Super-Insulation – A Solar Passive Essential Ingredient

If you take a look at our ‘lightning solar passive design guide’ (another blog on this website) you will see super-insulation there as a part of the solar passive ‘toolkit’.

Super-insulation is an absolutely crucial element in any solar passive house, because it helps keep solar and other heat gains within the building’s enclosure inside, keeping residents warm.

Some forms of super-insulation, such as the multifoil quilt shown in the leader image not only provide exceptional insulation but can also assist passive cooling by reflecting away potential heat gain even though it is not exposed to sunlight. This is a function of its use of plastic foil layers within the quilt. The use of plastic isn’t good, but if is has longevity – if it will last and make humans more comfortable without using carbon cooling forms like aircon – then it may be worth having.

Some forms of super-insulation need plenty of thickness but that is OK as long as space is available. Thermafleece and paper-based blown insulation is of this type. These insulation types need careful detailing to keep them dry and to keep vermin out of them. I have wanted to use natural insulation materials for many years but am put off by the vermin aspect. 

Typically, if using polyisocyanurate rigid closed-cell rigid insulation bats (RIBs) a minimum thickness of 200mm should be considered irrespective of what Building Regulations require. Ideally thicker, though this does come with some problems – the lateral rigidity and stability of such a thick multi-layer element being something of an issue. My own approach to really thick insulation is to contain it between ply ribs forming a kind of egg-crate. 

An energy advisor once told me that an eco-house need only be a box formed of super-insulating materials. He said that the heat generated by our bodies could provide much of the heat needed within this box. I do totally understand this notion of a superinsulated box, but I would hate to live in one – isolated from the world around me simply by the desire to save energy. 

There is an alternative, I believe, which starts with a super-insulated box, but which allows the use of large windows to allow us to look out onto the world around us. The windows in such a building would need to face the sun so they don’t lose heat (in fact they gain it), and one should then add solar shading, thermal mass and cross ventilation to help cool the building.. The desire to escape living in a super-insulated box led me eventually to the solar passive designs seen on this website. 

They are all essentially super-insulated boxes with windows facing to within 30 degrees each side of the solar direction, high thermal mass, solar shading, cross ventilation, etc. etc. So, the ‘insulated box’ exercise shows the importance of super-insulation in the makeup of a solar passive building.

Three-bedroomed solar passive house by Solarity. It all starts with an insulated ‘box’!

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