Environmental Design Solutions Limited (EDSL) was formed in 1989 to commercially develop Tas Software. EDSL sells Tas software and consultancy services using Tas. EDSL believe that the mixing of development, consultancy and software support leads to a focused software product, with quality support available to end users.

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Large Projects

Tas is capable of simulating very large buildings such as hospitals quickly and accurately. Our consultancy department is experienced in handling such projects.

Below is a recent case study of a new hospital tested for Part L compliance by our consultancy department.

Pembury Hospital PFI

New 512-bed PFI Pembury Hospital at Tunbridge Wells comprising 7 storeys of planned & emergency surgery, orthopaedics, women & children’s zone, day case theatres and outpatient services.

Design Ideas

All patient overnight sleeping areas are single occupancy bedrooms with individual en-suite bathrooms to meet high standards for hygiene and infection control.

1.2MW of the base load boiler power is provided by a biomass woodchip boiler in order to reduce the CO2 emissions of the building. Additional heating loads are met via three natural gas fired boilers.

Concept Stage

An initial study was undertaken to investigate peak temperatures in the single bedrooms which were naturally ventilated. For this, a small model of part of a wing of the hospital containing single bedrooms was created.

The diagram below shows the window configuration for a typical single bedroom. Fresh air is provided by openable aluminium louvre vents adjacent to each window.

The concept model tested the ventilation design to the client’s peak summer temperature criteria. The result was that the window panes had to be reduced in width to lessen solar gain and allow larger vents to be installed.

  • A: Fibre cement rainscreen (various types) on external wall.
  • B: Window Pane
  • C: Aluminium vents (each 1300mm high so as to achieve required free area).

Full Building & Part L2 compliance

The full building model was created using Tas 3D modeller. The Tas model comprised approximately 2300 zones, each with individual internal conditions, aperture controls, heating/cooling set points, etc.

The window and vent strategy was devised as a result of the concept model. Applying this to the full model was made easy by applying the same window group to each single bedroom. Therefore, changes could be made to all of the 500+ single bedroom windows simultaneously.


Once the geometry was in place, internal conditions, constructions, weather data and plant room parameters were input in to Tas building simulator.

The building complies with England and Wales part L2 building regulations and has 24% lower CO2 emissions per m2 than the target CO2 emissions rate.

Project Details