Fabic in Schools by Niall Lowther

WORKSHOP ON THE PUBLIC SECTOR NZEB INTERIM SPECIFICATION

Niall Lowther MRIAI Department of Education & Skills

Introduction

NZEB Schools Research Projects

PH Schools Research Projects

WORKSHOP ON THE PUBLIC SECTOR NZEB INTERIM SPECIFICATION 30th January 2017

Energy Efficient Buildings

Maximise Solar Gains & Natural Light

Minimise Heat Losses

Integration of Highly Efficient Systems

Applying Public Sector NZEB Interim Specification


Building Fabric

Thermal Performance of Building Elements

• Walls • Floors • Roof • Glazing

Thermal Bridging

Air Permeability of External Envelope

Achieving Building Fabric Performance






Heat Loss through the Building Fabric

U-value

rate at which thermal energy is conducted through the building element

Lower u-value = better thermal performance

Units : W/m2K



Maximum average elemental U-values (W/m2K)

Fabric Element TGD Part L Dwellings

2011

TGD Part L Other than Dwellings

2008

DES TGD’s

Interim NZEB Specification

2017

Roofs -horizontal ceiling -slope -flat roof

0.16

0.16 0.20

0.16

0.20 0.22

0.16

0.16 0.16

0.15

0.15 0.15

Walls 0.21 0.27 0.27 0.18

Floor 0.21 0.25 0.25 0.15

Windows & Doors

1.60 2.20 1.80/1.6 1.4



Ground Floor:

150mm Concrete Slab

U-Value (calculated in accordance with ISO 13370)

55mm Insulation (λ=0.021 W/mK) = 0.25 W/m2K





External Walls: U-Value (calculated in accordance with ISO 6946)

Cavity

110mm Cavity 70mm Insulation (λ=0.020 W/mK) = 0.21 W/m2K

150mm Cavity 110mm Insulation (λ=0.020 W/mK) = 0.18 W/m2K

External Wall Insulation

230mm Insulation (λ=0.034W/mK) = 0.15 W/m2K



Roof Construction:



Windows:

NZEB Interim Specification

U-value = 1.4 W/m2K

G-Value = 40%

Light Transmittance = 71%



Thermal Bridging: Definition ISO 10211:2007(E) part of the building envelope where the otherwise uniform thermal resistance is significantly changed by • full or partial penetration of the building envelope by materials with a different thermal conductivity, and/or • a change in thickness of the fabric, and/or • a difference between internal and external areas, such as occur at wall/floor/ceiling junctions



Types of Thermal Bridging Repeating Thermal Bridges timber or steel studs; rafters; joists Geometric Thermal Bridges building form; corner of external wall; wall floor junction; eaves Constructive Thermal Bridges rsj penetrating a wall



Psi Value (linear) ψ = W/mK





TGD Part L 2008

To avoid excessive heat losses and local condensation problems, provision should be made to limit local thermal bridging, e.g. around windows, doors and other wall openings, at junctions between elements and at other locations.

Any thermal bridge should not pose a risk of surface or interstitial condensation and any excessive increase in heat loss associated with the thermal bridge should be taken account of in the calculation of average U-value.







Air Tightness :

Reduces Heat Loss through Convection

Reduces passage of moisture into the building fabric

Air Permeability (m3/(m2h) Gross internal area less than 250 m2

5

Air Permeability (m3/(m2h) Gross internal area greater than 250 m2

3



Air Tightness :

• “Red Line” Boundary

• Site Supervision

• Airtight “Champion”

• Testing



Conclusion:

• Achievable

• Implications for funding agents

• Improved build quality & comfort for occupants

• Building typology

• Implications for designers

• Contractor standard of workmanship

• Building users

Design

Fabic in Schools by Niall Lowther