmosphere, second only to the car (Weissenfeld, 1983). Their climate changing potential is three times that of carbon dioxide. Solvents and other constituents in surface treatments can also have significant health effects both for workers and the indoor environment. Amongst both painters and workers in the paints industry there are considerably higher rates of cancer than amongst other groups (Stevenson et al., 2007).

Toxic substances can leach from painted facades and pollute surrounding soil and ground water (Andersson, 2002). Inside buildings a whole series of different volatile substances can be emitted from treated surfaces - especially when synthetic products are used - and can have a big impact because they extend over such large areas (Table 18.2)Table 18.1. Besides organic solvents, these can include residual monomers as well as additives like softeners and fungicides. Many of them are environmental toxins; others can lead to irritation in the respiratory system. Emissions often continue several months after the work is completed. As a general rule the thicker the layer of paint or varnish, the longer the time taken for the emissions to complete.

Surface treatments that are less permeable to vapour can also reduce the indoor air quality by blocking the moisture-buffering properties of the building materials treated (Table 18.5). This can imply higher ventilation requirements and energy use. Varnishes will also make floors 'colder' since they are good thermal conductors which can make it necessary to have higher room temperatures in buildings such as kindergartens. Certain surface treatments can also become quite heavily electrostatically charged, which can make cleaning more difficult as well as increase the electrostatic charge of the inhabitants (see Table 15.3).

Table 18.5 Vapour diffusion resistance of paints with thickness 0.05 mm

Surface treatment

Vapour diffusion resistance (Zp) (109 m2sPa/kg)

CO ■

Cement paints

0.4

DC

Lime paints

0.2

< 0.

Silicate paints

0.2-1.0

Acrylate paints/varnishes

0.7-2.7

Alkyd oil paints

2.5-5

Alkyd oil varnishes

19-39

Epoxy paints

40-50

Epoxy varnishes

39-72

Polyurethane varnishes

50

Collagen glue paints

0.2-0.3

Linseed oil, not pigmented

0.9-1.0

Linseed oil paints

1.0-3.5

Lower values indicate an increased potential for utilization of the moisture buffering capacity of the underlayer.

Lower values indicate an increased potential for utilization of the moisture buffering capacity of the underlayer.

When surface treatments are applied, a mixing of materials occurs that is almost irreversible. Materials that have had surface treatments are therefore not easily recycled. Exceptions include treatments that are easy to clean off (such as collagen glue paint), or where the treatment is similar in composition to the underlay (for example, cement paints on concrete). The same principle applies to the potential for energy recovery and the problem of waste. Painted materials often have to be treated as special waste. As waste, the pigments have the greatest impact since they can contain heavy metals.

Going Green For More Cash

Going Green For More Cash

Stop Wasting Resources And Money And Finnally Learn Easy Ideas For Recycling Even If You’ve Tried Everything Before! I Easily Found Easy Solutions For  Recycling Instead Of Buying New And Started Enjoying Savings As Well As Helping The Earth And I'll Show You How YOU Can, Too! Are you sick to death of living with the fact that you feel like you are wasting resources and money?

Get My Free Ebook


Post a comment