Strategic Design of Low Energy Buildings

1. Strategic Design of Low Energy Buildings

2. 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

3. 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 ….

4. Strategic Design of Building Systems architect designs building design team fabric and systems design evolves together engineers design services poorly performing buildings and systems! better performing systems, less energy used, smaller environmental impact

5. 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 ...

6. Constraints

7. Owner’s Requirements • Owners, developer’s requirements: • building function • cost limits • environmental strategy/awareness

8. 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)

9. 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

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

11. 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.

12. 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)

13. Design Choices ?

14. 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)

15. Building Fabric Options • amount and placement of glazing • insulation levels • response to heat input • heavyweight (materials exposed thermal mass) • lightweight • moisture transport

16. Building Form and Fabric Options • special features: • atria • solar chimneys • sun spaces

17. 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)

18. 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

19. 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

20. 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

21. 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

22. Strategies for Low Carbon Buildings

23. New Build Design Hierarchy for Low Energy LZC Energy Supplies cost effectiveness Efficient Systems & Operation Form & Fabric

24. 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 ….

25. Selecting/designing a system selection support environment design process design team implications

26. 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

27. 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

28. Technical Assessment Mathematical model Performance assessment