Low Energy Design

Energy use and associated carbon dioxide emissions is one of the largest contributors to the UK's greenhouse gas emissions and global warming, with homes and non-domestic buildings responsible for a large proportion of these emissions.  Low energy design is of great importance to us and we use our expertise to create buildings that require minimal energy to run whilst also creating healthy and comfortable internal environments.  Our focus is to design low energy buildings, implementing a fabric first approach, which reduces the need for heating and cooling and the requirement for expensive renewable technologies. Solar orientation, natural daylight and thermal mass are also key low energy design considerations. 

We are also advocates of the Passivhaus design approach and have the in-house expertise to design to this standard.

What is Passivhaus?

Passivhaus is a quality assurance and energy performance standard backed by a rigorous certification process, which provides a genuine benefit to both the user and the environment.  It is not easy to achieve the Passivhaus standard, but if realised results in better design and construction.  It ensures a higher level of detail is achieved at all stages from design inception through to completion on site.

To achieve Passivhaus in the UK will require:

  • Very high levels of insulation
  • An airtight building fabric
  • ‘thermal bridge free’ construction
  • High performance windows and doors with insulated frames
  • Installation of a Mechanical Ventilation Heat Recovery system
  • Design using the Passive House Planning Package (PHPP)

Quality assurance is provided by certification through organisations approved by the Passivhaus Institute in Germany. As well as providing high levels of comfort and exceptional indoor air quality, Passivhaus buildings have been proven to perform as designed by years of post-occupancy monitoring across Europe.

The Passivhaus standard is applicable to both new and existing buildings, however for the retrofit of existing buildings the slightly less onerous EnerPHit Standard is often more suitable due to restrictions with a set building form and orientation. For both standards the requirements below need to be verified in the PHPP software (PassivHaus Planning Package).

Passivhaus sketch.jpg




                         Primary energy demand

≤ 120 kWh/m2. yr

≤ 120 kWh/m2. yr + heat load factor

                            Space heating demand

≤ 15 kWh/m2. yr

≤ 25 kWh/m2. yr

                             Space cooling demand

≤ 15 kWh/m2. yr

≤ 25 kWh/m2. yr

                                 Specific cooling load

≤ 10 W/m2

≤ 10 W/m2


≤ 0.6 air changes/ hr @ n50

≤ 1.0 air changes/ hr @ n50



Retrofit and the EnerPHit standard

The refurbishment of homes and buildings is one of the greatest challenges of the future. The majority of our existing building stock requires some level of retrofit to enable us to live and work both more sustainably and comfortably.  We try to include retrofit measures in all of our projects. The extension and refurbishment of buildings will often present an opportunity to improve the energy performance of the existing building at the same time, either through building fabric or services upgrades. However retrofit can be complicated and it is important to know what should be done, when and how. Often the order that retrofit measures are installed will affect the options for future measures. The interaction of the measures with the existing building also needs to be carefully considered, especially when upgrading solid walls and improving airtightness (reducing draughts). If required we can produce a whole house strategy or retrofit plan, so even if the work is undertaken in phases the installation of future measures is not compromised.