{"id":9879,"date":"2019-07-11T09:46:03","date_gmt":"2019-07-11T09:46:03","guid":{"rendered":"https:\/\/designbuybuild.co.uk\/?p=9879"},"modified":"2019-07-11T09:46:03","modified_gmt":"2019-07-11T09:46:03","slug":"the-importance-of-breathability-and-real-world-research","status":"publish","type":"post","link":"https:\/\/designbuybuild.co.uk\/the-importance-of-breathability-and-real-world-research\/","title":{"rendered":"The importance of breathability and real-world research"},"content":{"rendered":"
The importance of breathability and real-world research<\/strong><\/p>\n The Alliance for Sustainable Building Products (ASBP) says \u2018breathability is the most effective way of maintaining stable and harmless moisture levels within the building fabric\u2019.<\/p>\n A healthy building uses natural materials which enables controlled ventilation and vapour- permeability to maintain a balanced environment for both the building fabric and its occupants.<\/p>\n Computer-model based research<\/strong><\/p>\n The primary issue of previous insulation research which is carried out using computer models is that it isn\u2019t based on real-world performance.<\/p>\n Computers make basic, unrealistic assumptions \u2013 such as insulation being perfectly installed<\/strong>, humidity only flowing inside to outside<\/strong> and ignoring leaks <\/strong>\u2013 which can wrongly predict the performance of insulation materials.<\/p>\n Six years of real-world data <\/strong><\/p>\n In 2011, working with the Society for the Protection of Ancient Building and ArchiMetrics, we installed four sensors into the external wall of a two-bed, 1820s home to monitor the real performance of our natural insulation materials.<\/p>\n <\/a><\/p>\n Unlike a typical insulation upgrade of plasterboard fixed to foam insulation, we installed woodfibre onto a parge coat (Lime Green Duro), followed by a coat of highly-vapour permeable lime plaster (Lime Green Solo) before coating with a mineral paint to retain breathability.<\/p>\n We placed sensors on both the external (S4) and internal (S3) faces of the brickwork, as well as onto the parge coat (S2) and beneath the plaster at the interface of woodfibre (S1). We monitored both saturation and humidity data every five minutes over a six-year period.<\/p>\n <\/a><\/p>\n Saturation margin (01 Nov 2017 \u2013 30 Jan 2019)<\/em><\/strong><\/p>\n The data, showing the performance of the wall over the most recent period, displays the sensors\u2019 measurements of the saturation margin data.<\/p>\n Condensation starts to occur when temperatures drop below 0\u00b0C.<\/p>\n The saturation margin at S1 showed no condensation – as you\u2019d expect with an inside wall where a big drop in temperature would be needed to create condensation.<\/p>\n S2 and S3 also indicated no condensation between the woodfibre and the Duro coat which, crucially, was not<\/u> the prediction of the computer model.<\/p>\n Moisture was detected at S4 \u2013 the external wall – during several periods, particularly during the winter months, suggesting it was affected by wet weather conditions.<\/p>\n Our data disproves the computer\u2019s assumption that temperatures of the external wall and environment match.\u00a0 Sharp increases in the saturation margin suggesting a hot surface \u2013 as a result of direct sunlight \u2013 causing vapour to flow back inside of the house.<\/p>\n