Reduce heating costs by isulating your home

Energy Efficiency – The Expert Advises

Physicist Joachim Zeller of ebök, an engineering office located in Tübingen (Germany), has been working on energy saving strategies for over 20 years. He reveals how small measures can increase your energy efficiency and cut your energy costs.

Just in Time to Lower Energy Costs for the Winter

Expert advice on how to save energy

Expert advice on how to save energy

The trend of everything getting more expensive is most noticeable in the rising energy costs for heating and hot water. In the past year, expenses for electricity, gas, heating oil and other fuels rose by almost ten percent. Physicist Joachim Zeller of ebök, an engineering office located in Tübingen (Germany), has been working on energy saving strategies, especially for private households, for over 20 years. The energy expert reveals where the worst energy thieves are hiding and what measures consumers can take to lower their energy costs, even with small measures.

Nearly half of energy costs in private households is spent on heating. Where are the energy wasters lurking?

Joachim Zeller: There is not just one energy thief that can be eliminated to achieve optimum energy efficiency. For older, non-restored buildings, there are weak points almost everywhere in the house. High heat losses occur, for example, on all exterior parts of the building, i.e. the exterior walls, roof, basement ceiling and windows.

Windows alone can account for as much as one quarter of total energy consumption. Why is that?

Joachim Zeller: Older windows, especially those with single glazing, have a very poor heat insulation effect. Gaps around windows that are not airtight are further weak points that lead to draft-induced heat loss and thus to higher energy costs.

What can one do to ensure that money for heating costs is not literally being thrown out the window?

Joachim Zeller: In principle, it makes sense to revamp your house energy-wise. A planned makeover for your house should be preceded by an analysis of your house's energy consumption/loss by a qualified energy consultant. This is the only reliable basis for a sound energy-saving plan that will have significant long-term savings.


Not everyone can implement a major energy-saving plan right away. How effective are interim solutions such as sealing window joints with sealing strips?

Seal gaps to exclude cold draught in winter

Seal gaps to exclude cold draught in winter

Joachim Zeller: A study on the air permeability of tesamoll® sealing strips certifies that the product range has very good sealing performance. Based on this, we calculated the energy-saving effects that can be achieved by weather-proofing window gaps of various widths. Our study focused on single-family homes and multi-household dwellings built in the 1960s and 1970s.

What results did you get?

Joachim Zeller: In all study models with gap widths of 2 mm or greater, the use of tesamoll® tapes shows a positive saving effect as early as after one winter. The cost savings for heating are then already more than the purchase price for the tapes. For a house with many non-sealed windows with larger gap widths, up to 20 percent of heating costs can be saved using the sealing strips. A case in point: For gaps 3 mm wide, you save around EUR 150 in heating costs per roll in four years. For wider gaps, you can save even more money.

Is this a solution only for tenants or also for home and condominium owners?

Joachim Zeller: In the long term, owners are betting on revamping their buildings – also in view of the energy certificate, which has been in place since mid-2008. It is recommended that condominium owners, who cannot decide by themselves whether to replace windows, as well as homeowners, who cannot or do not yet want to revamp, install sealing strips on their window joints before the onset of winter to minimize heat loss.

Can you also make mistakes when ventilating rooms, and not just with unintended air slipping through cracks?

Joachim Zeller: For health and energy reasons, appropriate ventilation through windows is desirable. This means that the frequency and intensity of ventilation is primarily related to the outside temperature and the humidity in the room. The rule of thumb for the months November through March is short, intense ventilation for 4 to 6 minutes every 2 hours, if possible. During the summer months, the ventilation intensity should be significantly higher, i.e. half an hour each time you ventilate.

It is not only possible to ventilate too much, but also too little. What happens then?

Joachim Zeller: By ventilating too little, you run the risk of not only having stuffy air, but also higher humidity, which can lead to the formation of mold. When sealing strips are installed, you should also ventilate more. Yet moderate ventilation is not an energy waster, in contrast to non-sealed window joints.

Why is that?

Joachim Zeller: Air inflow through window joints is driven by the weather. The colder and windier it is outside, the more air is forced through the joints. The required dehumidification occurs very quickly, yet the airflow through the joints continues. For energy reasons, this should be precisely the other way around: the warmer the outside temperature, the more intensely the room should be ventilated. The frequency and intensity of ventilation is best taken into your own hands.