[16469] Low Energy Building Design

[16469] Low Energy Building Design

Critique 2

Adam Boney, Fraser Cassels, Marc Breslin and Nick Burns

Our Design

1st Floor

Construction method: Timber Framing

•Required minimal energy to process

material

•Carbon neutral material

•Allows a greater thickness for

external walls therefore significantly

greater U values

•Can be sourced from local

companies on the Shetland island

Insulation : 2 possibilities

Cellulose Insulation:

•Sustainable and low embodied energy•80% recycled paper•20% less energy to manufacture than other fibres•Thermal conductivity 0.035 – 0.04 W/m KSheep’s Wool:

•Sustainable material which can be locally provided•14% of the energy used to manufacture glass fibre•Thermal conductivity 0.04 w / m K

U value target : 0.1 – 0.15 W/m K

Draught proofing and thermal envelope

Diagram above shows main sources of draughts.

•External door and garage are excluded from the thermal envelope.•Insulation installed below the concrete floor slab•Wall insulation continues down to bottom of concrete slab to prevent thermal bridging•Gaps filled with foam sealants

Doors and Windows

•High performance door threshold seals installed which seal air gaps reducing draughts and prevent water entering the building •Door draught extruders fitted to other side also

•Windows are one of the weakest points thermally in building envelope•Install high performance triple glazed windows•Low emissivity glass U value 0.6 W/m•Provide wooden window frames giving a U value of 0.16 W /mK to reduce thermal bridging

Lighting

• The disadvantages the natural light it our design

• Window size1. Glare2. Heat loss

Day lighting:

•Reduces the amount of artificial light need

•Benefits of natural day light1. Increase performance

2. Reducing in energy cost

Lighting CFL Bulb Standard Bulb 14 watts 40 watts

LED Bulb Standard Bulb 4.2 watts 40 watts Brightness

• Same brightness • Less wattage (about

1/10)Cool lighting

• reducing energy consumption

Brightness• Same brightness • Less wattage (about

1/3)Costing

• More expensive • Last longer

Wind PowerShetland wind power- supply renewable

energyTurbines produced by 3 main manufacturers

Westwind TurbinesProven Turbines Evance Turbine

Wind PowerOpting for a stand alone turbine:

Carry out comparison Assess best supplier and turbinePower calculation spreadsheet

P=0.5ρAV³ - www.REUK.co.uk

Wind Power- Small turbinePower

Speed

Area

Wind power- Large turbine

Power

Speed

Area

WaterAverage household water use is difficult to

pin downAverage annual levels of consumption (m3):

http://www.ccwater.org.uk/server.php?show=ConWebDoc.913

Average use = 182,000L/year

Technologies1. Rainwater harvesting:

Plenty of rain in Unst- average rainfall/year is 1,220mm1

Systems can provide 100% of water demand, however this is rarely done

1. http://www.shetland.gov.uk/council/documents/18170-Shet-in-Statistics.pdf

Technologies Rainwater harvesting: Variability within system design and details

Model agreements for sustainable water systems; CIRIA, 2004

Collection Initial thoughts on collection area focused on

roof

However, collection area can be expanded to other parts of the house as well- driveways/pavements, for example

FiltrationWater for different uses requires different

levels of filtration We thought it best to have one filtration

system for the whole system

Sediment pre-filtration Carbon or multimedia fibre UV sterilization

StorageUnderground Above ground

Heating Passivhaus requires consumption for

electricity, heating and hot water be < 120kW/m2/year

Typically, solar thermal panel is used to provide heat for some of hot water needs- not an option for Unst

An inline water heater could be used

Design calculationshttp://www.rainharvesting.co.uk/pages/design/dsgn4.html

Roof area = Width x Length of roof = 152.29m2

Run-off coefficient = 0.75 for pitched roof

Filter efficiency = 85% (A conservative estimate- example calculations typically gave efficiency as 90+%)

Rainwater yield (Litres/year) = Roof area (m2) x Annual rainfall (mm) x Run-off coefficient x Filter efficiency

Rainwater yield = 118,443L/year

-not enough

Possible solutions…Grey water harvesting

Sea water

The next steps of designComplete the day lighting calculations and

install low energy bulbs into the DiaLUX software

PV cells resultConfirm the water manage designFinalise the energy systems calculations

which are incorporated within the designWork on the MVHR system for the building.Finalise Electrical consumptionChoose turbine & manufacturer.