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Energy Efficiency E-modules - Guidance Application of Thermal Insulation to HVAC Services in Public Sector Buildings Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 2 CONTENTS 1 Introduction 3 2 Learning Objectives and Outcomes 3 2.1 Learning Objectives 3 2.2 Learning Outcomes 3 3 Overview and Principles of Thermal Insulation 4 3.1 Conduction 4 3.2 Convection 4 3.2.1 3.3 4 Thermal Convective Heat Transfer Coefficient Overall Heat Transfer Coefficient Thermal Insulation of HVAC Services 4 5 7 4.1 Scottish Building Regulations 7 4.2 Common Opportunities 8 4.2.1 Values, Flanges and End Caps 8 4.2.2 Hot Water Tanks 8 4.2.3 Plate Heat Exchangers 8 4.3 Common Factors in Installation Improvement Projects 9 4.4 Possible Risks 9 5 Useful Links and References 11 Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 3 1 Introduction This guidance follows the format of the e-module “Application of Thermal Insulation to HVAC Services in the Public Sector” and provides further details on the subjects covered in the module. Please note that module users working in a healthcare environment should always refer to the relevant Scottish Health Technical Memorandum (SHTM) prior to considering installation of the measures suggested in the module. The advice given in the SHTM may conflict with the advice given in this module, as it has been developed for the wider public sector. The relevant SHTM can be found on the Health Facilities Scotland website. 2 Learning Objectives and Outcomes 2.1 Learning Objectives The learning objectives for this module are to: Understand the benefits of thermal insulation for HVAC services; and Understand the applications of thermal insulation for HVAC services. 2.2 Learning Outcomes The learning outcomes for this module are to: Describe the principles of heat loss and the effects of thermal insulation; Identify opportunities for implementing thermal insulation to HVAC services installed in Scottish public sector sites and buildings; Be able to carry out an insulation survey of HVAC thermal insulation and identify opportunities for savings; Be able to prioritise the opportunities for applying thermal insulation of HVAC systems in public sector buildings; and Understand the key aspects in relation to thermal insulation of HVAC systems when building a business case. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 4 3 Overview and Principles of Thermal Insulation Whenever there is a temperature difference between two objects, or an object and a fluid, in close proximity, heat transfer will take place. There are three methods of heat transfer: Conduction is where heat moves through a solid object; Convection where heat is moved around in a fluid or gas, for example water or air; and Radiation where heat is transferred between objects by electromagnetic waves (primarily infrared). With regard to insulation, all three of these methods of heat transfer are important. Insulation can reduce heat conduction by slowing the rate that heat is passed from the source to the receiving medium. Convection can be reduced by slowing the movement of the air or liquid to slow the rate of heat movement. An example is stopping draughts. Radiation can be decreased by changing the nature of the radiating surface. This is why many surface insulation coverings have a shiny surface. The property of the surface that affects this is called emissivity. 3.1 Conduction Heat is transferred between two regions of a solid object with a temperature gradient. This leads to variation in temperature in two regions. An example is the heat transfer occurring through the metal in a pipe from inner diameter to outer diameter. The conductive heat transfer can be calculated using the following formula: Where Where Where Where Where is the heat transfer is the thermal conductivity of the material ( ⁄ ) is the heat transfer Area is the temperature difference across the material is the material thickness 3.2 Convection Heat is transferred between a solid object and a fluid at the object surface. The convention heat transfer can be calculated using the following formula: Where Where is the heat transfer is the convective heat transfer coefficient ( ⁄ Where Where is the heat transfer Area is the temperature difference across the material ) 3.2.1 Thermal Convective Heat Transfer Coefficient The thermal convective heat transfer coefficients are determined for any fluid depending on a number of factors including velocity and fluid mechanical properties. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 5 3.3 Overall Heat Transfer Coefficient The overall heat transfer coefficient can be calculated using the following formula: ⁄ ⁄ ⁄ ⁄ Where is the heat transfer per unit time Where Where is the contact Area of each side is the thermal conductivity of the material Where is the individual convection heat transfer coefficient for each fluid Where ⁄ ⁄ ⁄ is the wall thickness The value of U is representative of the convection with each fluid on either face of the solid and the conduction through the solid. Once U is calculated the overall heat transfer can be simplified using the following formula: Where Where is the heat transfer is the heat transfer per unit time Where Where is the contact Area is the temperature difference ⁄ Even a simple heat transfer calculation can be complicated, involving many variable parameters including the temperature of the surface, the temperature of the surrounding air and the properties of the materials. With regard to insulation, the simple reality is that insulating anything that is hot will lead to energy savings that will likely pay for itself in a short time period. The theory can be shown using an example. Figure 3.1 shows the annual saving from insulating 1 metre, of 80 millimetre diameter, heating pipework with different thicknesses of insulation, based on typical values and operating 24 hours per day all year round. From a loss of £77 per annum, adding just 5 millimetres of insulation would reduce the heat loss by over 60% (or £46). Adding a further 5 millimetres of insulation would reduce the loss by a further 13% (or a further £10). However increasing the insulation by a further 15 millimetres of insulation would only save an extra £5. The return diminishes for each incremental increase in insulation thickness, with the additional saving from increasing the insulation from 15 millimetres to 50 millimetres only saving an extra £8 per year. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 6 Figure 3.1 - Insulation Thickness and Heat Loss Cost This example shows it is better to have all hot surfaces insulated in some way, than only some insulated to a high level. In other words insulating a lot a little, is better than insulating a little a lot. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 7 4 Thermal Insulation of HVAC Services In 1999, the Thermal Insulation Manufactures and Suppliers Association (TIMSA) commissioned a study to assess the contribution of pipe insulation to possible further energy saving in the UK. It found that the use of pipe insulation was already saving in excess of 300 million tonnes of CO2 equivalent annually. However, there remained considerable opportunities to make further savings by insulating otherwise uninsulated pipes, with over 30% of the opportunity in the UK for retrofitting insulation in the area of commercial heating and hot water systems. A review of Scottish Public Sector Carbon Management Plans by the Carbon Trust found that the third most common improvement projects identified were related to insulation, including HVAC. Within the HVAC sector, installing valve insulation was found to have one of the best impacts with regard to return on investment and magnitude of carbon savings. 4.1 Scottish Building Regulations The Scottish Building Regulations stipulate when, where and how insulation must be applied in new installations. The Building Regulations Non-Domestic Technical Handbook Section 6.4.1 (Insulation of Pipes and Ducts) states that: “Pipes and ducts used for heating and cooling should be insulated to reduce uncontrolled heat loss in the case of the former and uncontrolled heat gain in the case of the latter.” This is not necessary where the pipes or ducts always contribute to the heating or cooling demands of the room or space, and the pipes or ducts are located at a height of 3 metres or less above the floor. Pipes that are used to supply hot water should be insulated against uncontrolled heat loss. This is to conserve heat in the hot water pipes between frequent successive draw-offs. Insulation for pipes and ducts should follow the guidance given for insulation thickness in BS5422, Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperature range -40°C to +700°C. For example the selection of insulation thickness should be representative of the environmental and fluid temperatures of the pipework. Recently, the Scottish Building Regulations have been extended to cover the insulation requirements for work on existing systems. The Building Regulations Non-Domestic Technical Handbook Section 6.4.3 (Work on Existing Buildings) states that: “Where a new boiler or hot water storage vessel is installed or where existing systems are extended, new or existing pipes, ducts and vessels that are accessible or exposed as part of the work should be insulated as for new systems. Replacement hot water storage vessels should be insulated as for new systems.” Where pipes, ductwork or vessels are being replaced in part, or being extended, the existing system should be improved to meet current standards. Guidance on the extent to which improvement should be made is given in Annex 6.G ‘Improvement to the energy performance of existing building services when carrying out building work’. It is recognised that complete insulation will sometimes not be possible, such as where services pass through or around structural building components for example floor joists, or where existing systems are wholly or partially retained as part of conversion works. In such cases, insulation should be fitted as for new systems as far as is reasonably practicable. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 8 Table 4.1 shows different types of insulation that can be commonly applied to HVAC services. Table 4.1 – Applications of different types of insulation Type of Insulation Maximum Temperature (°C) Application For hot services: Glass mineral fibre, aluminium foil faced, preformed 230 Internal, concealed services Glass mineral fibre, aluminium clad 230 Internal services, exposed to damage and external services open to the weather (joints sealed) 830 Internal, concealed services 830 Internal services, exposed to damage and external services open to the weather (joints sealed) Rock mineral fibre aluminium faced, preformed Rock mineral fibre aluminium foil faced, preformed, aluminium clad For services at ambient temperature or below: Polyethylene foam 80 Internal and external (joints sealed) 4.2 Common Opportunities 4.2.1 Values, Flanges and End Caps Although pipework is normally insulated, there remains a large opportunity for insulating valves, flanges and end caps. An exposed valve is equivalent to 1 metre of un-insulated pipe of the same diameter. It may be that they have never had insulation, or that it has been removed at some time in the past during maintenance and was not been reinstated or replaced. In this instance it is recommended that new jackets are installed which make replacement easy after maintenance tasks, for example Velcro or hook and eye fastening. The savings achievable will vary depending on the diameter of the pipework and the temperature of the water. Using standard rules of thumb, the cost savings from fitting a valve jacket in a school boilerhouse range from £3 for a 10 millimetre valve to £25 for a 150 millimetre valve. However, installing insulation in a building with extended hours of operation, such as a care home would lead to a quicker return on investment. In this example, the savings are over 3 times higher than in a primary school, with an annual saving of £95 for 150 millimetre valve. 4.2.2 Hot Water Tanks Hot water tanks are another common opportunity. Although the hot water tank will almost certainly be insulated, inspection hatches are often exposed, again due to insulation being removed at some time in the past during maintenance and was not reinstated or replaced. It is recommended that new jackets are installed with Velcro or hook and eye type fastenings. 4.2.3 Plate Heat Exchangers Another common opportunity is the plate heat exchangers. They may have been installed as part of an energy saving project, but they often do not have an insulation jacket which negates the benefit of their reduced size over hot water tanks. Once again it is recommended that new jackets are installed with Velcro or hook and eye type fastenings. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 9 A quick and relatively easy method of assessing the performance of existing insulation, or to assess whether inaccessible pipework is insulated, is to use a thermal imaging camera. The images in Figures 4.1 show a thermal image of insulated steam pipework. Figure 4.1 – Thermal image of insulated steam pipework The insulation is performing less well on the middle pipe and in certain areas the insulation has deteriorated quite considerably. In this case, it may more cost effective to undertake targeted replacement or upgrade sections of the insulation. 4.3 Common Factors in Installation Improvement Projects Opportunities for insulation can be prioritised based on a few factors: 1. 2. 3. 4. 5. 6. Safety. If a hot (or cold) surface is a risk to the occupants, insulation can be used as a control measure; High temperatures. The higher the temperature, the greater the heat loss, and the better the financial return from installing insulation; Longer building operating hours will lead to higher savings; Electrically or oil heated water. The cost of electricity and oil are significantly higher than for natural gas, meaning heat loss costs more in water systems heated in this way; Plant rooms that have external walls, floors and roofs. Heat is not actually lost until it leaves the building. Heat loss from an internal plant room will simply lead to uncontrolled heat gain in the adjacent spaces. Plant rooms that are external to the building or have external surfaces will offer higher savings from insulation; and External pipe work and ducts. Insulating external pipework and ductwork generally lead to higher savings due to the higher temperature gradient. Thermal insulation can also help protect the exposed surfaces from the weather, for example from corrosion and frost. 4.4 Possible Risks Three key risks need to be considered for installation improvement projects: health and safety; factors that could make implementation more expensive; and factors that could reduce the achievable savings. For example, if the surfaces to be insulated are at a higher vertical level, the contractor may have to use items that may increase the overall project costs, such as fall arrest systems, cherry picker hire, or scaffolding. Asbestos is a common issue, particularity during re-insulating projects. The presence of asbestos may make the project uneconomic, so reviewing the asbestos register is a priority when assessing the proposed project. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 10 Other risks include working near hot surfaces and working in confined spaces. Factors to consider that could affect the savings achieved against those predicted include: Being overly optimistic in the original assumptions to improve the business case. This is referred to as optimism bias and it is good practice to factor for this; A reduction in the operating hours of the system after the insulation has been installed; A fall in the cost of energy; and Investments in energy efficiency measures. Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 11 5 Useful Links and References Title Source Link Zero Waste Scotland - www.zerowastescotland.org.uk How to Implement Thermal Insulation (CTL145) The Carbon Trust www.carbontrust.com/media/147159/j8052_ctl145_how_to_imple ment_thermal_insulation_to_hvac_services_aw.pdf BS 5422:2009 Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperature range 40°C to +700°C Institute of British Standards www.bsigroup.co.uk TIMSA Guidance for Achieving Compliance with Part L Building Regulations – domestic and Non-Domestic Heating, Cooling and Ventilation Guide TIMSA www.timsa.org.uk/TIMSAHVACGuidance.pdf Building Standards Handbook 2013 – Non-Domestic Section 6.4 Insulation of Pipes Scottish Government www.scotland.gov.uk/Resource/0043/00435261.pdf Introduction to Heat Transfer The Heat Transfer Society www.hts.org.uk/downloads/introductiontoheattransfer.pdf How to implement thermal insulation (CTL145) The Carbon Trust www.carbontrust.com/media/147159/j8052_ctl145_how_to_imple ment_thermal_insulation_to_hvac_services_aw.pdf Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 12 BS 5422:2009 Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperature range 40°C to +700°C Institute of British Standards www.bsigroup.co.uk TIMSA guidance for achieving compliance with Part L of the Building Regulations Domestic and Non-Domestic Heating, Cooling and Ventilation Guide The Thermal Insulation Manufacturers and Suppliers Association www.timsa.org.uk Building Standards Handbook 2013 - Non Domestic Section 6.4 Insulation of pipes, ducts and vessels Scottish Building Standards www.scotland.gov.uk/Topics/Built-Environment/Building/Buildingstandards/publications/pubtech/th2013ndom6 Engineering Toolbox Engineering toolbox www.engineeringtoolbox.com/insulation-temperatures-d_922.html Application of Thermal Insulation to HVAC Services in Public Sector Buildings | 13