Low energy building

History

First generations of conceptual low energy buildings were build during 60. - 70. ties where the West thanks to generation of "flower children" has started to remind themselves the human connection to nature. New demands for living have looked for inspiration deep in history using the terrain, natural powers and local resources. But the first low energy buildings have had many failures and many things have been overlooked. Among the common mistakes were too big glass walls in order to get as much passive solar gain as possible but it often led to overheating in summer. Also the thermal bridges and uncontrolled air change. The good working low energy house has many advantages such as low energy demand and consumption, good indoor environment during the summer and winter, low air pollution.

National Standards and design guidelines

The development of low-energy buildings highly depend on evolving of Standards and Directives therefore the European Comittee for Standardizationwas founded in 1961 and set under Belgian Law. CEN produces a number of different publications: EN ISO (European Standards), prEN (Drafts of Standards) and other approved documents CEN TS (Technical Specifications). The European countries together work, develop and asses the Drafts of Standards where they specify and develop the new Standards based on their knowledge, information and existing international Standards and guidelines. ASHRAEorganization is dealing with Standards related to HVAC - Heating, ventilation and air-conditioning systems.

• List of some Standards
  • CEN TC 156 prEN 15271 Draft - Criteria for indoor environment including thermal, indoor air quality, light and noise. Specifying of classes for environment in buildings: Category A corresponds to high level of expectation (and leads to highest precentage of satisfied occupants in respect to indoor environment), category B a medium level of expectation and category C to a moderate level of expectation.
  • EN ISO 6946 - Building components and building elements - Thermal resistance and thermal transmittance - Calculation method (ISO 6949:1996). Calculation of thermal resistance for determining heat floow through the building components
  • EN 15217 - Energy performance of buildings - Methods for expressing energy performance and for energy certification of buildings
  • EN 15603 - Energy performance of buildings - Overall energy use, primary energy, CO2 emissions and definition of energy ratings
  • EN ISO 13790 - Energy performance of buildings - Calculation of energy use for space heating and cooling
  • EN15242 - Ventilation for buildings - Calculation methods for the determination of air flow rates in buildings including infiltration
  • EN 15241 - Ventilation for buildings - Calculation methods for energy losses due to ventilation and infiltration in commercial buildings
  • EN 15316 - Heating systems in buildings - Method for calculation of system energy requirements and system effciencies - Parts 1&2
  • EN 15243 - Ventilation for buildings - Calculation of room temperatures and of load and energy for buildings with room conditioning systems
  • EN 15316:3 - Heating systems in buildings - Method for calculation of system energy requirements and system efficiencies - Part 3: Domestic hot water systems (Parts 3.1-3.4)
  • EN 15193 - Energy performance of buildings - Energy requirements for lighting - Part 1: Lighting energy estimation
  • EN ISO 13789 - Thermal performance of buildings - Transmission and ventilation heat transfer coefficients - Calculation method
  • EN 15927-4 - Hygrothermal performance of buildings - Calculation and presentation of climatic data - Part 4: Data for assessing the annual energy for heating and cooling
  • EN TR 15615 - Explanation of the general relationship between various European standards and the Energy Performance of Buildings Directive

Design

• Climate challenge
• Construction, technology

There is wide range of materials available on the market, but some countries (especially Northern ones) still needs to be stimulated by importing for example good double windows.

Energy efficient features:

Daylight - illumination of interior space evenly by means of proper window placements and orienatations, skylights, etc.

Direct gain - the sun rays enter the room and bring the heat which can be stored in room or distributed over the buiding.

Glazing - performance the conductive heat losses and gains (U-value), vissible light transmission and solar heat gains.

Overhang or shading devices - stationary or movable, protect usually south-wall from overheating the building.

Thermal mass - heat absorbed by walls and floors which can be absorb in day time and release in night time to heat up the space. Or cool down at night in summer depending on the year period.

Overall U-value < 0.15 W/m2.K

Windows and door U-value < 1.0 W/m2.K

Insulation thickness roof > 300 mm

Insulation thickness wall > 240 mm

Permeability < 0.6 h-1

Those values which should be considered as required design values are valid for European conditions, for Norhern countries (for example Low Energy House in Sisimiut, Greenland) the wall insulation thickness is 300 mm and roof and floor 350 mm.

• Renewable energy
• Sustainable design

• Energy efficiency and consumption

Typical European house requires at least 250 kWh/m² per year and mostly they have been build when the resources of oil and electricity were still large and therefore the need of saving energy has not been primary target. Low energy buildigs require 10 times less energy for running.

Integrated design process of low-energy building

In order to build a low-energy building an integrated design process should begin and be implemented in early stage of building even before the first drawing sketch from an architect is produced. The integrated design process enables all the team members to work together and look upon the main requirements, possible ways and solutions that will lead to design of best possible building regarding energy and needs .

Early in building process the design team will meet to ensure the cooperation and understanding of commitments between members. In the project a “key person” can be named to connect the members of team together and ensure that the integrated process will be continue. In Europe this person is usually called the business process manager. The owner will play the main and critical role and will be often join by a financial manager. The perfect strategy would be for the members of designer team (or head) to stay on the project to the very end of building process. The members of team must meet throughout the various design stages and periodically, during construction. Also the integrated design reguires many simulations and software to use in order to achieve the best possible solutions.

The integrated design process team:

1. Owner (or representative)
2. Architect
3. Designer (facilitator, business process manager)
4. Civil Engineer
5. Construction manager (contractor)
6. Structural, Mechanical and Electrical consulting Engineers
7. Specialized consultants (energy, finance)

The first step of the process preparation is for a developer (owner, or his representative) to identify the needs, criteria and commitments for high performance and energy efficiency of building. In this stage the main information should be also collected (space, number of people, budget, information about building site, type of soil, orientation, height of surrounding buildings, etc).

Second stage could be called a pre-design where the architect and teams of specialist will produce, based on information from stage one, the early graphic suggestions for the building. There should be more solutions available for the Engineers and specialists to analyze. The systems should be analyzed together such as: lightning (daylight and natural) with mechanical systems, daylight with envelope system, water and heating and cooling, ventilation and lightning. The team undertakes the whole building system analysis and must consider the interaction between systems.

The design development allows the number of solutions to be narrowed to few possible solutions with the best possible energy and indoor performance with respect to financial and architect value of the object. Greater details and plans should be considered for all aspects of the building. This phase should end with detailed design which will be agreed on by all members of team and owner. After detailed project documentation will be done, the contract stage can begin which are needed for proper pricing, permitting and construction.

The contractor and construction part of team should be at very large projects from early beginning but in small projects he can join the process in construction stage and together with the team should be fully involved in the process. The design team is fully responsible for assuring that the building and energy requirements will be met together with design and contract.

How the building meets the criteria is set in stage commissioning where all function and systems of building are assessed and evaluated by the design and construction team, and can be still changed before the final and closing stage of building. After the building has been fully built and open sometimes post-occupancy evaluation is done to assess how the building works and meets the criteria, energy and indoor performance set at the beginning by owner and team.

Key actions recommended ensuring successful integrated design process:

• Integrated process begins at earliest stage
• Name “key person” of integrated design process
• Simulation and interaction among building systems
• Analyzing costs (building cost, life-cycle, maintenance)
• Energy and indoor performance at the best level
• Evaluation of criteria
• Rewards for extra work

Results shows that the integrated design process benefits from cooperation of all team members and the process provides the necessary information and strategies to plan, design and build the high low-energy performance buildings. The building will have reasonable initial and life-cycle costs over entire existence cycle. The design objectives which will be achieved are: safe, secure, flexible, aesthetic, functional/operational and sustainable. A succesfull integrated design leads to the perfect whole building design.

An interesting newly developed part of the Integrated Design Process is the idea that the process should start on "room level". The whole design and energy calculation should be done on room level using the new software iDbuild created by Technical University of Denmark. The software analyses one room using variation input data (orientation, geometry, window height and properties, thermal mass and insulation, ventilation and cooling, energy, etc.). First the reference room is designed and simulated and after that the two variation rooms can be calculated and compared. After the number of variation of the best possible room, the architect knows how the best performance room should look like and he uses these designed rooms to create the overall design of building. This approach is coming from Engineer´s point of view therefore the architects could feel limited but on the other hand this way of designing is very energy friendly.

Economy and costs

The extra cost for good and working low energy house will be around approximately 10 % of acquisition price and the difference should return in 10-12 years thanks to energy savings.

Examples

Low-Energy House in Sisimiut, Greenland

Resources

WBDG The whole building design

Overview of IDP The integrated design process