WHAT EXACTLY IS A PASSIVHAUS/PASSIVE HOUSE?

The Passivhaus standard is also:

  • Where the use of the free thermal gains is delivered by solar irradiation externally plus thermal gains from appliances and occupants internally.
  • Where economic thermal comfort is achieved in summer and in winter without needing a conventional perimeter heat distribution system.
  • Where the fresh air supply distributes the remaining space heating required solely by post heating (or post cooling) of the fresh air mass, which is required to meet regulatory indoor air-quality conditions.
  • Which adheres to the essential EU climatic conditions stated, where the building does not exceed:
    – the 15 kwh/(m²a) space heating requirement;
    – a 10 w/m² constant heat load;
    – the 42 kwh/(m²a) annual total amount of active energy; and
    – the 120 kwh/m²a total energy required for space-heating, domestic hot water and household appliances.

HERE IS THE SIMPLIFIED EXPLANATION

If physics does not happen to be your thing, then the following explanation might be easier to follow:

Passive Houses offer a status whereby a comfortable interior climate can be maintained without active heating and cooling systems. They assure comfortable indoor climates all year around without needing a conventional heat distribution system. To permit this, it is essential that, under climatic conditions prevailing in Central Europe, a building’s annual space heating requirement does not exceed 15 kWh/(m²a).

The amount of heating is so small that a 4 x 5 metre room could be heated with 10 tea lights in winter (so it is said), but the reality is that the individual characteristics should at least be optimised to allow for local conditions.

IT IS STILL A VOLUNTARY CODE

It is sometimes hard to remember that Passive House standard is still a rigorous voluntary standard for energy efficiency in a building and is connected to the reduction of ecological footprints. It is worth noting that local governments and municipalities have the option to incorporate such standards into their building codes, especially as many have signed up to the “Net Zero” ready standard of building and construction.

The Passivhaus Institute set the standard of insulation for walls at a U-value of 0.15.

The definitions of “standard” varies so much that they have become known as: Official, Semi-Official, and Unofficial.

Lines have also become blurred between both Passive schemes and low energy schemes. In Germany for example, they have RAL Passive and Passive House standard – the latter which includes measurements and accepted standards for building components such as heat exchangers and pumps.

In Germany, they have produced a chart rather like our energy ratings charts on domestic appliances and the A++ rating is for a wall U-value of 0.1 and the A+ rating for 0.15.

SO, WHAT IS THE STANDARD IN THE UK NOW?

Homes built to the Passive House standard in Ireland or the UK typically include a wall U-value of 0.15 W/m2K or better.

A 2016 analysis by Passive House Plus of data from the Sustainable Energy Authority of Ireland’s (SEAI)
National BER Research tool revealed that the average U-values for new Irish homes have been dramatically improved as a consequence of tightening building regulations – with respective average figures for walls, roofs and floors of 0.17, 0.13 and 0.14 W/m2K, though the backstops stipulated in the regulations are less ambitious. U-value requirements in building regulations in the UK lag some way behind at present.

In the “Passivhaus Primer: Designer’s guide”, they state that although the recommended standard is 0.15 in a North facing / increased shading aspect, it is better to be nearer 0.1 in order to maintain the HLP (Heat Loss Parameter). If this is not possible, then they recommend glazing with installed U-values of 0.85 and good solar transmittance “g” values of 0.5.

The International Passive House Association (iPHA) say the U-Value should not exceed 0.15,
but would recommend aiming for a U-Value of 0.1 as ideal.

Call us on: +44 (0) 113 733 5186 to find out more!