Published on : 23 July 20215 min reading time
A House of Efficiency – what is it?
Anyone who wants to build a new house today and at the same time pay attention to energy consumption and environmentally friendly heating is confronted with a multitude of complicated questions and technical terms.
With this two-part contribution, we would like to shed light on the vast field of energy-efficient construction.
Offers from developers, prefabricated house manufacturers or even questions from the architect can be very confusing for clients.
But there are still some important decisions to be made.
What do individual building standards and energy consumption data mean?
It all seems pretty fuzzy.
After all, the interaction of many different components and the heating system are part of an energy-efficient house.
Alone, there are many, many possibilities to build energy-saving.
Then there is the behavior of the users, which can be decisive in determining how much energy is really needed later and how much more to buy.
STATEMENTS ABOUT INDIVIDUAL COMPONENTS DO NOT HELP THE CUSTOMER
Let’s start with the individual components. There are offers from real estate developers or manufacturers of prefabricated houses that advertise with the characteristic value of the individual elements.
Here, the U-value, which is the heat transfer coefficient, is given for the individual building components.
This value describes the amount of heat lost by one square meter of wall, window or roof.
However, this is not useful for building owners.
Because there are many different components.
Finally, the interaction is decisive for the consumption, in connection with the heating system and the user.
These values do not allow statements about the heating energy consumption to be made later.
In the case of cars, it is also not possible to draw conclusions about fuel consumption from the rolling resistance of the tires.
THE MINIMUM STANDARD FOR THE ENERGY EFFICIENCY OF BUILDINGS IS DETERMINED BY THE ENERGY SAVING ORDINANCE (ENEV)
The minimum requirements for the energy standard of buildings are regulated in the Energy Savings Ordinance (EnEV).
The individual building components are included with their heat losses, ventilation heat losses and internal heat gains.
The efficiency of the planned heating system is also included in the calculation.
The result is a primary energy requirement per square meter of floor space per year.
This value can be used to compare individual buildings with different designs and equipment.
The final energy demand, on the other hand, always depends on the energy source.
EVERYONE KNOWS THE FUEL CONSUMPTION OF A CAR, BUT A HOUSE?
By analogy with the car, keyword car 3 liters, we can divide the energy requirements by a factor of ten and thus obtain a house of 5 liters, for example.
This factor is the energy content of heating oil.
However, it is important to distinguish whether the figure refers to primary or final energy demand.
CHANGES IN THE ENEV SINCE MAY 2014
The current version of the Energy Savings Ordinance has been in effect since May 1, 2014, and as of January 1, 2016, the requirements for primary energy demand will be increased by 25%.
This means that the calculated value must then be at least 25% lower than the value allowed today.
With the new version of the Energy Savings Ordinance of May 2014, energy efficiency classes were introduced on the energy certificate that is issued for each house.
These classes from A (very good) to H (very bad) are already familiar from household appliances and make it easier for the buyer to navigate.
MORE EXTENSIVE EFFICIENCY STANDARDS IN THE KFW EFFICIENCY HOUSE
Those who want to go beyond the minimum requirement can best be oriented to the levels of the KfW Effizienzhaus.
KfW offers attractive subsidies in the form of low-interest loans and repayment assistance.
The lower the energy requirements of the building, the better the promotion.
The KfW Efficiency House is available for new buildings in the standards 70, 55 and 40, which means that the energy requirement in these buildings is only 70, 55 or 40 percent of a building according to the Energy Savings Ordinance.
100 would simply mean meeting the requirements of the Energy Savings Ordinance.
The KfW Efficiency House 70 then has an annual primary energy requirement of 70 percent of the EnEV.
As a result, KfW Efficiency House 55 meets the EnEV requirements and KfW Efficiency House 40 only meets the primary energy requirement of the EnEV.
DIFFERENT WAYS TO GET TO THE KFW EFFICIENCY HOUSE
There are different ways to achieve these more efficient building standards.
Heat loss from the building can be reduced by better insulation of the exterior wall or roof, or by installing better windows, or by improving the efficiency of the heating system.
Since the primary energy requirement is decisive, heating systems based on renewable energies are advantageous.
These include, for example, solar thermal systems, wood pellet heating systems or heat pumps.
The path to the KfW Efficiency House must always be found in practice in each individual case.
Depending on the level of additional costs, the decision will be made to reduce the heat loss through the building envelope or to use a different heating system.
Often it is a combination of these measures.