Transcript Strategic Design of Low Energy Buildings

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
analysed
• 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
building
design team
engineers design
services
fabric and systems
design evolves
together
poorly performing
buildings and systems!
better performing 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
regulations
ALL of these factors will affect the design
choices and performance ...
Constraints
Owner’s Requirements
• Owners, developer’s requirements:
• building function
• cost limits
• environmental strategy/awareness
Occupants
• occupant density (ventilation
requirements, cooling/heating
requirements)
• 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,
etc)
• 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)
lightweight
• 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,
contaminants)
• lighting (daylighting, task lighting)
• humidification/dehumidification and air
conditioning
• 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:
•CHP
•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,
PID controllers, etc.
Localised generation of
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
Energy
LZC Energy Supplies
effectiveness
cost
Efficient Systems &
Operation
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
selection
design
team
design
process
support
environment
implications
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
occupancy
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