The Passivhaus is a voluntary building standard, that exceeds the present regulations by far. Homes developed according to this standard will have a 90% reduction in heating demand of c15kWh/m²a, compared to a conventional domestic building, which has an average heating demand of  150kWh/m2a. These principles can be applied not only to the residential sector as the name suggests, but also to commercial, industrial and public buildings.

How do they work?

PassivHaus buildings are highly insulated and very air-tight. This means that they can get most of their heat from the sun, human occupants and any appliances used in the building. They may need a small amount of heat from more conventional heating systems.

Design and construction

The PassivHaus uses a combination of low energy building design and use of renewable and low carbon technologies. Achieving the major decrease in heating energy consumption required by the standard involves a shift in approach to building design and construction. Design is carried out with the aid of the 'Passivhaus Planning Package' (PHPP)

At brilliant futures ltd we are trained to use PassivHaus Planning Package and are able to undertake the assessment and assist with the certification of your development. We are also regular attendees of the annual PassiveHaus conferences to keep up to date with both Passivehaus certified products and to new developments. If you are interested in developing a passive house we can assist with:

• completion a Passivhaus planning package (PHPP) assessment
• Advice on design and detailing of U values
• Assist with specification of components and building services

Passive solar design

Following passive solar building design techniques, where possible buildings are compact in shape to reduce their surface area, with windows oriented towards the equator (south in the northern hemisphere and north in the southern hemisphere) to maximize passive solar gain. However, the use of sollar gain  is secondary to minimizing the overall energy requirements.

PassivHaus houses  can be constructed from dense or lightweight materials, but some internal thermal mass is normally incorporated to reduce summer peak temperatures, maintain stable winter temperatures, and prevent possible over-heating in spring or autumn before normal solar shading becomes effective.

Passivhaus buildings employ super insulation to significantly reduce the heat transfer through the walls, roof and floor compared to conventional buildings. A wide range of materials can be used to provide the required low U values, typically in the 0.10 to 0.15 W/(m².K) range). Special attention is given to eliminating thermal bridges

A disadvantage resulting from the thickness of wall insulation required is that, unless the external dimensions of the building can be enlarged to compensate, the internal floor area of the building may be less compared to traditional construction.

To meet the requirements of the Passivhaus standard, windows are manufactured with exceptionally low U-values, typically 0.85 to 0.70 W/(m².K) for the entire window including the frame). These normally combine triple-pane glazing (with a good solar heat-gain coefficient, Low e coatings, argon or krypton gas fill, and 'warm edge' insulating glass spacers) with air-seals and specially developed thermally-broken window frames.

In Europe for unobstructed south-facing Passivhaus windows, the heat gains from the sun are, on average, greater than the heat losses, even in mid-winter.

Building envelopes under the Passivhaus standard are required to be extremely airtight compared to conventional construction. Air barriers, careful sealing of every construction joint in the building envelope, and sealing of all service penetrations through it are all used to achieve this. Airtightness minimizes the amount of warm (or cool) air that can pass through the structure, enabling the mechanical ventilation system to recover the heat before discharging the air externally.

Mechanical ventilation with heat recovery MVHR systems, with a heat recovery rate of over 80% and high-efficiency electronically commutated (ECM) motors, are employed to maintain air quality, and to recover sufficient heat to dispense with a conventional central heating system.

Space heating

In addition to using passive solar gain, Passivhaus buildings make extensive use of their intrinsic heat from internal sources – such as waste heat from lighting, white goods (major appliances) and other electrical devices (but not dedicated heaters) – as well as body heat from the people and animals inside the building. (People, on average, emit heat energy equivalent to 100  Watts.

Together with the comprehensive energy conservation measures taken, this means that a conventional central heating system is not necessary, although they are sometimes installed due to client scepticism.

Instead, Passivhaus houses sometimes have a dual purpose 800 to 1,500 Watt heating and/or cooling element integrated with the supply air duct of the ventilation system, for use during the coldest days.  The air-heating element can be heated by a small heat pump or simply by a gas or oil heater. Beyond the recovery of heat by the heat recovery ventilation unit, a well designed Passivhaus in the European climate should not need any supplemental heat source if the heating load is kept under 10W/m² . Because the heating capacity and the heating energy required by a passive house both are very low, the particular  enrgy source selected has fewer financial implications than in a traditional building, although renewable energy sources are well suited to such low loads.

To minimize the total primary energy consumption, low-energy lighting (such as compact fluorescent lamps) and high-efficiency electrical appliances are normally used.

Please contact us to discuss your building and we can tell you how we can help.