UNDERFLOOR HEATING A solution or a problem? Joakim Larsson Master Thesis in Energy-efficient and Environmental Buildings Faculty of Engineering | Lund University Lund University Lund University, with eight faculties and a number of research centers and specialized institutes, is the largest establishment for research and higher education in Scandinavia. The main part of the University is situated in the small city of Lund which has about 112 000 inhabitants. A number of departments for research and education are, however, located in Malmö and Helsingborg. Lund University was founded in 1666 and has today a total staff of 6 000 employees and 47 000 students attending 280 degree programs and 2 300 subject courses offered by 63 departments. Master Program in Energy-efficient and Environmental Building Design This international program provides knowledge, skills and competencies within the area of energy-efficient and environmental building design in cold climates. The goal is to train highly skilled professionals, who will significantly contribute to and influence the design, building or renovation of energy-efficient buildings, taking into consideration the architecture and environment, the inhabitants’ behavior and needs, their health and comfort as well as the overall economy. The degree project is the final part of the master program leading to a Master of Science (120 credits) in Energy-efficient and Environmental Buildings. Examiner: Hans Bagge (Building Physics) Supervisor: Dennis Johansson (HVAC) Keywords: Underfloor heating, Energy, Thermal mass, Energy efficiency, Heating systems Thesis: EEBD–15/10 Underfloor heating- a solution or a problem Table of content 1 Background ............................................................................................... 1 1.1 Energy and environmental issues 1 1.1.1 EU directives 1 1.1.1.1 National targets 1 1.1.2 Energy in Swedish residential buildings 1 1.2 Underfloor heating 2 1.2.1 Possible benefits of underfloor heating 2 1.2.2 Possible disadvantages with underfloor heating 2 1.2.3 Floor materials 3 1.2.4 System control 4 1.2.5 Underfloor heating in combination with heat pumps 4 1.3 Objectives 4 1.4 Limitations 4 2 Method ...................................................................................................... 7 2.1 Questionnaire study 7 2.2 Indoor climate measurements 8 2.2.1 Loggers and outdoor climate 8 2.2.2 Sorting of values 8 2.2.3 Analyses of the measured houses 9 2.3 Simulations 9 2.4 Industry knowledge and directives 9 3 Results and analysis ................................................................................ 11 3.1 Questionnaire study 11 3.1.1 Overall satisfaction 11 3.1.2 Discomforts 12 3.1.2.1 During heating season 13 3.1.2.2 During the whole year 13 3.1.3 Flooring materials 15 3.1.3.1 Cold floors 17 3.1.3.2 Varying temperature with different flooring materials 17 3.1.4 Wanted temperature 19 Underfloor heating- a solution or a problem 3.2 Indoor climate measurements 19 3.2.1 Temperature measurements 20 3.2.1.1 Distribution of logged temperatures 20 3.2.1.2 Influence of the outside temperature 25 3.2.1.3 Comparison between the two measured systems 26 3.2.2 Humidity measurements 27 3.2.2.1 Comparison between the two measured systems 33 3.2.2.2 Influence of the outside relative humidity 34 3.2.3 Analysing the measured residences 35 3.2.3.1 Comparing with the questionnaire answers 35 3.2.3.2 Moisture addition 36 3.3 Simulations 38 3.3.1 Energy simulations 39 3.3.2 Thermal mass 40 4 Discussion ............................................................................................... 43 4.1 Industry knowledge 43 4.2 Questionnaire study 43 4.3 Indoor climate measurements 45 4.4 Simulations 46 5 Conclusions ............................................................................................. 49 6 Future work ............................................................................................. 51 References ....................................................................................................... 54 Appendix A ..................................................................................................... 56 Appendix B ...................................................................................................... 57 1 Background 1.1 Energy and environmental issues According to the Intergovernmental Panel on Climate Change, IPCC, it is clear that humans have had a grave impact on the climate changes that has taken place since the 1950s. The atmosphere and the oceans are getting warmer which causes ice and snow to melt, raises the sea-levels and increases the risk for natural disasters. The anthropogenic emissions of greenhouse gases are at an all-time high, much because of the persistent use of fossil fuels. 80% of the world’s energy use still comes from fossil fuels. This might come as a surprise since the negative impact of using fossil fuel is well known and that the environmental question often is high on the political agenda. (IPCC,2013) There are several reasons for this, one being the exponential increase of human population, another is that although highly developed countries use of fossil fuel decreases the use in less developed countries increases as they are reaching for quick and cheap changes. Renewable energy sources, which have a much lower emission of greenhouse gases than fossil fuels, are becoming more evolved and more common. This is a step in the right direction, but it is not the only solution. In order to more effectively decrease the environmental impact the use of energy should be lowered. 1.1.1 EU directives In March 2007 the European Union leaders set new targets for its members in order to try reducing the environmental impact and to support the development of renewable energy sources. The three major objectives are; a 20% reduction in EU greenhouse gas emissions from 1990 levels, raising the share of EU energy consumption produced from renewable resources to 20 % and a 20% improvement in the EU’s energy efficiency. Because of these three key objectives the targets are known as the “20-20-20” targets and are aimed to be fulfilled in 2020. 1.1.1.1 National targets The Effort Sharing Decision sets national targets for 2020 which is binding for each member in the European Union. This decision targets the 60% of greenhouse gas emissions that is not produced by the industrial sector and therefore not covered by the EU Emission Trading System. The targets which is expressed in percentage-change from 2005s levels is decided by the wealth of each country, this means that a wealthy country have to lower its emissions more than a less wealthy. A less wealthy country is even allowed to increase their percentage in order to leave space for a growing economy, the main goal is that in 2020 the greenhouse gas emissions (covered by the Effort Sharing Decision) from all members of the European Union should be lowered by 10%. 1.1.2 Energy in Swedish residential buildings As set by the Effort Sharing Decision Sweden needs to lower its greenhouse emissions outside the industrial sector with 17% compared to 2005s levels. Greenhouse gases from residential buildings fall under this category and will be addressed by improving the energy performance of buildings. (Council of European Union, 2015) 1 Underfloor heating- a solution or a problem In 2013 the energy consumed within residential buildings in Sweden was 63 427 GWh and approximately 87% (55181 GWh) of this energy was used to heat the buildings. A good way to reduce the consumption of energy and thereby lower the impact on the environment could be to use more efficient heating methods. (Statistikcentralen, 2014) 1.2 Underfloor heating Underfloor heating is often promoted to be an energy efficient heating method and is becoming more and more common in Swedish single family houses. 61% of all single family houses built in Sweden during 1996-2005 was equipped with underfloor heating, which is a large increase compared to 1986-1995 where only 10% of new buildings where equipped. (Betsi, 2009) An underfloor heating system functions similar to the traditional radiator heating system, but instead of having hot water running through and heating small surfaces, such as radiators that are placed inside the room, the hot water runs through pipes that are casted in the foundation under the floor or placed underneath the flooring material and therefore heats up the larger floor area. According to the Swedish authorities the floor surface should not exceed 27°C. (T2, 2002) 1.2.1 Possible benefits of underfloor heating Underfloor heating should take away the factor of cold floors which is a desirable advantage for many. It is also hidden underneath the flooring and does not take away space or affect the appearance of the living area. The human head thrives in a temperature of about 18-20°C but the feet wants a temperature about 5°C higher than that. If a room is heated from the floor the general temperature in the room should thereby be able to be lower, because the human feet is the primary sensory organs for temperature i.e. if the feet are warm we feel warm. This should, according to experts, allow for a room temperature that is 2-3°C lower and an energy saving of about 15% than if a conventional radiator system were used. (Boverket, 2015) Since radiators are relatively small in area the water needs to be relatively hot in order to heat an entire room, the radiated heat will also mostly be located around the radiator. This should not be the case for underfloor heating. Since the entire floor is heated there is a lot of contact between the heated floor and the air, which should allow for lower water temperatures in the system and more dispersed heat in the entire room. (Boverket, 2015) Utilizing the thermal storage in a building is often a good way to lower the amount of energy needed to keep a building heated. Since the entire floor is heated when underfloor heating systems are used there is a lot of mass where the thermal energy can be stored.