Browse Forums Eco Living 1 Aug 03, 2009 1:56 am - Measuring the insulating properties of building materials borrows from a scientific technique used to determine the physical properties of a substance. - The technique involves placing the object between two conducting plates and measuring the amount of energy required to produce a steady state difference in temperature across the material. This produces a measure of how easily heat travels through the substance and therefore how easily heat enters or exits a building. - In building assemblies R values are useful in predicting how well heat flow is resisted based on the internal and external air temperatures. They are less useful in predicting the behaviour of materials when they are exposed to direct radiant heat. - R values (thermal resistivity) quantify a product's insulating value. The higher the R value, the more insulation. U value (thermal conductivity) is the reciprocal unit. The higher the U value, the less insulation. U values are more commonly used in window ratings - R values are often quoted for bulk insulators such as batts. They range from R 1.5 to 4.0. - Typical building materials have low R values - brick wall assemblies, windows, plasterboard all have R < 0.5 - R values have also been attributed to products such as foil radiant barriers and heat-reflective paint. Technically this is an incorrect use of the term. These materials retard radiant heat. Materials such as foil actually conduct heat readily if it is brought into contact with a hot object. The effectiveness of radiant barriers are better described by their surface emissivity (which is the inverse of reflectivity). A highly reflective object has an emissivity < 0.1. - Importantly, the methodology used to determine R value (and U values) ignore the effects of convective heat transfer. Any air movement across an object will decrease its apparent R value because it accelerates heat transfer. In an analogous situation a thick woolen jumper on a cold day may become inadequate when the wind picks up. - The implication of this observation is that a insulating batt or window loses heat much faster than determined by lab measures when they are exposed to moving air. - These effects can be mitigated by sealing the roof space or wrapping the wall cavity with a vapour barrier. In the case of window, adding a well sealed window covering will maximise the thermal performance of the product. For more technical reading: http://books.google.com/books?id=G47biv ... q=&f=false http://www.architerra.gr/EducationalMat ... ECTION.pdf I recently went through a similar renovation and move scenario when updating our family home. We also swapped some rooms around and tackled a major… 2 10032 Unless the room is for storage then it's non compliant BCA V2 2019 S3 P3.8 You have 2 options 1. The builder deconstructs the section and rebuilds as per plan /… 7 10683 The HIA contract, in the term & conditions section states that "Commencment" is deemed when the drainage is started or the piers are dug or the slab is formed up (incase… 2 6177 |