10 Jun 2019

Designing breathable buildings

Whether you’re working on an old or a new building, read on to discover why Simon Ayres of Lime Green believes lime has the answers. Simon gave up building to focus on manufacturing lime because he believes its more relevant now than ever.


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When you’re planning a building, does it ever cross your mind that your decisions might impact on the health of its occupants?

Reason 1: We live more healthily with lime than we do with concrete

The human race is increasingly to be found indoors. Sheltered from the elements, we’re led to believe we’re safe in our buildings but they may be making us ill and, in rarer cases, killing us.

Over 9000 deaths in the UK each year are attributed to poor indoor air quality (source: Allergy UK ). Respiratory diseases are the third biggest killer of Brits and we’re well behind our European neighbours.

“Open the doors and windows”, you may suggest, but in some UK cities, outdoor air quality is so poor that ventilation by opening doors and windows can result in letting more pollutants in than out. Those pollutants often take the form of vehicle fumes but other nuisances are let in as a result, for example traffic noise and cold air.

Everyone in the construction supply chain needs to get clear on how our decisions impact on indoor air quality.

Healthy buildings enhance their occupants’ health and the environment in which they sit.

Healthy buildings ‘breathe’ which means excess water – from cooking, showers etc – with appropriate ventilation and heating systems – can pass through its fabric instead of getting trapped. Excessive moisture in a building can build up and cause condensation and, in acute cases, mould or other unwelcome infestations.

We treat wine and cheese better than our children

Next time you visit a wine, cheese or whisky cellar, take note of the floors and walls. They’ll most likely be covered in lime mortar because it doesn’t emit VOCs – volatile organic compounds – and therefore it helps to create the ideal environment and regulate stable humidity levels for maturing these products.

Subtle changes in the humidity and indoor air quality may be imperceptible to the average person but it makes a detectable difference for finely calibrated air quality monitors as well as professional tasters.

Natural products – such as cheese and wine – mature differently when in a breathable environment because they are protected from VOCs arising from synthetic materials.

Lime is a natural antiseptic

For centuries, farmers have protected their livelihoods by washing down cowsheds with lime. Lime is still used today to sanitise livestock pens. Because of its high-alkaline properties, lime naturally repels germs and bacteria – a helpful property of lime when you consider how many germs are now beyond the reach of antibiotics.

So why are we treating our food and animals better than ourselves? Every builder and building owner should consider this before embarking on a building project.

Reason 2: It lets a building stand the test of time

If a building can’t breathe, vapour gets trapped as moisture in its fabric.

Despite being temperate, Britain’s climate is harsh on a building envelope because it is often subjected to the severe freeze-thaw cycle which – when water’s trapped – can break rocks.

Lime-based renders, plasters and mortars ‘mop-up’ any water which makes its way into the building’s superstructure. Moisture is then released gradually so avoiding the ‘breaking rocks’ forces of a harsh frost or sunlight.

Will our buildings be standing in 400 years’ time?

If that sounds far-fetched, this half-timbered, manor house was built 400 years ago.

It has stood the test of time thanks to its breathability and flexibility. Buildings need to flex as the land they sit upon, moves over time. The lime in its joints and renders protects it from Britain’s freeze-thaw cycling climate by letting water vapour discharge.

Interesting, this fine old building has recently added a modern level of comfort to its attic without compromising its breathability. The Warmshell system has been installed comprising:

1. Tongue and groove wood-fibre boards between the ceiling rafters.

2. Lime plaster onto the boards (Lime Green Onecoat Solo).

3. Insulating plaster (Lime Green Ultra).

4. All areas were painted with hydraulic lime-based paint (Lime Green Motif).

Given our track record with heritage buildings, we’re confident that these materials will work harmoniously with the existing materials, creating a healthy building for years to come.

Reason 3: Lime’s kinder to the environment

Lime is kinder to the environment as it absorbs carbon dioxide from the air – as do plants – whereas concrete is a massive contributor to the planet’s carbon load.

Concrete came into fashion after WW1 as cement became cheaper, quicker and easier to use. We needed lots of buildings, quickly. Cement was considered the dream material and lime fell out of favour.

Now prices for many lime mortars, renders and plasters, are on a par with cement-based products. Modern lime products are easy to work with and can be applied by hand or machine.

Lime can take longer to dry but it can enable faster working as you can build-up thicker layers more quickly, than with conventional materials.

Leaving aside it’s workability, environmental performance as well as its price-comparability, lime is more relevant now than it’s ever been simply for its health benefits.

To me it’s crazy that our wine, cheese and cattle are often in healthier environments than our office workers, shoppers or loved ones.

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