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There has never been a time when the environmental performance of housing and buildings has been of such importance. With increasing fuel bills and greater focus on renewable energy sources housing has become a major focus to reduce demand and increase energy performance. With new government legislation being put in place to drive new and existing housing to higher more stringent standards. This projects looks at the implications of this.
The aim of this project is to look at how feasible it is to bring an existing building down to the new Energy Performance Building Directive (EPBD) required standards for 2018. This will look at existing legislation and projects of similar nature and then go on to consider existing buildings and the recommendations to reduce said building to the new required standards. Fundamentally through looking at the data gathered and research done the aim will be to have a justified evaluation of the feasibility of achieving a "Net Zero" retrofit.
To achieve the goals set out a logical approach was implemented summarized below;
Look at existing Legislation (EPBD1&2,Passive house standards, Section 6)
Define "Net Zero" for the purposes of the project
Research current practice
Consider calculation method
Standard Assessment Procedure(SAP)
Passive House Planning Package (PHPP)
Integrated Environmental Solutions(IES)
Select existing building for project
Establish current model of housing
Develop Improved models
Select best model with justification
Compare with other projects
The current stage of the project is currently concluding the research phase and moving onto the modeling. This report will cover the work done so far and provide clear indications of the decisions made to date.
The research phase of the project was fundamental to establishing the existing legislation on the topic and developing parameters for the given task. The following information was gathered during this process
Energy Performance Building Directive 1
The EPBD was developed in reaction to the Kyoto protocol of 1991 in which the EU government made a commitment to reduce greenhouse gas emissions by a total of 8% with a deadline of 2008-2012. The EPBD 1 was implemented to reduce emissions from the building sector as it accounts for a large proportion of current CO2 emissions. (1) The simplified main objectives of the EPBD 1 are listed below.
Establish a calculation method to assess the energy performance of a building including all forms of energy use.
Set a minimum energy standard for energy performance requirements for new building and large existing buildings
A new Energy Performance grading system to be implemented making use certificates for all buildings called Energy Performance Certificates (EPC) Figure 1 shows an example of this
Regulation must be introduced for the regular inspection of boilers and heating systems including air conditioning
Figure (EPC for England & Wales)
Unlike a lot of other EU countries The UK decided to implement two EPC certificates one for the energy rating of the build and another for its CO2 this was intent to give a better indication of the performance of a building.
Energy Performance Building Directive 2
The EPBD 2 was a recast of the original directive to solve some issues that were discovered and introduce some additional constraints to the legislation. The most important change made with reference to this project was the introduction of "net zero" or "nearly zero" technologies. The idea being that a building could in fact be considered net zero over its life span if it made use of technologies that offset its emissions. This will be discussed in more detail later in the report. Other notable changes include the following (1);
Minimum energy performance standard must be established
New building to make use of Low/net zero-carbon technologies
Mandatory 'nearly zero-energy' building for new builds
Penalties to be introduced for non-compliance will be introduced
Other notable legislation of relevance to the project was researched to give an idea of similar projects in existence. The following is a brief summary of what was covered.
The concept of a passive house was introduced by Germany and act as a voluntary standard for buildings. It aims to bring buildings energy demand down to such a standard that it only requires a very small amount of energy to heat and power the building . This is achieved by extremely stringent building standards considering the following factors (2);
Insulation ( U values of <0.15W/m2.K)
Very low Air Leakage(AC/H<0.6 at 50Pa)
Next to no Thermal bridging (Psi<0.01 W/m.K ext)
High standard Glazing (U<W/m2.K)
High efficiency ventilation for healthy air quality
Measures to deal with solar overheating
This style of building has had relative success in in Germany however limitation have been discovered with attempts in the UK issues with damp and poor installation reducing the effectiveness of the concept.
Section 6 of the Technical handbooks 2011 Domestic energy was implemented in Scotland in 2011 with the aim to make sure that the most effective manners of energy conservation of both fuel and power were being implemented in new housing. (3) Unlike the passive house regulations section 6 looked at power generation technologies such as Photovoltaic, solar thermal and Combined heat and power systems. This links in more with the projects aim and is similar to the recommendations of EPBD 2
The green deal
The Green deal is a new government scheme to fund the installment of energy reducing technology in existing homes. The scheme avoids all upfront costs by allowing home owners to pay back the money through their power bill. This is intended to cost no more than the energy saving gained by the installment of the technologies hence stopping homeowners having to burden themselves with large debts. (4) This inactive ties in nicely with the project giving additional motivation for homeowners and landlord to retrofit there houses.
One of the main requirements of the EPBD was to develop a calculation method that could determine the current performance of buildings as well as estimate performance after improvements. For this the government developed the Standard Assessment Package (SAP). This establishes the current rated of a building and can simulate the improvements effectiveness. SAP will be used throughout the project to establish the base model and effectiveness of improvements. As well as SAP there are other dynamic programs that will be used to model improvements and assess options such as Integrated Environmental Solutions package (IES) which allows the modeling of any structure as well as providing an energy rating for the building. Also to help establish the base standard of the selected building EDEM can be used another dynamic calculation package. Using these calculation methods the building will be assed and the options will be taken into consideration.
Definition of "Nearly Zero" or "Net Zero" home;
For this project a definition of a "Nearly Zero" or "Net Zero" home was to be established. After research was conducted a definition was set for the project because many existing definitions exist within current and old legalisation. The aim is to find and set a definition with respect the project title "Retrofit of existing housing to EU EPBD nearly zero standards". As stated in the title the EU EPBD's legislation is to be used in the definition. Below is a quote taken from the directive giving an outline of its definition?
"A nearly zero-energy building is defined as one that has, 'a very high energy performance', and for which 'the nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced onsite or nearby." (5)
The key elements of importance can be broken down into fundamental points. Below is an extract form HM Government 2008 "Definition of Zero Carbon Homes and Non-Domestic Buildings" article. It indicates some of the main areas of importance with reverence to zero carbon homes
Box 1: What does a zero carbon home mean?
Building A Greener Future (July 2007) set out that all new homes are to be
built from 2016 in such a way that, after taking account of:
â€¢ emissions from space heating, ventilation, hot water and fixed lighting
â€¢ expected energy use from appliances
â€¢ exports and imports of energy from the development (and directly
connected energy installations) to and from centralised energy networks,
the building will have net zero carbon emissions over the course of a year.
The present consultation retains the approach of looking at net emissions
(including from appliances) over the course of a year. It proposes that, to
meet the zero carbon homes standard, homes should:
â€¢ be built with high levels of energy efficiency
â€¢ achieve at least a minimum level of carbon reductions through a
combination of energy efficiency, onsite energy supply and/or (where
relevant) directly connected low carbon or renewable heat; and
â€¢ choose from a range of(mainly offsite) solutions for tackling the
The concept of "Net Zero" is when a building can be above and below zero emissions at any given time as long as it's net or annual emissions meet the relevant standards. This makes it more achievable to become net zero given the variance in demand dependant on season and time. Other import aspects to consider are that the minimum levels of carbon reductions can be achieved through both onsite and offsite low carbon or renewable sources. This again makes the target reductions mare achievable.
As the EPBD 2 states that participating countries must define minimum energy performance standards a value for the relevant UK's minimum must be established for the purposes of this project. The following extract taken from the carbon compliance interim report suggests that a reduction of 70% as a national standard for all dwelling by 2016 is relatively unachievable. The extract below sets a more realistic standard for the minimum requirements.
"The Task Group concluded that the currently proposed 70% improvement over 2006 is not
deliverable as a national minimum standard for all dwellings from 2016 as it would significantly
constrain the range of house types (and designs) which could be built.
From 2016 the 'built performance' emissions from new homes should be required not to
exceed the following limits:
â€¢ 10 kg CO2(eq) /m2/year for detached houses
â€¢ 11 kg CO2(eq) /m2/year for other houses (semi-detached, terraced etc)
â€¢ 14 kg CO2(eq) /m2/year for low rise apartment blocks." (7)
The above minimum requirements will be used for the project. As a benchmark of how appropriate the given solution is.
For this project an existing building had to be selected to analysis and assess the feasibility of the "net zero" concept. The choice was made to make to select an existing set of flats located locally in Glasgow. The Strathclyde ESRU team have already done an assessment of the feasibility of bringing the flats to passive house standards this provides a lot of data already available to help with modelling flats and assessing what changes are required to bring the building to "net zero". (8) Given the data and the selected building a strategy had to be devised to achieve the goal to devise this strategy some industry research was performed to establish how similar problems are solved in industry.
PV/Solar thermal etc..
Investment in Wind farms
Energy Demand Reduction
High efficiency systems
Cost and Technical Difficulty
Order of Approach
To gain a better idea of how to approach the task given a consultancy firm (Rambol UK Limited) was contacted with the aim to gain some insightful knowledge on how the approach similar tasks. The results of this were successful providing some useful information of how to approach the problem. Below shown in Figure 2 is a representation of an adapted strategy that combines the information acquired from the research with the requirements of the project.
Figure (Strategy Triangle)
The first stage is to look at the existing building fabric and assess the areas that can be improved. The existing ESRU report provides data on a selection of different improvements which gives a good insight to the general effectiveness of each improvement against its cost this is shown in Figure 3. However as stated before Passive house standards are much more stringent on the fabrics to be used and the demand reductions to be achieved. As this project aims to bring the building down to "Net zero" standards it's the building fabric will be reduced down to a cost effective level before moving on to look at the efficiency of existing systems. (8)
After the building fabric has been assessed the next step is to look at the existing systems such as the boilers and ventilation(if any exists) once again some data does already exist on this shown in Figure 4 providing an indication of how effective system improvement can be. The project will take these into consideration when justifying recommendations of improvements to be made.
Stage three looks at ways to compensate for the remaining emissions and demands of the buildings by considering allowable solutions and renewable technologies. Allowable solutions are a concept that has been introduced to make "net zero" buildings more cost effective. The idea is that after a building has gone through stage one and two it can make investments in near-site or completely off-site low carbon initiatives. This would allow the developer to buy carbon credits that offset the remaining emissions of the properties. This is intended to be less costly than developing on-site solutions which are notoriously expensive. Also providing larger scale projects and wind warms with incentive. (9) Alternatively on-site renewable solutions can be considered with cost in mind. There are feed in tariff scheme and funding available for certain technologies.
Figure (Existing Data on Tracoba flats (8))
This approach has been adopted to establish whether the selected building can be brought down to "net zero" standards and at what cost. The focus of the project will fall on stage three as stage 3 explores the new idea of allowable solutions which may enable building such as the Tracoba flats to financially achieve the given definition of "net zero". As well as looking at the Tracoba flat buildings this project aims to look at another types of structures and compare the feasibility of implementing the same strategies to achieve the goal of "net Zero". If time permits there is the potential of looking at a community building such as a village hall as well as assessing the feasibility of a new build operation. This will all be done with the aim of giving rounded general assessment on how able the building sector will be achieve the new goals set out by legalisation.
Figure 4 below shows the Gantt chart for the project. This gives an indication of how the project has been approached and the time scale of which the given tasks are expected to be completed. Figure 4 shows that during the research phase of the project parallel tasks dominated the majority of tasks. However as the research phase comes to close its noticeable that each task relies on its predecessor this reflects the nature of the work. For example once a base model has been established the triangle mythology is adopted which will determine the outcome of the given best case models. This causes a certain amount of ambiguity as if the modelling of the Tracoba flats goes over its time constraint a decision will have to be made to assess if there is enough time to consider other buildings. To mitigate this risk the "modelling of community building/new build" and "Accumulate data" sub categories has been overlapped running in parallel to allow for unforeseen time delays. Mile stones are also indicated for major deadlines and achievements
Figure (Gantt chart)
This report has aimed to give a technical briefing on the project "Retrofit of Existing Housing to EU EPBD 2018 Nearly Zero Standards" developing the general aims of the project and exploring its relevance to real world issues. The project provides challenges in both the electrical and mechanical engineering field, requiring a mechanical understanding of the renewable technologies and materials thermal properties as well as a grasp of how to model proposed solutions. The report has indicated the proposed methodology to approach the task in an analytical and logical manor. With the indicated approach the aim is to establish the feasibility of the defined "net zero" standard for it least one building. The results will give an overall assessment of how effective the "net zero" concept is for retrofitting existing buildings within the UK. Feasibility of models will be assessed on the factors of cost, effectiveness and technical complexity. This report has established the general aims of the projects, method of approaching problem and the project schedule.