UPGRADING AN OLD RESIDENTIAL BUILDING FOR ENERGY PERFORMANCE AND SUSTAINABILITY.
DEMOLISH AND REBUILD OR REFURBISH?
The intent of this dissertation is to provide a homeowner with the breakdown of the advantages and disadvantages of both a retrofit and a new build upgrade when considering the energy performance and sustainability of a residential property.
The information assessed informs the reader of the issues and different aspects that should be considered when investigating energy performance and sustainability.
Relevant information has been evaluated to demonstrate where each home fails in terms of energy performance to provide an understanding of the need for potential upgrade.
The basic design options for improvement have been assessed while elaborating the importance of each one. Other key influences have been addressed and evaluated, such as cost and ensuring a balance between the different factors.
All the information evaluated within this dissertation has been taken from real-life upgrade examples and provides practical guidance for the interested party, with noted limitations.
Improvements, in terms of thermal gain, have been reviewed to achieve the building regulation standards compared to higher-active standards. The referenced section highlights the lack of energy performance that is gained when constructing to meet the building regulations and what steps can be taken to avoid this.
The result of the research undertaken has found that each upgrade is unique and should be assessed against a number of questions and subjects before an informed decision can be made. In conclusion, this dissertation has not been able to identify a definite answer to the subject in question. Instead it has identified all aspects of an upgrade project that should be considered to allow an informed decision.
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The subject of this dissertation is the assessment of improving old housing stock for energy efficiency and sustainability. The improvement methods include retrofitting old housing stock compared to demolishing old housing stock and building new, both options will be analysed and evaluated in this report with the aim of providing a conclusion to the most sustainable option.
In the UK, residential construction produces 32.4 million tonnes of CO2 emissions each year, this equates to 27% of the total CO2 emissions produced by construction as an industry. To reduce this figure, the government released the Carbon Change act in 2008.
The Carbon Change act 2008 states on page C27 section 1.1 that;
- It is the duty of the Secretary of State to ensure that the net UK carbon account for the year 2050 is at least 80% lower than the 1990 baseline.
There are currently 27 million houses in the UK and by 2050 there will be an approximate 400,000 additional homes with an average of 12000 homes being built every year. To enable the United Kingdom to meet the Carbon Change act target, old housing stock needs to be either refurbished for energy performance or demolished and rebuilt, relying on new housing stock will not be enough to reduce the current figures. Current and future residential construction and retrofit projects need to be as energy efficient and sustainable as reasonably possible, meaning that the implementation costs and efforts do not outweigh the benefits gained.
The housing stock that have reduced energy performance ratings were built during a time when energy performance and fuel consumption was not seen to be a problem, it was not something that would have been considered during design, procurement and construction. Houses would have been built in the most cost effective way and in line with the methods and materials that were popular at that current time.
In the case of construction Embodied energy is the total energy it takes to complete a project from cradle to grave. This includes items such as the fuel used during construction for the machinery.
Cradle to grave consists of three different aspects of a project; construction, use and demolition. The embodied energy consists of but is not limited to; the energy taken to make the material, the energy taken to transport the material onto site and the construction process its self. The use aspect consists of the energy the building would use during its working life for any necessary maintenance. And the demolition aspect is the energy taken to demolish a building including the waste that cannot be recycled.
Embodied carbon is the amount of carbon that is produced due to the construction of the building, for example the amount of carbon dioxide produced from utilising the materials used for making concrete. And the amount of carbon emitted from the fuel used for the construction of the house.
To reduce the total embodied energy and thus the embodied carbon, all aspects of the build must be considered for improvement.
It is important to note that cradle to grave approach does not include the energy needed and carbon produced from the running life of the building, for example the cost of heating up the home.
Fuel poverty is when the residents of a building spend more than 10% of their income on keeping their home in a comfortable state. By improving the energy efficiency of old housing stock, the cost of running houses will reduce and as a direct impact the amount of homes in fuel poverty will drop. Fuel poverty for residents is defined by the Department for Business, Energy, & Industrial Strategy in the annual fuel poverty statistics report 2016, page 7 as;
- They have required fuel costs that are above average (the national median level)
- Were they to spend that amount, they would be left with a residual income below the official poverty line.
The number of homes in the United Kingdom classed as living in fuel poverty between the year 2003 and 2014 fluctuated between 2.28 million and 2.57 million homes, equating to 10.7% to 11.9% of total homes in the UK.
There are three factors to be taken into consideration that will determine if a household is in fuel poverty. Stated by the department for business, energy, & industrial strategy in the fuel poverty statistics 2016 page 9, Section 1.1.2 as;
- Household Income
- Household Energy Requirements
- Fuel Prices
To be able to improve a home’s energy performance the occupier must first find out what needs improving and where the building fails for energy use. A reliable way of finding out how energy efficient a home is and what improvements are necessary is by having an EPC survey carried out. EPC stands for Energy Performance Certificate, where the workings of a house is surveyed in terms of heat retention, boiler performance and similar. A rating is then given to the house stating the energy efficiency, the effect it has on the environment and the estimated cost of running the house.
Ratings awarded start from A, being the best rating to receive to G, the worst energy performance that can be received. When receiving the homes rating the resident is advised on how to improve the energy use of the building.
This dissertation will investigate the difference in a new build project and a retrofit project in terms of the different design options and materials that are available. Due to the three pillars of sustainability; Environmental, Social and Cost, this dissertation will also endeavour to assess the other aspects that should be considered to allow an informed decision on the best method of construction for energy performance and sustainability.
The aim of this dissertation is to provide the reader with an evaluation and comparison between the energy performance and sustainability that can be achieved with a retrofit project and a new build project
- Identify what building regulations are applicable and must be adhered to for the purpose of this dissertation. (Chapter 4)
- Identify design options for improvements and evaluate the benefits gained from each design solution. This chapter will examine fabric first design improvements along with energy renewable improvements. (Chapter 5)
- To appraise a case study for a new build project and evaluate the design options chosen for improvement. (Chapter 6)
- To appraise a case study for a retrofit project and evaluate the design options chosen for improvement. (Chapter 7)
- Compare the standards of building in the United Kingdom that are built following the Building Regulations to homes built in Germany that are built using the passivhaus standard for energy performance.
- Discuss a mass retrofit upgrade project compared to a new build upgrade of the same standard and size. Cost and Embodied carbon will be the focus of this objective. (Chapter 9)
This literature review discusses relevant information and reports that would need to be considered when undertaking residential improvements for energy performance and sustainability.
The Building Regulations 2010 can be accessed on the legislation.gov web site, where a PDF version can be viewed. Building Regulations have been created to ensure that any new build, alterations, or extensions on older houses are carried out so that the building when complete is safe to inhabit and that minimum living standards are met. There are several Regulations covering the requirements of the different aspects of a building. These are stated in the Buildings Regulation 2010 document, such as but not limited to;
- Water efficiency on new dwellings
- Completion certificates
- CO2 emissions for new buildings
Schedule one of The Buildings Regulations 2010 page 29 provides the requirements that need to be met to ensure the building complies to the Buildings Regulations. The requirements cover but are not limited to;
- PART B FIRE SAFETY
- PART H DRAINAGE AND WASTE DISPOSAL
- PART L CONSERVATION OF FUEL AND POWER
To provide guidance on how to meet the regulations, approved documents can be accessed on the gov.uk website. They are practical examples that can be used to help builders and home owners meet the applicable regulation. The Approved documents include but are not limited to;
- Fire safety Approved document B
- Ventilation Approved document F
- Drainage and waste disposal Approved document H
The Building Regulations are important for this dissertation as for the reader looking to undertake new work the applicable Building Regulations will need to be followed to ensure that any alterations carried out to improve old housing stock or any new build is compliant and thus safe to use.
Passivhaus can be accessed on the Passivhaus.org.uk website. The Passivhaus standard is a standard that has been created in Germany to allow the construction of a maximum energy efficient house. The Passivhaus standard concentrates on making the makeup of the building as thermally efficient as possible with maximum air tightness and effective ventilation methods. The first house was built to Passivhaus standard in 1991 and since the standard has continuously improved.
Passivhaus has also created the EnerPHit Standard which is a standard that can be used for upgrading old housing stock. The energy performance will not be as affective with the EnerPHit standard as a new build would under the Passivhaus standard. This is due to having to work with the materials and design of the old building when carrying out a retrofit compared to starting from scratch with a new build. However the improvements under EnerPHit standard will be carried out to maximum efficiency, working with the current make of up the building.
This is useful information for this dissertation as if a house was going to be rebuilt to improve the energy usage, the building would be constructed in a method and using materials that would gain maximum energy efficiency. This standard also provides good guidance on how to refurbish old housing stock gaining maximum energy performance and improvement. It is important to note that the methods used for refurbish and new build are same in terms of addressing air tightness, ventilation and heat retention.
The book tilted; The old house eco handbook by Suhr and Hunt (2013) focuses on retrofitting listed buildings. This book highlights the importance of respecting how the building has been designed to work and ensure that the solution for renovation does not cause another more serious problem. For example using cement based render when a limestone render would be the initial material used.
The old house eco handbook is useful when refurbishing listed housing stock as it addresses the typical issues with older buildings and where the energy performance can be improved. The old house eco handbook also states what building regulations are applicable to each improvement for example what regulations need to be followed when replacing windows. It also simplifies the regulations and states what needs to be done to comply with each applicable standard.
The old house eco handbook would be useful to a reader who was planning to upgrade a listed building as it states the general improvements that should be considered and gives information on what regulations are applicable giving practical examples that could be followed.
Similar to The old house eco handbook, Residential retro fit case studies by Baeli (2013) is also very useful as it describes the steps taken in retrofitting older housing stock. If a retrofit project was being carried out to make a house more sustainable this book would act as a guideline with practical examples from previous successful projects, it has several different types of buildings and from different periods all with different solutions being bespoke to the certain house. This book focuses on fabric first solutions which mean improving the existing structure of the building before thinking of additional improvements such as solar power for example.
Retrofit project case studies in Camden can be found on the Camden.gov.uk website. By improving the insulation, heat recovery methods and preventing draughts they have successfully improved the energy performance and reduced the CO2 emission by up to 80% for two Victorian properties resulting in a substantial saving on energy bills.
Like The old house eco handbook and Residential retro fit case studies, the retrofit project case studies in Camden have all used the same methods for improving the energy performance of old houses.
Information for BREEAM which stands for Building Research Establishment Environmental Assessment Method can be found on the breeam.com/Website. For a building to gain a BREEAM certification the building is assessed against different categories and how well it performs in each category. The BREEAM categories’ cover but are not limited to aspects such as; procurement of the material, energy saving methods and waste disposal.
Supply chain and methods of demolition will be mentioned as ways of improving energy performance and sustainability further on in this chapter.
Aspects of a build such as demolition and the supply chain might not be part of construction that people may think of as having an impact on how energy efficient an upgrade method is. However by having the BREEAM scheme it allows a wider range of thinking when considering different improvement methods. The BREEAM scheme is good background information for this dissertation as it makes the reader who is undertaking a retrofit or new build project consider more than just the finished product.
Information on listed buildings can be found on the historicengland.org.uk website. To protect chosen buildings of interest built before 1945 they are placed on the National Heritage List of England (NHLE). Buildings constructed after 1945 can also be on the NHLE however currently that stands at a very small percentage of 0.2% of total listed buildings. That building is then protected and given a category listing of which there are three different categories; Grade I, grade II* and grade II.
Historic England, on the listed buildings web page under categories of listed buildings writes;
-Grade I buildings are of exceptional interest
-Grade II* buildings are particularly important buildings of more special interest
-Grade II buildings of special interest
Listed buildings can be altered and improved only after gaining permission, in some cases the approval will dictate the changes that can be made for example the colour of the render or type of tile used on a roof. This information is relevant to this dissertation as this knowledge would be critical when carrying out improvement works on a listed building.
Supply chain school information can be found on the supplychainschool.co.uk website. This is an online school that provides training to suppliers on how to improve the sustainability of their working process. Suppliers must answer questions on how the business works and trades, from this information each company is given a bespoke training guide, along with modules to meet and a plan of development.
This is a very useful tool to be aware of when planning on either refurbishing a home or constructing from new. If chosen suppliers work in line with the supply chain school, the methods of improvement that have be chosen are as sustainable as possible with regards to procuring the materials and thinking about the cradle to grave approach of the project.
By being part of the Supply chain sustainability school the project is working towards a BREEAM certificate by considering and improving the procurement of the project.
Due to the need to reduce the amount of construction waste that is sent into landfill this is a good report to be considered when thinking about demolition as it provides recommendations to assess and act on before deciding to demolish. The Report promotes pre-demolition audits where surveys are taken on the existing structure to see how much can be reused or recycled. It will also give the amount of material that would need to go into landfill.
This is relevant to this dissertation as the audit figures of the project will provided the reader with the facts about the demolition of the property in terms of waste.
This report also includes case studies of buildings that have been upgraded including residential properties. This information is informative when thinking about demolishing a building as the case studies provide guidance on if the building would be appropriate to demolish and the most appropriate methods.
By assessing the demolition impact of the building the project is working towards a BREEAM certificate with the assessment of the waste disposal, like considering the supply chain.
This chapter has summarised case studies of residential homes that have previously under gone improvements for energy performance including eco-friendly new builds. It has discussed the building regulations that are the foundations of any home alterations or new home construction. Listed buildings have also been reviewed and would be highly relevant if the home in need of upgrading was itself listed, however for this dissertation listed buildings will not be investigated further. Secondary information such as supply chain and demolition and may be touched on when evaluating an appropriate improvement method however this will not be looked into in great detail.
After assessing the current literature surrounding home improvements, it is concluded that to ensure the improvements are as sustainable as possible the “cradle to grave” aspect of the project must be analysed. Considering things such as, where the materials are being supplied from and the waste that will be produced from the chosen method. However this subject is very broad and so the cradle to grave approach for the purpose of this dissertation will concentrate on the embodied carbon and the energy use for the life time of the house.
In terms of the methods used to improve the energy efficiency and sustainability the research carried out shows that the fabric of the building such as the walls, roofs and windows should be focused on for improvements for heat retention, ventilation and air tightness. By carrying out improvements in the fabrics, the energy efficiency of the building will improve by reducing the energy used to keep the residents in a comfortable living state, this not only makes the house sustainable as the running cost will reduce, the co2 emissions emitted will also reduce.
Renewable energy methods like solar power and hydro power is a secondary improvement but should be investigated further due to the benefits.
Due to the information gained, this dissertation will first identify the design options available in improving the makeup of a home; this could be for both retrofit and new build. This dissertation will then focus on the differences and similarities between a retrofit and a new build project to endeavour to provide a conclusion as to the more sustainable option.
The methodology of this dissertation is to focus on past projects that have been successfully undertaken. This includes home retrofits, where older buildings have been renovated for maximum energy performance, and new build projects that have been designed and constructed using the most sustainable method possible. A mass upgrade case study has also be assessed which has been compared to its equivalent standard in a new build.
This dissertation also investigates other standards that can be used rather than the Building Regulations for maximum performance, the difference in the standards are also evaluated and interpreted.
The limitation of the information in this dissertation is the wide range of design options that are available. The following chapters only provide the basic options and design methods of improving the energy performance of a home, the information in this dissertation should be looked at as a starting point.
Another limitation is the mentioned mass upgrade project. The findings for the cost and CO2 emission for the equivalent new build were made on a number of assumptions and therefore may not be as accurate as a real life upgrade.
The strength in the following chapters is the explanation of the Building Regulations that must be followed for the purpose of this dissertation regardless of what design method and option is chosen. It also contains case studies of previous successful work carried out for home improvements and can be used as good practical examples and guidance for the reader.
Not all construction work will be regulated by the standards set out in the Building Regulations that are available on the legislation.gov web site. This chapter will explain in which circumstances Building Regulations must be followed and in which instances they can be ignored. This is only relevant to building and upgrading for energy performance, and not for the structure of the house or alike, and so all other building regulations that are not applicable for energy performance have not been mentioned.
All new build homes are regulated under the Building Regulations, and all standards must be met while constructing. There are several different regulations that must be followed when designing and constructing a building, such as but not limited to part A Structure and part P electrical safety. But when considering the energy performance of a home Part L “Conservation of fuel and power” from the building regulations 2010 is the most relevant.
Like the new build projects, the Building Regulation to focus on is Part L “Conservation of fuel and power”. However, the reader is asked to focus on Part L1B “Existing dwellings.”In Part L1B of the Building Regulations there are three sections;
- Thermal elements
- Thermal envelope
- Controlled services
Between the three mentioned sections the standards are set for walls, floors, windows, and doors, also mentioned is heating and hot water systems. All are relevant for the assessment of the improvements in the following chapters of this dissertation allowing an evaluation on the achieved performance of the upgrades and new builds.
U values are used to indicate how much heat a material lets pass through it, all building materials will have a U value and this can be used as a good indicator to how much heat energy will be retained in the building. The lower the U values the less conductivity the material has and is therefore a better insulator.
Due to having to work with existing fabric the U values that are expected to be met in the standard for retrofit projects are higher than the U values stated in the regulation that controls a new build. This proves it is known that retrofit projects will not achieve such a low thermal conductivity as a new build will when built in a traditional sense.
In some instances, Building Regulations do not apply when making changes to an existing home. One criteria is that no more than 25% of the building which affects the building envelope is being upgraded, for instance the walls, windows and ceilings. Another is the no more than 50% of part of the building is being changed, for example if insulation was only being installed in 45% of a wall.
For the purpose of this dissertation it is assumed that any retrofit project being carried out for maximum energy performance would need a greater change then 25%. Therefore the Building Regulations should be adhered to when carryout the improvements.
It is important to note that homes that have solid walls are not expected to meet the U values set out for existing dwellings. This is due to the way the building breaths, by trying to improve the wall in a more modern solution it may cause the building more problems with moisture and ventilation. If improvements are necessary negotiations are advised with local building officers on appropriate methods to improve the walls U values of the wall.
The Building Regulations must be understood and followed for a reader who is looking to either upgrade or build a new home to ensure that the building meets the standards set. It is also important to understand what regulations need to be followed when assessing the individual situation to ensure the correct amount of work is carried out. If the Building Regulations are not adhered to it is possible for building control officers to enforce removal of all materials that do not meet the standards costing money, time and the waste of materials, which as a process doesn’t make the project very energy efficient and sustainable.
This chapter will identify the possible design options that are carried out for energy performance improvements and evaluate the benefits that each design option provides. This chapter will focus on the fabric first approach as well as renewable energy options.
All the solutions for improvements analysed in this chapter are subject to the original design of the house, for example the solution would be different depending on if the floor was concrete or timber suspended. In practice, each improvement method will need to be bespoke to each house chosen for improvement. For a new build house, this could be considered before design stage with the most appropriate improvement methods designed into the house.
The design options are stated by Suhr & Hunt (2013) & Baeli (2013)
For the residents of a property to be comfortable, the living space is heating to an appropriate temperature. Generally this will result in the temperature inside the house being higher than the temperature outside the house. The fabric of the house will conduct the heat from the inside area due to the outside surface being colder. The heat will continue to transfer through the material until it has reached the outside atmosphere. This will then be transferred by convection into the surrounding air, which will then move away from the house as hot air travels up and will be replaced with colder air. As the hot air is moved from the inside to the outside by conductivity the room temperature drops. To combat this homes will have heating systems on for longer periods of time or at higher temperatures resulting in more energy being used for space heating. This cycle will continue as long as there is a difference in the inside and the outside temperature, this process can however be slowed down by the following construction designs.
To stop heat escaping from the external walls an effective improvement design is insulating each wall to retain the heat, the heat takes a longer time to pass through the insulation layer than it would if there was just an air pocket in-between the two wall leaf’s. If a building has a cavity wall, then insulation can be fixed in between the two leaves of the walls. See appendix A.1. The type of insulations varies and is personal preference however the most common is mineral wool. An effective non invasive method for a retrofit is to blow mineral wool fibres into the cavity, by carrying out this activity the face of the wall does not need to be removed in order for a sheet of insulation to be fixed into place.
As Suhr & Hunt (2013 pg 103-105) states; to insulate solid walls would result in the loss of space on either the inside of the property or the outside of the property. It may be more practical in insulate the outside of a property if the home is already restricted with space. However, there are more factors to consider when insulating the wall externally such as moving gutters or surface water drainage gully’s and if there are any man holes or access gullies that would be covered. This type of insulation would not be wool but XPS thermal laminate or a similar material. Insulating solid walls works in the same way as a cavity insulated wall, it slows down the heat loss process by providing another skin to the building that has good insulation property’s. See appendix A.2 & A.3.
As hot air travels up it is beneficial to insulate not only the roof of the building but the intermediate floors too. This is achieved by installing insulation in-between the joist of each floor along with the joists in the roof and in-between the rafters of the roof structure its self. See appendix A.4.
10-15% of the heat from a home escapes through the ground floor. This is due to the foundations/floor structure of the building being a lower temperature than inside the home. Depending on the design of the ground floor structure, insulation would be placed in-between the joists and the battens.
Or for solid concrete floors as Suhr & Hunt (2013 page 123) states, a layer of insulation can be placed on top of the concrete slab along with an Orientated stand board floor. This solution however can only be done if the loss of space is acceptable for retrofit projects. If this was going to be used for a new build the extra required space could be designed in. See Appendix A.5.
As Baeli (2013 page 114) states, Double glazed windows work in the same way insulated walls work, the window consists of an outside pane of glass with an air void normally filled with the gas argon in the middle then closed off with another pane of glass on the inside. The heat from the inside of the building hits the inside glass pane and is conducted. If the home has single glazed windows the heat passes through the single pane and is now on the outside surface of the window, the heat will then be absorbed into the surrounding air. If the windows were double glazed the heat would need to travel through a gas pocket and then another pane of glass. Double glazed windows will not stop heat loss but they will slow down the process meaning the buildings loses less heat and uses less energy to keep the home warm. Triple glazing works in the same way but with three panes of glass and two gas voids, triple glazing does have lower U values and is found to make the living space more comfortable, however triple glazing has a 50% higher embodied energy value and cost compared to double glazing. For the reader thinking about the improvement on the windows in the home, this section should be investigated further as climate, position of the windows and budget will have an impact on the best windows to use. See appendix A.6.
As Suhr & Hunt (2013 page 37-55) states, When buildings are constructed they can contain gaps in the structure that are very small but can still allow air to flow through. The gaps in the structure could be but are not limited to connections between windows and doors, gaps around pipes and leakage through the walls. The walls will be insulated but insulation will not stop draughts. As a result in the pressure difference, air will get pulled through the gaps from the outside of the building where the temperature is lower than the inside of the building this is called infiltration. As a result the temperature of the room has reduced therefore more energy will be used to increase the temperature starting the cycle once more. A design method to reduce this is by using Orientated stand board or a layer of plywood internally in the structure, this can be placed on the walls ceiling and floor providing better air tightness qualities than if nothing was used. See appendix A.7.
There is a difference between air tightness and ventilation. A home should be both air tight but with appropriate ventilation. Ventilation is very important in residential homes as it removes any stagnant or moist air. Ventilation should be designed into the building and is controlled. For example, having an extractor fan above the cooker and air bricks placed into the walls of the structure, Air ventilation systems installed correctly will not result in general heat loss. If appropriate ventilation is not achieved the building will start experiencing problems such as moisture and damp patches, this could result in the deterioration of the home from decay inside the fabric of the building. Air tightness is preventing the uncontrolled loss of heat to the external environment.
As stated by Suhr &Hunt (2013 page 151-167), by using renewable sources less traditional forms of energy are necessary. Renewable energy is also a very sustainable solution to running a home, once the equipment has paid for its self by the savings in energy cost, the resident gets effectively free power without a negative effect to the environment.
Wind turbines work by the movement in the propellers created by the passing wind. The movement in the turning propellers transfers the wind energy into the connecting generator. The energy is then used in the form of electricity and transferred into the local community. A average wind turbine can generate enough power to enable electricity to 1000 homes at any one time and can pay for its self within 1 year. The energy generated can be stored in a battery and so the wind doesn’t need to be blowing during the need for power. However one downside to wind power is that there may be time where not enough electricity has been generated by the wind and so the need for nuclear power may arise as a backup.
Using panels on the side or top of a building is a very effective way of providing energy to heat the home and provide hot water as stated by Suhr & Hunt (2013 page 158). Heat from the sun is absorbed by the panel which than will be used to heat the water to be distributed into the heating system (radiators) and the hot water taps around the house. This is a effective way of reducing the use of energy used to heat a home; however a boiler or another chosen method of heating the building will need to be installed as back up for the months where sunlight does not provide enough energy. Solar panels for an average sized homes cost £6500 this will results in a saving in energy cost on average £750 a year. It will take the solar panels just over 8 years to pay for them self’s, however the life span of a solar panel is approximately 12 years and will need replacing after to keep up efficiency.
This chapter has appraised solutions that are available when upgrading a property, the designs evaluated in this chapter are not the only solutions to improving the energy performance of a building, however they are basic improvements that one would carry out as a good starting point.
Fabric improvement designs work simply by retaining the heat inside the home, by doing this less energy is used to continually heat cold air. Using renewable resources for energy means that you are using natural resources that will not run out, or cause a negative effect by using them such as the production of carbon emissions. The down side to using natural resources is depending on the method a backup heater/electric supply may be needed to ensure energy is always available.
A new build project was carried out in Milton Keynes to full Passivhaus standard by the eco design consultants. Information on the new build can be found on the ecodesignconsultants.co.uk website. The building was designed to be as energy efficient and sustainable as possible. Optimizing natural energy by the location of the windows and using solar panels for power. The materials that were used were also chosen for their natural properties and sourcing methods.
In the location of the new home there was an old derelict building which had previously been burnt out. Due to the condition of the building the best option was to demolish and rebuild as retrofit would not be possible as the existing building was past saving.
When identifying what materials to construct with, several factors were taken into consideration, the insulation levels of the material would be assessed for example. The Eco design consultants recognised the importance of thinking about the embodied carbon of the material and wouldn’t use it unless the embodied carbon levels were low, this was achieved by using local materials, ensuring that they were natural and sourced with as little negative impact as possible. Another important factor they considered is can the material be recycled when the house is demolished, by using recyclable materials the amount of waste from the building reduces further.
Some traditional building materials need to be maintained to retain the purpose of the element in the structure, for example timber soffits and facer boards over time weather and need to be treated with outdoor paint and treatments on a regular basis, ideally, they would also be replaced every 13-15 years. When constructing an eco house building the materials used are chosen for their durability and longevity. The cladding used on the exterior of the house was a softwood which only takes 25 years to mature whereas hardwood takes 65. However generally hardwood will last three times longer than softwood before it needs replacing and so hardwood is more sustainable when considering the life span. The softwood cladding that was used was exposed to a natural process making the softwood more durable to enable the softwood to achieve the same life span as the hardwood, due to this process and the lesser amount of time to grow softwood was used for the cladding as it was seen to be overall more sustainable.
The house was designed to utilise the energy of the sun. This was achieved by having large windows for the open floor living area on the south facing side of the house. To compliment the windows the roof overhung the south side of the house more than a standard house design, this meant that in the summer the overhanging roof provided shade, not allowing too much solar energy to reach the windows causing the house to overheat. In the winter this was also affective as the sun is lower in the sky, the position of the roof does not cease the conduction of heat through the large windows, providing a natural heating system in the colder months. Due to the larger roof facing the south solar panels were also installed and were in the perfect location to utilise the solar energy through the day.
As assessed in chapter 4 ventilation is very important while still avoiding draughts. However, a traditional ventilation system will pump out the heated air from inside the home and pump in cold air from the outside atmosphere, more energy is then used to then heat the new air to a comfortable temperature. To overcome this issue a MVHR was used in the new build home as ventilation and heating system. MVHR works by transferring the heat from the removed air to the air that is being pulled in from the outside atmosphere and pumped into the home. This works at approximately 90% exchange rate so minimal additional heating will be necessary. A MVHR system does however cost over £11000 for an average 3 bedroom houses while reducing the annual energy bills by £1000, the stated cost and savings mean the payback period is over 11 years.
To determine how effective a building is at retaining the heat each element of the building is given a U value. The minimal U values that need to be achieved are stated in the Building Regulations 2010, Conservation of fuel and power LA approved document, page 15, table 2. And can be seen below in table one, table one also states the U values that where achieved for the new build case study project.
|Building Element||Building Regulations W/m²K||Milton Keynes new build W/m²K|
|Windows||2||0.6 – 0.97|
As evident in table one the design and material used for the new build house achieved much lower U Values then is required by the Building Regulations.
In the new build project natural sustainable materials were used as much as reasonably practical, including designing the home to utilize natural energy in the form of solar power. The building has been designed to work with the surroundings to take advantage of the natural resources. By constructing an eco home from scratch maximum sustainability and energy performance can be achieved as there are no limits in the form of an existing structure restricting the improvements that can be made and the designs do not have to fit in with any current building. New designs can be bespoke to maximize the local benefits available in the area, for example hydropower if there was a local stream.
As compared in table one a new build project gained a 40-50% improvement on U Values of the building, meaning a home built for maximum sustainability following Passivhaus would be 40-50% more energy effective than even homes being built today following the building regulations. 40-50% improvement is only on the heat retention of the building and does not include the energy that can be saved from using renewable energy sources.
In this case to demolish and rebuild was an evident decision due to the existing building being uninhabitable. However, this will not always be the case; homes that need upgrading generally are being lived in and are structurally sound. In this situation, more analysis will need to be undertaken before deciding to demolish a structurally sound building to make sure the effort does not outweigh the benefits.
In this chapter a retro fit project of a mid -terraced Victorian house undertaken to improve the energy performance will be evaluated. The improvements were designed by the Eco design consultancy and the standards followed were the passivhaus standard (this project was carried out before the EnerPHit Standard was created for retrofit projects) the improvements carried out will be analysed and evaluated. Information for this retrofit project can be found on the ecodesignconsultants.co.uk website.
The home in question has solid brick walls but in insulation levels of the walls needed to improve, to avoid the risk of damp in the walls any insulation that was placed internally would have been limited in terms of thickness and so would not have been efficient. Therefore external insulation was chosen as the best option. As the house is mid – terraced only the front and the back of the house needed to be insulated, the assumption would be made that both homes either side where kept at a similar temperature and therefore heat transfer would be minimal. A 250mm thick layer of insulation was fixed onto the external face of the front and rear of the home, this was then covered using rendering.
The ground floor was also solid concrete and due to the height of the first floor ceiling insulation was not an option straight on top of the floor as this would have reduced the size of the room dramatically. To overcome this, the ground floor was excavated and then brought back up to finished floor level with a 300mm layer of insulation finished with a screed of concrete.
The roof and intermitted floors were also filled with 270mm thick insulation in between the joists and rafters as discussed in chapter 4 reducing the heat transfer between the separate rooms in the house.
The load bearing walls of this home continued straight onto the foundations with the insulation for the ground floor either side of the wall. This means that the brick wall will be cold from the foundations in the ground. The cold air then gets conducted by the wall and will travel through the wall into the home. This would create a cold patch on the wall which is also prone to damp due to the difference of temperatures between the walls surface and the surrounding atmosphere. To reduce this cold bridging an insulated layer was used around the load bearing walls, this was in a form of a thick skirting board. This will reduce the cold air transfer in those rooms and reduce the likelihood of any damp patches at the ground floor.
To ensure that the energy usage of the home is kept to a minimal the retrofit project also focused on improving the white goods that where in the home, this included the fridge-freezer and alike. A rating of A++ was necessary for each appliance as a minimum. By using efficient white goods available the amount energy wasted reduces therefore less energy is used. This will also help to reduce the cost of running the home. The most energy efficient rated whites goods is A+++ which using a fridge freezer as an example produces around 206kWh compared to A rated fridge freezer producing 412kWh.
The first step taken to reduce the demand for heating water in the home was by installing shower heads and taps with lower than normal flow values. To ensure that using low flow appliances does not affect the efficiency of the shower, aerators were used to give the impression of a normal flow shower, thus receiving the same performance. To continue to reduce the amount of energy used to heat the water, hot water recovery systems were also installed. The system works by being connected under the shower to the out-flow pipe, the heat from the water once the occupant has finished having a shower is then used to heat the water through the inflow pipe. This cannot heat the water enough for a shower so another heating system is also needed, however it will reduce the amount of energy used for this purpose by 60%.
The Building Regulations 2010 conservation of fuel and power in existing dwellings Approved document L1B, page 18, table three gives A Threshold U Value and an improvement U Value. As stated in the building regulations if a home is undergoing a retrofit then the current materials must meet the threshold values as a minimum, if they do not then the material must be replaced and the improvement values must then be met. The U values for a retrofit project stated in the building regulations are more lenient then the U values expected of a new build project.
Table Two shows the comparison between the Building Regulation values as a minimum and the U Values that are achieved for a EnerPhit standard retrofit project.
|Building Element||Building Regulations W/M²k||Retrofit Project EnerPhit Standard
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As table two shows, a retrofit project built to EnerPhit standards achieve significantly lower U Values then are required from constructing to the building regulations.
The improvements carried out in the house discussed in this chapter have had a mixture of fabric improvements, services improvements, and renewable energy equipment. All of the designs chosen had to be appropriate for the existing house and had to take into consideration the design and workability of the existing structure, gaining maximum benefit by best reasonable means. The designs carried out for this home may not be appropriate for another retrofit project. It is important to take note that planning permission had to be gained to add insulation to the external face of the wall even though this home is not listed.
As proven in table two the improvements gained from constructing to EnerPhit standards achieve a 70% improvement on wall requirements along with 60% on the windows and 40-20% improvement on the floor and roof. This improvement value has been compared to the minimum standard set out in the building regulations. In setting a much tighter minimum requirement, EnerPhit has an average improvement percentage of 50%.
Photo taken from http://www.ecodesignconsultants.co.uk/passivhaus/hiley-road/
The only building standards that have been produced in the United Kingdom are the Building Regulations, however Passivhaus Standard is being used widely. This chapter will compare how the English standards compare to the German standards (Passivhaus) and evaluate the difference.
The information in this chapter was gained from a visit to Eco build, the data for Passivhaus information is also available on Passivhaus trust (2013) and the English design information called the Standard Assessment Procedure (SAP) can be found on buildenergy.co.uk website.
The latest Building Regulations were approved in 2010 and even though there is an approved document that is dedicated to the use of fuel in homes in both a new build and a retro fit home the minimal standards have been written with the assumption of traditional construction. When a home in the United Kingdom is designed to meet the Building Regulations, SAP calculations must be carried out during the design phase. SAP calculations are the process of considering all the materials used in construction to provide the energy performance of the purposed building. Using SAP is largely generic and is not bespoke to each home, it doesn’t take into consideration important variables that play a part in the efficiency of the building for example protection from overhanging trees or existing structures. Because of the generic nature of SAP the actual energy performance achieved after construction is different to the planned performance during design, this will still however need to meet the building regulations.
Generally, homes designed to meet the Building Regulations would be designed traditionally. This would result in the building having cold bridges in the structure, draught voids present and not taking into consideration what direction the windows face. These small details make a significant difference when considering the energy performance of a home and by designing them into the home using standard UK building designs you are reducing the efficiency of the home.
Even though the building would be constructed using a qualified contractor homes built to meet the Building Regulations only have generic tests carried out by the building officer at certain stages and the structure is not scrutinised at each step to ensure that maximum performance is achieved. This could result in poor workmen ship causing voids, unintentionally cold bridging, and general standard fixings.
The Passivhaus standard was published in 1990’s and was written with the aim of achieving a home build for maximum energy performance and sustainability. This standard is a choice of construction and not mandatory however due to the high performance of the homes there are now several design consultants that will design a home to this standard if that is what the owner decides. When a passivhaus is designed, a spreadsheet called Passivhaus Planning Package is used. This spreadsheet designs the home taking into consideration variables that would affect the performance of the building. These variables include the location of the home in the United Kingdom, the orientation of the building to the sun and the type of house for example detached. Unlike the Building Regulations using the Passivhaus Planning Package means a greater level of detail can be obtained and it has been proven for the last 15 years of constructing to Passivhaus that the buildings constructed delivers the energy performance that the home was designed to.
Compared to the Building Regulations Passivhaus designs cold bridging areas out of the building. It evaluates the effect of the position of the sun on the building and how that can be utilised. Unlike the Building Regulations by considering these factors the designer removes any possible “low performing area”from design stage.
When a home is built to Passivhaus there is a quality assurance protocol that must be followed. The materials used and workmanship get tested at each construction phase, the build cannot move on until the stated U Values at design stage have been achieved. Because of this tight procedure, the homes meet the standard that it has been designed to, unlike the Building Regulation homes that have intermittent and general testing. Passivhaus also only build with contractors that are familiar with the standard or contractors that work with listed buildings. This is due to the attention to detail needed and the importance of the workmanship in achieving the standard. This is compared to general building to Building Regulations where standard building contractors are used generally for cost saving purposes or general home construction experience.
As demonstrated in chapter six and seven when a house is built to either Passivhaus or EnerPhit standard the home achieves an overall better U value then a home constructed to meet the Building Regulations, with an average improvement of 50%.
As written by Passivhaus trust (2013 Page 11). Compared to A home built to Building Regulations, passivhaus buildings achieve;
- 78% Reduction in Heating Demand
- 84% Reduction in Energy Demand
- 88% Reduction in CO2 Emissions
Also, a standard house uses 140kWh/m²/yr on heating the rooms, this value is compared to 15kWh/m²/yr that is used to heat the living space in a Passivhaus home.
The78% reduction in heating demand includes the design options that have been used for example solar panels and ventilation systems. When stated a 50% improvement from the building regulations this is referring to the U values gained only.
When comparing the Building Regulations with the Passivhaus standard it is evident that in order to achieved better energy performance, reduce embodied carbon and achieve sustainability a home would be designed to meet the Passivhaus standards.
Building to the Building Regulations could be improved with several changes and tighter checks at each step, this may be necessary to ensure the improvement of building standards in the future. If the Regulations are not improved to the high standard that can be achieved in the construction industry, then the applicable regulation may be made redundant due to the high popularity of Passivhaus.
A mass upgrade project was carried out by Radian in Petersfield to Reema buildings. Built after the war using hollow pre cast concrete walls, the homes would achieve minimal energy efficiency before the upgrade.
Once the retrofit project was completed, Camco was instructed to carry out research to assess what the difference would have been if the same project was carried out as a demolition and new build. The information can be found on the superhomes.org.uk website in the lifetime Emissions of retrofit versus new build report.
A number of assumptions were made to conclude the new build values and therefore is subject to inaccuracies, however practical and conservative assumptions were made to make inaccuracies minimal.
The different comparisons assessed in this chapter are the Embodied carbon, lifetime use and cost between a new build and a retrofit project.
During construction the retrofit produced just over 23 tonnes of CO2 emissions, a new build project constructed to the same standard was found to produce just over 44 tonnes of CO2 emission. Giving a difference of 21 tonnes, 14 of which were produced by the higher amount of materials needed. With another 4 tonnes produced from the higher value in energy used in the form of gas oil, this is due to the method of construction causing higher volumes of work. The other 4 tonnes were accumulated from transport and removal of waste from site to landfill.
The second to compare is the energy that the building will use for the first 50 years of its life. Assumptions were made for both a retrofit and a new build project for this purpose. These values include heating space and use of appliances, therefore gas and electric use in this exercise. The retrofit project produces a total of 115 tonnes of CO2 emissions; this number is compared to 115 tonnes for the new build project. The amount of CO2 emissions produced from both are the same due to the standard of improvements that can be carried out.
The retrofit project carried out was found that a 85m² home would cost an average of £91,900 per dwelling. This figure can be compared to £144,700 for each new build also 85m², resulting in a difference of £52,800. The difference comes from the amount of material that would be needed for a new home and the demolition and removal of the old structure.
Baeli (2013) also gives costs for each retrofit project undertaken. As a means of comparison and verification Baeli (2013) states the cost of a retrofit project ranges from £53,000-£134,000. The difference in cost verifies that each upgrade will have a different cost depending on the nature of the building and the efforts necessary to upgrade a different type of structure. Based on these figures £91,900 is an accurate average cost to be used for a retrofit project.
This chapter can summarise that from the findings in the report a retrofit project is cheaper due to the less amount of work the upgrade consists of. It Produces the same amount of lifetime emissions due to the high standard that a retrofit project can be carried out to, and has less Embodied carbon due to less material being needed and overall produces less waste.
These figures are however based on assumptions and therefore could be slightly inaccurate. This is also only applicable to this certain type of upgrade due to the nature of the building in question and can’t be taken as a conclusive result.
Chapter 6 and 7 evaluated a case study for both a retrofit project and a new build project, there are differences in the way the two were upgraded as the new build could be designed totally for energy performance as it has a “clean slate”, where as the retrofit project had to carry out the work around the existing structure and so were more limited in any chosen solution. Even though the home retrofit project was more limited the energy retaining values that were gained after the work was carried out was not much different to that of the new build.
|Building Element||Building Regulations W/M²k||Retrofit Project EnerPhit Standard
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Table 3- Comparison of U values achieved between the Building regulations, Passivhaus standard and EnerPhit Standard
Table three shows the difference gained between a retrofit project and a new build project. The retrofit project is expected to achieve a maximum of 0.02 W/M²k difference.
This data does slightly differ from the findings in chapter 9 where a mass upgrade project was undertaken and found that if the same work was carried out as a new build the CO2 emission would be the same for both.. It could however be said that due to the mass upgrade being based on a number of assumptions that a small difference like the passivhaus which is a real project is a more accurate CO2 figure.
It is also important to note that from the research carried out a new build allows sustainable methods of gaining energy to be designed into the building, for example in chapter 6 where the south facing wall is a window this type of design allows a substantial energy gain through solar power, but cannot be incorporated into a retrofit project on the same scale, or if it was possible to included in an existing structure the upgrade would have a significant cost. Therefore in that sense a retrofit project is limited in how far the home can be upgraded for sustainability when compared to a new build project.
The two methods can be compared however in the type of material that can be used to improve the energy performance. Even though for a retrofit project the shell of the building is there, the same types of insulation can be used as long as the design of the existing structure does not inherit the use in some way. Both types of upgrades could also use methods to improve energy performance such as the same ventilation system like MVHR mentioned in chapter 6, and the types of white goods that are being used inside the home discussed in chapter 7.
An important factor to consider is also the aesthetics of the structure. For example upgrading a block of concrete façade flats, keeping the structure may be more sustainable than a new build however is the old appearance something that the owner or investor would want to preserve? In this case it would be beneficial to investigate into façade replacement. Like façade replacement, façade preservation could also be considered. If there is an older Victorian home with character that ideally would be demolished and re built the façade could be saved and incorporated into the new structure.
The question does need to be asked however as to is either solution practical? In chapter 9 the cost of both a new build and a retrofit project are discussed and found to be expensive for either option. As discovered in the introduction of this dissertation for the UK to meet the Carbon Change act 2008 old housing stock will need to be upgraded, in reality this means working families living in the UK upgrading their homes. For a working class family wishing to improve the performance of their 3 bedroom semi detached home on a budget, a renovation would cost around £91,700 which is most cases is unaffordable. A new build and even an intense retrofit would also mean a temporary relocation for a period of time, which would have a significant cost and disruption to their lives.
It is also questionable for a family that could afford to rebuild or renovate as to whether they would ever see a return on their investment and if financially either solution is feasible. An average home has energy bills of £1600 a year; with the 84% saving on energy stated by Passivhaus this reduces the energy bills of the homes to £256 a year. Considering just the return on the investment this would take over 68 years to get back.
In the northern part of the country the value of homes are significantly lower than that of London and the surrounding areas however the construction material has the same cost throughout the country. If a home owner was to undertake a new build or retrofit project for the reason to gain maximum sustainability and better energy performance, would the owner ever be able to get the cost of the renovation or new build back in the value of his or her home if they were to sell?
It is an important thought that a mass upgrade being either a retrofit or new build may be more likely to happen in a real world situation than an individual home owner carrying out the work due to the excessive cost. For a normal working class citizen they may chose to have new windows, upgrade their boiler or have solar panels installed to improve the energy performance of their home but would not be able to afford a full renovation. This is compared to a property developer or owner who can invest and may be more likely to carry out a full upgrade on a number of homes at one time as demonstrated in chapter 9.
The subject of this dissertation is; upgrading an old residential building for energy performance and sustainability. Demolish and rebuild or refurbish?
This research has previously been carried out by other interested parties and depending on which report or case study the reader would observe would depend on the conclusion given. This would mainly be down to the priority of that writer, if it was an individual talking about his or her home they are more likely to preserve their home and gain maximum energy performance where possible, where as if it was a mass investor they would choose the most profit effective method.
There are many areas in which the two can be compared. As discussed in chapter 10 the energy performance of the two solutions when upgraded to the same standard are very close with a new build having 15% lower thermal conductivity values. Therefore if the reader was just looking at these values then a new build is more energy efficient. However is 15% improvement enough to warrant knocking down a structurally sound house?
To demolish and re build a property would cost an additional £52,800 compared to a retrofit project therefore if cost or budget was a driver or restrictor then the retrofit project would be considered. It could also be said that a £52,800 additional cost is not worth a 15% energy performance improvement, especially when considering demolishing a home for this to be achieved.
Something that needs to be considered in a real world situation is what is more appropriate for that property? Neither solution can be compared for this question as even thought it has been found that in a ideal situation retrofit will be more sustainable a retrofit may not be possible. In chapter 9 a mass retrofit project was undertaken. Due to the nature of the build consisting of hollow concrete walls, insulating the homes was an easy process and was cost effective. Another older home may be constructed in a way that a retrofit would cost much more than a standard retrofit project.
One thing that hasn’t been mentioned in this dissertation or the other research projects that have been assessed is people’s attitude towards saving energy in the home. Regardless of if the project was a new build or a retrofit project if the resident are not energy performance aware than neither will have the impact that is required.
The heat retention gain difference between the two is minimal and is not enough to make a decision based on that value when there are vast amounts of other variables to be considered.
Therefore this dissertation can conclude that both solutions have substantial advantages and disadvantages, and that each project should be assessed on a number of different considerations before making the decision.
Questions that should be asked are;
- Does the building in question need a substantial upgrade? Could minor changes improve the performance of the home to an efficient level? Where does the home need improving? Walls, floors, windows?
- Does the home need any structural work? Is it more effective to start the building from scratch? Can it be saved with minor improvements?
- What’s the remaining life span of the home? Would the reader want to save a 90 year old property that isn’t listed or has any characteristic significance.
- Is the current building going to allow an effective retrofit? Will the existing design allow for cold bridging to be constructed out and efficient insulation placed?
- Will a retrofit inert the nature of the building or how the building works and breathes? Will problems arise from trying to improve the energy performance such as damp?
- For demolition purposes how much of the existing structure can be reuse either elsewhere or in the new building?
Other factors that should be asked and addressed are;
- What standard is going to be used for construction – both solutions will not be effective if a substandard regulation is going to be followed.
- Are their residents to consider? Is re-homing necessary, if so where and for how long?
- Are the residents educated in how to inhabit a home and preserve energy by reasonable means?
- What energy preserving means are going to be used inside the home? After the fabric of the building has been addressed? Effective Water heating systems? White good appliances?
- What type of material will be used? Where can it be sourced? How is it procured?
- What is the budget? Are the improvements going to be cost effective?
The limitation of providing an answer to the subject of this dissertation is due to how generic the question is and how many different factors must be considered. There is not a “one answer fits all” for this subject, however the conclusions provided should give guidance and a good starting point on how to make the decision and what information should be assessed, further research may need to be carried out that is bespoke to the project before a decision is made.
A recommendation for this research to continue would be to further investigate available design options that are more advanced than that mentioned in this dissertation for both a retrofit and a rebuild project. This would provide a more extensive pool of improvement options which may assist in determining which option of upgrade is the most appropriate.
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