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Swegon Air Academy seminars in Denmark: Part 2 – Large potential in energy renovation of existing buildings by Carsten Rode
June 20, 2013

Swegon Air Academy seminars in Denmark: Part 2 – Large potential in energy renovation of existing buildings by Carsten Rode

Carsten Rode is the Head of the Section of Building Physics and Services at the Technical University of Denmark (DTU) and he is involved in various research projects dealing with heat and moisture transport in buildings. Carsten has presented his thoughts on energy and renovation of buildings that works including his thoughts on energy policy objectives and potentials, energy renovation measures and challenges including some interesting projects.

As an opening statement Carsten said: “There is a huge potential in energy renovation of the existing building stock. We must not again have this opportunity escaped to us as it has happened already in the energy crises of the 1970s. By using common principles for building stock we can improve energy and provide an overview of the advantages and disadvantages of different methods to assess the risks and potential for reducing energy consumption while improving indoor air quality, comfort and durability.”

In EU, the Energy Policy from Article 7 for existing buildings from EPBD (recast, April 2010) states: “Member States shall take the necessary measures to ensure that when buildings undergo major renovation, the energy performance of the building or the renovated part thereof is upgraded in order to meet minimum energy performance requirements set in accordance with Article 4 in so far as this is technically, functionally and economically feasible. Those requirements shall be applied to the renovated building or building unit as a whole. Additionally or alternatively, requirements may be applied to the renovated building elements.”

In Denmark, the BR10 deals with energy requirement in the following article 7.4.1. Rentabel varmeisolering skal foretages i forbindelse med vedligeholdelse af bygningsdele. The average consumption in buildings in Denmark is approximately 170 kWh/(m2.a) and the building code 2010 only permits to use approximately half of this amount. The building sector in total uses approximately 440,9 PJ and almost half of this energy goes to the residential buildings for district heating and fuels. Out of this energy there is a future potential to actually save up to 108,7 PJ in the residential buildings, especially in single family dwellings. To save this energy there are certain energy measures which need to be carefully applied and it includes the attention to the building envelope and air tightness, air- and water-borne installations in buildings, and other issues connected with energy supply and renewables. Just a reminder that most of renewable energy in Denmark comes from wood (62.9%), wood pellets (19.1%), heat pumps (9.7%), straw (6.7%), solar heating (0.7%) and woodchips (0.2%).

Carsten has showed two wonderful examples of a typical Danish single family dwelling where the consumption was decreased from 190 to 37 kWh/(m2.a) and a multi-residential building with original heating consumption of 80 kWh/(m2.a) decreased to 40 kWh/(m2.a) by energy renovation and furthermore down to 19 kWh/(m2.a) with installation of ventilation heat recovery system.

From the research done by DTU it can be seen that the following measures can be considered such as external insulation and air-tightening of wall/roof/ceilings/slab including insulation of foundations and crawl spaces. Furthermore, the windows need to be replaced with energy-efficient windows and there must be an installation of mechanical ventilation with heat recovery (ventilation loss is typically 35-40 kWh/(m2.a), of which 80-90% could be recovered) with efficient fans (consuming typically about 7 kWh/(m2.a), but may be reduced to 3 kWh/(m2.a)). There are also opportunities in technical installations such as insulation of non-insulated pipes and heat exchangers, etc. In public buildings, there are significant profitable energy savings to be made and energy savings can be realized profitable by providing different and more stringent energy requirements. Based on analysis, the estimated energy savings potential is to be 15.9 PJ/a (including electricity 3.7 PJ/a).

Another exiting thing was to hear about the project Ryesgade 30C which is a test building for testing energy saving measures such as two different kinds of insulating materials (aero wool and vacuum insulation, i.e. VIP) including the temperature and humidity measurements within structure. Also four different window systems are tested along with decentralized ventilation system with heat recovery. Carsten has actually showed actual samples of insulation materials and talked about their thermal characteristics and price (aerogel with λ=0.014 W/(m.K) and price of 2-3,000 €/m2; VIP with λ=0.021 W/(m.K) and price of 2,000-2,500 €/m2, aero wool with λ=0.019 W/(m.K) and price of 4,000 €/m2, and glass wool with λ=0.032 W/(m.K) and price of 80 €/m2).

Carsten has also shared some of his interesting points from the research in Greenland and his experience with rather unprofessional ventilation installations. He also described other angles which need to be considered when renovating in order to take in humans´ aspects (comfort & health, working environment, aesthetics, invasiveness, image & exposure), impact on planet (energy use & environmental impact) and consideration for economy (robustness and profitability). Carsten has ended his presentation with the lookout in the future where we are on a way to significantly fulfill the energy saving goals by 2050 (with the largest potential being in application of heat recovery system in buildings) and that even such a small country as Denmark has to contribute to achieve the goals by 2050.