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How to Deliver Near

& Zero Energy Homes

“Fabric First” case studies

Good Homes Alliance

Tom Dollard

Head of Sustainable Design

Pollard Thomas Edwards

@dollardtom

@ptearchitects

CONTENTS

Fabric First approach? What is it?

Case studies:

Virido – zero carbon development

Cygnus E-Smart House

Designed to perform? New book launched in November 2017

Pollard Thomas Edwards

PTE - 2016 stats

28 September 20173

Element or system Part L Notional Value (Baseline for TER) FABRIC FIRST for Zero Carbon?Passivhaus typical values dependent on form / PHPP

External walls 0.18 W/m2K <0.15 W/m2KParty walls 0.0 W/m2K 0.0 W/m2KFloor 0.13 W/m2K <0.15 W/m2KRoof 0.13 W/m2K <0.15 W/m2KWindows, roof windows, glazed rooflights and glazed doors

1.4 W/m2K (whole window value, double glazed)G-value = 0.63

0.85 W/m2K (whole window value, triple glazed)G-value = 0.5

Opaque doors 1.0 W/m2K 0.85 W/m2KSemi glazed doors 1.2 W/m2K 0.85 W/m2KAir tightness 5.0 m3/(h.m2) 1.0 m3/(h.m2) or 0.6 ach for passivhausLinear thermal transmittance

Psi values in Appendix R – 0.05 calculated Psi values in Appendix R – less than 0.04 calculated, (Psi external = <0.01)

Ventilation type “Natural” = System 1:intermittent extract fans, trickle vents, openingwindows

Mechanical = System 3(MEV) or System 4(MVHR)Opening windows but no trickle vents

Air conditioning None NoneHeating system Gas boiler with radiators. 89.5% efficient. Required?? If so, with heating coil in ventilation? Electric? Heat pump? CHP?Controls Time and temperature zone control with weather compensation. N/A

Hot water Stored hot water from boiler for houses (instantaneous combinationboilers for apartments). Thermostat controlled.

Renewable or low carbon = Solar Thermal / electric?

Primary pipework Fully insulated All pipework fully insulated – including valves, checked on siteSecondary space heating None NoneLow energy lighting 100% low energy lighting 100% low energy lighting – is this delivered in reality? LEDs.Renewables / Low Carbon N/A– but commonly PV to make up shortfall PV, solar thermal, Heat pumps, CHP

What is fabric first?(table adapted from table 4, Part L1 2013)

Differences

MINIMISING HEAT LOSSES = FABRIC DETAILING

A good building fabric consists of three key elements:

− Continuous insulation (low U-values)

− Minimal thermal bridging (low PSI-values)

− Continuous air barrier (low air permeability)

Walls

Roofs

Windows

Floors

Doors

ELEMENT LOSSES (U-VALUE, W/m2K)

TOTAL HEAT LOSS =

Junctions

Junction

THERMAL BRIDGE LOSSES (PSI-VALUES. W/m.K)

InfiltrationInfiltration

Infiltration

INFILTRATION AND VENTILATION LOSSES

+ +

Continuous Insulation� Key recommendations

O Choose a construction method that readily allows continuous insulation.

O Consider specifying high performance insulation at key junctions.

O Consider the construction sequencing and installation methods.

O Insulate party walls/floors and sheltered walls to the same standard as external walls and floors.

MINIMISING HEAT LOSSES = FABRIC DESIGN

Q. What is a thermal bridge?

Airtightness?Total space heating costs in an airtight building may be as much as 40% less than in a leaky one (BRE, Airtightness in Commercial and Public Buildings 2002, p.3 )

Figure of heat losses per P. Jennings, ‘Airtightness in Buildings’ Building for a Future Winter ‘00/’01

‘We are at the stage where it is likely that any further increase in thermal insulation levels would be ineffective until levels of airtightness in construction have improved considerably.‘

Niall Crosson, Ecological Building Systems

Pollard Thomas Edwards 28 September 20179

Back to Zero Carbon: Carbon offset Assessment for GLA – sliding scale…..

Image courtesy of SWECO

Improved Measures Cumulative on-site savings (%)

Incrementalcost increase

Incrementalcarbon offset

Cumulativecarbon offset

saving

External Wall & Roof 0.12 41.7% ? £17,834 £17,834

Triple Glazed Windows

0.9 45.30% ? £14,299 £32,132

Air Permeability 3 47.80% ? £19,732 £51,864

Thermal Mass Medium 51.70% ? £3,399 £55,263

Heating & DHW Communal boilers 57.90% ? £15,145 £70,408

PV + 104 No. PV panels 67%- 100% £106,000 £27,941 £98,349

Current strategy = 35% + offset payment

Maximising carbon savings

Image courtesy of Metropolis Green

Case study – Virido, Clay Farm, Cambridge

− Zero Carbon on site (code for sustainable homes code 5)− 209 homes + mixed use (retail/community centre), complete 2016-17− 50% affordable rent / 50% private – Cambridge City Council and Hill − LEAN: Enhanced fabric (passivhaus spec. with SIPS but did not achieve PH airtightness or thermal

bridging so not certified PH)− CLEAN = Gas CHP district heating− GREEN = Photovoltaic solar panels to make up to 100% reduction regulated energy.

Not just zero carbon operational energy but low embodied carbon materials, biodiversity, flooding, climate change adaptation, public realm, placemaking

Stage 2+3 report for planning

DETAIL

Energy strategy

FABRIC - SIPS Renewables – PV

Stage 6-7 Post Occupancy Evaluation

Virido, Cambridge Building performance monitoring

Site photos = phased completion during 2017


− Offsite timber panellised construction combined with offsite services in the E riser

− Passivhaus performance with solar thermal and electric heating/hot water

− With PV panels it is zero carbon− 4-6 week construction time− Completed prototype in Duxford, and

planning first 2 developments

Cygnus Homes, Duxford


Fabric

Air permeability 0.6 ach

Roof 0.1 w/m2/k

Walls 0.1 w./m2/k

Windows - Triple glazed (Rationel)

0.85w/m2/k

Ground Floor 0.1 w./m2/k

Psi values (external) Less than 0.01 w/mk(external)

Services

Heating Electric Radiators

Hot Water Solar Thermal Hot water / Electric Immersion

Ventilation MVHR or dc-MEV

ZC option Power PV - approx. 2Kwp

Cygnus Homes, E-smart House, Duxford

Image courtesy of Cygnum Timber FrameImage courtesy of Cygnus Homes

Image courtesy of Cygnum Timber Frame


Demonstration house layout – 2.5 storey, 3B5P, 130m2


Cygnus Homes demonstration house, Duxford

GHA Site visit on 12th October, 3pm Images courtesy of Cygnus Homes

Pollard Thomas Edwards 28 September 2017Designed to perform25

How to build zero carbon?

Attention to detail!


Do we need buildings to be completely zero carbon?

Why not minimise heat loads (passivhaus) and de-carbonise grid?

Why create power stations for every large site? E.g. CHP plants

Most appropriate strategy for each site / home, but generally advised toreduce heat/cooling load as much as possible:

1. Lean Fabric = best (passivhaus) with active ventilation system2. Clean Heating = Not gas. CHP only on district scale (500+)3. Hot water? WWHR, solar thermal/electric / PV ?4. Green Power = Renewable, smart electric e.g. PV and storage5. Easy to use controls / smart controls throughout.6. Design / Procurement / Construction method to ensure delivery

THANKYOU –questions / discussion @dollardtom

Conclusions/questions?

New book available from RIBA bookshops in November 2017

Diespeker Wharf 38 Graham Street London N18JX020 7336 7777 [email protected] @ptearchitects www.pollardthomasedwards.co.uk

Copyright in this document and all contents belongs to Pollard Thomas Edwards LLP (excluding only material reproduced from other sources where shown).

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