Insulation is key for energy efficient homes

Energy efficiency is a huge focus for the UK government in its drive to reduce carbon emissions, while businesses and residents are keen to mitigate rising energy costs. Insulation can play a crucial role in preventing heat loss, corrosion of pipework and condensation, so it’s vital that plumbing and heating engineers are familiar with the standards, such as the updated BS 5422, which covers insulation of building services.

Why is the new standard important?

Proper installation and performance of pipe insulation is essential to maximise efficiency and safety, which is why there is an extensive set of standards and regulations that are overseen by governmental and industry organisations.

The British Standards Institution’s (BSI) BS 5422 specifies how to use thermal insulation materials for pipes, tanks, vessels, ductwork and equipment. This helps designers, specifiers, contractors and thermal insulation manufacturers to work out the minimum insulation thickness needed to control heat losses and gains from building services. The standard covers operating temperatures from 40°C to +700°C in domestic, non-domestic and commercial buildings, so will be applicable in almost every setting that British installers and engineers work on.

What is it intended to do?

BS 5422 addresses a range of applications, including:

• conservation of energy for both cooled and heated systems
• preventing slow freezing of contents
• controlling condensation on cold surfaces
• protecting personnel from exposure to extreme surface temperatures
• managing process or service temperatures
• limiting the effects of a system on indoor building temperature.

UK pipe insulation standards and regulations cover a wide range of requirements, including:

• Insulation materials: specifications for materials such as mineral wool, elastomeric foam, plastic foams and calcium silicate.
• Insulation thickness: minimum insulation thickness mandated for pipe diameters and temperature ranges.
• Installation procedures: proper techniques for securing, sealing and covering insulation materials.
• Testing and certification: standards for evaluating insulation product performance through testing.
• Health and safety: requirements to minimise risks such as fire hazards, corrosion, surface condensation and other dangers.
• Energy efficiency: stricter limits on heat loss to reduce energy waste and carbon emissions.

Compliance with UK pipe insulation standards is required for new building construction, but it is also encouraged for retrofit programmes of existing buildings.

What has changed?

The latest edition of the standard, BS 5422:2023, came into effect on 30 June 2023, replacing the 2009 version. For new projects, including those with planning permission granted after this date, BS 5422:2023 applies. However, for projects where tender documentation was issued or contracts were awarded before the update, BS 5422:2009 continues to apply.

“While the minimum performance requirements of BS 5422:2023 remain the same as the 2009 edition, the standard now features enhanced performance tables for certain applications,” explains Will Wigfield, HVAC and fire protection product manager at Rockwool. “While compliance with these enhanced tables is optional, they are presented as the default option. Should a specifier wish to continue using the base level performance tables, this must be noted in their specification.

“The standard now covers district heating networks and provides maximum permissible heat loss figures for this application.”

The updates to BS 5422 also included a move from national fire classification of insulation material to the European system, which will align current building regulations and the relevant harmonised product standards for HVAC insulation. According to BSI, Euroclass fire ratings give a more comprehensive and clear definition of the behaviour of materials exposed to fire than the more limited legacy BS 476 (British Standard Fire Tests).

“The Euroclass system determines a product’s fire performance by measuring a comprehensive set of characteristics, including ignitability, flame spread, heat release, smoke production and propensity for producing flaming droplets or particles,” explains Wigfield. “The classifications run from A1 to F, with products achieving A1 and A2-s1, d0 typically defined as non-combustible.”

Tables have also been revised and simplified where possible and higher thermal conductivity values for obsolete or rarely used insulation materials have been removed, with single wall plastic pipes classified as having no insulative value of their own.

Choosing the right material

The changes to BS 5422 have been positively received by the industry, because the introduction of simplified tables has made the specification process easier. The thermal conductivity values in the new standards are also based on the most commonly used insulation materials. In the UK, the thermal performance of pipe insulation is typically measured using the U-value, which indicates the rate of heat transfer through a material, and is calculated based on the insulation’s thickness and its thermal conductivity (lambda value), with lower U-values signifying better insulation performance.

“It’s important to note, however, that the thermal performance of some insulation materials deteriorates over time,” says Wigfield. “In such cases, an aged thermal performance is declared, which typically takes the form of a ‘time averaged’ lambda value over 25 years.”

The thermal performance of material such as stone wool does not change over time, so it’s important for installers to bear this in mind when deciding which material to use, based on the expected lifespan of the building or HVAC installation.

“When choosing insulation, plumbing and heating engineers need to make sure products are suitable for all weather conditions and that they include UV protection,” says David Smith, founder of Primary Pro and Condensate Pro. “Engineers need to take care not to damage insulation in transit or storage as this can impact its efficiency.

“It’s also important for engineers to remember that BS 5422 is for reference only and the guidance mainly applies to internal insulation,” he adds. “When engineers are specifying external insulation for heat pumps and condensate piping, it’s essential that they use products that can withstand all types of weather to ensure thermal efficiency.”

Thermal bridging

Further guidance to help avoid thermal bridging has been included in the updated standard to avoid pipe supports and fixtures being overlooked during insulation calculations.

The standard states that load-bearing insulation should be used between the pipes and any support or fittings to avoid a gap in the insulation caused by compression of the material.

“When it comes to clips, it’s essential that they are fitted on the outside of the insulation,” says Smith. “If they are clipped directly onto the pipe, insulated over the top and secured with tie wraps, moisture will be able to get in between the gap and impact thermal conductivity. Every 1% of moisture ingress on external insulation will increase thermal conductivity by 7.5%, so if it doesn’t have a decent water-resistant coating this will have a massive impact on the insulation’s efficiency. Ensuring joints and gaps are sealed correctly is just as important as the insulation.

“Making sure all insulation is correctly installed and maintained is the key to maximising efficiency. Therefore, maintenance of insulation is vital over the lifetime of the heat pump, particularly external pipes, so when engineers are servicing heat pumps it is essential to check the external insulation.”

Other structural elements, including stiffening rings, should be insulated externally to prevent thermal bridging. Pipe support inserts have historically been made from wood, and although they successfully support pipes and protect insulation, wood is combustible and doesn’t provide the thermal performance required by BS 5422.

“Pipe supports made from insulating non-combustible materials, such as stone wool, have now been introduced, which ensure that the fire classification of the system will not be reduced while also complying with the requirements of BS 5422,” adds Wigfield.

“Overall, the revised standard brings the insulation parameters for HVAC systems in line with current building regulations, making it easier to specify the appropriate insulation needed.”

THREE STEPS TO TAKE NEXT

1. Get to know the standard You can access BS 5422, and other British Standards, through bsol.bsigroup.com. It can also be accessed for free through your library.
2. Talk to your suppliers Insulation manufacturers are up to speed on the latest guidance and can help you specify the right material and thickness for your job. Some firms, including Rockwool, have developed their own CPD materials to help installers apply the new standard.
3. Talk to your customers Make your customers aware that correct specification and fitting of insulation in their building is a vital tool for saving money and improving sustainability.