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Code for sustainable homes

Water efficiency and surface water runoff

Jonathan Reed

Atkins Water & Environment

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Introduction Atkins Water – why important? The Code objectives

Water efficiency Surface water runoff

Conclusions

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Atkins at a glanceWith a turnover of c.£1.2bn, Atkins is: One of the top 10 Best Big Companies to work for The largest engineering consultancy in the UK The largest multi-discipline consultancy in Europe The 4th largest design firm in the world Voted no.1 with ‘Best Reputation’ in Environment

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Water

“[water efficiency has] minimum standards that must be achieved at every level of the code, recognising [it’s] importance to the

sustainability of any home.”

Why? Water efficiency can be implemented now; Range of sustainability benefits – energy, environmental impacts,

etc. Improved adaptation to climate change.

Two areas covered by Code: Water efficiency Surface water run-off

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Water Efficiency

Weir Wood Reservoir in August 2005

Lowest recorded levels Increase in demand for

water should be minimised

Demand for water measured as a ‘Per Capita Consumption’, i.e. litres per head per day

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Surface water run-off and flooding

Impact of hard surfacing on run-off, infiltration and drainage

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Water Efficiency

Code Objectives

Predicted internal consumption

Points Awarded Required for code level

≤120 l/hd/d 1.5 1(), 2()

≤110 l/hd/d 3 -

≤105 l/hd/d 4.5 3(), 4()

≤90 l/hd/d 6 -

≤80 l/hd/d 7.5 5(), 6()

External consumption Points Awarded -

Rainwater collection and use (eg water butts)

1.5 -

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How water is used

Components of household water use for average days (WRc 2005)

Components of demand 2/3 of total consumption

through: Toilets Taps Showers

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Step 1 – minimise water use Toilets

Dual flush 6/4 litre Can be reduced further

Showers Flow rates of 6-9 l/min Aerating shower heads Flow restrictors

Baths Shaped baths

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Step 1 – minimise water use Taps

Aerated taps (downstairs sinks) Flow restrictors

Appliances Dishwashers Washing machines

External Fit a water butt

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Water Efficiency

Code Objectives

Predicted internal consumption

Points Awarded Required for code level

≤120 l/hd/d 1.5 1(), 2()

≤110 l/hd/d 3 -

≤105 l/hd/d 4.5 3(), 4()

≤90 l/hd/d 6 -

≤80 l/hd/d 7.5 5(), 6()

External consumption Points Awarded -

Rainwater collection and use (eg water butts)

1.5 -

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Step 2 – use of non potable water

Source Uses

Rainwater Roofs and hardstanding Toilet flushing, garden watering and vehicle washing

Greywater Wastewater from sinks, baths and showers

Toilet flushing and garden watering

Rainwater and greywater Risk assessment Secondary pipework system

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Surface water runoffNew development has two main impacts:

1 Increases runoff rates – making flooding worse elsewhere

2 Reduces volume available for floodwater in the floodplain

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Surface water run-off Code objectives

Reduction of surface water run-off Points Awarded Required for code level

Attenuation covering hard surfaces 0.5 1() Peak run-off and annual run-off volume no

greater than before development

Attenuation covering roofs 0.5

Flood risk Points Awarded -

Low annual probability of flooding 1 -

Medium/high annual probability of flooding. See code requirements.

0.5 -

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PPS25 – Development and flood risk Environment Agency are statutory

consultees Aims to minimise the risks of

development in flood risk areas Areas designated by the risk of

flooding

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Benefit of SUDS

Manages water at source and reduces peak flows Improves water quality Improves both visual and natural habitats

Hard surfacing

Natural runoff rate

Run

-off

Time

Run-off vs Time for storm event

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SUDS techniques

Permeable paving Allows water infiltration

Swales Flow attenuation and

conveyance

Green roofs Reduce run-off volume and

rate

Underground storage High density development

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Long term maintenance of SUDS Maintenance

Long term maintenance of SUDS needed

Who by? Sewerage undertaker Local Authority Highways Authority

How? Early consultation needed Sewers for Adoption Model agreements for

SUDS

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Conclusions

Water efficiency Water efficient appliances

Toilets and showers

Non potable use of water Rainwater or greywater for toilet flushing

Water butts

Surface water runoff SUDS to reduce and improve surface water runoff Flood risk controlled through links with PPS25

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Thank you