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Strategies for Zero Carbon Homes

Info: 5357 words (21 pages) Dissertation
Published: 11th Dec 2019

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Tagged: ConstructionSustainability


Anthropogenic climate change is a phenomenon that has received much attention in the last few decades, and for good reason. Since the renowned studies carried out by Dr. Rowland and Dr. Molina, which began in the 1970s on Ozone depletion, subsequent studies have revealed that human activity is causing the planet’s atmospheric and surface temperatures to rise and may also be a major contributor towards climate shift, due by and large by the release of carbon dioxide, methane and other greenhouse particulates and gases in to the atmosphere. The effects of climate shift include severe weather conditions, receding glaciers and ice caps, rising sea levels and drought, with the poorest countries being affected the most.

Since the introduction of the Kyoto Protocol in 1997, the UK government is committed to the agreement to reduce UK carbon emission by 80% by the year 2050. It has been suggested that the 21 million homes in the UK account for around a quarter of the total carbon emissions into the atmosphere. With the current government’s indication to increase the number of dwellings to 3 million by the year 2020 due to the rising population, a greater effort is needed to reduce carbon emissions within the housing sector; a drive that will aid the UK Government’s long-term commitment to the United Nations Framework convention on Climate Change and Kyoto Protocol.

The government is responding to the challenge quite firmly and has set out strict targets to reduce energy use in new dwellings. To implement such a monumental task, the government has put in place a scheme called the Code for Sustainable Homes (CSH), which sets out criteria for reducing energy for all new dwellings. Gordon Brown’s Governments’ main objective is for all new dwellings to be Zero-Carbon by 2016. The current research paper sets out to identify the impediments that may prevent Gordon Brown’s policy of achieving the zero carbon homes challenge and also to determine the drivers in achieving zero carbon homes across the board by 2016.


The author would like to thank the individuals who have assisted in the production of this dissertation.

A special thank you must go to my supervising tutor Dr. Michael Coffey, whose wisdom and guidance provided support and inspiration towards completing this dissertation.

I would also like to thank all those persons who responded to the research questionnaire, which made a significant contribution towards the production of this dissertation.

Finally I would like to thank my wife Uzma and children Saqlain, Aaliyah and Owais for their support and for putting up with my neglect towards them in the last few months.

Thank you again!

Section 1 – Introduction

Nature of the Problem

Since the Industrial revolution in the late 18th century, greenhouse gas emissions have increased considerably. Scientists have observed that a third of the Sun’s energy that is directed towards the boundaries of the Earth’s atmosphere is reflected back into space, whilst the remaining energy is absorbed by the surface of the planet and to a lesser extent by the planet’s atmosphere.

Anthropogenic influence upon climate change is partly caused by the escalation of excess greenhouse gases emitted in to the atmosphere, such as carbon dioxide, principally influenced by the burning of fossil fuels. The effects of climate shift include severe weather conditions, receding glaciers and ice caps, rising sea levels and drought, with the poorest countries being affected the most.

The problem scientists have determined is that the sun radiates tremendous amounts of light energy emitted in short wavelengths, however the heat energy released from the surface of the planet itself is released in long wavelengths. Whilst carbon dioxide does not absorb the sun’s energy, it does however absorb heat energy from the planet i.e. long wavelength energy. Therefore when a molecule of carbon dioxide absorbs heat energy, the molecule goes into an excited unstable state. The molecule becomes stable again by releasing the energy that is absorbed. Therefore much of this energy remains within the earth’s atmosphere, whilst the rest of the energy will go out into space. Carbon dioxide therefore allows the light energy from the sun to pass but does not allow all of the heat within the earth’s atmosphere to be released into to outer space, thus intensifying the greenhouse effect. Ultimately causing the temperature of the planet to rise.

Illustration courtesy of www.dinosaurfact.net

Pro-Active Response to the Problem

In response to the Kyoto Protocol’s commitments to reduce carbon dioxide emissions, the UK must reduce it’s baseline greenhouse gas emissions by 12.5% by 2008 – 2012 from a baseline target set in 1990. Furthermore, the draft Climate Change Bill commits the UK to reductions of C02 emissions of at least 26% by the year 2020 and also to a long-term goal of an 80% reduction by 2050 (Energy Saving Trust)

Housing within the UK contributes significantly to greenhouse gas emissions. The UK’s 21million homes account for around 27% of the overall carbon emissions released in to the atmosphere (Skandamoorthy, 2007) and with the current Government’s promise to construct 3 million new homes by the year 2020, the need to address the carbon situation within the housing sector is of paramount importance (BBC News, 2007. New agency to drive home building)

Traditionally the construction industry has had little regard for the environment, which makes common ground for producing buildings without energy efficiency in mind. It is only until recent times has the consumption of energy been an important agenda in the house building industry, as advancements in energy efficiency playing an important role in the design of buildings built today, due partly to the crucial role being played by the stringent building regulations; pushing the boundaries further to make buildings more energy efficient.

In response to the current situation with regards to reducing carbon emissions within the housing industry the government introduced in 2006 the Code for Sustainable Homes (CSH) scheme (a successor to the Eco Homes rating scheme). At the moment the code is a voluntary standard for energy efficiency and sustainability, applying to newly built homes in the private sector however, it is mandatory where public sector (Homes and Communities Agency) funding is involved. The code aims to deliver a standard guideline for house builders in the UK and addresses key areas of sustainability such as water use and C02 emissions in house building and use. A rating system has been developed within in the code, which measures the ability of the building’s efficiency in terms of energy use. The code’s rating system ranges between levels 1 and 6. Level 6 being the highest level of efficiency and is the level that is most appropriate and applicable to the current study, which is the attainment of ‘zero carbon status’ (Code for Sustainable Homes Technical Guide, 2007)

The Government has indicated that the code will become the single national standard for the design and construction of sustainable homes and is set to become a vehicle for the development of sustainable home building practice in the UK (Code for Sustainable Homes, 1997)

The subject of interest is whether the government and the building profession can implement and administer an effective strategy that will allow all new homes to achieve the highly challenging standards of incorporating level 6 rating to dwellings across the board to allow zero carbon status of newly built homes by 2016.

Why is there a lack of zero carbon dwellings in the United Kingdom?

The problem that presents itself is that the conscious world has accepted that the global warming phenomenon is a serious threat to the planet. Up until recent times carbon emissions and the negative effects being imposed by them upon the environment were not clearly understood, or even thought about in many respects and therefore not a major issue in the housing industry. Recent studies have reported that homes contribute around 27% of total UK carbon emissions. For this reason the housing industry may not have grasped the technologies sufficiently to mass-produce zero carbon homes. Because demand may have been low for zero carbon dwellings it may indicate that there may be a premium cost to build zero carbon homes and therefore not in the best interests of financiers and developers, who may not receive healthy returns on assuming risk for building such assets. Lack of enforceability may be another issue why such dwellings have not been mass-produced. Maybe the supply of materials to produce such assets may be lacking in availability; again this may be as a consequence of low demand, which may also contribute towards extra cost.

It is not clear that any of these scenarios are either singularly or collectively responsible for the slow progress in developing zero carbon homes. Therefore the current study will examine the various drivers and barriers that influence the development of zero carbon developments such as cost, legislation, market demand, available technology and the supply chain. The identification of these factors will provide a basic analysis to determine whether the policy of achieving the zero carbon homes policy by 2016 across the board is actually feasible.

Section 2 – Review of zero carbon homes legislation

Few green policies have had quite such an impact on a sector as the zero carbon homes policy has had in housing says John Alker, Head of Advocacy at the UK Green Building Council. In December 2006 the government introduced a commitment plan which formulated a requirement that all new homes are to be zero carbon from the year 2016 onwards. The initial proposal was formally communicated via the Code for Sustainable Homes (CSH) technical guide, which is based on and replaces the Ecohomes national standard for sustainable design and construction for new housing in the UK in April 2007. The code stated that a building would emit zero net carbon emissions from heating, hot water, lighting, appliance use and cooking. All CO2 reductions had to be achieved by local off-site means connected to the building by a direct physical connection. However, more recently the government defined a zero carbon dwelling as one which generates 70% of the energy it uses for heating, ventilation and lighting from on-site renewable energy (The Energy Saving Trust). Meeting the criteria would enable the home to be rated as a code level 6 home; the highest star rating achievable in terms of the Code, thus certificating the home as a zero carbon dwelling. The acquisition of a code level 6 certificate will allow first hand purchasers of zero carbon homes up to the value of £500,000 exemption from paying stamp duty land tax (SDLT). Homes above the £500,000 threshold will enjoy a £15,000 reduction towards the stamp duty bill (Section 58b, 2007 Finance Bill)

It should be noted that the Code for Sustainable Homes (CSH) is currently UK legislation and its implementation is optional to use apart from developments funded by the government (BRE, EcoHomes, 2007). The government has indicated that home builders are encouraged to follow the guidelines of the Code now as adherence to the Code will become mandatory in the future for all new house building (Code for Sustainable Homes, 2006)

The government has also provided an incentive for the installation of energy saving materials and micro-generation apparatus by reducing the VAT to 5%. This VAT decrease only applies to the UK however, “the European Commission is committed to bringing forward proposals for a change to the Principal VAT Directive to allow an EU-wide reduction in VAT for green products, particularly those aimed at improving energy efficiency in buildings” (HM Treasury, 2008)

The UK government aims to reach their stated goal of 80% carbon dioxide reduction in the UK by 2050 through implementing progressive tightening of the building regulations. The tightening of the regulations is to be maintained in three phases in 2010, 2013 and 2016 (Building Regulations – Energy efficiency requirements for new dwellings, 2007).

The graph on the previous page shows the target reductions for each phase. These target reductions equate to the energy performance standards in the governments vehicle for reducing CO2 in housing; the Code for Sustainable Homes (CSH) Levels 3, 4, and 6 respectively; highlighting the governments progressive strategy to achieving carbon zero homes by 2016.

Source: (Building Regulations – Energy efficiency requirements for new dwellings, 2007).

The primary method of measurement of energy efficiency for the Building Regulations is the dwelling Carbon Dioxide Emissions Rate (DER), which is an estimate of CO2 per metre squared of floor area. Currently (2010) the improvement in the DER is said to be 25% compared to the 2006 level. An improvement of 44% is required in 2013 and ultimately a 100% improvement which is incidentally zero carbon for all new homes built in 2016.

An analysis of the Code for Sustainable Homes (CSH)

The code seeks to make improvements in energy efficiency and water usage upon those required by the Building Regulations Part L 2006. The code will compliment the system of energy performance certificates that was introduced in 2007 by the Energy Performance of Building Directive (EPBD).

At present the Code is voluntary, however house builders are encouraged to utilise the Code as a guideline for house building practice, as the government states that the code will be mandatory in the future.

Energy efficiency is measured at every level of the code by assessing nine individual design categories, with higher level of sustainability performance achieving a high code rating.

The Code measures the following design categories:

* Energy/C02

* Health & Well being

* Surface water run off

* Pollution

* Materials

* Ecology

* Water

* Management

* Waste

The code implements a procedure which mirrors the BRE’s EcoHomes system in its method of assessment, which relies on trained and accredited independent assessors to inspect the homes. Design stage assessments are conducted by the assessors who on completion of the assessment recommend a sustainable code rating for the home being assessed and will issues an interim certificate. On completion of the development a post completion assessment is carried out by the inspector, who will on completion of the final checks issue a final code certificate which states the level achieved and therefore be given a CSH code rating.

A home meeting any level of the Code will have to meet minimum standards for certain items depending on what Level is desired. For Level 6 this means:

The home will have to be completely zero carbon (i.e. zero net emissions of carbon dioxide (CO2) from all energy use in the home). This could be achieved by:

• Improving the thermal efficiency of the walls, windows, and roof as far as is practically possible (by using more insulation or better glass for example);

• Reducing air permeability to the minimum consistent with health

requirements (a certain amount of air ventilation is needed in a home for health reasons);

• Installing a high efficiency condensing boiler, or being on a district heating system;

• Carefully designing the fabric of the home to reduce thermal bridging (thermal bridging allows heat to easily escape between the inner walls and the outer walls of a home);

• Using low and zero carbon technologies such as solar thermal panels, biomass boilers, wind turbines, and combined heat and power systems (CHP). It would mean for example that energy taken from the national grid would have to be replaced by low or zero carbon generated energy, so that over a year the net emissions were zero.

The home will have to be designed to use no more than about 80 litres of water per person per day. This could be achieved by fitting such items as:

• 6/4 Dual Flush WC;

• Flow Reducing/Aerating taps throughout;

• 6-9 litres per minute shower (note that an average electric shower is about

6/7 litres per minute);

• a smaller, shaped bath – still long enough to lie down in, but less water

required to fill it to a level consistent with personal comfort;

• 18ltr maximum volume dishwasher;

• 60ltr maximum volume washing machine.

To achieve the standard would also mean that about 30% of the water requirement of the home was provided from non-potable sources such as rainwater harvesting systems or grey water recycling systems.

Other minimum requirements are required for:

• Surface water management – this may mean the provision of soakaways and areas of porous paving;

• Materials – this means a minimum number of materials meeting at least a ‘D’

grade in the Building Research Establishment’s Green Guide (the scale goes

from A+ to E);

• Waste management – this means having a site waste management plan in place during the home’s construction, and adequate space for waste storage during its use.

But to get to Level 6 you need a further 64.9 points. So the builder/developer must do many other things to obtain the other points. In fact they will need to do 90% of everything in the Code to achieve Level 6, including:

• Energy efficient appliances, and lighting;

• Supplying accessible water butts;

• Reducing surface water run-off as much as possible;

• Using highly environmentally friendly materials;

• Minimising construction waste;

• Maximum, accessible provision for recycling;

• Improved daylighting, sound insulation and security;

• Building to the Lifetime Homes standard;

• Assessing and minimising the ecological impact of the construction of the home

Source of information: Code for Sustainable Homes – A step change in home building practice guide (2006)

Section 3 – Cost implications of constructing zero carbon homes

During the last ten years house prices have continually increased due to the rising population and a slow response to the demand in terms of house building says Kate Barker in her 2004 survey on housing supply (Barker, K. 2004) See figures 1 and 4 below.

It was the Barker report commissioned by Prime Minister Gordon Brown which gave recognition to the home building industry to investigate into improving the level of housing supply in the UK. The report concluded that the UK had a serious shortage of homes and was in much need of around 120,000 homes per year built by private house builders. The figures are in addition to the 150,000 homes which are currently being constructed per year by the house builders. The Barker report engaged the government to set an objective to increase the supply of houses being built in England of at least 200,000 per year by the year 2020.

The housing market in the UK is considered by the UK government as an important arena in contributing towards regulating the nation’s economy. Putting this into perspective it is ironic that the Labour government since coming into power has changed housing ministers nine times in the last thirteen years. During the first year in office by the Labour government, it has seen a housing crisis which has seen a 190% increase in house prices with a house price to earnings ratio increase from 3.1 to 5.8. What this means is that whilst house prices have climbed dramatically, average salaries have not increased in proportion to the rising cost of house purchasing. The solution to controlling current house prices is to build more homes, however in 2009 only 118,000 new homes were constructed, which is less than half the annual amount required if the government’s target of an additional 3 million homes are to be constructed by the year 2020 (Alexander, 2010). How does this piece of information relate to the cost of constructing zero carbon homes? Quite simply; the government has introduced a policy which aims to build an additional 3 million homes by the year 2020. The government is also pressing with the policy which aims to see all new homes constructed by the year 2016 to be zero carbon. The problem that presents itself is that the cost of building zero carbon homes includes a premium cost for building and subsequently purchasing such a property. If in the year 2009 only 118,000 homes were built, when quite clearly the government’s target is at least 200,000 per year to be in a position to meet the 3 million new homes target by 2020 and the cost of housing is already quite high, then how does Gordon Brown intend on maintaining the road map for two extraordinary targets which clash quite apparently. Last years figures prove that house building was at an all time low since 1946. These figures indicate that Gordon Brown’s government may have overlooked the situation and set a target which is perhaps extremely challenging if taking account of the current economic position of the UK economy.

The Cyril Sweett Consultation

In 2006 Cyril Sweett construction and property consultants were approached by the English Partnerships and Housing Corporation to report on the implications of the move from the Ecohomes standard of ‘Very good’ rating to the level 3 Code for Sustainable Homes. The research carried out by Cyril Sweett consultants reviewed six different types of houses which included four types which were constructed using traditional methods of construction and two with modern construction techniques. Cyril Sweett say that the findings of the research are not necessarily standard for all construction and consideration should given to project specific variables such as the area of construction, type of development, the supply chain etc; each having a variable effect on the cost of building in the stated methods of construction. Whilst the figures do not represent code level 6 developments, they do however give an indication of what the expected cost of building level 6 zero carbon homes may be if factored. The study made consideration to a whole host of construction methods and technological solutions to improve the performance of the home. The sole purpose of the research was to assess which methods of construction were the most economically viable to achieve the various code levels of the CfSH. However four scenarios were given in the report for expediency which are as follows:

Scenario 1

Initial energy efficiency measures followed by the use of solar thermal technology, then photovoltaic and biomass systems.

Scenario 2

Initial energy efficiency measures initially followed by the use of small scale wind turbines and then biomass systems.

Scenario 3

Development with shared energy services, such as combined heat and power (CHP). For this scenario costs per unit are averaged for different infrastructure options for a theoretical 200 unit development.

Scenario 4

Achievement of Code level 3 without recourse to renewable energies through the use of a whole house mechanical ventilation system with heat recovery and by assuming the use of proprietary construction details.

The findings of the study found that projects which allowed for wind energy or site wide CHP technologies had scope for achieving the lowest costs. Again, it is stressed that projects are site specific therefore areas with low wind speeds may not be able to achieve satisfactory wind speeds to justify using wind energy technologies.

The following tabulated data highlights the additional cost of achieving the code level 3 over the Ecohomes Very Good standard.


Traditional detached house

Traditional terraced house

Low rise apartment

High rise apartment

Scenario 1

£4,525 (4.8%)


£2,579 (3.2%)

£4,900 (3.8%)

Scenario 2

£2,852 (2.9%)

£2,786 (3.5%)

£1,498 (1.9%)

£2,699 (2.0%)

Scenario 3

£3,131 (3.2%)

£3,165 (4.1%)

£946 (1.2%)

£643 (0.4%)

Scenario 4

£5,090 (5.4%)

£4,748 (6.2%)


£3,942 (3.0%)

The baseline cost for the abovementioned homes is £92,107 for a 116m² detached home and £75,230 for a 101m² end of terrace home, as specified or compliant with the 2006 building Regulations.

It is an interesting observation that the implementation of Scenario 4 to achieve a code level 3 rating costs £5,090 for a detached house and £4,748 for a terraced house; an increase in cost of 5.4% and 6.2% respectively. What’s interesting about these figures is that Scenario 4 does not implement any renewable energy solutions such as photovoltaic cell technology but does make use of mechanical ventilation with heat recovery systems. Scenario 4 does in many respects mirror the PassivHaus dwelling or Scandinavian homes method of building. Scenario 4 combined with advanced micro generation technologies could achieve level 6 zero carbon status but to enable this industry would need to invest further in research and development of enhancing the micro generation technologies, however the cost will be greatly increased. As with anything that is new there is a premium cost to be paid. But as more efforts are made and competition increases due to demand the cost of such technologies should decrease in time.

The costing data provided in the Cyril Sweett report (2007) went further to report on the cost of achieving a level 5 rating of the Code for Sustainable Homes (CfSH), which is incidentally the highest level of code attainment data provided in the report. The following cost comparison data only makes reference to detached dwellings as the costing data for terraced houses are not too dissimilar to the detached houses.

Scenario 1

The table shown above shows the cost of achieving a code level 5 rating of the CfSH using scenario 1, which to reiterate includes the use of solar thermal technology with photovoltaic and biomass systems. The cost attached to upgrading to level 5 costs an additional £20,270, as shown in the table. Therefore an 18% increase above the baseline cost of building a detached home with a 116m² area to the 2006 building regulatory standard, which totals £111,476.

Scenario 2

Utilising Scenario 2, a 116m² Home built with small scale wind turbine and biomass technology will achieve a CfSH level 5 rating at a cost of £14,206 above the baseline cost. A 14% increase totalling £106,146

Scenario 3

Utilising Scenario 3, a 116m² Home built using site wide CHP technology will achieve a CfSH level 4 rating at a cost of £2,622 above the baseline cost. A 3% increase totalling £93,828

Scenario 4

Utilising Scenario 4, a 116m² Home built with improved air tightening and mechanical ventilation will achieve a CHS level 3 rating at a cost of £4,481 above the baseline cost. A 5% increase totalling £95,687

The cumulative graph shown above shows the cost of achieving each level of the Code for Sustainable Homes (CfSH) up to level 5, in comparison to each scenario detailed on the previous pages.

The interesting thing about the comparative cost data provided by Cyril Sweett consultants is that to achieve level 5 of the code using scenario one costs £36,070, which is an increase above the baseline cost of 28.6%. Obtaining a code level 5 rating using scenario two is achieved by allowing for an increase in cost above the baseline of £20,746 which is a 22.7% increase. These figures provide an indication of what the likelihood cost for building code level 6 zero carbon homes are going be. Therefore it is estimated that for a similar type of dwelling the cost will be in excess of 30% above the 2006 Building Regulations baseline cost. A 30% increase in cost is quite substantial considering a home built to the prescribed building standards would cost approximately £92,107, thus around a £40,000 increase to implement code level 6 to the dwelling is a substantial amount and therefore cost is going to be a major factor in determining the success or failure of achieving the zero carbon homes by 2016 target.

Clearly the figures shown in this report show that the cost of producing zero carbon homes across the board is going to be a major obstacle if drastic changes and new solutions to reduce the cost of zero carbon technologies do not surface within the next few years leading up to the year 2016. The situation appears to be quite discomforting as affordability is going to negate the possibility of achieving not just the 2016 target but may also interfere with the 2020 target of building an additional three million new homes in the United Kingdom as less demand due to affordability will result in less homes being built and therefore cause a stalemate situation if the government alongside industry does not take steps to resolve the situation fast.

Reductions in cost for bulk purchasing

As stated earlier in the report cost reductions can be made through advances in technology and through competition as demand for zero carbon homes increases. Whilst the cost of achieving zero carbon is quite high at the moment, cost will gradually subside. The Cyril Sweett consultancy further reported that the purchase of materials and technology in bulk order will reduce the cost of producing zero carbon homes. Cyril Sweett representatives approached a number of suppliers of water and sustainable technologies. It was found that for large scale procurement i.e. 5000 units plus reductions in cost were achieved for the following technologies.

Sustainable technologies

Savings in cost (%)

Grey water recycling solutions

10 – 20

Surface water collection

20 – 30

Biomass Boilers

10 – 20



Solar thermal technologies

20 – 30

Ground Source Heat extraction pumps

30 – 60

(Cyril Sweett, 2007)

Section 4 – Methodology

This chapter focuses on the methodology used in the production of the current research paper and will highlight the various stages of the research method. The purpose of the methodology is to provide the reader with an insight into what is expected in the report and how the research is to be conducted.

The current study focuses on the UK government’s policy of “all homes to be Zero Carbon” by the year 2016 and investigates into the feasibility of the policy and further considers the impediments preventing the policy to materialise. The study also aims to identify the key drivers and barriers of achieving zero carbon homes by 2016 across the board.

The study will explore key areas in the

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