HALMBALSHUS – EN STUDIE MED FOKUS PÅ FUKTPROBLEM : Begränsning av fuktlasten med hjälp av fallstudier utförda i Wufi

Sammanfattning: The purpose of this work has been to create substrates that can contribute to more moisture-proof straw bale constructions through simulations in Wufi Pro. The aim was to simulate different cases with incremental variations of different parameters and to investigate the moisture significance of the parameters. This in order to later, with the help of the results, draw conclusions about how a moisture-proof construction of straw bales can be achieved. The method of carrying out the work was to utilize; previous studies and literature on the subject, Wufi Pro 6 and Wufi Bio 3.5. The results showed that: ·         The moisture content of the straw layer varies, among other things, depending on the facade orientation and geographical location. For Karlstad facades to the south-east and south are most exposed to moisture when rain cover (coat or hat) is lacking. ·         Most exposed to moisture is the straw layers near the cold side of the outer wall. ·         Increasing the interior clay thickness slightly reduces the moisture content of the straw layer. ·         Increasing the outside clay plaster thickness slightly increases the moisture content of the straw layer to a certain thickness and then decreases the same. ·         Addition of outer panel and air gap reduces RH (relative humidity) in the straw layer by about 9%. ·         Constrution in the spring is preferable given the risk of microbial growth (for Karlstad). ·         Surface treatments prolong the drying time but reduce moisture in the straw layer afterwards. ·         Straw structures are exposed to less risk of microbial growth in warmer climates. The conclusions can be summarized as follow: ·         Moisture design should take into account differences in moisture load depending on facade orientations. ·         It is very important to protect the facade from direct rainfall. ·         It is desirable to have thicker plaster on the warm side of the outer wall campared to the cold side plaster (about twice as thick as the cold side plaster thickness). ·         Work steps that add moisture to the straw layer, such as plastering, should take place during the spring. ·         The building moisture must be minimized. ·         Increasing the diffusion density of the wall surfaces increases the drying time, which entails moisture risk in the event of moisture leaks to the straw layer. ·         Straw can be used as insulation in conventional buildings with moisture brakes, provided that moisture leaks caused by unforeseen damage do not occur. ·         If surface treatments are to be used, this should be done after the building moisture has dried out.