Definition: Passive house and Passive house windows


>> What is a Passive house?

A building standard that is truly energy efficient, comfortable, economical and environmentally friendly at the same time. The Passive House is not a brand name, but a building concept open to all – and proven in practice. That is why the Passive House is more than “just” an energy-saving house:

>>  A Passive House consumes 90 percent less heating than a house in existing construction. And even compared to an average new building, more than 75% is saved. The heating energy consumption of a passive house lies with around 1.5 l fuel oil equivalent per square meter of living space and year around a multiple under that of a low-energy house. Heating remains affordable – even in times of crisis.

>> In addition, the living comfort in a passive house is significantly improved. The passive house uses the energy sources available inside it, such as the body heat of people or incident solar heat – heating is thus fundamentally simplified.

>> Special windows and an envelope of highly effective thermal insulation in the exterior walls, roof and floor slab keep the heat inside the house in a protective manner.

>> A ventilation system ensures constant fresh air without drafts, in which a highly efficient heat recovery system makes the heat from the exhaust air available again.

Passive houses achieve the enormous energy savings through particularly energy-efficient building components and through ventilation technology. The comfort is not saved, it is even noticeably improved

Passive houses are the means to become independent of rising raw material prices. That applies to the individual building family – and it applies to each place, each region, each country. Passive Houses can be built anywhere – and the building materials for them are available everywhere. The most important principle is the energy balance – the know-how for this can be learned by every building expert.

>> What can a Passive house do?

Through the coordinated concept, a quality is achieved that leads to very good comfort in winter as well as in summer and still reasonable construction costs. The experiences of the users reflect this.

In Passive Houses, good thermal insulation and airtight construction have proven to be excellent. Another basic principle is “thermal bridge-free construction”: Insulation is placed around the entire building without weak points. This leaves neither cold corners nor excessive heat loss. This, too, is a contribution to high-quality, comfortable and damage-free construction and thus substantially increases the quality of the building. These quality improvements should actually be a matter of course in any new building anyway – in the Passive House they are.

>> How a Passive house works

The Passive house is the world’s leading standard for energy-saving construction: Energy savings in heating are more than 80% compared to the legally required standards for new buildings. The Passive House concept is a comprehensive approach to low-cost, high-quality, healthy and sustainable building.

Anyone can easily understand the concept:

>> Today’s new buildings are built so airtight that air renewal through joints and cracks alone is insufficient. But even the often-recommended window ventilation does not produce convincing results. Fresh air is not just a matter of home comfort, but a necessity for healthy living. Therefore, home ventilation is the key technology for all residential buildings and home renovations of the future.Of course, home ventilation systems require additional investment funds. But if they are built highly efficiently, they save energy costs noticeably. Ventilation systems with passive house quality allow economical operation.

>> Now comes the decisive “trick” of the Passive house concept: Air comes into every living space anyway with the fresh outside air. If this air also takes over the heating task – without high air volumes, without recirculation, without noise and without drafts – then the ventilation pays off twice.

>> However, this concept of “fresh air heating” is only possible in a house with really good thermal insulation. In a passive house. For the experts: The maximum transmission heating load must be less than 10 W/m² so that the fresh air can also transport the heat.

>> Passive house criteria:

>> The heating requirement in a Passive house is less than 15 kWh/(m²a) (based on living space) – or the heating load is less than 10 W/m².

>> The primary energy demand does not exceed 120 kWh/(m²a).

>> The air tightness reaches at least n50 = 0.6/h.

>> The excess temperature frequency in summer should be below 10%.

They always apply to specific uses within a specific climatic context. For residential and office buildings in tropical humid climates, for example, own numerical values can and must be derived on the basis of the Passive House definition, which may deviate from the Central European values.

>> What does the term annual primary energy demand mean?

Annual energy quantity which, in addition to the energy content of the fuel and the auxiliary energies for the system technology, also includes the energy quantity required for extraction, conversion and distribution of the fuels used in each case (upstream process chains outside the building) with the aid of the primary energy factors applicable to the respective energy sources. Primary energy can also be used as an assessment parameter for ecological criteria such as CO2 emissions, because it includes the total energy required to heat the building.

>> What makes a house a Passive house?

According to its name, the Passive house generates its thermal energy primarily from passive heat sources such as solar radiation and waste heat from technical equipment and the occupants. To achieve this goal, optimal thermal insulation is necessary, which, among other things, places high demands on the insulation of windows and exterior doors.

>> Which components can call themselves Passive house components?

The Passive House Institute in Darmstadt/Germany maintains on its website a list of certified components that can be used for an energy-efficient building. The components are divided into 3 categories: Opaque Building Envelope, Building Services, and Transparent Envelope. Passive house certified components are approximately two to four times more efficient than the corresponding commonly used products.

Products bearing the “Passive House suitable component” certificate have been tested according to uniform criteria, are comparable in terms of their characteristic values and are of excellent energy quality. Their use makes the planner’s task much easier and contributes significantly to ensuring the proper functioning of the resulting Passive house.

>> Why are windows so important in a Passive house?

The building energy quality behind a Passive house results from the sum of its energy-saving construction and the materials and components used for this purpose – one of them: particularly energy-saving windows.

Thermal insulation and heat recovery are key features for Passive House windows in order to passively use solar energy and heat sources available inside. The orientation of the building also plays a major role in maximizing solar gains, especially in winter. Thus, large window fronts with a southern orientation make sense in order to be able to passively use as much solar radiation as possible.

Windows are one of the most important thermal bridges on buildings and lose energy through both the glazing and the frame. To avoid this, the window and frame design of high-quality Passive house windows is very complex.

>> What are the requirements for Passive house windows?

To achieve Passive house certification, Passive house windows must not exceed a window U-value (Uw-value) of 0.80 W/m²K according to EN 10077. The Uw value is also known as the heat transfer coefficient and, according to the DIN EN 10077 standard, indicates the amount of thermal energy per m2 of window area that is lost from the inside to the outside through a window. The Uw value is made up of the heat transfer coefficient of the frame (Uf) and the glass (Ug).

The certified ENERsign® primus wood-aluminium passive house window is the premium window with the best insulation values. With ENERsign® products, the construction of passive houses, zero-energy houses, plus-energy houses and KfW efficiency houses 40 and 40+ can be excellently realized.

>> U-value window >> Fixed: 0.59 W/m²K according to EN 10077
>> U-value window >> Turn + Tilt: 0.60 W/m²K according to EN 10077

>> Passive house window certified

The passive house standard is characterized by very high energy savings compared to conventional new buildings. This saving is achieved through highly efficient buildings and building services. In addition to careful detailed planning, this requires the use of particularly energy-efficient components. As a rule, these components are around two to four times more efficient than the corresponding commonly used products. This high energy efficiency is crucial for achieving the passive house standard.

However, it is often difficult for the designer to assess components in terms of their energy efficiency, durability and the energy characteristic values to be applied: Available characteristic values from standardization are often unrealistic or not sufficiently accurate. Reliable project planning is often not possible on the basis of the manufacturer’s specifications alone.

As an independent body, the Passive House Institute tests and certifies products with regard to their suitability for use in passive houses. Products bearing the “Passive House Suitable Component” certificate have been tested according to uniform criteria, are comparable in terms of their characteristic values, and are of excellent energy quality. Their use greatly facilitates the task of the designer and significantly contributes to ensuring the proper functioning of the resulting passive house.


>> What does the U-value say about certified Passive house windows?

Window construction is very complex in Passive house windows because, in addition to the glass, the frame is another factor in thermal insulation. The heat transfer coefficient of the entire window (Uw) is divided into Uf value and Ug value, where the Uf value reflects the heat transfer coefficient of the window frame and the Ug value reflects the value of the glazing:

>> Uw (U-value window): Heat transfer coefficient of the entire window.
>> Uf (U-value-frame): Heat transfer coefficient of the window frame
>> Ug (U-value glass): Heat transfer coefficient of the glazing.

According to the DIN EN 10077 standard, the Uw-value indicates the total amount of heat energy per m2 of window area that is lost from the inside to the outside through a window. Click here for our Uw-value calculator.

The interaction of the frame profile and the edge seal between the seal and the glazing is indispensable for achieving optimum thermal insulation. Another value is the pane bond, which is given as the psi value per linear meter of glass bond.

In passive house buildings, however, windows are important not only for limiting heat loss, but also for energy gain. Therefore, the total energy transmittance (g-value) as well as the TL-value for the light transmittance (transmittance for visible light) must also be correct:

>> low U-value means better insulation
>> high g-value means higher energy gain
>> high TL value means more light

Welcome to ENERsign® Price Configurator with U-Value window Calculation:

You don’t want to go through the trouble of obtaining various offers, but would like to find out the recommended prices and U-values for our high-quality ENERsign®primus window? Then try our price configurator, here you can put together your desired windows as you wish and try out different sizes and designs.

All you need is the desired dimensions and window types and you can configure immediately. The window price and U-value window will be adjusted automatically, so that you always have an overview and can compare directly.

We are uncompromising in the product we offer:
ENERsign®primus elements with at least triple glazing with a U-value glass of 0.52 W/m²K and a g-value of 53%. Other designs and special glasses are available on request.

Welcome to the ENERsign® U-Value window configurator:

The U-value window is also called heat transfer coefficient and according to the standard DIN EN 10077 it indicates the amount of thermal energy lost through a window to the outside.

The U-value window is calculated using the formula W/(m²K), i.e. watts per square metre and Kelvin. This value refers to the entire window and defines the amount of energy per unit of time that flows through an area of one square meter when the air temperature on both sides differs by one Kelvin. The lower this value is, the less energy or heat the window emits.

Add a product
Add a product
Add a product
Add a product

Configure window

Gesamtpreis (inkl. 19% MwSt)
0€ - 0
Potentially avoided CO2 emissions over 30 years :
Potentially saved energy and CO2 costs over 30 years:
Export to Excel
0 (W/m2K)
Please add a product to configure it.