Passivhaus: What is it, and what has it got to do with me?

Underhill House: Seymour-Smith Architects

Passivhaus: What is it, and what has it got to do with me?

Midland Counties Regional GroupInstitution of Structural Engineers

David SharpeThomasons

adapted from Passivhaus Trust materials

25th November 2014

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 1994MSc Structural Design in 1995IStructE Part 3 CEng Exam in 2001Certified Passivhaus Designer in 2013

Certified Passivhaus Designer:

Individual Member:

Chartered Structural Engineer:

Thomasons:

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

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

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)

“I was working as a physicist. I read thatthe construction industry had experimentedwith adding insulation to new buildings andthat energy consumption had failed toreduce.

This offended me – it was counter to thebasic laws of physics. I knew that they mustbe doing something wrong.

So I made it my mission to find out what,and to establish what was needed to do itright.”

Dr Wolfgang Feist, Passivhaus Institut

Denby Dale – Photo: Green Building Store

Passivhaus History

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

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

Low Energy Buildings

The criteria for any Passivhaus in a central European climate is:

• Space Heating demand of ≤ 15 kWh/m2/yearor peak space heating load of ≤ 10 W/m2

• Space cooling demand of ≤ 15 kWh/m2/yearor peak space cooling load of ≤ 10 W/m2

• Primary energy demand ≤ 120 kWh/m2/yearincluding hot water, space heating & cooling, fans, lighting, appliances, computers, televisions, etc.

• Airtightness of ≤ 0.6 air changes / hour at 50Pa

Provable & Measureable

Figures show

that for

Passivhaus

the average

measured

heat energy

use is

15kWhr/m2/yr

How is it achieved?

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%

How is it achieved?

Modelling with Passive House Planning Package (PHPP)

Images: Passivhaus Institut, JPW Construction, Green Building Company, Simmonds.Mills

Passivhaus in the UKWe started quite late…

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.passivhaustrust.org.uk/projects/passivhaus_projects_map/

…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)

Passivhaus in the UK…but many projects have been completed

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

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.

What’s needed on site?

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 UKNorth Wales (2006/7)

Passivhaus in the UK

Canolfan Hyddgen, the first Non-domestic PH project in the UK

North Wales (2008)

Measured performance

Primary Energy: 80 kWh/(m².yr)

Space Heating: 14.8 kWh/(m².yr)

Internal temperatures never below 20 or over 26 C

Passivhaus in the UK

Plummerswood, GAIA Architects

Passivhaus in the UK

Bushbury Hill Primary School, Wolverhampton, Architype Architects

Passivhaus in the UK

Hadlow College Rural Regeneration Centre, Eurobuild

Passivhaus in the UK

Crossway, Kent, Hawkes Architecture Ltd

Passivhaus in the UK

Underhill House, Seymour-Smith Architects

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…

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

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

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.

Three layers of low-e glazing, insulated frames, insulated spacers and optimised insulation, typically with a U-value of 0.8W/m2K

Why use triple glazing?

Impact on Structural Engineering

Taking viewpoints from two structural engineers who have designed Passivhaus projects in the region:

Gary Corden, Senior Engineer, Building Structures, RambollCentre for Medicine, University of LeicesterArchitects: Associated Architects; Structural Engineers: Ramboll

Jonathan McIver, was Associate at Pryce & Myers, now Associate Director at constructureOakmeadow Primary School and Bushbury Hills Primary SchoolWolverhampton City CouncilArchitects: ArchitypeStructural Engineers: Pryce & Myers

Project Example:

Centre for Medicine, University of LeicesterAssociated ArchitectsRamboll

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.

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.

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.

Project Example:

Oakmeadow Primary School and Bushbury Hills Primary SchoolWolverhamptonArchitypePryce & Myers

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.

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.

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.

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.

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 thatdifferent to other buildings

Once you understand the concept, and know why thermal bridges etc. are important, you are half way there…

see the Passivhaus Trust website for more information

www.passivhaustrust.org.uk www.passipedia.org