#2 prototype interactive element

Traditional Construction

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To understand and identify the key aspects of moisture management, ventilation and airtightness, and thermal performance in traditional construction techniques

Learning Objective

3. Moisture Movement: Walls

5. Indoor Moisture Production

8. Additional links

6. Ventilation and airtightness

7. Thermal Performance

4. Moisture Movement: Roofs

2. Windows

1. Materials

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Materials

Traditional buildings were constructed with solid walls of earth, stone or brick, or timber frames with infill panels. Usually, these were locally available materials. They reflect the UK's varied geology and the distribution of different rocks (such as limestone, sandstone, chalk or flint) and superficial deposits (such as soils, sand or clay) across the country. In some places, lack of stone or brick-making clay and sand meant timber from the then abundant woodlands was the most readily available resource. The exception was where wealth and/or status meant that building materials could be transported long distances by cart or boat (e.g. building stone from the Isle of Portland). The transport of materials became cheaper, easier and a more readily available option following the Industrial Revolution and the burgeoning age of the canal.

Windows

Early medieval ‘windows’ were generally simple openings in the walls, sometimes covered with oiled fabrics. Plain and coloured glass used in England during the medieval period was mainly imported, and the use of glass didn’t become widespread until late in the 16th century. Glass manufacturing and opening layouts have evolved since then.

Rievaulx Abbey © Historic England Archive

Internal face

External face

Wind driven rain

Evaporation

Lime render and limewash

Lime or earth plaster

Water vapour buffering

The interaction looks at moisture movement in walls, click on the numbers to reveal the information

Walls

Moisture movement

Roofs

The interactions below looks at moisture movement in roofs, click on the numbers to reveal the information

Moisture movement

Indoor moisture production

Another important characteristic of traditional buildings is that they were built to accommodate different living patterns to modern ones. Moisture production indoors was mainly limited to cooking and occupant's breath and perspiration, with indoor moisture production being much lower than nowadays.

Ventilation and airtightness

Ventilation contributes to providing a healthy indoor environment by removing excess moisture and pollutants and providing fresh air. Traditional buildings manage air movement through non-designed and designed ventilation.Because traditional buildings are not air-tight, there was non-designed or unintentional ventilation (known as "infiltration"; "air leakage" or "draughts"), which was essential in contributing to the moisture management of the whole building.

Thermal performance

Traditional construction's thermal transmittance [rate of heat transfer through a building assembly expressed as U-value in W/(m2⋅K)] is often overestimated, leading to the belief that solid wall construction is not as thermally efficient as it actually is. Keeping a building in a good state of repair in which the moisture content of permeable materials is in equilibrium with the surrounding environment, will minimise conductive thermal losses, as damp fabric loses heat around 30% faster than fabric in moisture equilibrium.Some traditional materials, such as cob (earth) and thatch, are inherently good insulating materials.

Publication by the Pebble Trust - SUSTAINABLE RENOVATION improving homes for energy, health and environment

Additional links

Research Report by Historic England - Ventilation and Conservation

Recording of the Historic England IHBC conference: Damp, Masonary decay and sustainability

Follow this link to read through case studies on Energy Effiecincy and Historic Buildings

By the Victorian period, window protection had evolved to include shutters, awnings, blinds and curtains to reduce sunlight radiation or keep warmth in when needed and to manage ventilation.Although draughts are one of the traditional mechanisms of moisture regulation, uncontrolled air leakage is a significant cause of convective heat loss in traditional buildings.

Tiles and slates are fixed over laths, battens or boards (without felts or membranes), allowing a small amount of air exchange to the outside so that moisture produced inside the building would get out. Additionally, the timber structure has hygroscopic properties and contributes to regulating air moisture content in the roof space.

Walls were generally load-bearing solid masonry or earth construction, but sometimes, they were built using timber framework with infill panels. Although builders and architects started to experiment with cavity or ‘hollow walls’ early in the Victorian period, these didn’t become standard construction practice until the 1920s.

Link to video

Highly capillary active lime renders and limewash finishes were a common protective external finish to permeable masonry walls, particularly rubble walls.They reduce rainwater penetration into the fabric and act as a drying poultice, maximising evaporation.

Waterproof coverings such as lead relied on a certain level of ventilation to prevent underside corrosion.

In exposed locations, these coverings could be installed over a sarking board with penny gaps (providing certain level of airflow).In other situations, permeable lime mixes were used as a bedding material or torching (applied to the underside of the roof covering) to protect from wind-driven rain, provide specific wind-uplifting resistance and absorb and release moisture, helping to keep the internal space in equilibrium.

Solid floors were made of compacted earth or permeable fills, with finishes such as clay bricks, floor tiles or stone slabs. At the beginning of the 18th century, boarded floors were introduced, firstly on timber joists resting directly on the ground, and later, on sleeper walls. Permeable floor assemblies would help regulate internal moisture content thanks to their hygroscopic properties.

Good building detailing (e.g. projecting eaves shedding rainwater away from the wall head), alongside the use of high-quality materials (e.g. long-lasting) and regular maintenance regimes (essential to the care and operation of traditional buildings), led to buildings being in equilibrium with their external environment.

Natural ventilation was provided through intentionally provided openings, such as windows and passive ventilators. Natural ventilation was also aided by air movement through chimney flues (stack effect).Additionally, some construction assemblies were designed to allow certain level of airflow with the aim of reducing moisture content and minimising the risk of condensation.

Roofs were typically pitched and covered with naturally water-resistant materials such as tiles, stones, slates or thatch. Waterproof materials such as lead and copper were later used for low-pitched roofs.

Another property of a traditional solid wall construction is its thermal mass. The wall stores heat and then releases it when the surroundings are cooler, helping regulate temperature fluctuations in cold and warm external conditions. This process can be a useful heat sink to buffer and regulate internal temperatures during the increasingly hot summers.

Traditional solid wall construction, made of primarily permeable materials, regulates moisture content in both vapour and liquid forms. Such walls allow water to pass through their thickness as a liquid via capillary flow or as vapour via diffusion due to water vapour pressure differences between the external and internal environments.Permeable materials tend to be hygroscopic and provide a ‘buffering’ effect. They manage moisture content by spontaneously absorbing water vapour from the ambient air and releasing it through evaporation when environmental conditions allow.

Most permeable materials are capillary active and can temporarily absorb liquid water in their near-surface pores and then dry out through evaporation. This process happens on the external face of the walls, which are subject to continuous wetting and drying cycles, with rain wetting their surface and wind promoting drying via evaporation.

Lime render and limewash

Evaporation

Wind driven rain

External face

Internal traditional finishes, such as lime plaster, provide this ‘buffering’ effect during fluctuations in indoor air temperature and vapour pressure. In most cases, hygroscopic materials help to maintain a healthy indoor environment by regulating relative humidity levels, minimising the risk of surface and interstitial condensation and diminishing the risks of mould growth and fabric decay.

Internal face

Lime or earth plaster

Water vapour buffering

Traditionally constructed thatched roofs had very little ventilation, and moisture content was regulated by the permeable, hygroscopic materials used in the roof assembly (i.e. thatch, timber and lime).

a little more on thatch

Internal traditional finishes, such as lime and earth plasters (hygroscopic materials), always have a certain level of moisture within their pore structure.A traditional building in its natural state when the inherent moisture content of its materials has reached equilibrium with the surrounding environment.

#2 prototype interactive element

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