Let’s begin with what exactly this terminology means.
The Passivhaus System was devised in a Swedish/German partnership (of course) and there are very specific construction standards that have to be met to comply with the criteria laid down.
The remit sounds quite simple…
Build a house with excellent thermal performance, outstanding airtightness and use mechanical ventilation. The result is a building with extremely low heat requirement – by low we mean the amount of heat generated by a heated towel rail for example. The mechanical ventilation heat recovery system (MVHR) then recovers the heat and recirculates it. In theory, and it seems, in practice, this can eliminate the need for traditional heating systems – not especially good news if you are in the sector supplying these services – but really good news for reducing energy bills, energy use, and therefore carbon emissions. This system can be used globally in any climate and works just as well in either warm or moderate climates with the system tested from Europe to Australia and the USA (30,000 buildings to date).
Of course it never is quite as simple as it first looks…
The building has to be airtight and highly insulated. The windows need to be high performance therefore at least twice as good thermally compared with much of our existing glazing. Energy use must be no more than 15kWh per square metre per year (heating and cooling) which is around 17 times less than an average house currently uses. Ideally a South Facing property works the best and there is an increased cost to the build of between 8 and 10%. However if recent reports are correct of a scheme in Oldham where super low energy houses have been built by regeneration group Keepmoat , an energy bill of just £20 a year on a 3 bedroomed property seems to suggest the idea may just catch on. And that’s just the start, Alan Higgins, director of Oldham council public health quoted recently as saying that 20,000 homes in Oldham suffer from fuel poverty. If this is remedied, it could generate savings of as much as £250 per person for the NHS as a result of improved health.
If a Passivhaus is on your wish list then the good news is that a retrofit to a suitable existing property is possible with an estimated reduction in energy consumption of 75%. Which all lends itself to helping industry achieve the 80% reduction in carbon set as a legislative target for the UK.