quinn building products thermal bridging at ecobuild 2016

How to save on construction costs with effective thermal bridging solutions

Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd

Introduction

Jason MartinSpecification Manager

[email protected]@QuinnBPLtd_Jason

Part of the technical services team at Quinn Building Productsw : quinn-buildingproducts.come : [email protected] : +44 (0) 286774 8866

Andrew LundbergBuilding Fabric Consultant

[email protected]

• Structural Design• Project Management• Product Technical & Specification

• NSAI Accredited Thermal Modeller• Building Fabric Consultant• Lecturer in Thermal Bridging and Passive

house design in DIT

mailto:[email protected]

mailto:[email protected]


About Quinn Building Products

• Quinn Building Products manufactures a wide range of building materials.

• Providing multi-product systems and blended product logistics

• Supported by an in-house team of technical experts.

SectorsQuinn Therm High Performance PIR InsulationQuinn Lite-Pac Versatile & light weight EPSQuinn Lite Aircrete Thermal BlocksQuinn Rooftiles Concrete Roof and Ridge TilesQuinn Precast Pre-cast Concrete ProductsQuinn Cement Bulk and Bagged CementQuinn Quarries Concrete Products & Aggregates

Quinn Tarmac Blacktop tarmacadam products


The Objectives

• What is a thermal bridge?

• Different types of thermal bridges.

• Psi-values and y-values.

• Part L1a, SAP 2012 & how

compliance is achieved for the

building fabric

• Solutions to thermal bridging using

Quinn Lite.


U-Values

U-Value = 1 / Resistance= 1 / 4.928= 0.202= 0.20W/m2K

KEY POINT: • U-values can only measure heat flow in 1-dimension, that is they only

estimate heat loss which travels through the building envelope perpendicular

to the internal surfaces!

• As we rely on U-values to estimate building fabric heat loss, we are missing

heat loss in the 2nd and 3rd dimension (reality!).

• The vast majority of SAP assessments are done using default values for

thermal bridging, which in many cases grossly over-estimate heat loss

from thermal bridging!


Thermal Bridge

A thermal bridge occurs

anywhere in the building

envelope where the otherwise

uniform flow of heat is altered

or disturbed due to a change in

the building fabric, or due to an

increase in internal or external

areas due to the building form.


Repeating vs. linear thermal bridges

Ceiling joists in cold pitched

roofs that are insulated at

ceiling level.

Ground floor joists in an

insulated suspended timber

ground floor.

INCLUDED IN THE U-VALUE!

INCLUDED IN THE U-VALUE!

INCLUDED IN THE PSI-VALUE!


Linear Thermal Bridges


Measuring Linear Thermal Bridges

Psi VALUE (Ψ)• A measurement of the additional heat loss at a junction,

measured in Watts, for every linear metre of that junction and one degree temperature difference between inside and outside.

• Determined by the assembly of the junction and the thermal conductivities of the materials used to construct the junction, as well as the measurement convention (e.g. SAP) used on the building.


Thermal Bridging In Part L1a

Under Part L1a (new dwellings), accounting for thermal bridging can be done by any one, or combination of, the following methods:

• Assign a global y-factor of 0.15W/m2K to the entire dwelling.

• Use default individual values from table K.1 of the SAP document.

• Adopt the DCLG approved construction details (ACD’s), and assign psi-values from Table K.1 of the SAP document.

• Use psi-values that have been developed by a competent assessor

POOR VALUES NOT BASED ON ANY SPECIFIC CONSTRUCTION TYPE OR U-VALUE RANGE

LITERALLY TWICE AS BAD AS VALUES FROM THE ACD’S

IN ALMOST ALL CASES ARE GROSS OVER-ESTIMATION OF HEAT LOSS FROM THERMAL BRIDGING

THE ONLY ROUTE TO PROJECT-SPECIFIC LOW ENERGY DESIGN & CERTIFICATION


Thermal Bridging In SAP

Compliance with Part L1a must be achieved by demonstrating that the building achieves a TER (Target Emission Rate) and TFEE (target fabric energy efficiency) at least as good as the reference dwelling of the same size. In terms of building fabric, what does this account for?

• U-values of opaque and transparent components, e.g. walls, floors, roof, windows, doors etc.

• Air permeability of the building fabric• Thermal mass• Exposed sides• Thermal bridging (y-factor)• Key point: Optimised efficient design involves the use of highly developed,

tested & certified junctions & their respective psi-values.


Measuring Linear Thermal Bridges

Y-factor: a single value which represents the sum of all linear thermal bridges in the building envelope as a function of the exposed thermal envelope

Y-Value = HTB / AHTB = transmission heat transfer coefficient from thermal bridging (W/K)A = Heat loss envelope area


-0.141

-0.149-0.007

0.018 0.027

0.037

Quinn Lite certified values

SAP values


Example 1

Average U-value of dwelling is 0.16 W/m2K

Envelope Area = 450 m2

No consideration for thermal bridges, therefore default Y-value = 0.15 W/m2K0.16 + 0.15 = 0.31 W/m2K

By using the default value, the SAP software estimates that 48% of total fabric heat loss is from thermal bridging!

The Impact Of The Y-value


Example 2

Average U-value of dwelling is 0.16 W/m2K


Accredited construction details & values from Table K.1 (SAP 2012)

Y-Value = 0.07 W/m2K0.16 + 0.07 = 0.23 W/m2K

By using the values from Table K.1 of the SAP document, it is estimated that 30% of total fabric heat loss is due to thermal bridging!

The Impact Of The Y-value


What’s The Solution?

• Continuity of insulation

• Good junction design, detailing &

specification

• USE OF PROJECT-SPECIFIC PSI

VALUES



Example 3

Average U-value of dwelling is, say 0.16 W/m2K


Bespoke Y-value calculated using ‘Quinn Lite Accredited Construction Details’

Y-value = 0.015 W/m2K0.16 + 0.015 = 0.175 W/m2K

By using Quinn Lite accredited details, fabric heat loss from thermal bridging is reduced to just 8.5%. This is optimal!


Avoidance of mould growth & increased comfort


Summary

• Using the default y-value of 0.15W/m2K will almost always have a significant &

detrimental impact on the heat loss of the proposed building and calculated FEE.

• Using the default y-value of 0.15 can involve the unnecessarily high specification of

other building fabric elements.

• Specifying and installing properly insulated junction designs will reduce the building’s y-

value, which will decrease capital and installation costs in other areas.

• By 2020, all buildings must be built to the nZEB standard. It will be extremely difficult to

achieve this standard using default psi values or y-values.

• We are mandated by Europe under the Energy Performance of Buildings Directive (EPBD

– 2010 recast) to deliver cost-optimal design solutions to our clients…there is no room

for guesswork and defaults in that!


• Visit us at stand 3039 to discuss your thermal bridging needs or use the Y-value calculator live!

• Check out the Y-value calculator at http://www.quinn-buildingproducts.com/resources/y-value-calculator/


Resources


Technical ServicesContact our Technical Team : t : +44 (0) 286774 8866e : [email protected]

[email protected]

Visit Our Stand : 3039 (Beside BRE Stand)Virtual Reality DemoIPad Competition Mini Presentations

Or visit : quinn-buildingproducts.com/thermalbridging

quinn building products thermal bridging at ecobuild 2016

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