WE-001-Rain Water Harvesting
Technology Overview
- Rainwater harvesting systems collect rainwater from roofs for use in buildings as a means of reducing reliance on mains
water.
- Systems can be individual or communal, the latter often being cheaper particularly when integrated into a stormwater
attenuation facility.
- This is a relatively simple technology and does not normally require professional maintenance.
- Depending on system: around 15years for pump, longer for the tank
Description
Simple individual systems would simply collect rainwater in a butt connected to a down pipe for re-use in the garden.
More sophisticated systems can service the WCs and the garden and sometimes also the washing machine. Rainwater
harvesting is always additional to mains connection and does not replace it. Pipework carrying rainwater needs to be
marked clearly to distinguish from mains pipe work. Some roofs can colour the water slightly but rain water is not
chlorinated and therefore better for plant growth in garden. If used for washing machines, it can save up to 50% detergent
in areas of hard water and reduces limescale build-up in the washing machine. They are easier and cheaper to install
than grey water systems.
Code for Sustainable Homes / BREEAM Support/ Points Awarded
Credit
Maximum % Achievable % Credit Description
CSH Wat 1
7.5%
1.5%
Credits for reduced water consumption
CSH Wat 2
1.5%
1.5%
Credits for rain water use for landscaping
BREEAM Wat 1
3.0%
3.0%
Minimum requirement for 'GOOD' rating and higher. If the base case is
above 5.5m3/person/year, all 3 credits could be achievable
Financial Implications
Maintenance costs communal £700/ yr
3000
2500
Cost £
Simple water butts for the garden retail at around £30. Cost
for full individual systems feeding WCs etc. are around
£2.5k- £3k. Where communal systems are used costs can
come down to as little as £500 per dwelling (all including
pipe work, but excluding earthworks). It is particular cost
effective to combine rainwater harvesting with stormwater
attenuation tanks. An indicative cost curve is set out on the
right:
2000
1500
1000
500
0
1
5
10
20
30
40
50
100
500 1000
number of dwellings
Maintenance cost individual: usually undertaken by owner - no cost. (Costs based on 2008 prices)
Potential Water and Carbon Savings
Carbon resulting from processing and pumping mains water is at 0.0004 kg/ litre very small. Apart from simple gravity-fed
garden systems rainwater systems will emit more carbon through pumping and filtering than the equivalent amount of
mains water. A rainwater harvesting system for a 60sqm roof could save up to 15,000 litres per annum.
Environmental Costs and Effectiveness
Rainwater systems reduce unnecessary use of mains water, reducing associated energy costs and purchase costs. They
can also mitigate for drought conditions and hosepipe bans in summer. Environmental impact is low, and there can be a
positive impact on flood risk by reducing run-off rates. There is a small amount of energy involved in the manufacture of
water butts and slightly more in larger rainwater harvesting systems; however this is negligible in comparison to the
overall savings in consumption of treated, potable, water.
Indicator
Effectiveness Rating
Capital Cost per m3 water saved
£166-200/m3 water saved
Ease of implementation
medium
Exposure to water markets
The cost savings currently are low, but as climate change affects precipitation, and
as energy prices rise, rainwater harvesting will isolate the user from such risks
Scale at which it becomes effective
Individual systems – any scale.
Communal systems become cost effective for 50 units or more and or where
attenuation tanks are required. A management company should also be in place
for maintenance
Suitability & Current Levels of Use
In planning terms there are few concerns over installing rainwater harvesting. Rainwater systems are now widespread in
other EU countries. In the UK simple collection systems for garden watering only are now relatively common, also a small
number of domestic and commercial systems that feed WCs.
New Residential
Existing Residential
New Commercial
Straight forward
Straight forward for
Straight forward
garden use only;
extensive and complex
building work required
for full system to WC
etc.
Existing Commercial Listed / Conservation
Easier than residential No visual impact, as
tanks usually buried.
retrofit, as buildings
tend to be larger
It is possible that rainwater harvesting could be used in conjunction with grey water recycling technologies, however the
viability of combined approach will largely depend on the annual volume of rain water that can be captured on-site There
can be conflicts with rain water collection systems, as run-off may be insufficient and may contain substrate particles.
System Example
Further Resources
Thales, Poundbury, Dorchester
http://www.ukrha.org/
- Commercial rain water harvesting system
www.aqua-lity.co.uk
- Water collected from the building roof, filtered and
stored in 3,500 litre underground storage tank.
http://www.freerain.co.uk/
- Water used for flushing, washing machine, and outside
taps.
http://www.envireau.co.uk/
- Developed by ZeroC
http://www.eca-water.gov.uk
http://www.rainwaterharvesting.co.uk
www.zerocholdings.co.uk
WE-002-Grey Water Harvesting
Image Courtesy of Aquality (2008)
Technology Overview
- Grey water harvesting technology recycles lightly contaminated water from showers and wash hand basins.
- The grey water is captured, filtered and processed for uses that do not require pristine drinking water such as for
washing clothes and flushing WCs or watering the garden.
- Grey Water systems are more expensive then rain water systems, due to the need of a secondary drainage system to
collect water from showers, baths and washbasin as well as filtering requirements.
- Should the supply of grey water run out, it will automatically be topped up from the mains.
- Grey water pipes must be labelled.
- Communal systems are more cost effective.
- Life span: around 15 years for pump, longer for the tank
Description
Grey water systems are more complex than rainwater systems and typically require maintenance by professional staff.
Previously the sustainability credentials for grey water recycling were questionable due to the use of chemicals or UV light
required for treating grey water. Technologies which are solely based on biological and mechanical filtering systems are
preferable. Since grey water is available wherever baths and showers are used, therefore supply is more predictable than
rainfall. Collection tanks can be smaller than those for rainwater systems. There is also a system that captures water from
shower and bath. It filters the water within a full height structure within the bathroom for re-use in the WC. Pump, filter and
concealed cistern are all contained in the casing on which a wall-hung WC is mounted.
Code for Sustainable Homes / BREEAM Support/ Points Awarded
Credit
Maximum % Achievable % Credit Description
CSH Wat 1
7.5%
1.5%
Based on water consumption per person per day. There are target
consumptions that must be met for each level of the Code. (i.e. to
achieve Code level 3, the water consumption should be less than 105
litres/person/day.
BREEAM Wat 1
3.0%
3.0%
Minimum requirement for 'GOOD' rating and higher. If the base case is
above 5.5m3/person/year, all 3 credits could be achievable, however
grey water recycling generally provides less water than rainwater.
Economic Cost
Maintenance costs communal ~£2000/ yr
Maintenance cost individual: ~£200/yr
Payback – 7-30 years
6000
5000
Cost £
Costs for individual systems are around £4.5k- £5k. Where
communal systems are used costs can come down to as little as
£650 per dwelling (all including pipe work, but excluding
earthworks). It is particularly cost effective to link a grey water
harvesting system to a storm water attenuation tank. An indicative
cost curve is set out on the right.
4000
3000
2000
1000
0
1
5
10
20
30
40
50
number of dwellings
100
500 1000
Potential Water and Carbon Savings
Carbon resulting from processing and pumping mains water is at 0.0004 kg/ litre very small and is often outweighed by
emissions resulting from pump powering. A grey water system could potentially save up to 22.5 litres per person per day,
equivalent to 20,500 litres per annum.
Environmental Costs and Effectiveness
Grey water systems save a precious natural reserve and reduce dependency on mains water. However, the above
carbon impacts need to be considered. Avoiding systems that require chemical or UV treatment will reduce environmental
impact. Grey water recycling systems is still an emerging technology and as such there is currently no data on the
embodied energy of these products.
Indicator
Effectiveness Rating
Cost per m3 water saved
£220-245/m3
Ease of implementation
Two sets of pipe work and treatment makes this potentially complex
Exposure to water markets
Current savings are poor for domestic consumers – water prices are expected to
rise and grey water will protect occupants from such rises. Paybacks in hotels
and other commercial premises can be very good.
Scale at which it becomes effective Individual systems – any scale.
Communal systems become cost effective for 50 units or more and or where
attenuation tanks are required. A management company should also be in place
for maintenance.
Suitability & Current Levels Of Use
Grey water systems are still very uncommon in the UK though there are some grey water systems in off-mains ecodevelopments. Sophisticated grey water systems are common in other parts of Europe and Japan and first commercial
UK applications are now beginning to emerge. Hotels are rolling out combined grey and rainwater systems with multifunctionality including feed store for fire-sprinkler systems.
New Residential
Existing Residential
New Commercial
Straight forward, but Only suitable in extensive Straight forward, but
refurbishment situations complex pipework
complex pipework
required
required
Existing Commercial
Listed / Conservation
Only suitable in extensive No visual impact, as
refurbishment situations tanks usually buried.
Attention should be given to the types of users for a proposed grey water system. The design must ensure that it does not
incur discomfort or additional burden to the end user that may result in it being disconnected. Grey water systems can
also be used in tandem with rain water harvesting although the viability of the grey water system will depend on the
volume of rain water that can be captured.
System Example
Further Resources
A pilot project has been implemented in a hotel in
Doncaster, for future replication across a national hotel
chain. The system collects water from the showers of 60
rooms and re-uses it in WCs. Water is treated using a
biological-mechanical ultra-filtration system. Treated water
meets the standards of the European Bathing Water
Directive.
http://www.freewateruk.co.uk/
http://www.aquaco.co.uk/index2.htm
http://www.aqua-lity.co.uk
http://www.eca-water.gov.uk/
WE-003-Water-Saving Devices
Technology Overview
- Average water use in England and Wales is just less than 150 litres per person per day (Ofwat 2007). Water saving
devices can reduce the amount of water use to as little as 105l, if combined.
- Low-flow fittings can be unpopular with users, due to the much reduced flow of showers and taps. It is therefore crucial
that users are educated as to the benefits of these devices.
- Life span: similar to standard water using devices.
Description
Water consumption in the buildings represents a significant consumption of energy. While the householder or business
pays either a fixed charge or one per cubic metre of water delivered, there is a considerable amount of energy in both the
production of potable (drinking quality) water and the treatment of waste water (sewage). Both the Code for Sustainable
Homes and the BREEAM has mandatory requirements for the reduction of water consumption which increase with higher
levels of accreditation. There are a number of devices that can be used in the home, commercial and public buildings that
can reduce water consumption and its associated carbon emissions. The following devices contribute to water savings
•
Taps with reduced flow and automatic shut-off taps (e.g. using PIR, or timed shut-off valves)
•
Low volume single and dual flush WCs and waterless urinals
•
Low-flow showers and smaller baths or baths with lower over-flows
•
Water saving washing machines and dishwashers
Code for Sustainable Homes / BREEAM Support/ Points Awarded
Credit
Maximum %
Achievable %
Credit Description
CSH Wat 1
7.5%
1.5%
Points awarded for reducing water consumption. Minimum
consumption standards apply each code level.
BREEAM Wat 1
3.0%
2.0%
Minimum requirement for 'GOOD' rating and higher. If the base
case is above 5.5m3/person/year, typically 2 of the 3 credits could
be achievable through specification of low flow appliances.
BREEAM Wat 4
1.0%
1.0%
Credit for installing sanitary supply shut off, designed to reduce
wasted water when washrooms not in use. Will also be of benefit
when calculating water use for Wat1.
Economic Cost
Product
Typical Cost
Cost per m3 water saved
Reduced flow taps (1.7 - 5 l/min
4.5l single valve flush WC
2/4 l dual flush
Low-flow showers (6 to 12 l/min)
Smaller bath/ lower over-flow
Washing machines
Water saving dishwashers
Same as standard taps
£260
£260
£12
£260
£500
£350
£0
£ 111
£ 46
£ 0.94
£ 89
£ 685
£ 959
Environmental Costs and Effectiveness
Water-saving devices produce genuine reductions of water consumption, which is a precious natural resource and may
become less abundant with the onset of climate change. The embodied energy of these devices is broadly similar to
those it replaces.
Indicator
Effectiveness Rating
Cost per litre water saved
Varies depending on appliance – see previous table
Ease of implementation
Easy to implement for new build and homeowners
Exposure to water + energy markets Current savings from water are poor for domestic consumers, water prices are
expected to rise with metering becoming more common. Saving hot water will
however save considerable water heating energy.
Scale at which it becomes effective Effective at all sizes of developments
Suitability & Current Levels of Use
In recent years use of water savings appliances has been driven by Ecohomes / Code for Sustainable Homes
requirements. Due to perceived loss in comfort use is not as widespread as it could be.
New Residential
Existing Residential
Easy to incorporate into Easy to retro-fit
specification, but need
to consider when sizing
water heating
New Commercial
Existing Commercial Listed / Conservation
Easy to incorporate Easy to retro-fit
into specification,
but need
to consider when
sizing
water heating
Has no visual impacts,
may not be possible if
internal fittings are listed.
Water-saving devices are ideally combined with rainwater harvesting or grey water recycling in developments seeking
very low water consumption and in particular those striving for high levels within the Code for Sustainable Homes or
BREEAM accreditation systems.
Examples of Water Saving Devices
Further Resources
- Reduced flow taps (1.7 - 5 l/min)
Up to 28 litre *
http://www.greenbuildingstore.co.uk
- 4.5l single valve flush WC
Up to 6.4litre *
http://www.eca-water.gov.uk/
- 2/4 l dual flush
Up to 15.5 litre *
- Low-flow showers (6 to 12 l/min)
Up to 35 litre *
Defra Market Transformation Programme
www.mtprog.com
- Smaller bath/ lower over-flow
Up to 8 litre *
- Washing machines
Up to 2 litre *
- Water saving dishwashers
Up to 1 litre *
*Daily water saving based on CSH methodology
WS-001-Green Roofs
Technology Overview
- Green Roofs are vegetated roofs or roofs with vegetated spaces.
- Modern green roof systems are highly durable and have good sound insulation properties.
- There are currently no UK testing standards for green roofs but the German FLL standard is commonly used. Vegetated
roofs provide an extra protection to waterproofing systems from Ultra-Violet light, frost, erosion and other forms of
weathering.
- If in the rare case that they do leak, this is usually down to poor roof construction, and not the green roof system itself.
- Any landscape feature on a roof will have loading implications and the saturated weight of any such features must be
used to calculate the structural load (Extensive Green roof: 60–150 Kg/m2). Sedum roofs are much lighter than fully
vegetated roof.
- Life span: up to 60 years with good quality construction
Description
Green roofs are one of the earliest building constructions dating back hundreds of years. Whilst not commonly found in
the UK, they are popular in mainland Europe and are becoming more popular here due to the variety of systems
available. Green roofs can provide a habitat for wildlife, particularly in densely populated areas where there is little green
space. The vegetation forming the top layer is self-replenishing protecting the waterproof membrane below Green roofs
can be divided into two categories: intensive and extensive. Intensive green roofs have a deep growing medium, which
allows the use of trees and shrubs. These are generally more costly due to the extra structural design required. Extensive
green roofs are less costly and generally have a thin growing medium and require minimal maintenance, and in general
do not require irrigation. There are three types of extensive green roof currently used in the UK:
- Sedum Mats - Sedums are wind, frost and drought resistant.
- Substrate based roof: 7cm of crushed recycled brick is placed on the green roof system as base for planting.
- Green / Brown roofs for biodiversity: Similar to previous but can use recycled aggregate from site and can be left to
colonise naturally or seeded with a wildflower mix or similar.
Green roofs generally do not have high performance insulation characteristics. While some systems use polystyrene
under trays, separate insulation should be designed to meet the required level of energy saving.
Code for Sustainable Homes / BREEAM Support/ Points Awarded
Credit
Maximum %
Available %
Credit Description
CSH SUR 1
1.1%
1.1%
Could contribute to credits as an attenuation measure
BREEAM
0%
0%
Could contribute to credits as a component of a SUDs strategy,
which must be designed to minimize flooding.
Financial Considerations
Intensive: £100 - £140 m2
Extensive: £60 - £ 100 / m2
For small roof areas costs can reach around £200 / m2
Maintenance costs extensive roofs: £0-1/m2 per year (Similar to that of a park or garden)
Potential Carbon Savings
It has been reported repeatedly that in a retrofit situation the installation of green roofs is effective in reducing heating and
in particular cooling needs and related carbon emissions. For new build the roof would be factored into over-all energy
calculations and would be unlikely to provide additional carbon savings.
Environmental Costs and Effectiveness
As green roofs can often be left to grow without maintenance, they can turn into valuable habitats for insect and wild plant
species. For this reason they can occasionally be requested by planners as planning condition. Green roofs also provide
protection from urban heat islanding (UHI). Also known as the albedo effect, UHI is the rapid build up of heat on hot days
in urban environments. They can also reduce the demand on drains from storm water by absorbing up to 25-40% of the
rain and releasing it to the drain over a longer period of time. There can be conflicts with rain water collection systems, as
run-off may be insufficient and may contain substrate particles. There is some embodied energy in the underlying
structure but this is no greater than equivalent manufactured systems and offers an on-going sequestration of carbon
throughout the life of the building.
Indicator
Effectiveness Rating
Ease of implementation
Structural implications need to be considered, brown roofs are easier to integrate,
as much lighter.
Scale at which it becomes effective Any size of roof
Suitability & Current Levels of Use
‘Living Roofs’ have undertaken ‘Green roof Audits’ of London and the UK and identified 78 sites in London and 58 sites in
the rest of the UK. Uptake is low in the UK compared with Germany, where most of the recent technological advances
have been made. In the past 5 years the UK has witnessed a significant renewed interest in green roofs, and a marked
increase in green roofs being designed and installed. Green roofs are promoted by Greater London Authority (GLA)
sustainable design and construction supplement.
New Residential
Existing Residential
New Commercial
Straightforward, but Possible, where existing Straightforward, but
has structural
structure can take the
has structural
implications
loading
implications
Existing Commercial
Listed / Conservation
Possible, where existing Depends on individual
structure can take the
case, but can improve
loading
look of unsightly flat
roofs.
In West Dorset there maybe certain circumstances where the roof design might be appropriate and assist with wider
design objectives, but this is unlikely to be an issue for mass use and is very site specific. Intensive green roofs that have
an adverse impact upon the visual amenity and character of the landscape / townscape would not be permitted. For
example a tropical garden of non-native plant species would not be considered appropriate in an open rural chalk
landscape setting. Within some schemes, opportunities may exist for creative designs. In the interest of design and
amenity a landscape scheme may be required. Details of hard and soft landscape proposals will be required.
Consideration will be given for appropriate species, depths of growing medium and specialist maintenance details.
System Example
Further Resources
Kingston Maurward College, near Dorchester
www.livingroofs.org
- Extensive ‘sedum’ green roof
http://www.thegreenroofcentre.co.uk
- Approximately 300 square metres
www.kmc.ac.uk
- Improves wildlife and reduces storm water run-off
The Green Building Bible – Volume 1
- Owned and maintained by Kingston Maurward College
WS-002-Lifetime Homes
Technology Overview
- Through thoughtful design, Lifetime Homes allow residents to stay in the same dwelling for as long as possible, even
where circumstances change.
- Their key purpose is to provide accessible and adaptable accommodation for everyone, from young families to older
people and individuals with a temporary or permanent physical impairment.
- The standard is not linked to a formal accreditation scheme. Lifetime Homes have to comply with 16 design criteria.
Description
Lifetime Homes is a voluntary design standard that sets out criteria that aim to enable residents to live in the same
property for the majority of their lives. It is awarded credits under the Code for Sustainable Homes if all criteria are
adopted. The criteria are as follows:
1.
Car Parking Width: to disabled users standard or provisions for future conversion
2.
Access from Car Parking
3.
Approach Gradients: has to be level or to specified gradient
4.
Entrances: All entrances to be illuminated, with level access over threshold, main entrances to be covered.
5.
Communal Stairs & Lifts: easy access and fully accessible.
6.
Doorways & Hallways: wider than building regulation minimums, need to comply with detailed LTH specification.
7.
Wheelchair Accessibility: space for turning a wheelchair in dining and living rooms and adequate circulation space
8.
Living Room: to be at entrance level
9.
Entrance Level bed-space: a space at entrance level that could be used as a bed-space.
10. Entrance Level WC & Shower Drainage: a wheelchair accessible WC, with drainage provision to retro-fit a shower
11. Bathroom & WC Walls: Walls must be capable of taking adaptations such as handrails.
12. Stair Lift/Through-Floor Lift: The design should incorporate provision of a stair lift or a suitably identified space for a
through-the-floor lift from the ground to the first floor
13. Tracking Hoist Route: provide a route for a potential hoist from a main bedroom to the bathroom.
14. Bathroom Layout: incorporate ease of access to the bath, WC and wash basin.
15. Window Specification: Living room window glazing should begin at 800mm, and be easy to open/operate.
16. Controls, Fixtures & Fittings: Switches, sockets, ventilation and service controls should be at 450mm to 1200mm
from floor.
Code for Sustainable Homes / BREEAM Support/ Points Awarded
Credit
Maximum %
Achievable %
Credit Description
CSH Hea 4
4.6%
4.6%
Full score awarded if ALL requirements of LTH are implemented.
Mandatory for CSH Level 6
BREEAM
n/a
n/a
Not applicable to BREEAM methodology
Financial Considerations
Costs range from £165-£545 per dwelling (not including land cost implication of designing corridors, bathrooms etc. to
larger dimensions than those required by Building Regulations. (Costs based on 2008 prices).
Potential Carbon Savings
Due to reducing the amount of works needed for converting the dwelling, some construction energy use and related
carbon will be saved and the need for purpose-built care home places reduced.
Environmental Benefits and Effectiveness
The Lifetime Homes specification aims to provide design criteria that enable people to remain in their homes throughout
the majority of their lives. Whilst there are no specific environmental benefits these measures provide esoteric social
benefits that can result in a more diversely populated and sustainable community.
Indicator
Effectiveness Rating
Ease of implementation
Easy if considered early on in the design process, various requirements (e.g. car
parking) conflict with density
Scale at which it becomes effective Any size of dwelling, though difficult for small in-fill flats
Suitability & Current Levels of Use
The Lifetime Homes Standard has been set up in 1991. There are no figures held centrally on how many dwellings are
built to this standard to date, but all public sector funded housing in England will be built to the Lifetime Homes standard
from 2011 (it is a requirement now in Wales and Northern Ireland), with a target of 2013 for all private sector dwellings.
New Residential
Existing Residential
Easy if considered
early on in the design
process
This is specifically a
new-built standard,
though existing homes
can be adapted to
achieve similar results.
New Commercial
Not Applicable
Existing Commercial Listed / Conservation
Not Applicable
Windows standards are
the only element that
could conflict with
conservation issues.
There maybe difficulties in implementing Lifetime homes in small properties where space is at a premium and space for a
downstairs shower room must be provided.
System Example
Further Resources
Bower, Gold Hill, Child Okeford, North Dorset
www.lifetimehomes.org.uk
- Developed for Synergy Housing Association
www.westerndesignarchitects.com
- Accredited to Lifetime Homes
- Designed by Western Design Architects
Glossary
ASHP
Air Source Heat Pump
BER
Building Emission Rate
BREEAM
Building Research Establishment Energy Assessment Methodology
Capacity Factor
A measure of the actual energy produced compared to the potential energy produced based on the
installed sized.. For example a 1 kW wind turbine could potentially produce 8760 kWh of electricity per
year (8760 hrs x 1kW). If it has a capacity factor of 10% it will only produce 876 kWh of electricity (i.e.
8760 kWh x 10%).
CSH
Code for Sustainable Homes
DER
Dwelling Emission Rate
EPC
Energy Performance Certificate
GSHP
Ground Source Heat Pump
GWP
Global Warming Potential
Kg
kilogram
kW
kilowatt
kWe
rated electrical output in kilowatts
kWh
measure of energy consumption in rated output in kilowatts (kW) multiplied by time in hours (h)
kWp
maximum possible output in kilowatts (typically referred to in solar PV systems)
kWth
rated thermal output in kilowatts
MVHR
Mechanical Ventilation with Heat Recovery
NCM
National Calculation Methodology
PCM
Phase Change Materials
SAP (2005)
Standard Assessment Procedure (2005 Edition)
SBEM
Simplified Building Energy Model
Sqm
Square Metre
SIPS
Structural Integrated Panel System
TER
Target Emission Rate
U- Value
Measure of energy loss through an insulating material in Watts per square metre of material