Strategic Design of Low Energy Buildings

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					Strategic Design of Low Energy Buildings
Low Carbon Design Aim
• “Providing a healthy comfortable building that
  meets the occupant’s requirements whilst
  minimizing the impact on the wider
  environment through consuming the minimum
  resources possible in the building’s
  construction and operation”

• We need a coherent design strategy to help
  us achieve this
 Building & Systems Design
• Meeting the needs of occupants (comfort, utility,
  etc.) whilst considering environmental impact
  and meeting a host of other sustainability and
  legal criteria means that building design is a
  complex process
• Fundamentally a building a complex, integrated
  energy system
• It will not “work” unless properly designed and
• The majority of buildings in the UK are poorly
  designed: poor occupant comfort, high energy
  consumption, reliant on systems to overcome
  basic design faults
• Requires an integrated, team based design
  process ….
Strategic Design of Building Systems

  architect designs             design team

  engineers design         fabric and systems
      services               design evolves

  poorly performing      better performing systems,
buildings and systems!   less energy used, smaller
                           environmental impact
  Strategic Design
The design of a low-carbon building requires
many factors (constraints/objective
functions) are taken into into account:
     • owner requirements (function, cost)
     • cost
     • occupant characteristics and
       requirements (comfort, health)
     • site and location
     • energy and other utility supplies
     • building regulations
     • environmental impact and
ALL of these factors will affect the design
choices and performance ...
  Owner’s Requirements
• Owners, developer’s requirements:
   • building function
   • cost limits
   • environmental strategy/awareness

• occupant density (ventilation
  requirements, cooling/heating
• occupant activity (design
  temperatures, ventilation,
  cooling/heating levels)
• occupant type (children,
  adults, old/sick)
• occupation of the building
  (intermittent, 24 hour)
    Costs and Construction
•   Capital Cost (owner/developer)
     • cost and availability of money
     • available budget for building – site,
       materials, equipment, labour
•   Running costs (occupant)
     •   fuel costs: electricity, gas
     •   maintenance costs
• NB distributed generation, renewables
  integration and energy efficiency, all increase
  the capital cost of a building
• Very often energy costs are much less than
  other costs e.g. wages and so energy
  consumption/environmental impact is often
  low down on the list of priorities
  Building Location

Building location:
   • warm/cool climate
   • available solar energy
   • wind speeds
   • rainfall
   • urban/rural location (site constraints)
   • surroundings (shading, shelter from wind)
  Energy Supplies

• grid availability, grid connected
• gas availability
• solid fuel availability
• other local resource, e.g. district heating, CHP
• solar resource (geography, climate, site)
• other resources - wind, biomass, etc.
  Building Regulations
• UK building regulations:
   • insulation requirements (SAP)
   • ventilation levels
   • systems, etc.
• national and local planning
• building designation (retrofit)
• special location
• local regulations (e.g. London
  Energy Strategy)
• European Regulations (Buildings
  Performance Directive)
Design Choices

  Building Form and Fabric Options
• building   form:
    building orientation
    building depth (shallow plant/deep plan)
    glazing areas/shading
    structure (heavyweight, lightweight)
    infiltration (surface area/volume)
• space usage (kitchen, office, toilet,
• layout - flexibility of use (changes of
  use in building lifetime)
  Building Fabric Options
• amount and placement of glazing
• insulation levels
• response to heat input
   heavyweight (materials exposed thermal mass)
• moisture transport
  Building Form and Fabric Options
• special features:
   • atria
   • solar chimneys
   • sun spaces
  System Options

• heating and/or cooling
    quick response (dynamics - building fabric)
    delivery mechanism (convective/radiant/mixed)
• ventilation (mechanical, natural,
• lighting (daylighting, task lighting)
• humidification/dehumidification and air
• special processes (industrial, commercial)
sources: boilers, chillers,
electricity supply

distribution: cables, ducts,
fans, pumps, piping, etc.

delivery: radiators,
underfloor heating, lights,
diffusers, etc.
control: thermostats,
dampers, valves, timers,
PID controllers, etc.          environmental system
  Low Carbon Options

• A range of energy efficient or “clean” technologies is also
  available to the designer:
   •Photovoltaics PV
   •Micro turbines
   •Ducted Wind Turbines
   •Fuel Cells
   •Heat Pumps - air source and ground source
   •Solar thermal/passive solar
sources: boilers, chillers,
electricity supply

distribution: cables, ducts,
fans, pumps, piping, etc.

delivery: radiators,
underfloor heating, lights,
diffusers, etc.
control: thermostats,
dampers, valves, timers,       Localised generation of
PID controllers, etc.          heat and power -
                               distributed generation
Buildings and Environment

• So there are many options available in a low-energy
  building design
   • well insulated, well maintained fabric
   • passive solar technology,
   • day lighting, efficient lighting
   • well maintained, efficient distribution systems
   • natural ventilation
   • mechanical ventilation/heat recovery
   • energy saving controls
   • high efficiency heating and cooling devices
Strategies for Low Carbon Buildings
New Build Design Hierarchy for Low
                         LZC Energy Supplies
                         Efficient Systems &

                         Form & Fabric
  Evaluating Options...

• the design of for a building and selection of
 systems and components is an iterative process
• probably the most important evaluation is the
  performance evaluation
• this is best done looking at all the elements of the
  building design as they evolve together
• this type of design model requires feedback on the
  likely performance of a system ….
Selecting/designing a system


  design          design
  team            process

  Performance Evaluation

• an appropriate support environment for the building design process is
  building environmental simulation
• simulation is the mathematical modelling of a building operating in
  realistic dynamic conditions
• allows the design team to assess environmental performance (human
  comfort, energy consumption, emissions, etc.):
    building form and fabric
    orientation and site
    controls action
  Technical Assessment

• simulation enables a design team to make informed choices on a likely
system’s performance accounting for the complex interactions between
the fabric-occupants and systems
  Technical Assessment

Mathematical model       Performance assessment

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