Achieving a high insulation rating

A Sanctuary reader asks how to achieve an R4 insulation level.

Question

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?

— Rachel

Answer

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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Cover of Issue 18
You can read more about Achieving a high insulation rating in Issue 18 of Sanctuary magazine.

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