A presentation on Passivhaus delivered by David Sharpe of Thomasons to the Midland Counties Regional Group of the Institution of Structural Engineers at the Technical Meeting and AGM on 25th November 2014

1. Passivhaus: What is it, and what has it got to do with me?
Underhill House: Seymour-Smith Architects
Midland Counties Regional Group
Institution of Structural Engineers
David Sharpe
Thomasons
25th November 2014
adapted from Passivhaus Trust materials

2. Who am I?
David Sharpe
Profile: http://uk.linkedin.com/in/dmsharpe
I have over nineteen years experience of
building structures, undertaking the structural
design of new-build & refurbishment projects.
I have also been exploring recently how I can
integrate structural design with the principles
of low energy use, such as the Passivhaus
standard, for new and retrofit projects.
BEng (Hons) Civil Engineering in 1994
MSc Structural Design in 1995
IStructE Part 3 CEng Exam in 2001
Certified Passivhaus Designer in 2013
Certified
Passivhaus
Designer:
Chartered
Structural
Engineer:
Individual Member:
Thomasons:

3. What is Passivhaus?
• An approach providing buildings with a healthy + comfortable
internal environment
• Buildings that use very little energy for heating and cooling
• Quality Assured, Provable and Certified system
• Design and construction with a focus on every detail
- Orientation - of building on site, overall plan and individual elements
- Good insulation throughout
- Draught-free construction
- Efficient ventilation
• Suits any site, type and style of building

4. Not just housing
The Passivhaus standard is not confined to residential properties & has been
achieved in several office buildings, schools, supermarkets etc around Europe.
Bushbury Hill Primary School, Wolverhampton, Architype Architects Mildmay Community Centre (formerly
Mayville), London , Bere Architects

5. Lena Gardens
Also refurbishment - EnerPHit
“Quality-Approved Energy Retrofit with Passive House Components”
The goal was to create a standard for an economically and ecologically optimal energy
retrofit, for old buildings that cannot achieve Passive House Standard with reasonable
effort. (PHI)

6. “I was working as a physicist. I read that
the construction industry had experimented
with adding insulation to new buildings and
that energy consumption had failed to
reduce.
This offended me – it was counter to the
basic laws of physics. I knew that they must
be doing something wrong.
So I made it my mission to find out what,
and to establish what was needed to do it
right.”
Dr Wolfgang Feist, Passivhaus Institut
Denby Dale – Photo: Green Building Store
Passivhaus History

7. Passivhaus History
• Developed by Dr. Wolfgang Feist and Prof. Bo Adamson in the 1980s
• Around 37,000 Passivhaus projects have been completed world-wide.
• Passivhaus is now the leading international low-energy standard.
• It is a building concept that can be adopted by anyone

8. Healthy + Comfortable
• Passivhaus designs improve comfort of building users by ensuring:
• Less than 2°C difference between 0.1 m and 1.1 m (ankle to neck
level of a sitting person);
• Less than 3°C difference between room temperature and any
surface
• No draughts:
- ‘air-tight’ construction;
- ventilation air supply into room at very low speed;
• Sufficient ventilation ensured to every space to control air quality –
humidity, CO2 levels, etc.
From research, the above aspects are all part of what produces sense
of ‘comfort’ in building users – and all are delivered by Passivhaus

9. Low Energy Buildings
The criteria for any Passivhaus in a central European climate is:
• Space Heating demand of ≤ 15 kWh/m2/year
or peak space heating load of ≤ 10 W/m2
• Space cooling demand of ≤ 15 kWh/m2/year
or peak space cooling load of ≤ 10 W/m2
• Primary energy demand ≤ 120 kWh/m2/year
including hot water, space heating & cooling, fans, lighting,
appliances, computers, televisions, etc.
• Airtightness of ≤ 0.6 air changes / hour at 50Pa

10. Provable & Measureable
Figures show
that for
Passivhaus
the average
measured
heat energy
use is
15kWhr/m2/yr

11. How is it achieved?

12. How is it achieved?
• High levels of insulation
Fabric U-value < 0.15 W/m2K; Windows < 0.8 W/m2K
• Minimal thermal bridging – Design them all out
• Continuous air barrier to achieve < 0.6 ach @ 50 Pa
• Provide controlled ventilation and heat recovery during heating season
with MVHR. Can use natural ventilation in summer.
• Maximise use of solar and internal heat gains & protect against
overheating. Overheating frequency < 10%

13. How is it achieved?
Modelling with Passive House Planning Package (PHPP)

14. Passivhaus in the UK
We started quite late…
Images: Passivhaus Institut, JPW Construction, Green Building Company, Simmonds.Mills

15. Passivhaus in the UK
>270Passivhaus buildings
have been completed in
the UK, with >1000
others in planning an on
site;
UK is seeing significant
numbers of larger scale
projects in planning and
early stages of
construction;
See
http://www.passivhaustr
ust.org.uk/projects/passi
vhaus_projects_map/
…but many projects have been completed

16. Passivhaus in the UK
…but many projects have been completed
Images top (l-r): Wimbish (Hastoe), Dormont (CCG), Bushbury (Architype), Interserve (Interserve)
Images bottom (l-r): Sampson Close (Orbit), Montgomery School (BAM), Viking House (Van Developments)

17. Passivhaus QA
• Quality assured process with Certification
• Buildings
- Through UK based certifiers
• Products / Components
- Through Passive House Institute
- Is a demonstration of performance but not
required (except for MVHR systems)
• Designers / Consultants
- Through CEPH courses
- List of CEPH designers / consultants on the PH
Trust website
• Tradesmen / Installers
- Through Certified Tradesman courses

18. What’s needed on site?
Passivhaus requires the following beyond
Building Regulation standards:
1. Maximise insulation and minimise thermal bridges – responsibility shared
amongst all trades at all times;
2. Airtightness – frequent testing on all buildings at key stages, plus ensuring no-one
penetrates or damages the air-tightness barrier;
3. MVHR, supply and extract ducts – installed and fully commissioned;
4. Use PHPP – for all stages of design including assessing site alterations;
5. Quality Assured Process – evidence of actual build quality achieved on each part
of the construction required as part of certification;
6. Consistent use of as-designed components – ensuring any site changes are
assessed with PHPP to ensure short-term savings do not jeopardise project.

19. Passivhaus in the UK
2011 Measured performance
Primary Energy: 100.19 kWh/(m².yr) (Everything,
including space/water heating)
Space Heating: 8.86 kWh/(m².yr)
Y Foel, the first Certified PH project in the UK
North Wales (2006/7)

20. Passivhaus in the UK
Measured performance
Primary Energy: 80 kWh/(m².yr)
Space Heating: 14.8 kWh/(m².yr)
Internal temperatures never below 20 or over 26 C
Canolfan Hyddgen, the first Non-domestic PH project in the UK
North Wales (2008)

21. Passivhaus in the UK
Plummerswood, GAIA Architects

22. Passivhaus in the UK
Bushbury Hill Primary School, Wolverhampton, Architype Architects

23. Passivhaus in the UK
Hadlow College Rural Regeneration Centre, Eurobuild

24. Passivhaus in the UK
Crossway, Kent, Hawkes Architecture Ltd

25. Passivhaus in the UK
Underhill House, Seymour-Smith Architects

26. But what does it mean for the structure?
Avoidance of thermal bridges is key part of the design approach
Understanding the principles involved allows structural
engineers to be collaborative members of a design team
Knowing when problems could be caused by our details before
they leave our design office, for example:
- Thermal bridges
- Airtightness detailing
- Triple glazed windows
- MVHR duct routes
Knowing why other members of the design team in a Passivhaus
project are asking us for changes – and when to challenge…

27. Wimbish Passivhaus: Samuel Ashfield Photography
Why maximise insulation &
minimise thermal bridges
to achieve 15kWh/m2 ?
By insulating the fabric and thermal bridges:
• Heat loss is reduced & meets design
targets
• Surfaces are warmer
• Condensation & mould growth is
eliminated
• Space heating energy demand is reduced
• CO2 emissions are reduced in a simpler,
cheaper way than bolt-on renewables

28. Craigrothie Passivhaus
Why be so airtight?
Through careful measures, reducing holes in the
fabric to a minimum, airtightness can be
reduced below 0.6ACH, compared to typical
levels 10 times higher.
Benefits of greater airtightness include:
• Reducing heat loss
• Minimising draughts
• Reducing noise from outside
• Preventing the damage caused by moist air
condensing on the structure as it leaves
• Allowing a controlled ventilation strategy

29. Why use triple glazing?
Three layers of low-e glazing, insulated frames, insulated spacers and
optimised insulation, typically with a U-value of 0.8W/m2K
Denby Dale – Photo: Green Building Store
Benefits of Passivhaus windows:
• Reduces heat loss further
• Warm surfaces
• Better use of space close to the windows
• No condensation
• Reduced noise from outside
Note: Windows can and should be opened,
when needed.

30. Impact on Structural Engineering
Taking viewpoints from two structural engineers who have
designed Passivhaus projects in the region:
Gary Corden, Senior Engineer, Building Structures, Ramboll
Centre for Medicine, University of Leicester
Architects: Associated Architects;
Structural Engineers: Ramboll
Jonathan McIver, was Associate at Pryce & Myers, now
Associate Director at constructure
Oakmeadow Primary School and Bushbury Hills Primary School
Wolverhampton City Council
Architects: Architype
Structural Engineers: Pryce & Myers

31. Project Example:
Centre for Medicine,
University of Leicester
Associated Architects
Ramboll

32. Impact on Structural Engineering
Gary Corden, Senior Engineer, Building Structures, Ramboll
1. Know your thermal bridges: Thermal bridges are inevitable
and for the Structural Engineer not always practical or
advisable to eliminate – for example the thermal bridge
through a piled foundation. The best way to overcome these
is to identify them as early as possible in the design process so
that they can be taken into consideration in the Passivhaus
calculations.
2. Be prepared for lots of insulation! Consider if the insulation
is going to have an impact on the structural design, notably for
substructures or cavity masonry walls.

33. Impact on Structural Engineering
Gary Corden, Senior Engineer, Building Structures, Ramboll
3. Understand the air-tightness line: As Structural Engineers
we often don’t worry too much about air-tightness. In
Passivhaus buildings the requirements are so onerous that
air-tightness may have an impact on the structural design,
particularly in the detailing of cladding supports, roofing
details or secondary steelwork supporting cladding elements.
4. Collaboration with the other design disciplines is essential.

34. Impact on Structural Engineering
Gary Corden, Senior Engineer, Building Structures, Ramboll
5. Understand the fundamentals of Passivhaus
accreditation: Understand what is actually required to
achieve Passivhaus - the balance of energy gains and losses -
particularly in a large building.
As Structural Engineers we may be put under pressure to
eliminate all thermal bridges at all costs, but thermal bridges
alone typically account for a relatively small percentage of
the overall heat loss from the building.
Many other design factors contribute to successful
Passivhaus accreditation, so the Design Team should consider
the best way to collaboratively achieve Passivhaus criteria.

35. Project Example:
Oakmeadow Primary School
and
Bushbury Hills Primary School
Wolverhampton
Architype
Pryce & Myers

36. Impact on Structural Engineers
Jonathan McIver, now Associate Director at constructure
What does it mean to structural engineers?
Apart from being a really interesting concept, the bulk of the
tricky work lies with the architecture and building services which
is where the clever stuff happens.
The main thing for the structural engineer to think about is
eliminating thermal bridging.

37. Impact on Structural Engineers
Jonathan McIver, now Associate Director at constructure
• On a Passivhaus school which required piling due to the
ground conditions, we had to isolate the piles from the rest of
the structure - highly unusual.
This was done by incorporating an additional set of RC ground
beams beneath a raft slab with a continuous layer high
density, low creep insulation separating the two.

38. Impact on Structural Engineers
Jonathan McIver, now Associate Director at constructure
• Any external canopies or solar shading, which often have to
cantilever from the building, must be supported on the
outside of the thermal envelope so there tends to be more
secondary structure fixed to the outside of the building,
concealed by rainscreen cladding which also lies outside the
insulation.
• Also, depending on the nature of the construction, some
juggling of the structure at the edges of the building may be
required to simplify the line of the air-tightness membrane as
this is far more important than in most buildings.

39. Impact on Structural Engineers
Jonathan McIver, now Associate Director at constructure
• A simple, smooth external surface which can easily be
wrapped by large sheets is ideal. Each time the membrane has
to be cut and joined around a projecting beam etc, there is an
extra chance for it to be compromised.
• Prefabrication is favoured as this allows the bulk of the
construction to be carried out in highly controlled conditions,
leaving the joints to be sealed on site.
• Finally, due to the ventilation systems required for larger
buildings, expect to see rather large ducts flying around which
will need careful coordination with structure.

40. Passivhaus - Summary
Passivhaus is an approach providing buildings that provides:
• Have a healthy + comfortable internal environment
• Use of very little energy for heating and cooling
• Quality Assured, Provable and Certified system
• Design and construction with a focus on every detail
• Suits any site, type and style of building
The Structural Engineering approach to projects is not that
different to other buildings
Once you understand the concept, and know why thermal
bridges etc. are important, you are half way there…

41. see the Passivhaus Trust website for
more information
www.passivhaustrust.org.uk www.passipedia.org