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Quinn Building Products Thermal Bridging at Ecobuild 2016
- 1. How to save on construction costs with effective thermal bridging solutions
- 2. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd Introduction Jason Martin Specification Manager Jason.martin@quinn-buildingproducts.com @QuinnBPLtd_Jason Part of the technical services team at Quinn Building Products w : quinn-buildingproducts.com e : technical@quinn-buildingproducts.com t : +44 (0) 286774 8866 Andrew Lundberg Building Fabric Consultant andrew@passivate.ie www.passivate.ie • Structural Design • Project Management • Product Technical & Specification • NSAI Accredited Thermal Modeller • Building Fabric Consultant • Lecturer in Thermal Bridging and Passive house design in DIT
- 3. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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. Sectors Quinn Therm High Performance PIR Insulation Quinn Lite-Pac Versatile & light weight EPS Quinn Lite Aircrete Thermal Blocks Quinn Rooftiles Concrete Roof and Ridge Tiles Quinn Precast Pre-cast Concrete Products Quinn Cement Bulk and Bagged Cement Quinn Quarries Concrete Products & Aggregates Quinn Tarmac Blacktop tarmacadam products
- 4. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
- 5. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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.
- 6. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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!
- 7. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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.
- 8. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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!
- 9. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd Linear Thermal Bridges
- 10. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd Linear Thermal Bridges
- 11. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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.
- 12. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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
- 13. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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.
- 14. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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 / A HTB = transmission heat transfer coefficient from thermal bridging (W/K) A = Heat loss envelope area
- 15. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd -0.141 -0.149 -0.007 0.018 0.027 0.037 Quinn Lite certified values SAP values
- 16. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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/m2K 0.16 + 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
- 17. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd Example 2 Average U-value of dwelling is 0.16 W/m2K Envelope Area = 450 m2 Accredited construction details & values from Table K.1 (SAP 2012) Y-Value = 0.07 W/m2K 0.16 + 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
- 18. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd What’s The Solution? • Continuity of insulation • Good junction design, detailing & specification • USE OF PROJECT-SPECIFIC PSI VALUES
- 19. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd What’s The Solution?
- 20. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd What’s The Solution?
- 21. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd What’s The Solution?
- 22. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd What’s The Solution? Example 3 Average U-value of dwelling is, say 0.16 W/m2K Envelope Area = 450 m2 Bespoke Y-value calculated using ‘Quinn Lite Accredited Construction Details’ Y-value = 0.015 W/m2K 0.16 + 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!
- 23. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd Avoidance of mould growth & increased comfort
- 24. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd 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!
- 25. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd • 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/
- 26. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd Resources
- 27. Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd Technical Services Contact our Technical Team : t : +44 (0) 286774 8866 e : technical@quinn-buildingproducts.com Jason.Martin@quinn-buildingproducts.com Visit Our Stand : 3039 (Beside BRE Stand) Virtual Reality Demo IPad Competition Mini Presentations Or visit : quinn-buildingproducts.com/thermalbridging
Editor's Notes
- Objectives: As mentioned before, the objective of this CPD is to highlight how thousands of pounds can be saved by reducing heat loss through thermal bridges instead of specifying renewable technologies. Learning aims: We’ll do this by demonstrating the importance of insulation, by distinguishing between types of thermal bridge, by explaining the impact of thermal bridges and how to reduce the heat loss through them.
- Heat loss: Steady-state heat losses and gains are determined by the heat transfer through the building’s envelope. The heat losses and gains determine the capacity of the heating or cooling system required to maintain the inside of the building at the designed condition. Which in turn impact capital and running costs. Thermal Transmittance, U-value: Steady-state heat losses and gains are determined by the building envelope’s U-value, the thermal transmittance (W/m2.K). The heat loss through the component (per unit of temperature difference between internal and external conditions) is calculated by multiplying the U-value by the area of the component. Adding insulation reduces the U-value of the component, and therefore reduces the heat loss through the component. The U-value takes account of repeating thermal bridges. However, linear thermal transmittances (Ψ-values) arise at junctions between different components (more about thermal bridges next).
- As airtightness levels increase and U-values fall, the heat lost through thermal bridges becomes more important. What is a thermal bridge: A thermal bridge is a localised area of the building envelope with considerably higher heat transfer than the surrounding material. How do thermal bridges ‘happen’: Thermal bridges occur when a conductive component of the build, passes through the building envelop and its insulation. A path of lesser resistance is created through the insulation, which allows heat to pass through the thermal barrier. Factors: The rate of heat transfer through a thermal bridge depends on several factors; * The conductivity of the material which passes through the insulation. * The cross sectional area of the conductive component. * The temperature either side of the thermal bridge. * The ease at which heat can pass into and out of the thermal bridge.
- There are three types of thermal bridge, we will go into more detail in the following slides.
- Examples of repeating thermal bridges; Ceiling joists in cold pitched roofs that are insulated at ceiling level. Ground floor joists in an insulated suspended timber ground floor.
- Speaker to expand: Examples of construction details that give rise to linear thermal bridges.
- Speaker to expand: Examples of construction details that give rise to linear thermal bridges, when floor meets wall or wall meets roof.
- Linear thermal transmittance, Ψ-value: The units of linear thermal admittance, psi-value are W/m.K. It is used to calculate the heat loss through non-repeating thermal bridges, which can occur at the junctions of different building elements, such as a wall joining a roof. In additions to heat loss, such junctions can create issues with condensation and mould growth. Psi-values are used to calculate the y-values for use in the SAP calculations. Psi-values can only be calculated using thermal modelling software or by using ‘approved’ details and the given psi-value.
- Linear thermal transmittance, Ψ-value: The units of linear thermal admittance, psi-value are W/m.K. It is used to calculate the heat loss through non-repeating thermal bridges, which can occur at the junctions of different building elements, such as a wall joining a roof. In additions to heat loss, such junctions can create issues with condensation and mould growth. Psi-values are used to calculate the y-values for use in the SAP calculations. Psi-values can only be calculated using thermal modelling software or by using ‘approved’ details and the given psi-value.
- Linear thermal transmittance, Ψ-value: The units of linear thermal admittance, psi-value are W/m.K. It is used to calculate the heat loss through non-repeating thermal bridges, which can occur at the junctions of different building elements, such as a wall joining a roof. In additions to heat loss, such junctions can create issues with condensation and mould growth. Psi-values are used to calculate the y-values for use in the SAP calculations. Psi-values can only be calculated using thermal modelling software or by using ‘approved’ details and the given psi-value.
- Transmission heat transfer coefficient, HTB: The length of each thermal bridge is measured and multiplied by its respective psi-values. The sum of all of these is known as the transmission heat transfer coefficient, HTB. The unit is W/K.
- Example of using the default y-value of 0.15 W/m2K.
- Example of using a y-value provided by accredited construction details, of 0.08 W/m2K.
- More detail in the following slides.
- Image on the left shows heat lost due to the linear thermal bridge created when floor meets wall, with a typical dense block inner leaf detail. Image on the right shows thermal bridge solution using Quinn Lite thermal block.
- Speaker to expand: This figure shows the thermal bridge created when two spaces of different design temperature requirements are adjacent to one another, such as the colder, unheated attic and a heated bedroom, when celling/floor meets wall. Quinn Lite provides the thermal break between the two spaces.
- Speaker to expand: The thermal image effectiveness of the effectiveness of using Quinn Lite products.
- Speaker to expand: This is an example of using a bespoke y-value, calculated using Quinn's construction details, of 0.015 W/m2K. A massive reduction in the overall amount of calculated heat loss when compared to the default value of 0.15, or the accredited construction detail y-value of 0.08 W/m2K.
- Summary, to be kept concise. However, go into more detail about how massively reduced calculated heat losses and properly insulated buildings and thermal bridges can lead to avoiding costly renewable plant such as biomass boilers.