The building project is the design and build of a new state of the art pioneering office development to Passivhaus standards in Devon off a main highways route and next to a major train station. The building project is funded by a private client whose existing business owns the site and rents office space to various businesses from the existing buildings on site. One of the main aims of the project is for it to be passively designed and not require air conditioning in both the current and future climate change scenarios. Another aim is for the building to have a noticeable positive impact on productivity and health. Office buildings are increasingly becoming unhealthy places to use, suffering from Sick Building Syndrome SBS and can be contaminated with high levels of VOCs, ozone, pollutants, chemicals and poor fresh air quality particularly in offices which are sealed and air conditioned. The proposed office building is designed to meet Passivhaus certification.
Main climate change risks this project aims to address are:
Designing for comfort
- Increased internal and external temperatures
- Unstable/changing internal surface temperature levels resulting in uncomfortable internal conditions
- Increased pollen count, air borne particulates and manmade pollutants due to higher external temperatures and at times less wind to help clear localised air quality.
- Increase temperatures and UV on building envelope
- Increased weather severity on building fabric – wind and rain.
- Reduced water availability in summer
- Increased rainfall in winter
Further project details
1 What approach did you take in assessing risks and identifying adaptation measures to mitigate the risks?
To identify and assess potential climate change risks for this building project a site independent, generic, qualitative risk assessment has been prepared. Potential risks were based on the Design for Future Climate report, and Gale & Snowden’s experience from their work on a previous D4FC project. The risks were structured in three main sections ie comfort, construction and water management. Each risk was rated on a scale of one to five for its probability and impact and as a result of the multiplication of these two factors was given a risk magnitude. A graphical analysis of all individual risk magnitudes was used to identify the overall vulnerability of this building type to specific aspects of climate change.
This assessment was then used to also inform the decision on the selection of appropriate weather files from Exeter University’s Prometheus project.
Methods to assess thermal comfort:
- Various forms of thermal modelling of design throughout the design process from initial concept.
- Literature review – guidance on overheating (EN7730, EN15251, CIBSE, ASHRAE), internal and external planting, green roofs and façade greening in terms of temperature and water attenuation.
- Case studies UK and abroad.
Methods to assess water management:
- Assess water use and potential savings.
- Assess existing ground conditions, characteristics, topography, and environmental impact on sub-soils.
- Assess flood risk using EA maps.
- Review landscape mitigation options (surface water retention and rainwater harvesting).
- Review construction techniques/options.
Methods to assess impacts on construction:
- Literature review – guidance on detailing for extreme weather (British Standard, Trada, Building Regulation etc.).
- Case studies UK and abroad – visit to Solar XII passive cooled building in Portugal and Passivhaus offices in Germany.
- Review of design guidance from countries experiencing more extreme weather events like Northern Norway, New Zealand etc.
The following mitigation measures are currently being considered:
- External shading
- Cross flow and stack ventilation through the office
- Intermediate or heavy weight construction
- Ground cooling via earth tube or soil to brine heat exchanger
- Reduction of internal gains by relocating plant outside the thermal envelope
- Landscape design and green roof to moderate microclimate and to introduce external work spaces for extreme weather events.
The following measures are currently being investigated to address the risk of flooding/droughts under future climate scenarios:
- Inclusion of green roofs and landscape design that allows to retain water on site using pemaculture design principles
- Rainwater harvesting and storage
- Inclusion of SuDS
- Use of water saving appliances for showers, toilets etc to reduce water demand.
2. How have you communicated the risks and recommendations with your client? What methods worked well?
CCA risks and communication have been communicated to the clients as follows:
- The clients are part of the design team and attend all meetings so are fully informed on all aspects of the project.
- Notes of meetings and building precedent case studies are disseminated to the team including the clients.
The presentation of thermal modelling using CGI has worked well to graphically show the client what effects future climates could have on the building design.
3. What tools have you used to assess overheating and flood risks?
- PMV/PDD method in accordance with BS EN 7730 to analyse comfort range.
- IES dynamic modelling to assess energy use and overheating.
- PHPP to assess energy use and overheating and to show compliance with the Passivhaus methodology.
- Consultation with EA to identify flood risk.
4. What has the client agreed to implement as a result of your adaptation work?
At present the project costs are under consideration so no decisions have been made to what is or is not to be incorporated into the building. Subject to the above, it has been agreed that the following will be adopted:
- Passivhaus design methodology
- Optimised solar orientation and daylight strategy
- Cross flow and stack ventilation
- Night cooling strategy
- Intermediate weight construction
- Low water use appliances
- Rainwater harvesting
- Green roof for rainwater attenuation
- Rainwater attenuation pond
- Ground cooling via earth tube or soil to brine heat exchanger.
5. What were the major challenges so far in doing this adaptation work?
Lack of guidance: currently there is limited literature or good practice guidance on upper acceptable temperature levels in office buildings.
Compatibility with current design and good practice guidance: a high performance building envelope that fulfils the Passivhaus standard requires minimal thermal bridging. Standard structural engineering solutions for foundation details often do not achieve this level of thermal performance and re-thinking from all design disciplines is required to develop new more appropriate solutions.
Planting is a living building material: when considering the climate change scenarios to 2080, it is unclear on how plant species will or not adapt or succumb to pest and diseases with gradual change. So it was considered appropriate to concentrate on the structure and principles of the external design and associated characteristics of the plants, for future climate change.
Site restrictions: the limited size of the site restricted the design of the building and restricted the use of certain CCA strategies, eg ground cooling, incorporating the surface water storage needs of future extreme events, extensive landscaping to successfully moderate the microclimate.
6. What advice would you give others undertaking adaptation strategies?
- A simple passive design approach at concept stage can provide a robust strategy to mitigate impacts from future climate scenarios, e.g. layout of the building to allow cross ventilation and to control solar and internal gains.
- Passivhaus principles provide a robust approach to future climate change.
- Introduce thermal modelling at concept stage and use it as a design tool and not a compliance tool.
- Consider the role the landscape and external planting can play at introducing micro-climates and dealing with changing rain fall patterns at the outset.
- If the site and budget allow it, build in the possibility for using active cooling systems. For example, MVHR systems can use ground cooling to reduce excessive heat build up in prolonged periods of high external temperatures.
- A detailed study of built examples and construction approaches in different climates has proven helpful.