British Blind & Shutter Association - solar shading impact report

Against the backdrop of global warming and rising energy prices, there is a pressing need to design buildings that do not overheat, exploiting passive design strategies. In this context, the British Blind & Shutter Association commissioned the National Energy Foundation to assess the impact of solar shading in the UK built environment.

In the UK, the efficacy of solar shading as a passive solar control and daylight management tool still tends to be poorly recognised. Our Solar Shading Impact report for the British Blind & Shutter Association presented an evidence-based investigation into the current and potential impact of solar shading in the UK built environment, leveraging on the full benefits intrinsic to the optimal use of shading. These go beyond the mere energy implications (reducing overheating), to include its broader benefits such as comfort and productivity.

Solar shading services and key activities we provided:

Context setting: review of the evidence stemming from correctly specified and operated building shading systems around:

  • Comfort (thermal, visual, acoustic).
  • Operation (indoor air quality, productivity, security and privacy, controllability).
  • Energy (operational savings and overheating mitigation).

Quantifying the impact: an extensive cost-benefit analysis of representative solar shading configurations against alternative strategies and products across:

  • Thermal, visual and functional performance.
  • User controllability and responsiveness to varying conditions (weather and occupants).
  • Installation, durability and service life.
  • Maintenance requirements.
  • Aesthetics ('aspirational' aspect and status symbol).
  • Cost.
  • Operational energy savings and carbon dioxide reduction (via dynamic simulation modelling).

Looking to the future: a business case for key players, strategic vision, and action plans to overcome the key barriers faced by the industry by 2020 and 2050.

Solar shading study results

  • Use. In addition to enhanced privacy and the provision of functional/visual separation, experimental and modelling studies prove year-round improvements in the thermal comfort of occupants from more even thermal radiation flows and less extreme operative temperature ranges, as well as in visual comfort thanks to regulation of luminance levels and reduced glare. Allowing more glass to be used maximises the harvesting of circadian-effective daylight, thereby providing a more comfortable workplace. Shading also improves the perception of indoor air quality, which degrades at higher indoor temperatures.
  • Energy and carbon. Solar shading can effectively be a self-financing climate control system in terms of solar control and daylight management. Dynamic simulation modelling of a highly-glazed office carried out in EnergyPlus showed operational energy savings of 5-12% for internal shading and 37-40% for external shading, if the reference building was provided with standard roller shades or blinds. Graph 1 below breaks down the energy uses of the reference building (RB) without shading against four alternative scenarios featuring internal or external shading configurations, all of which resulted in some sort of savings compared to the baseline, and the associated reduction in the system nominal capacity consequent to the diminishing space cooling loads. Graph 2 illustrates the reduction in running energy costs and operational carbon dioxide emissions on a m2 basis.
  • Short term. Over the short term, the whole industry ought to commit to CPD, training and best practice; partner with the UK government towards whole-building approach based on nearly Zero Energy Building roadmaps and contribute to revising Part L. Work is also needed to overcome regulatory and non-regulatory barriers to retrofit and learn from occupant behavioural research.
  • Long term. In the long term, the industry should aim to lead on research, development and innovation; lobbying effectively at the UK and EU tables. Shading should be seen as a pre-requisite of building design, supported by internationally-agreed metrics for ‘soft’ (non-financial) benefits. It should be optimised by using occupancy-driven learning algorithms and should complement the government’s energy efficiency strategies and carbon targets (80% less greenhouse gas emissions by 2050).

Graph 1. Energy modelling outputs per internal (SSI1) and external (SSE1) shade; internal (SSI2) and external (SSE2) blinds against a shading-free reference building (RB): (a) annual energy use breakdown per end-use, (b) total nominal capacity breakdown per system component.

 

 

 

 

 

 

 

 

 

 

 

Graph 2. Total operational running cost and CO2 savings per internal (SSI1) and external (SSE1) shade; internal (SSI2) and external (SSE2) blinds against a shading-free reference building (RB).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Solar shading assessment statistics

  • 90% of time among humans in developed countries is spent indoors.
  • Work performance diminishes below 19-22°C and above 23-24°C.
  • 80-90% of total operating costs in offices are staff-related.
  • 15% improvement in wellbeing is achieved with biophilic design.
  • 6% increment in productivity is achieved with biophilic design.
  • 21-38% and 13-25% reduced U-values of double glazing windows, between clear and coated.
  • 16-82% and 13-85% reduced g-values of double glazing windows, between clear and coated.
  • 5-12% less energy is used in a highly glazed office unit with internal shading - equivalent to a cost saving of £1.4-3.2 per m­2.
  • 37-40% less energy is used in a highly glazed office unit with external shading - equivalent to a cost saving of £10.0-11.2 per m­2. and a 62% reduction in the nominal capacity of space cooling equipment.