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Varmeakkumulering i beton
Bilag 1. Danish case stories on the
thermal performance of concrete
Carried out by:
Dorthe Mathiesen, Danish Technological Institute
Lars Olsen, Danish Technological Institute
February 2004
Introduction
The purpose of this note is to present an overview of best practise examples of utilising the heat accumulation capability of concrete in order to lower the energy consumption for heating and cooling in buildings in Denmark and to present an overview related R&D projects where Danish companies are involved.
The heat accumulation capability of concrete can be divided in three different types.
- Passive utilisation where heat gains through windows or from other sources is accumulated in the concrete structures as floors, walls and roofs.
- Active utilisation where heat or cold is actively supplied to building integrated storage’s e.g. walls or floors. The heat is transported to the concrete structures by means of air or water in tubes or channels. The heat can e.g. come from solar collectors. The cold can e.g. come from cold external air during the night. The heat and cold are normally emitted passively from the storage to the rooms.
- Solar walls where solar radiation heats a concrete wall directly. A layer of glazing reduces heat losses from the concrete wall. The heat is in most cases emitted passively from the wall to the room.
Another type of projects deals with reduction of thermal loss through the joints of the constructions e.g. thermal bridges.
Most of the buildings presented as case stories in this note are constructed as a part of a project funded by different authorities and companies. It has therefore been difficult to distinguish between case stories and R&D programmes. The examples presented in this note are therefore gathered in the chapter “Case stories” covering both actual buildings and R&D projects.
It has been chosen to limit the case stories presented to be not older than 5 years. It shall be mentioned that a lot of work has been done earlier, which might be of interest if the overview shall be further elaborated.
The note is prepared by searching in the literature, by contacting engineering companies, Danish universities and institutes and by searching information available on the Internet.
In the last chapter of this note other references which appeared during the work is presented. These references cannot be presented as Danish case stories of the thermal performance of concrete but the references are found relevant for this project.
Case stories
Thermal active construction for hybrid heating and cooling of office buildings
Project no: ENS-1213/01-0020 (Danish Energy Authority)
Partners: COWI, Danish Technological Institute, Spæncom a/s and BYG·DTU
Completed: December 2001.
Abstract
A thermo active construction is a construction which is an ordinary building component like a concrete slab constructed with pipes for liquid and which at the same time can function as both a heating and a cooling surface.
The storage capacity of a thermo active construction is well suited for utilisation of renewable energy, e.g. from solar facades. The operation temperature will typically be around 17-27 °C. The utilisation of thermo active constructions removes visible radiators and cooling plants. The heating is affected by low temperature operation, and cooling is effected in earth tubes, by night cooling, ground water or pipes embedded in piles.
The potential of the energy savings from use of thermo active constructions instead of traditional cooling is 10-15 kWh/m². Furthermore, it will be easier to design the offices. This project dealt with evaluating the possibilities of system solutions with thermo active constructions acting both as heating and cooling system under Danish conditions and with integration of renewable energy.
Thermo active constructions are often used in e.g. Germany and the concept is based on in-situ cast concrete constructions. There is a need for developing solutions for the pre-fab industry, which Danish building traditions is based on.
References
1. ”Termoaktive konstruktioner. Fase 1 – forprojekt. Slutrapport”; COWI A/S, Teknologisk Institut, - Energi, BYG.DTU; Maj 2002. (In Danish)
2. ”Det skjulte indeklima – Termoaktive konstruktioner”; Hansen, J. O.; Jacobsen, T. D. og Weitzmann, P.; VVS 13 – 2002., www.techmedia.dk (In Danish)
3. http://www.energistyrelsen.dk/sw1592.asp (The website of Danish Energy Authority)
4. www.buildvision.dk/termoaktivekonstruktioner.asp (A micro site from Danish Technological Institute)
5. www.dsbo.dk (De store bygningers økologi) (In Danish)
Heat accumulation in concrete prefab elements
Project no.: ENS j. Nr. 51181/98-0063 (Danish Energy Authority)
Partners: DTU, Institute for Building and Energy, Danish Technological Institute and COWI A/S
Completed: June 2000
Abstract
The aim of this project was to investigate and optimise heat storage in building components. Especially heat storage in concrete walls with embedded pipes was studied in order to study the thermal behaviour. This was done with numerical models and the results of these studies were compared with existing results from laboratory measurements and field measurements.
The influence of the storage on the heat demand of buildings was studied. A numerical model of a building with a solar air system was implemented in a numerical simulation program (TRNSYS). Simulations of different designs of the heat storage were used for optimisation of the design of heat storage in concrete constructions.
Finally guidelines for design of heat storage in concrete elements were prepared. These guidelines were intended to be used by architects and engineers in practical design situations and in that way ease the design of solar air systems.
References
1. ”Varmelagring i betonelementer”. Del 1 - Generelle retningslinier for dimensionering; Hummelshøj, R.; Rahbek, J.E. (2000) (In Danish)
2. "Varmelagring i betonelementer”. Del 2 - Modellering med TRNSYS.; Dalsgaard Jacobsen, T.; Østergaard Jensen, S. (2000). (In Danish)
3. "Varmelagring i betonelementer”. Del 3 - Modellering med FEMLAB og MATLAB; Rammer Nielsen, T.; Holck, O.; Svendsen, S. (2000). (In Danish)
Concrete elements with better insulation and less thermal bridge effect
Project no.: ENS-1213/99-0008 (Danish Energy Authority)
Partners: BYG·DTU, By og Byg (Statens Byggeforskningsinstitut); Betonelement-Foreningen; Spæncom a/s; Jægersprisvinduet a/s; Arkitektfirmaet Rørbæk og Møller a/s
Completed: September 2000
Abstract
In this project new concrete sandwich panel solutions with better thermal properties have been developed, usable for highly-insulated buildings, responding to the needs that occur when the demands to the permissible energy consumption for heating is further increased. The improved thermal properties have been obtained without increasing the costs more than of the extra insulation. Removing concrete ribs at window reveals and horizontal joints enables a thermal improvement as well as reduced costs due to simpler manufacturing of the panel.
A natural grouping of concrete sandwich panels into two categories formed the basis of the work. The first category is panels covering concrete reveals as typically used in residential housing and office buildings. The other is about panels with load bearing ribs serving as columns typically used in industrial and commercial buildings. Of course there are panels that are a combination of the two categories, but this fact has not been crucial for the analyses in this project.
References
1. ”Betonelementer med bedre isolering og mindre kuldebroer”; DTU-IBE-R-038. vp; Tommerup, H.M. (2000). (In Danish)
Development, optimisation and planning of new building envelope structures made of concrete elements, which demonstrate appliance with heat insulation requirements in Building Regulations 2005
Project no.: ENS-1213/01-0005 (Danish Energy Authority)
Partners: BYG·DTU, By og Byg (Statens Byggeforskningsinstitut); Betonelement-Foreningen; Spæncom A/S; Betonelement A/S; Primo A/S; H. S. Hansen A/S
Completed: 2003
Abstract
The main goal of the project was to strengthen the continued development and usage of the new types of concrete elements that were proposed in the project 'Concrete elements with better insulation and less thermal bridge effect', se case story 3.3.
The project deals with the following three element types, which constitute a great part of the market for concrete elements.
1. One storey high concrete sandwich panels (office, institutional and residential buildings).
2. One storey high concrete elements with rain screens consisting of non-concrete material (brick, wood, glass, metal).
3. Industrial elements in the shape of high sandwich panels with load-bearing ribs.
The joints between elements and their connection to windows need to be further developed before good solutions can be determined. Developing and constructing integrated standard solutions of which the functions will be documented in laboratory tests are carried out in this project.
Furthermore, investigations on optimisation of the insulation thickness corresponding to different economic scenarios have been carried out.
Finally detailed price calculations have been performed on façade sections to illustrate the economic advantages compared to traditional solutions.
References
No publications yet.
Integration of solar heat storage in the ground floor
Project no.: ENS-51181/99-0039 (Danish Energy Authority)
Partners: BYG.·DTU and Danish Technological Institute
Completed: 2000
Abstract
In this project a calculation model for evaluation of integrated solar heat storage in ground floors is developed.
In the report documenting this project, investigations of the possible reduction in heating demand for space heating in two houses fulfilling the present and the coming building code has been carried out.
It has been found that the potential for reduction of the energy consumption for space heating is between 60 and 130 kWh/m² of solar collector depending on among others the heating demand of the house and the construction of the ground floor.
It has also been shown in this project that floor heating can be eliminated as comfort heating during summer time.
Finally it is found that, at the same level of construction costs, the heat storage system will reduce the energy consumption needed for space heating more than if the insulation layer is increased.
References
1. “Bygningsintegreret varmelagring af solvarme i terrændæk”; Weitzmann, P. Holck, O.; Svendsen, S.; 2001. (In Danish)
12 City Ecological Demonstration Buildings – Experiences and Recommendations
Project funded by: The Danish Ministry of Housing and Urban Affairs
Abstract
A report has been prepared containing an evaluation of twelve city ecological demonstrations buildings constructed during 1995-2000. The demonstration buildings have shown that it is possible to construct with significant environmental benefits.
The project involved many different methods for lowering the environmental impact from buildings. Of relevance for this project one of the initiatives was to use the heat accumulating ability of heavy building elements in combination with facades of glass and large window areas, see case story 3.7 below.
References
1. ”12 Byøkologiske forsøgsbyggerier - Erfaringer og anbefalinger”; Hans Bjerregård Rådgivning ApS, December 2001 (In Danish); http://www.ebst.dk/publikationer/rapporter/forsogbyg/12byokolo/html/index.htm
2. ”Miljørigtigt byggeri og miljørigtige byer – arkitektonisk kvalitet er også miljøkvalitet”; Øehlenschlager, R, Dansk Center for Byøkologi www.dcue.dk ; Real Dania 2003. (In Danish)
Ecological new built housing with utilisation of solar energy.
Project no.: ENS j. Nr. 1213/97-002 (Danish Energy Authority)
Partners: COWI, Institut for Bygninger og Energi, DTU, Nielsen, Nielsen og Nielsen arkitekter m.a.a.
Completed: June 2000
Abstract
A demonstration building in Kolding ”Økohus 99” was constructed. 59 constructions of public utility housing in two storeys were built. In the southern façade a solar wall were integrated in order to heat the air, which was ventilated through pipes in the concrete party walls. The concrete is warmed up during the day and the accumulated heat is emitted during the night.
The saving in heat loss is evaluated to approximately 1000 kWh/year.
References
1. ”Økologisk nybyggeri med solenergiudnyttelse - energioptimering & måleprogram”; COWI, Institut for Bygninger og Energi, DTU, Nielsen, Nielsen og Nielsen arkitekter m.a.a; Juni 2000. (In Danish)
The Ecology of the Large Buildings
Project: De Store Bygningers Økologi (In Danish)
Funded by: Ørestadsselskabet, Københavns Kommune and Byøkologisk Fond.
Partners: Dansk Center for Byøkologi
Lading arkitekter + konsulenter PAR
Københavns Kommune
Ørestadsselskabet
Abstract
As a part of the work with this project the domicile of Pihl & Søn A/S is described as an example of an ecological building.
The domicile is constructed with intelligent systems for controlling of heat, light, ventilation etc., but the building actually perform very well without the intelligent systems because the building is constructed with an interaction between the windows area, the heat accumulation ability in the heavy building components, the ventilation demand and the daily use of the building. A reduction of 30% of the energy needed for heating, ventilation and cooling is evaluated.
There are no false ceilings and the storey partition in concrete is therefore able to storage both the heat from the sun and the cold from open windows – an effect which is enhanced by the fact that the walls and the floors also are constructed in heavy components like concrete and rocks. The combination of natural ventilation with the right size of openings and heavy building components is in particular effective to ensure a comfortable climate on hot summer days – and this can be difficult in a building with large areas of glass facades which is the case in this domicile.
References
1. De Store Bygningers Økologi; Dansk Center for Byøkologi; www.dcue.dk (In Danish)
Competitive low energy office building
Project no.: ENS-1213/98-0010 (Danish Energy Authority)
Partners: Danish Technological Institute, Energy, Jensen (C.G.) A/S; Skanska Ùresund
Completed: 1999
Abstract
The objective of this project was to develop a new concept for an energy efficient office building, a concept where the overall energy consumption is reduced by 50% without increasing the cost of the building. This objective was achieved by implementing an integrated design process, where the overall building design process is analysed.
Areas were identified where lower energy consumption can be achieved using new design concepts, new systems, new components or new materials. The energy design strategies considered were among others: use of natural daylight, use of high performance windows, passive night cooling and natural ventilation.
The concept for an energy efficient building was demonstrated in an approximately 8,000 m² office building.
References
1. ”Det halve energiforbrug til den samme pris” Teknologisk Institut (2000) (In Danish)
Status on thermal energy storage in small buildings
Project no.: ENS 51181/98-0038 (Danish Energy Authority)
Partners: Technical University of Denmark, Institute for Buildings and Energy. Aidt Miljø. Danish Technological Institute.
Abstract
This project gives a survey of results of techniques and experiences with storage of solar heat in smaller buildings. A part of this concerns experience with solar walls of concrete and storage in building constructions of concrete.
References
1. ”Status for aktiv varmelagring i mindre bygninger”; BYG·DTU-01-23. 31. p. Duer, K., Dalsgaard, T. Ellehauge, K. Ladekarl, P (2001). (In Danish)
International project competition – Architecture and sustainability in Danish housing construction
Abstract
This example is mentioned in this note in order to illustrate that sustainable building is seen more and more and in many of the cases investigated. The thermal indoor climate with a low energy demand for heating and cooling is of great importance. Many of the cases involve heat accumulation in heavy building components as a tool to obtain a good thermal indoor climate.
In April the building society “Ringgården” arranged an architectural competition with the purpose to gather proposal for 130 constructions of public utility and sustainable housing.
The project is a part of a co-operation under the 5th FP between Italian, French and Portuguese building societies called the SHE “Sustainable Housing in Europe”. The purpose of this co-operation is to construct a number of sustainable demonstration buildings in the four countries.
One of the goals in the competition was a maximum heat requirement of 30 kWh/m²/year, which is half the requirement in the present Danish Building code.
References
1. “Arkitektur og bæredygtighed I Dansk boligbyggeri” – Dommerkomiteens betænkning; Boligforeningen Ringgården; September 2003 (In Danish)
Other references
Fabric Energy Storage (FES)
The Reinforced Concrete Council has launched the Fabric Energy Storage (FES).
FES is the ability of concrete and other heavyweight materials to absorb and store heat. The thermal mass of concrete can reduce the temperature peak by 3° – 4°, and delay its onset by up to six hours.
FES reduces carbon dioxide emissions by up to 50% compared with air conditioning.
As other advantages of the use of FES cost savings due to the fact that suspended ceiling systems are unnecessary and thereby reduction in building height, savings in health problems associated with the sick building syndrome (SBS) are mentioned. The SBS cost UK business around £600 million every year in lost time.
The potential is significant as about 90 % of the total energy use in buildings is from heating, cooling and lightning.
Reference
1. www.rcc-info.org.uk (The website of Reinforced Concrete Council)
2. www.concretecentre.com (The website of the Concrete Centre (UK))
Lecatermâ - blokke
Leca is launching their Lecatermâ – blocks as a product, which minimise thermal bridges and used as walls, they should act as an effective heat accumulator and contribute to a comfortable indoor climate.
Reference
1. www.leca.dk/Vaegge/Blokvaegge/lecaterm.html (The website of LECA)
Thermal benefits of solid construction
A research project carried out by the Cement and Concrete Association of Australia (C&CAA) and Concrete Masonry of Australia (SMAA) assesses the energy efficiency of various combinations of wall and floor construction to determine the contributions that thermal mass and insulation can make.
Reference
1. Concrete Data; November 2002; Cement and Concrete Association of Australia.
Characterisation of thermal delay of light concrete blocks made on expanded clay
A Fifth Framework Programme completed in 2001.
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