This blog post is a review of “The Passivhaus Designer’s Manual: A technical guide to low and zero energy buildings” published in October 2015 and edited by Christina J. Hopfe and Robert S. Mcleod. Until now, there hasn’t been an English language manual for Passivhaus Designers. Training courses include relevant teaching material, but it is only available for course attendees and makes the most sense in the context of the course. This book covers all the main topics of a Passivhaus Designer course in an accessible and technically detailed format.
It is intended to provide a technical reference on important topics that often require more detailed explanations than can be found in most introductory handbooks. It is assumed that those reading the book will already be familiar with the fundamental principles of low energy design.
It is a design-focussed manual, bringing the academic and practice-based knowledge of the long list of authors together into one volume. Suitable background information is provided for each topic, but the main thrust is towards practical application in designing Passivhaus, or low and ‘zero-energy’ buildings.
Passive buildings are not all about technology. Their greatest benefits are not in avoided costs and emissions but in quality of life. Why did people meeting around our dining room table stay alert and cheerful all day, than in an ordinary office, become sleepy and irritable in half an hour?
– Amory B. Lovins, Cofounder and Chief Scientist, Rocky Mountain Institute
The Passivhaus Designer’s Manual could easily be the textbook for a Passivhaus Designers course. It will certainly become the reference book of choice for many Passivhaus Designers and the source of self-study for many aspiring Passivhaus Designers
1. Does the Passivhaus Standard go far enough?
Chapter 1 is by Robert S. McLeod and Christina J. Hopfe: Introduction – Climate change and the built environment.
This chapter provides an important background and history to the development of the Passivhaus Standard. It includes some details on how the critical “peak heating load” metric came about. It also puts the role of Passivhaus into the wider context of European “Nearly Zero Energy Buildings” (NZEBs) and regional standards and requirements. The workings of Passivhaus design and some of the limitations are touched on briefly.
The wider context is important. Sometimes enthusiasm for Passivhaus can lead to the impression that it is the only standard and approach to building design needed in the anthropocene. This isn’t the case.
In order to be sustainable in the broadest sense, the transition towards zero energy and plus energy buildings must be robust. The Passivhaus standard offers a well-established template for ultra-low energy building that is both economical and resource-efficient, whilst at the same time providing high levels of occupant comfort and resilience to future climatic changes. Whilst some parties have suggested that the Passivhaus standard is a step too far, others are questioning whether in its classic form it goes far enough towards addressing equitable carbon emissions. (p5)
The Passivhaus standard should be seen as an important and necessary starting point, not the end point. Although this might seem challenging to some, others are already taking this approach.
Passivhaus is the foundation for sustainable building design in the anthropocene.
2. Comfort from head to toe, or at least, ankle
Chapter 2 is by Louise Finnerup Wille and Darren Woolf: Thermal and occupant comfort.
The premise of Passivhaus is that optimum conditions for human comfort (including for health) are achievable with radically low energy input. So it’s no surprise that this is an early chapter in the manual.
If a human body registers an air temperature difference of more than 2 K between the head and the ankles whilst sitting, this can lead to feelings of discomfort. (p44)
The chapter covers the background and basis of comfort in buildings. This includes temperature stratification, perhaps one of the lesser-known aspects of thermal comfort, despite that we have probably all experienced cold ankles!
Comfort isn’t just about hard metrics, it’s also about psychology and personal preference – such as, how many people will be dissatisfied with the indoor conditions. There are still key metrics, though, and the science to back them up, such as air nd surface temperatures, radiant temperature asymmetry, temperature stratification, draughts and overheating.
Understanding ‘comfort’ is vital for Passivhaus design – or any building design, really.
3. Heat moving fast and slow, through materials
Chapter 3 is by Niall Crosson, Robert S. McLeod and Christina J. Hopfe: Introduction to building Physics – Implications for opaque and transparent building components.
To understand the international Passivhaus Standard, you need to understand at least some basic physics. To be a Passivhaus Designer, you need to understand and be able to apply some very specific building physics. This chapter covers all the important physics that underlies Passivhaus and is seen in the calculations of the Passivhaus Planning Package.
Key equations are explored and illustrated with graphs and diagrams so they don’t remain abstract. Passivhaus is very much about the practical application of physics, after all. Thermal conductivity, thermal transmittance, thermal bridging are all covered in detail. So too is thermal mass and thermal diffusivity.
The Decrement delay is the heat transmission delay time (hours) resulting from the thermal diffusivity of a particular construction element. The Decrement factor is the ratio by which the amplitude of the external temperature sine wave is dampened as a result of the materials’ specific thermal capacity. (p65)
The Decrement delay and factor of materials is where it is apparent that not all insulation materials are equal, even if they have the same thermal resistance/transmittance (R/U-value). Insulation with a high decrement delay means that there might be several hours gap between when it is hottest (or coldest) outside and when it reaches the peak temperature indoors. Clearly this can be useful in certain climates: some heat still moves through insulation. Similarly, insulation with a high decrement factor will reduce what the eventual peak temperature on the inside reaches.
The physics of Passivhaus windows gets an appropriately detailed treatment. Windows remain weak points in the building envelope, even in Passivhaus buildings. As such they are critical components and important for Passivhaus Designers to have detailed working knowledge of.
Physics and its application to buildings is the backbone of Passivhaus.
4. Don’t overlook lighting
Chapter 4 is by Myriam B. C. Aries and Jan Wienold: Lighting and daylighting for visual comfort and energy efficiency.
The key energy metrics for the international Passivhaus Standard are the heating demand or the peak heating load and the primary energy or the renewable primary energy. Lighting doesn’t feature specifically so it is easy to think it isn’t so important for Passivhaus. However, this isn’t the case –
Lighting accounts for approximately 8 percent of a typical UK household’s energy bill. In a Passivhaus, the total energy consumption is supposed to be drastically lowered compared to a standard (new) house. However, the electrical power for lighting often stays approximately the same, hence making up a relatively large part of the total energy consumption. (p100)
The chapter covers the principles of daylight design – it’s not just the metrics either, delight is an important part of daylight.
Suggested solutions for reducing the electrical consumption of lighting include:
- Good daylighting design – access to daylight but not too much contrast that might result in electrical lights gets switched on.
- Good electrical lighting design – the right amount where it is needed.
- Low-energy fittings.
- Good controls – easy to use.
- Automation – occupancy sensors to turn on when someone enters, absence detection to turn off when there’s no movement for a period of time, daylight sensors to dim electrical lighting
It is questioned, however, whether sophisticated controls or automation actually deliver energy savings in domestic situations. In my personal experience, both should only be used sparingly and intelligently in non-domestic situations also.
And the easiest single thing to do to save lighting energy in a Passivhaus home? Install (and use) dimmers on the electrical lighting. Less electrically produced light = less energy consumed.
Good daylighting design and intelligent electrical lighting design needs to be a focus for Passivhaus Designers.
5. How wet will the building envelope get?
Chapter 5 is by Florian Antretter, Matthias Pazold, Marcus Fink and Hartwig Kunzel: Hygrothermal simulation (transient heat and moisture assessment).
This chapter is largely about the WUFI® Passive software which can implement both the ‘monthly method’ that is used in the PHPP and dynamic simulation for energy balance simulation. It is also able to undertake dynamic simulation of moisture movement in building components.
The Hygrothermal component assessment is used to assess the risk of moisture damage occurring in individual building components. The assessment usually contains two parts. First, the total water content and water content of layers is assessed. In simple terms, the total water content should not continuously increase over time and its annual fluctuations should remain within certain limits.
. . .
Second, the hygrothermal conditions for critical locations can be assessed. (p121-123)
Different materials can absorb and manage different quantities of moisture. It is normal to expect seasonal changes in moisture content, particularly components and materials exposed to external conditions, along with the substrate materials. There will be higher moisture content for some of the year (due high humidity, driving rain etc) and lower moisture content as the component and materials dry out for other parts of the year.
Dynamic simulation is able to assess the risk of mould growth. It is particularly useful if the risk is likely to be high or borderline acceptable. In these situations, steady-state assessments might not give a detailed enough picture. The WUFI® software enables visualisation of the fluctuations in temperature, water content and relative humidity.
The WUFI® Passive software has other hygrothermal and energy simulation capabilities that the chapter explains and illustrates with a worked example.
At the time of publication WUFI® Passive is recognised by the US organisation, PHIUS, for design and certification purposes to the national standard PHIUS promotes. It is not, however, recognised by the PHI as a certification tool for the international Passivhaus Standard.
Hygrothermal analysis is important for airtight well-insulated buildings where moisture behaviour in materials and components can be critical.
6. Passivhaus heating: for spaces or for water?
Chapter 6 is by Marek Miara: Heat and hot water generation for domestic buildings.
In all residential buildings, a heating system has to cover two types of energy demand: the space heating (SH) and the demand for domestic hot water (DWH). In a Passivhaus, the space heating demand is reduced by approximately 70-80 percent in comparison with a conventional (new) building, with the DWH demand remaining typically the same for all types of houses. Thus, whereas in a conventional building, the space heating demand dominates, in a Passivhaus, both energy demands are at approximately the same level, or the space heating demand may be even lower. These considerations have a large impact on the choice, design and operation of a heating system in a Passivhaus. (p127)
Space heating for Passivhaus is so low that it can be covered by post-heating the ventilation air. And in fact, this is the basis for the 10 W/m peak heat load requirement of the international Passivhaus Standard. This is possible, largely due to the fabric first approach. It doesn’t mean that post-heating the air is the only option though, Passivhaus is a performance standard and doesn’t prescribe a specific heating system.
An exceptionally good building envelope also means that radiators aren’t required under windows to reduce the discomfort caused by cold windows. The high-performance building envelope effectively produces a shorter heating season, further reducing the size of the heating system needed.
The chapter suggests that in some situations it is even worth considering an independent heating system dedicated to providing domestic hot water. This might make sense sometimes, after all, hot water is needed all year round and at different times to space heating. Care should be taken not to overcomplicate the heating system though – a marginally less efficient Passivhaus heating system combining both space heating and domestic hot water still consumes very little energy. And, importantly, it may by simpler to use and maintain than a more sophisticated combination of separate systems.
The very low space heating demand opens up the possibility of using a low temperature wet heating system. This can be supplied by lower grade heat, for example, from a heat pump, with much higher efficiency than otherwise would be possible.
The following heating options are discussed with economic, primary energy and ecological implications considered:
- Direct electric
- Heat pumps (both standard air and ground source, as well as compact service units that combine ventilation with heat recovery and use the exhaust air as the source for a heat pump)
- Natural gas
- Wood-based approaches
- Solar thermal collectors
Designing a Passivhaus heating system needs equal consideration to space heating and domestic hot water. Take care to avoid overcomplication though.
7. Architecture + Physics
Chapter 7 is by Doreen E. Kalz: Heating and cooling of nonresidential Passivhaus buildings using passive and environmental energy strategies.
In this chapter, the reference to passive strategies mainly refers to Thermo-active building systems (TABS). Environmental energy strategies refer to using ground water and air sources for both heating and cooling.
Harness the building’s architecture and physics in order to considerably reduce the annual heating and cooling demand (building envelope, daylighting concept, natural ventilation, passive heating and cooling technologies). (p154)
The chapter covers the different types of environmental energy available, which is particularly applicable at the larger scale of non-domestic buildings. These include:
- Ground source heat / heat sink
- Water source heat / heat sink
- Ambient air source heat / heat sink
The types of Thermo-active building systems (TABS) and the associated benefits and requirements are covered. This essentially comes down to passing warm or cool air or liquid through screed, concrete or plaster surfaces with a building.
Different types of cooling aside from TABS are also covered including passive and mechanical systems. It is worth bearing in mind that even in cool climates, comfort cooling is almost always important in non-residential Passivhaus buildings.
The chapter advocates a holistic approach to design, with Passivhaus as the foundation, carrying on the theme from the introduction.
A design approach that integrates architecture and physics is key for sustainable and environmentally responsible non-residential Passivhaus buildings.
8. Ventilation is crucial
Chapter 8 is by Michael Swainson: Ventilation Concepts – planning and implementation.
It is always good to be reminded on the broad purposes for ventilation. Too often it is forgotten or not prioritised in building design, and people suffer the consequences.
The key reasons for ventilating are:
- To provide oxygen for the occupants. […]
- To remove moisture generated internally. Elevated levels of moisture in a building lead to dampness and mould growth. […]
- To remove odours generated by Human activity and provide a “fresh” feel. […]
- To dilute and remove pollutants generated internally. The generation of pollutants within a building may not have any direct relationship to occupancy. […] (p159-160)
This is the most detailed chapter in the manual – with very good reason. It is one of the most important aspects of Passivhaus design and perhaps the aspect where things most often go astray. The following topics are covered in lucid detail:
- “The why” of ventilation and specifically how it is approached in Passivhaus design
- Different methods of ventilation and the associated pros and cons
- Highly detailed and illustrated consideration of an example MVHR unit. Ever wondered how a summer bypass works? It’s explained and illustrated with photos of a unit with the cover off. Passivhaus certification information is also touched upon.
- Duct system design, installation, layout and insulation
- External terminals
- Post heating – that is, delivering space heating via the ventilation air
- Supply valves (diffusers)
- Extract valves
- MVHR system layouts
- Types of MVHR
- Fire and ventilation systems
- System design – including how to provide the needed ventilation, how to minimise noise nuisance, how to ensure low and easy maintenance so it is maintained, how to design for low energy
- Different climate regions and seasons – MVHR can help maintain cool temperatures as well as warm temperatures
- Overheating and the role of ventilation
- Installation and site practice
This is an incredibly detailed and well-illustrated chapter that will certainly serve as a ventilation design reference for me. For this chapter alone, I would recommend The Passivhaus Designer’s Manual to all Passivhaus Designers or those aspiring to be one.
Ventilation is rarely given the consideration it deserves, Passivhaus design is changing that.
9. Renewable energy is now important for Passivhaus Designers
Chapter 9 is by Andrew Peel: Renewable Power Technologies.
Traditionally, the international Passivhaus Standard has been solely focussed on energy conservation and efficiency. However, the release of the Passivhaus Planning Package version 9 incorporates the concept of Primary Energy Renewable (PER). This accounts for the dedicated use of renewable energy sources in a Passivhaus design.
Aside from this, there are many other factors that encourage or require Passivhaus Designers to include renewable energy generation in their designs. These include regional policy and standards, broader environmental standards, client wishes, subsidies, etc..
This chapter covers all the critical factors that need consideration. Renewable energy, like all other aspects of Passivhaus design, needs a rigorous approach. System losses should not be underestimated.
Another factor that affects performance, but is not generally included in the system losses, is localized shading. This occurs when an object shades only a portion of one panel. This can include fallen leaves, branches, and bird droppings. Areas with large bird populations or surrounding foliage are more prone to this. …[A] series of panels will only perform as well as its weakest panel. Therefore, a drop of 50 percent in one panel results in the same drop for all the panels connected to it serially. (p235)
This highlights the importance of technical design rigour. It also highlights why the energy efficiency first approach of Passivhaus is vital and resilient. A poorly performing building that is overly reliant on renewable technologies to reduce energy bills and CO2 emissions is not suitably resilient. Small effects on the renewable technologies can have big impacts.
Passivhaus Designers mustn’t ignore renewable energy. However, resilient buildings prioritise a fabric-first energy efficiency approach, followed by renewable power technologies.
10. The PHPP is a top-level project management item
Chapter 10 is by John Morehead: Project and site management, contractual arrangements and quality assurance.
Project and site management are important aspects of the quality assurance aspect of the international Passivhaus Standard. Ensuring that what gets designed is also what gets built is partly how Passivhaus has for all intents and purposes eliminated the performance gap. The Passivhaus Planning Package is another important part of eliminating the performance gap.
Once initial designs are at scheme design level, meeting the requirements of the project charter and incorporating the defined objectives of the project scope, it is time to put the design through the rigour of PHPP. The objects of the initial PHPP study are to:
- Rely on default or basic, informed values initially to get a preliminary result.
- Identify the core characteristics of the project model at an early stage. An experienced designer will be able to achieve Passivhaus levels of performance without too much difficulty at scheme design stage, although certain projects may be more problematic in this respect.
…It is important that the nomenclature used will readily assist in identifying individual entries and their corresponding locations in the drawings. (p266)
The PHPP can contain a mass of information, as can the contract drawings and other documents. Keeping naming clear, simple and consistent across the whole project is equally important for the Passivhaus Designer’s benefit as it is for the Passivhaus Building Certifier’s benefit. It only creates more work for the designer when data or components can’t be found. Or when the link between construction elements and energy performance isn’t obvious.
The chapter also covers the pros and cons of a variety of procurement and contract approaches, and how the Passivhaus design process fits within the project management process.
Management of construction process is of course not usually the remit of a designer and the same applies to a Passivhaus Designer. However, there are important aspects of the construction process where the Passivhaus Designer has an important role – such as briefing the site manager and relevant teams on the airtight barrier and junctions. Not every project will have a Passivhaus Builder, so there may be significant education and support to provide.
Such is the importance of airtightness for site quality control that it gets a whole section in this chapter, as well as getting referenced in many other sections in the chapter.
PHPP comes back again during the construction stage for updating and iterating as any changes to the design are considered or implemented on site.
The chapter rounds out with the final handover process and certification requirements fo the international Passivhaus Standard, including the PHPP file.
The PHPP is developed throughout the project with key milestones, as part of the project management.
11. The economics of keeping the boat afloat
Chapter 11 is by Nick Newman: The economics of Passivhaus Construction
This chapter builds on the work done earlier by Nick Newman and published in “An Introduction to Passive House”. (Read my review here.) It starts out with a broad discussion about the purpose of buildings, critiquing Le Corbusier and developing an amusing and illustrative analogy of a boat.
Likening once more the goal of ‘maintaining a comfortable indoor environment’ to the sailor’s goal of ‘keeping water out of a boat’, one valid design proposal would be to find a leaky boat and buy a pump to bail out the water that poured in. This design might be named ‘the conventional building’.
A bolder designer who wanted to challenge convention could buy a much larger pump, cut some extra holes in the hull and then tip the boat on its side for good measure. this second design might be named ‘the avant-garde building’.
…Though it sounds radical, the Passivhaus pioneers realised that if the boat is turned the right way up, and some of the holes in the hull are fixed, only minimal energy is needed to keep it afloat. What is more, the energy inputs and outputs are much slower, it becomes very easy to maintain a nice bobbing equilibrium. (p282)
The economic basis of Passivhaus is discussed in useful and accessible detail. A glossary of reference terms is provided and worked examples illustrate the concepts at each step of the way. The economic basis centres around the principle of net present value (NPV) rather than simple payback, so interest rates and inflation are both covered.
The chapter finishes with a case study of the Larch and Lime houses by bere:architects by Nick Newman and Richard Whidborne.
Net Present Value: the measure of economic value of Passivhaus construction.
12. Deep retrofit produces holistic results
Chapter 12 is by Ludwig Rongen: Passivhaus EnerPHit and EnerPHit+i – case studies
A concise overview of the two retrofit options available to Passivhaus Designers is given. The options are; retrofit to the full EnerPHit standard which is essentially the same as Passivhaus but with slightly relaxed requirements, or retrofit using Passivhaus certified components. A case study of each option is included with project narrative, data and before and after photographs. The 1950’s church case study (EnerPHit+i) also includes a cross-sectional drawing which helps to illustrate the extent of retrofit work undertaken.
It was a requirement that the outward appearance of the church remained identical after the refurbishment. That meant that internal insulation was necessary…
…In terms of the quality of the renovation work, visitors to the Church in Heinsberg have provided positive feedback regarding the high quality of indoor air despite closed windows and doors. In addition, the excellent acoustics have been repeatedly praised – especially at readings and concerts. (p308-309)
Often the focus of retrofit work is a mixture of energy saving and comfort improvements. As with Passivhaus, an integrated deep retrofit produces more results that just improved energy consumption and comfort. In the case of the church retrofit, the additional benefit of acoustic improvements was noted.
The second case study is a school retrofit that managed to achieve the full Passivhaus standard.
Retrofitting our extensive existing building stock is an enormous and necessary task. It can also be very specialist, so it might not be something every Passivhaus Designer will be involved in. Nevertheless, it builds upon the knowledge and skills of trained Passivhaus Designers that is covered in the previous chapters. Illustrating specific examples can help to make the task of retrofitting less daunting, so this is a good place for the manual to finish.
Illustrated examples of successful EnerPHit projects help make the massive task of retrofit less daunting.
The Secret of Integrated Design
Passivhaus Designers need to have a comprehensive toolbox of skills available to them. Passivhaus design encompasses comfort, physics, daylighting, electric lighting, energy efficiency, building envelope design, moisture movement in building materials, heating and hot water generation, heating systems, cooling systems, ventilation, renewable energy, project management, site support, economic understanding, possibly retrofit designs, and much more.
But each one of the skills in their toolbox doesn’t stand alone and by itself. It is part of the comprehensive, integrated design approach that Passivhaus encourages.
…the deepest lesson I hope you will take away is not the virtue of simplicity, the value of eliminating mechanicals, and the importance of meticulous attention to detail. Rather, it’s the secret of integrative design – optimizing the whole building for multiple benefits, not isolated components for single benefits.
– Amory B. Lovins, Cofounder and Chief Scientist, Rocky Mountain Institute
The Passivhaus Designer’s Manual is an excellent guide to the many facets of Passivhaus design. And it will become the reference book of choice for many Passivhaus Designers.
To purchase a copy of this book I highly recommend supporting your local independent bookshop if possible or purchasing direct from Routledge. However, if you do choose to purchase from any of the links on this site, Amazon will pay me a small commission (at no cost to you) which will support this site. You can click on the image above to go to the Amazon page for the book, or visit my Passivhaus Books page for more information about this book and other Passivhaus books.
My thanks to Routledge and the editors for providing me with a review copy of the book.