WOODFUEL FOR THE CONSTUCTION INDUSTRY

Architects Point of View

+Building Regulations

Wood as a fuel

• Multi use of wood fire in the home

• Wood fire one of longest standing forms of heating in human history

• Simple wood fired room heaters to supplement central heating – independence

• Burning wood logs gives connection to nature + sense of belonging

• Burning wood can reduce the potential impact of global warming and dependence when compared to fossil fuels.

Considerations for the designer

• Advantages of wood fuel

• House design

• Wood storage

Context

• Context with better performance building

• 4 primary design parameters - They are solar orientation, insulation, air tightness and thermal mass.

General Categories

1. New Build Single House Primary Heat SourceStott House Log cooker ( Rayburn)

Pellet boiler Pellet Stove

Logs stove with back boiler

2. Single retrofit to thermally inefficient buildingParrot Gasification log boiler

3. Larger single structureExtension to FCS Office Dingwall Wood Chip boiler with bulk

storage

4. Larger group houses / mixed use Servite Pellet boiler with accumulator

tank + hopper• All above require different approaches

Costs

• The capital cost of wood-fuel system V Lifetime running cost

• Boiler room and fuel store size

• Installation Costs

• Grants and Incentives www.rhincentive.co.uk

Potential Cost Savings on fuel

• Peak electricity 13p per KW/h• 1 litre oil on average = 60KW/h of energy 6p per KW/h• 1 tonne pellets = 4800 KW/h of energy 3p per KW /h

( based on £160 a tonne, min 4 tonne delivery from Balcas)

System comparisons

Room Heater stove of feature stove boilerHopper Capacity – 15 – 53kgAverage Refill Time – 1-2daysBoiler Location – internallyAverage approximate cost - £2000 - £7000Fed – manually with pellets.

Gasification Log BoilerHopper Capacity –180kg + Average Refill Time – dependant on size of thermal

storeBoiler Location – utility / garage / shedAverage approximate cost - £11000Fed – manually with wood logs

Stove boilerHopper Capacity – 70 – 180kgAverage Refill Time – 2-3daysBoiler Location – utility / garageAverage approximate cost - £5500Fed – manually with pellets.

Pellet boiler with bulk storageHopper Capacity – 3 – 6 tonnesAverage Refill Time – 6 months – a yearBoiler Location – utility / garage / shedAverage approximate cost - £15000Fed – suction / auger, pellets fed from lorry.

Potential C02 Savings

CO2 emissions per kilowatt - hour (g/kWh)

• Wood fuel 25

• Wind energy 8

• Gas 194

• Oil 265

• Coal 291

• Section 6.1 of the Building Regulations

Boiler Selection

• Space

• Size of fuel store

• Access

• Fuel supply

• Efficiency

• Operation and maintenance

Bulk storage of woody biomass fuel

• Consideration of storage requirements at early stage in design process

• Design must allow for: Access for large eight wheeled vehiclesDirect delivery into store by tipping / vacuum Fuel storage for up to 50m3 chip / 4 tonne pellet in one delivery

• Design must avoid:The need for one off specialist vehiclesSmall fuel stores requiring constant refuelling – this adds £s to the fuel cost.Two stage handling ie chipping and then filling the fuel store.Bulk handling takes time and costs money

• Storage provision relative to number of deliveries.

• Storage space from building

• Storage Protection

Building RegulationsThe following works require a building warrant:

• A building exceeding 8m2 in area.

• A building containing a flue, a fixed combustion appliance installation does require a building warrant

• Any work associated with a solid fuel appliance having an output rating more than 50 kW

• Any work associated with a chimney, flue-pipe or constructional hearth.

• For example:

1. If retro fitting a wood fuel stove or boiler into an existing house this will require a warrant as the work will involve fitting a flue unless there is an existing chimney that could be used.

2.Similarly a small dedicated external boiler room with hopper will require a warrant as they may be over 8m2 and will contain fixed combustion appliances and flues.

3.Replacing an existing boiler with stove with one of the same kind will not require a warrant.

See guidance note for further info from the Domestic 2009 building regulations:

• Storage of woody biomass fuel - accommodation + safety• Storage vessels, pipework and controls• Chimney + Hearth Design• Air Supply / Extraction• Ventilation • Distances to combustible materials• Commissioning + Installation

• Building regulations also apply to other aspects of the work such as electrical installation and plumbing work in connection with the system

CASE STUDY 01: Single New Build thermally efficient 2 bedroom house, Farr, Inverness

• Boiler Specification: Rayburn solid fuel Heat ranger 355 SFW for cooking / domestic hot water and central heating.

• Fuel Type: Wood log manual feed

• Output: 12kW

• Efficiency: 85 %

• Accumulator tank: 250 litre internally housed

• Fuel Delivery : On site

• Wood-fuel Store capacity: External log wood shed.

• Back Up System: 4.4m2 solar collector + immersion

• CO2 emissions : 0.4 tonnes per year

CASE STUDY 02: Single house -retrofit to thermally inefficient building

Batch burning, quick burst and trap energy in accumulator tank

Boiler: Specification: Baxi Log Boiler

Fuel Type: Wood Logs -Manual feed

Output: 50KW

Efficiency: 90%

Accumulator tank: 2500 litre

Woodfuel Store capacity: 3m3

Boiler Housed : Timber Outbuilding

CASE STUDY 03: Extension to FCS Office Dingwall, Wood Chip Heating supplies 2 no heating circuits + hot water to building

• Boiler Specification: Froeling Turbomatic Wood Chip Boiler

• Fuel Type: Pellet – Wood Chips

• Output: 35kW

• Efficiency: 90%

• Accumulator tank: 1500 litre

• Woodfuel Store capacity: 30m3

• Back Up System: Existing Oil boiler

• Boiler Housed : Externally

CASE STUDY 04: Servite Housing Association (32 dwellings).

• Achieved a prestigious "Excellent" rating for sustainability, achieving the highest score in Scotland in areas of sustainability including energy + CO2 performance.

• Boiler Specification: 3no Okofen 56KW

• Fuel Type: Pellet: Wood Pellets

• Output: 56kW each

• Efficiency: 90%

• Accumulator tank: 3no 2000litre

• Wood fuel Store capacity: 6 tonnes per hopper

• Back Up System: If one boiler goes down then the other two are linked to circuit until fixed.