Episode 92

Hello and Welcome to the Part3 with me podcast, 

The show that helps part 3 students jump start into their careers as qualified architects and also to provide refresher episodes for practicing architects. I am your host Maria Skoutari and this week we will be talking about Passivhaus basics. Todays episode meets PC1 & PC2 of the Part 3 Criteria.

So what is Passivhaus:

Passivhaus is a building that is built to a set of criteria involving keeping the heat in the building resulting in using less energy to keep warm and is defined by Energy Balance, Specific Criteria, Health & Comfort, Quality Assurance, & Costs. A Passivhaus building uses half the energy of a typical Building Regulations compliant new-build in the UK.

The basic principle of Passivhaus is to keep the heat in the building to avoid using too much energy to keep it warm. In a typical building, a lot of energy is continuously lost through walls, roof, floor and windows so a lot of active heat is needed to keep the building comfortable, whereas in a passive building, heat loss is reduced to a minimum, so little additional heat is then required to maintain a comfortable temperature. 

The fundamental principle of Passivhaus is to reduce heat losses significantly so that the buildings heating demand can be met by the sun, people and internal machinery and have a small contribution from the heating system to top it up. So in a Passivhaus, all these opportunities for heat to leave the building have been greatly reduced meaning less demand is needed from the heating system and a passivhaus greatly minimises fabric losses. The key target for Passivhaus is to have space heating demand down below 15kWh/sqm.year is one of the key aspects that defines passivhaus.

Now lets revert back to what defines a Passivhaus, which includes:

• Airtightness
• Internal Surface Temperatures: >17C at all times 
• Summer overheating: less than 10% of the year >25C
• Ventilation: 30m3 of fresh air per person per hour
• Heating Demand: < 15kWh/m2year
• Primary Energy : <135 kWh/m2year
• or Primary Energy Renewable: <60 kWhm2year 

These are derived from research into how as humans we feel comfortable in relation to temperature, humidity, air movement and air quality. 

Then we have Health & Comfort:

So the basic criteria when it comes to Health & Comfort is for a building to have and achieve very low heat demand, have surface temperatures above 17 degrees, be very airtight, have continuous mechanical ventilation and an overheating limit providing warm comfortable buildings with healthy indoor air quality and to be comfortable throughout the year and different seasons. These criteria then in return prevent condensation or mould, and external and internal pollutants which are found in most typical older buildings in the UK.

Passivhaus is not just about setting criteria but also about closing the performance gap and essentially having no performance gap, meaning a building using a lot less energy than predicted.

Although costs may be higher during the construction stage for a Passivhaus, the benefits are greater in the long run with much lower operational costs over the buildings lifetime.

Some common preconceptions include that: 

• Passivhaus needs no heating - although it is very efficient and uses internal heat gains it still needs a small amount of heating to balance the temperature.  
• Passivhaus overheats - it can if its design parameters are exceeded, shading needs to be considered alongside occupancy levels to avoid overheating. 
• Can’t open windows in passivhaus buildings because of airtightness, yes you can just like any other building to keep to cool in the summer. 

Now, when it comes to building a passivhaus, a few considerations need to be taken on board, such as:

• Its form, known as the form factor which is the ratio between a buildings external heat loss areas and the internal floor area. Form needs to be considered from the outset to avoid having to compensate later with thicker insulation or higher specification glazing 
• Orientation - this is key in terms of summer sun exposure. A south facing window for example with a good overhand will get most of the winter sun and little summer sun. East and west facing windows will get almost the same proportion of solar energy in summer and winter, meaning they can contribute to overheating so need to be carefully considered and designed.
• Insulation - continuous insulation is key meaning wrapping the whole building in one continuous insulation run and it may be slightly thicker than in standard buildings 
• Airtightness - meaning there has to be a dedicated airtightness layer or boundary inside the insulation  layer and must also be continuous to have the desired airtightness level
• Thermal Bridging - as mentioned if the insulation isn’t continuous, then thermal bridging may occur 
• Glazing - triple glazing is the most common in passivhaus buildings to both keep heat in and to ensure that the inside surface temperature stays at a comfortable level
• Ventilation - So having made the building airtight, proper ventilation is then required which can be achieved by using a Mechanical Ventilation systems with heat recovery which is a system that runs quietly in the background 24 hours a day removing stale and humid air from bathrooms and kitchen whilst bringing in fresh air from the outside into the bedrooms and living areas at the same time. MVHR units ensure excellent indoor air quality all year round without wasting energy 

So what are the benefits of a Passivhaus, they are predominantly known for:

• Delivering very low energy buildings 
• Improving building performance, meaning low energy demand, reduced performance gap, high levels of comfort, effective and healthy ventilation, higher performance building components, better site QA procedures resulting in better construction quality, lower risk of building fabric damage, resilient and future proofed buildings
• Tackling the climate emergency by producing lower carbon emissions, lowering peak demand and overall requirement for renewable energy, more economical to save energy than to generate it, gives greater chance of achieving net zero, enables decarbonisation without increasing fuel bills, can support the demand response and has a lower cooling requirement in a future warmer climate 
• Improves health and wellbeing by eliminating cold homes, guarantees good levels of ventilation, reduces internal pollutants, addresses internal humidity, improves quality of life for people with chronic illness or disabilities, protects against external air pollutants, reduces risk of airborne infection and impact of external noise and also reduces the risk of the building overheating in the summer 
• Improves people performance by reducing absenteeism, improves productivity and learning outcomes and assists in attracting and retaining staff
• Long term financial benefits due to lower energy bills, fewer and shorter rental void periods, reduces fuel poverty, increases Capital value, provides lower maintenance and management costs, provides access to cheaper time of day tariffs, lower whole life costs, lower borrowing costs and ability to access green finance, holds value in the event of future carbon or efficiency legislation, lower risk of defect litigation and repetitional damage due to quality issues 
• And social benefits by improving health and wellbeing of communities, reduces demand on health and social services, improves learning outcomes for children, economic stimulus of construction, upskilling of construction workforce, clear statement of intent for transition to a net zero economy, demonstrates compliance with social value policies and targets and aligns with several UN sustainable development goals

So how does a building receive Passivhaus Certification:

To achieve PH Standard in the UK involves:

• Accurate design modelling using the Passivhaus Planning Package (PHPP)
• Continuous gap free insulation
• Good quality triple glazed windows installed in line with the insulation
• Airtight building fabric 
• Thermal bridge free construction by external dimensions 
• High quality silent ventilation with heat recovery, properly designed and commissioned 

Certification can only be achieved through a registered Passivhaus Certifier. There are 3 Certification Types:

1. Passivhaus Building Standards, which is tested and calculated using PHPP, by a person/organisation by the German Passivhaus Institute and an assessment of the building at the point of handover. This certification involves carrying out an assessment of the project when complete, alongside an extensive site supervision provided by the contractor and design team and the contractor provides a signed Contractors Declaration to assure that the on site execution is in accordance with the designs 
2. Component Certification, whereby components must be tested and reach a certain performance, data on performance is easy to find and certification must be carried out by PHI or appointed bodies. Typical components include windows, MVHR and so on. 
3. Designer & Tradesperson certification, this person has undergone sufficient and passed an exam to demonstrate their understanding of Passivhaus principles 

An initial check carried out by a certifier at the early stages of a project is not a required part of certification but it can reduce the risk to the team of failure. The scope and time input is determined by the certifier in discussion with the client and Passivhaus consultant. Typically an initial check is carried out at the end of RIBA Stage 2 and it should cover a sense check of the PHPP and input data to identify any optimistic values or errors, review of the design and identify any risk aspects and confirm acceptable assumptions.

What makes PH different: 

• Concept for low energy buildings based on best knowledge and tested results 
• A tool to model building energy and give feedback to designers
• Certification quality assurance process to verify the process

Fabric First is also key for Passivhaus buildings:

It is key in achieving four of the five basic characteristics of the Passivhaus Standard. It ensures the energy target is not met at the expense of comfort by having the fabric do all the work and is a long term solution. Therefore, the choice of construction affects the ease of achieving insulation thickness, airtightness and insulation continuity. The easiest way to achieve high thermal and airtight performance is to design the thermal envelope to be as simple as possible. The key rules for good construction is: 

• Continuous insulation with no air gaps
• Airtightness layer always on the inside of the insulation 
• No air cavities next to insulation 
• Structure not crossing through the insulation 
• Service zone always on the inside of the airtightness layer

All this then feeds into the model used for certification to ensure the Passivhaus criteria are being achieved during the construction phase. 

So that briefly covers the key principles of Passivhaus, in order to promote it as a standard to be adopted across the industry, the RIBA together with the Passivhaus Trust have also implemented tools and guidance on how the Passivhaus standards can be implemented alongside the RIBA Stages. 

Starting with RIBA Stage 0:

• Before starting to implement any Passivhaus standards to the design, the Client Requirements need to be confirmed and the RIBA Core Tasks complete. Then an experienced Certified Passivhaus Designer/Consultant should be engaged to assist preparing the project in accordance with the Passivhaus Project Responsibility Matrix. In order to develop awareness and understanding of the Passivhaus standard and how it can support the aims and ambitions of the potential project. 
• The correlations between the Passivhaus Benefits Guide, the Business Case, Strategic Brief, Cost Information and other core project requirements including other performance criteria/standards should be mapped out and then assessing how early briefing/design decisions will impact upon the cost-effective delivery of a Passivhaus building. Then the initial Passivhaus Plan should be prepared as well as, undertaking relevant Research and Development to identify useful Design Metrics and Case Studies and refine the Business Case and Benchmarks in order to assist in the preparation of the Brief, Site Information and Cost Information. Previous comparable Passivhaus projects should then be reviewed as well as carrying out visits to comparable Passivhaus buildings and develop Case Studies to set Benchmarks, gather Cost Data, and learn from the experience of others. This information can then be used to inform the Initial Project Brief. 
• This will then as a result, assist in developing a Procurement Strategy. An experienced Passivhaus Designer/Consultant should then be appointed to assist with Stage 0 to the end of 1 so that they can inform the Strategic Definition and assist with Preparation and Briefing.

Then at RIBA Stage 1:

• Once the Project Brief is approved by the client and confirmed that it can be accommodated on the site and the RIBA Core Tasks are complete. The project should be prepared in accordance with the Passivhaus Project Responsibility Matrix, the Project Execution Plan should be agreed including the Design Responsibility Matrix, Schedule of Services, Information Exchanges, Technology and Communication Strategies and consideration should be given to the Common Standards. It should also be ensured that the Cost Information and Feasibility Studies consider the advice of an experienced certified Passivhaus Designer/ Consultant.
• The Passivhaus Standard should be emphasises in the Initial Project Brief, as well as establishing the intended Certification Strategy. Then, an experienced certified Passivhaus Designer/Consultant will undertake Research and Development to prepare useful Design Metrics and refine Benchmarks which assist in the preparation of the Feasibility Studies and Cost Information which will be included in the Initial Project Brief. The initial Passivhaus Plan should then be refined and developed for discussion with the Passivhaus Certifier once appointed. 
• When assembling the project team and developing the Procurement Strategy, consideration should be give as to how the project team members with Passivhaus experience will be selected and ensure the Stage 2-7 tender information encourages the behaviours required for effective collaboration, creative problem solving, and the experience needed to identify early opportunities for Passivhaus optimisation. 

Then at RIBA Stage 2:

• The architectural Concept will be approved by the client and aligned to the Project Brief and RIBA Core Tasks complete. 
• Then again the project should be prepared in accordance with the Passivhaus Project Responsibility Matrix, the Project Risk Assessments and Maintenance and Operational Strategies should be reviewed, as well as, ensuring that the Cost Information considers the complexity/simplicity of the Concept Design and the strategies set out in the Passivhaus Plan.
• The Passivhaus Plan should then be updated to reflect this stage of design development, review a cost optimised design against Passivhaus certification criteria using the Passivhaus Planning Package (PHPP) and review the Certification Strategy and the Certification Status as well as identifying any opportunities for optimisation and initiate any appropriate Research and Development.
• Then spending on the Procurement Strategy a Passivhaus Designer/Consultant and Passivhaus Certifier should be appointed to assist with future stages of the project (Stage 2-7). It should also be determined if its appropriate to engage in Early Contractor Involvement (ECI), the update Procurement Strategy accordingly and hold discussions with contractors and specialist subcontractors relevant to the procurement route and test Passivhaus objectives set out in the Concept Design including the Passivhaus Plan. 

Then at RIBA Stage 3:

• The Architectural and engineering information should be Spatially Coordinated and the RIBA Core Tasks complete. 
• The project should then be prepared in accordance with the Passivhaus Project Responsibility Matrix, alongside preparing a schedule considering potential conflicts with national (or other) standards, including the Passivhaus standard. The Cost Information should then be updated accordingly to take into account discussions with potential contractors, specialist subcontractors and suppliers leading to the Project Risk Assessments and Maintenance and Operational Strategies to be updated taking into account Passivhaus considerations. 
• This will then inform the optimisation of synergies through whole systems design and simplifying controls and optimising usability. The Principles of handover process and post completion service should be agreed at this stage and opportunities identified for optimisation initiating any appropriate Research and Development. The Passivhaus Plan should then be updated to reflect this stage of design development, review a cost optimised design against Passivhaus Certification criteria using PHPP and review the Certification Strategy and the Certification Status. A PASSIVHAUS CERTIFICATION DESIGN REVIEW should be undertaken at this stake. 
• And further discussions should be held with contractors and specialist subcontractors relevant to the procurement route to test the Passivhaus Plan components and coordination exercises set out in the Developed Design.

Then at RIBA Stage 4:

• All design information at this stage required to manufacture and construct the project should be completed alongside the relevant RIBA Core Tasks. 
• At this stage, the manufacturing and assembly risks should be reviewed in the updated Project Risk Assessment. Components should be developed more accurately considering the implications of the possible methods of manufacturing or fabrication and well as developing the interface details and specifications including structural, airtightness, thermal bridging, water/ moisture/ vapour penetration and acoustic issues. Consideration should be taken in consulting a constructor that has experience completing Passivhaus buildings.
• Then opportunities for optimisation should be identified and initiate any appropriate Research and Development. Any proposed variations should be tracked and reviewed as well as validating the cost for optimised variations against Passivhaus certification criteria using PHPP before making design changes. Then the construction documents should be updated, and variations to be recorded accordingly. Then as a result, the Passivhaus Plan should be updated to reflect this stage of design development, review a cost optimised design against Passivhaus Certification criteria using PHPP and review the Certification Strategy and the Certification Status. A PASSIVHAUS CERTIFICATION DESIGN REVIEW should be undertaken again at this stage.
• Review how the Passivhaus standard impacts on the assembly of the construction team (inc. sub-contractors) including how the project team will achieve a collaborative approach and how creative problem solving can be incentivised and ensure Stage 5 tender information encourages the behaviours required for effective collaboration, creative problem solving, and the experience needed to identify early opportunities for Passivhaus optimisation. 

Then at RIBA Stage 5:

• Manufacturing, construction and Commissioning should be completed alongside the RIBA Core Tasks. 
• At this stage the project should be prepared in accordance with the Passivhaus Project Responsibility Matrix. Consideration should be given on how to capture commissioning and ‘As-Built information in a manner that will assist the In-Use stage, including the potential disassembly of the building. The Maintenance and Operational Strategies and Plan for Use should also be reviewed and updated at this stage. 
• Identify opportunities for optimisation and initiate any appropriate Research and Development as well as tracking and reviewing the impact of any proposed variations and validate the cost optimised variations against the Passivhaus Certification criteria using PHPP before making changes on site. The construction documents, the Construction Programme should then be updated accordingly to record the variations. Site evidence, certificates, and documentation should also be obtained and compiled, the building services should be commissioned and the Passivhaus Plan updated to reflect this stage of design development, review a cost optimised design against Passivhaus Certification criteria using PHPP and review the Certification Strategy and the Certification Status. And a possible pre-start PASSIVHAUS CERTIFICATION DESIGN REVIEW may be undertaken at this stage.
• It should also be ensured that sub-contractors tender information encourages the behaviours required for effective collaboration, creative problem solving, and the experience needed to identify early opportunities for Passivhaus optimisation. 

Then at RIBA Stage 6:

• The building should have been handed over, the Aftercare should be initiated, and the Building Contract concluded. 
• At this stage, commissioning and ‘As-Constructed’ information should be captured in a manner that will assist the In Use stage including the potential disassembly of the building. It is also advised for a Feedforward Action Plan to be developed to capture feedback from the Construction stage alongside a document of successes, challenges, obstacles and lessons learned for future use and repurposing on future projects (inc. procurement, sequencing and buildability and cost). At this stage, the Maintenance and Operational Strategies and Plan for Use should reviewed and updated.
• Site evidence, certificates and documentation should also be obtained and compiled, the Passivhaus Plan should have been updated to reflect this stage of design development, the as-built design reviewed against Passivhaus Certification criteria using PHPP and review the Certification Strategy and the Certification Status. Evidence should be issued to the Passivhaus Certifier at this stage enabling the Passivhaus Certifier to conduct their review, request clarifications and, upon compliance: PASSIVHAUS CERTIFICATION AWARDED 
• It is also advised to gather Feedback on the capability and performance of specialist subcontractors who delivered Passivhaus aspects at this stage.

And finally at RIBA Stage 7:

• The building should be in use, operated and maintained efficiently. It is advised for seasonal Commissioning to be undertaken and a Feedforward Action Plan developed to capture feedback during the In Use stage necessary to inform future projects. Disassembly or potential reuse of materials during demolition at the end of the stage should also be monitored and Feedback provided, as well as undertaking a Building Performance Evaluation - set up and commission monitoring equipment.Is should also be considered to extend aftercare for 12 months or more after practical completion and implement the Maintenance and Operational Strategies and Plan for Use. 

So that’s how a Passivhaus building is monitored and the standards painted throughout the design and construction process from RIBA Stages 0-7.

Now, a Passivhaus Plan has been mentioned a few times at different points of the RIBA Stages process, The Passivhaus Plan is used to identify the types of information that are required and the RIBA Stages at which they are useful it is a live document synthesising the team’s input and outlining the next steps, it provides a structure which can be used when reporting the status of the Compliance Risk Management Information. The Passivhaus Plan confirms when this information becomes useful in order to help project teams reduce risk and deliver better quality projects. This Plan and its reporting is managed by the Passivhaus Designer/Consultant and working with the client team and the Passivhaus Certifier, the Passivhaus Designer/Consultant will establish the level of development required for each RIBA Stage. Then, as appropriate, the Passivhaus Designer/Consultant will review available evidence against Passivhaus certification criteria, review the Certification Strategy and then endeavour to inform the development of relevant strategies.

So to sum up what I discussed today:

• Passivhaus is a building that is built to a set of criteria involving keeping the heat in the building using less energy to keep warm. 
• Passivhaus plays a huge part in reducing emissions and carbon dioxide which is vital for the health of the planet
• Achieving Passivhaus standards involves having continuous insulation and airtightness layer avoiding thermal bridges and providing ventilation for optimum comfort and health and orientated to take advantage of sunlight and avoid overheating 
• Passivhaus is not just about setting criteria but also about closing the performance gap and essentially having no performance gap, meaning a building using a lot less energy than predicted.
• The key considerations when designing a Passivhaus building include form, orientation, insulation, triple glazing, airtightness, thermal bridging and ventilation
• Certification can only be achieved through a registered Passivhaus Certifier. There are 3 Certification Types, Passivhaus Building Standards, Components & Designer & Tradesperson
• In order to promote it as a standard, the RIBA together with the Passivhaus Trust have developed tools and guidance on how the Passivhaus standards can be implemented alongside the RIBA Stages and I have provided a link to the guide in the episode notes

There are a lot of aspects to Passivhaus, todays was just a general overview of the standard and I will be following up with additional episodes to provide further information on Passivhaus, its standards and processes.