Ben Warren, Managing Director at global building materials manufacturer, Baumit UK, offers a guide to sustainable construction for the self-builder.
According to a Green Building Council report, more than one home every minute will require refurbishment in the UK if the government is to make good its pledge to reduce carbon emissions – a third of which originate from heating draughty buildings – by 80% over the next 23 years. Local authorities and large-scale developers will be expected to have their house in order when it comes to improving the thermal efficiency of their building stock, but what about smaller, private housing projects?
Before any plans are drawn-up and in lieu of materials being specified, the first thing a self-builder requires in order to construct a sustainable home is the right mind-set. They have to begin the project intent on creating a property that will be theirs to reside in for the rest of their lives. This attitude of domestic permanence is more prevalent in Europe than the UK. In Austria, where Baumit has its HQ, the sustainable mentality is ingrained in the culture – from the food they eat, to the properties they build. Many Austrian restaurants will not source food outside a 15-mile radius, whilst builders on average construct houses to a 0.2 W/m² U-value, a higher tightness level than the country’s 0.4 W/m² U-value regulation for new homes. Their housebuilders’ general view seems to be: ‘I’ll build my property with the right materials and employ the correct methods in order to minimise energy consumption’. By going beyond the call of duty to construct homes which excel in terms of thermal performance, building regulations regarding energy-efficiency have little relevance to the Austrian self-builder – they view sustainability as a matter of course.
One course wonder
Having discussed the mentality – which materials make for a successful sustainable build? A timber-frame shell offers an established, quick and reasonably energy-efficient solution, but if we are to pursue the Austrian model and construct homes which exceed thermal regulations, alternative technology is worth considering. Porotherm, a clay block walling system, is a popular infrastructure choice in homes across Europe. It’s lightweight in construction and extremely thermally efficient. Porotherm only requires one course of bricks, rather than the two used in cavity wall construction – the favoured building method in about 90% of largescale building developments in the UK.
A combination of high-spec external wall insulation and Porothem can produce a spectacular thermal envelope. At a development in Norwich, Baumit’s OpenSystem – a thermally-superior EWI solution which uses unique open-air technology to allow walls to breathe – was used in conjunction with Porotherm to achieve Passive House performance: 0.15 W/m², in all 14 homes. Thermal efficiency doesn’t guarantee a home’s comfort and wellbeing, however. Applying a standard Expanded Polystyrene (EPS) system to clay block walling may well result in good levels of airtightness, but it would be akin to wrapping a house in plastic: walls wouldn’t breathe and moisture would build-up as a result. The same moisture retention would occur with an acrylic top coat applied to an EPS system. To prevent such occurrences, the construction of the wall from the inside-out needs to be considered. OpenSystem’s perforations and the application of a breathable topcoat such as Nanapor, a mineralic and highly vapour-permeable technology found in Baumit paints and renders, offers free movement of water vapour through the wall and exits through the whole system.
Lime-based products when applied to walls enhance a building’s interior sustainability. Lime is a very adaptable product, offering more flexibility in material, enabling it to accommodate structural movement. It also acts as a moisture buffer. When working in conjunction with a clay block walling system, it absorbs and releases moisture in a regulatory fashion.
‘Multi-comfort’ is a phrase currently applied to sustainable building which suggests sensory aspects such as sound, touch, light and colour are all important factors in increasing levels of wellbeing as well as thermal efficiency inside homes. In terms of paint, colour as well as consistency is important. As with oil paints, acrylic coverings can contain VOCs which emit a noxious vapour and strong odour that can lead to headaches and nausea for a building’s occupants. Baumit produces a number of mineral-based paint products that are kinder to the environment and the senses of those living within the walls to which it is applied.
Embarking on a sustainable build requires a massive investment, and not just in monetary terms. Every detail, however small, should be pored over as if it were the most important: time should not be spared on any aspect of the project. Among the more lateral questions to consider at a building’s design stage might be: where does the sun rise and set? This will determine the amount of thermal gain through glass and help regulate comfort levels in a conservatory, for example, which can be unbearably hot in summer if the style or size of panes is left to chance. It’s a reminder that a home’s year-round interior comfort not only depends on its resistance to cold in winter; its ability to deflect heat in summer is just as important, particularly with climate change’s warming effect so reflective in current, global temperatures.
Finally, once plans are drawn-up and approved and a programme of building works has been agreed, there’s only one thing a sustainable self-builder has in mind – get on with the job and get it done. Having highlighted the thermal benefits of Baumit’s OpenSystem when combined with a Porotherm clay block walling, aside from the comfort and wellbeing it creates, it’s also a rapid-build alternative to cavity wall construction methods. With only one course of bricks required and the EWI in place, work can begin on a building’s interior, which ultimately leads to reduced on-site working times and energy consumption. It’s a process that guarantees a project’s sustainability from beginning to end.