Achieving a high insulation rating
A Sanctuary reader asks how to achieve an R4 insulation level.
We’re building a winery shed in Yarragon, West Gippsland, from recycled wood and tin. We’d like to use pure wool for the insulation but have not been able to achieve a high enough rating with the space available. We’re aiming for R4 minimum with 150mm deep roof perlins and 100mm wall spacing. Do you have any suggestions?
It is difficult (if not impossible) to get an R4 rating with the spaces you have available. Most insulation materials come in R values of between R1.5 and R3.5. To achieve higher R values, bulk insulation batts can be as much as 300mm thick. Use of polystyrene products with a reflective surface can give reasonably high R values for little width, but you will have to use a combination of a material such as Foilboard (www. foilboard.com.au) or Aircell (www. kingspaninsulation.com.au) plus a bulk insulation to achieve R4.
There is one other possibility: thick polystyrene insulation panels of the type used for cool rooms may give you a higher R value. I don’t know of anyone using them in homes though, and you would probably have to get them custom made, but it might be worth investigating.
I recommend you discuss this with your designer. You may have to compromise on either wall and ceiling thickness or on insulation values.
— Mick Harris
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