Passivhaus / Passive House Deisgn
Architect Chester, Tarporley Cheshire
Matt Davenport of NWD Architects is a Certified Passivhaus Designer. That means NWD Architects is the only Architectural Practice covering Chester, Wirral, North & Central Wales and the Northern Welsh Marches. We are uniquely placed to provide a full design and management service for your low energy project.
What is the Passivhaus Standard?
The Passivhaus Standard, also known as 'Passive House', is a system to ensure building quality. It is governed by a thorough process of certification. Its value comes from the assurance that the performance levels it projects are closely met in real terms and genuinely benefit the user and the environment.
Significantly reduced energy consumption and therefore bills.
Improved construction, allowing excellent levels of thermal comfort and indoor air quality.
Elimination of building defects that can cause both mould growth and building failure.
Optimised lifecycle costs that can be accurately predicted prior to commencing the building.
Anecdotal evidence suggests health and well-being benefits, such as reduced respiratory ailments, allergies and improved concentration levels.
The definition of Passivhaus is also driven by air quality and comfort:
"A Passivhaus is a building in which thermal comfort can be achieved solely by post-heating or post-cooling the fresh air flow required for a good indoor air quality, without the need for additional recirculation of air." - Passivhaus Institut (PHI)
The Passivhaus Standard was established over 20 years ago and has proved its ability to provide predictable, high quality and low energy environments. It is based on sound physics principles, centred on a 'fabric first' approach, and is not subject to Government influence unlike other standards such as 'EcoHomes' or 'The Code for Sustainable Homes'.
Passivhaus is for all sectors
Despite the word 'haus' or 'house' in the name, the Standard can be applied across all construction sectors. It is proven to work in the residential, extra care, education, office, industrial and sport sectors. Because it is based on using a 'fabric first' approach to create very efficient buildings, with high degrees of thermal comfort and air quality, designs can be tailored to suit the end process. The physics behind the method remain the same – the building design is simply scaled and adapted to reach the desired outcomes.
The EnerPHit standard – for refurbishment or retrofit
The principles of improved thermal efficiency, reduced space heating and cooling, and reduced primary energy demand can also be applied to existing buildings via the EnerPHit Standard. EnerPHit is a slightly relaxed standard for retrofit projects, where the existing architecture and conservation issues mean that meeting the Passivhaus Standard is not feasible.
Criteria to achieve the Passivhaus Standard in the UK
To achieve a certified Passivhaus building there are a number of principles and minimum criteria that must be met. Minimal standards that must be met include:
Whole element U values for the floor walls and roof of 0.15W/m²K or better.
Whole unit U values for external doors and windows of 0.8W/m²K or better.
An airtightness test result of 0.6 air changes at a test pressure of 50 pascals.
The elimination of thermal bridging at all junctions/joints.
A mechanical ventilation and heat recovery system of very high efficiency, that can provide high quality fresh air in all seasons.
However, the above will not guarantee Passivhaus performance on their own.
To ensure the building performs as it should, it must be run through comprehensive software designed by the Passivhaus Institut. This software, known as Passivhaus planning package (PHPP) allows the designer to optimise the form, material performance and orientation of the building. It also ensures that the designed building achieves the following per-requisites:
The overall primary energy of the building does not exceed 120kWh/m²/year.
The thermal heating / cooling requirement of the building does not exceed 15kWh/m²/year.
The building does not overheat beyond permitted parameters.
Passivhaus can bridge the all too apparent performance gap between predicted performance and real-life performance of buildings. It allows the refinement of buildings during the design process and can accurately predict future costs and pay back periods of different elements. By adopting a fabric first approach, the standard enables the direct reduction in energy consumption by design, rather than relying on additional bolt-on elements to provide solutions or meet performance targets. This can further improve the viability and environment footprint of a scheme.
There is a growing amount of anecdotal and some empirical evidence that indicates that building to the standard provides improved health and well-being.
Passivhaus has other benefits too. Design options for a building can be worked up, providing clients with the opportunity to fine tune the cost implications of a scheme to meet their own parameters – be it for speculative build, build and let or build and occupy.
Social housing landlords have cited that Passivhaus dwellings also provide:
a reduction in fuel poverty for occupiers.
a reduction in rent areas for the operator.
reduced voids between tenancies because of the appeal and benefits the standard offers potential tenants.
reduced responsive repairs and maintenance of Passivhaus certified properties than for “standard” dwellings.
To be able to proudly call a building a certified Passivhaus, it must be certified. To gain certification, a significant amount of evidence must be submitted, reviewed and approved by a certified Passivhaus Certifier. The process starts with the submission of the PHPP file and continues with detailed evidence from site. This includes proof of purchase of materials and fittings, performance certificates for items, and photographic evidence that the building has been constructed as modelled/designed.
Limitations of Passivhaus
Passivhaus is the most reliable and proven low energy building standard. Its approach means an optimised building that limits the need for additional bolt-on options. The standard is essentially a vehicle focused on modelling the energy performance of a building in use.
However, it doesn’t address wider issues of sustainability such as:
The embodied energy of the fabric of the building.
Water usage – limiting it, or encouraging reduced use.
The enhancement of the environment the building is in, or of the ecology surrounding it.
Sustainability of the location of the building – ie. close to green transport options.
Source of the energy being used in the building – therefore the building's C02 footprint.
All of the above issues can be addressed in addition to Passivhaus, but it is reliant on the design team and, ultimately, the client to opt in to addressing them.
As designers, our desire is to do as much as we can to limit the impact of buildings and reduce the energy consumption of them and the industry as a whole. We believe that the Passivhaus Standard is an effective way of doing this. We have invested heavily in the training and software and have a Certified Passivhaus Designer in-house. Whether you wish to pursue full Passivhaus standards, or meet other sustainability targets then we have the experience and resources to assist with you project.
If you have a project that you want to build to Passivhaus or other highly sustainable standards in the Chester, Cheshire, Wirral or North Wales area then please get in touch.