How to Save Money When Buying Phenolic Insulation Board

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Insulation is a crucial element in any construction project, and selecting the right insulation board can have a significant impact on a building's energy efficiency and overall performance. Kingspan is a leading manufacturer of insulation boards, offering a range of products designed for various applications. In this blog, we will discuss how to choose the right Kingspan insulation board for your construction project.

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Kingspan is one of the leading manufacturers of thermal and acoustic insulation in the UK. The company is renowned for its high-quality products and innovative solutions, which have made it a popular choice among contractors, architects, and builders alike. Kingspan's insulation boards are known for their excellent performance, durability, and ease of installation, making them a preferred choice for a wide range of applications in the construction industry. The company is also committed to sustainability and has developed a range of eco-friendly insulation products, which have helped it to maintain its position as a market leader in the UK.

Here are some of Kingspan's innovative products:

This is a range of ultra-thin insulation boards that offer excellent thermal performance with a thickness that is up to 70% thinner than traditional insulation materials.

Here is the list of products from Kingspan's Kooltherm K-range, along with a brief description of each:

Kingspan Kooltherm K103 Floor Insulation Board

Kingspan Kooltherm K103 Floor Insulation Board is an unbeatable floor solution with no equivalent to K103 superior thermal performance designed for suspended floors, ground supported floors and underfloor heating systems. Kooltherm K103 is manufactured with a blowing agent that has zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP).

K103 is manufactured to the highest standards under a management system certified to ISO : .

The use of Kooltherm K103 (in thicknesses of 25 - 150 mm) is covered by BBA Certificate 16/. Most commonly used thicknesses for Kingspan Kooltherm K103 Floor Insulation Board in the UK are 25mm, 30mm, 40mm, and 50mm.

 

Kingspan Kooltherm K106 Full Fill Cavity Board

Kingspan Kooltherm K106 Full Fill Cavity Board is a premium performance rigid fibre-free phenolic insulation core factory bonded to a water-tight, vapour-open polypropylene fleece and to a inner facing of a low emissivity composite foil.It has excellent fire performance and is suitable for buildings up to 18 metres in height. The most common thicknesses used in the UK are 90mm, 100mm, and 115mm.

The product can also help achieve higher Building Regulation standards and reduce carbon emissions.

The average cost per square metre ranges from £35 to £45. It is recommended to obtain a quote from a supplier to get an accurate price for a specific project.

 

Kingspan Kooltherm K107(K7) Pitched Roof Board

Kingspan Kooltherm K107 (K7) Pitched Roof Board is a premium performance insulation board designed for use in pitched roofs, specifically as an underlay beneath tile or slate coverings.

It is commonly used in thicknesses of 50mm and 120mm in the UK and has a cost range of £24-£35/m².

 

 

 

 

 

 

Kingspan Kooltherm K108 Partial Fill Phenolic Cavity Board

 Kingspan K108 Partial Fill Phenolic Cavity Board is an insulation product specifically designed for use in cavity walls. The board is made of a high-performance rigid thermoset phenolic insulation core, which is sandwiched between two layers of low-emissivity foil facing. This construction provides excellent thermal insulation while also preventing heat loss through radiation.

The board is available in various thicknesses, and its commonly used thickness in the UK is 90mm. The K108 Partial Fill board is easy to install and helps to improve the energy efficiency of buildings, reducing heating costs and carbon emissions.

 

 

Kingspan Kooltherm K110 Soffit Insulation Board

  Kingspan Kooltherm K110 Soffit Insulation Board is an advanced soffit rigid phenolic insulation sheet with a thermal conductivity of 0.019 W/mK used for an extremely thin structural ceiling (soffit) construction. It has a fibre-free rigid thermoset phenolic insulation core, which provides excellent thermal performance with a low profile. The board is easy to cut and fit and has a foil facing for enhanced insulation performance.

It is commonly used in commercial and residential buildings to improve energy efficiency and reduce heat loss.

Its typical thickness ranges from 65mm to 85mm, and the price per square metre can vary depending on the thickness and quantity purchased.

 

Kingspan Kooltherm K110 PLUS Soffit Insulation Board

Kooltherm K110 PLUS Soffit Insulation Board is a high-performance insulation product designed specifically for insulating the underside of concrete and masonry roofs or soffits. It has a low thermal conductivity and a high compressive strength, making it ideal for use in areas with high loads.

This insulation board is made from a closed-cell phenolic foam core with a glass tissue facing on both sides, providing excellent thermal insulation and fire performance.

Kooltherm K110 PLUS Soffit Insulation Board is commonly available in thicknesses of 71mm to 126mm and typically costs around £60 to £80 per square metre.

 

Kingspan Kooltherm K112(K12) Framing Board

 Kingspan Kooltherm K112 is used for timber and steel framing applications, offering high thermal performance in a slim profile.

It is commonly used in thicknesses of 50mm and 60mm in the UK and has a cost range of £23-£34/m².

Framing boards are lightweight insulation panels that are easy to transport, handle and install. 

The use of Kingspan Kooltherm® K112 is covered by BBA Certificate 16/. 

Framing board is an eco-friendly product that can be used to control potential condensation problems, if combined with a vapour resistant layer placed on the warm side of the insulation.

 

Kingspan Kooltherm K15 Rainscreen Board

Kingspan Kooltherm K15 is designed for use in rainscreen cladding systems, providing excellent thermal performance and fire resistance. It is commonly used in thicknesses of 60mm and 80mm in the UK and has a cost range of £50-£70/m². 

Kooltherm K15 is commonly used as insulation for rainscreen cladding systems with non-proprietary external finish, rainscreen cladding systems with terracotta clay tile external finish and rainscreen cladding systems on steel frames. 

Kingspan Kooltherm® K15 is manufactured to the highest standards under a management system and is covered by BBA Certificate 14/.

 

 

Kingspan Kooltherm K118 Insulated Plasterboard

Kingspan Kooltherm K118 combines plasterboard with insulation, providing a slim profile and high thermal performance.Kingspan Kooltherm K118 range is a fibre-free rigid phenolic thermoset insulation core with a certified thermal conductivity (lambda value) of 0.019W/mK bonded to a premium 12.5mm plasterboard. It is commonly used in thicknesses of 27mm and 37.5mm in the UK and has a cost range of £35-£55/m².

These easy to install and decorate premium insulation panels are suitable for new build and refurbishment projects.

The insulation core and facings used in the manufacture of Kingspan K118 resist attack by mould, fungi, bacteria and microbial growth.

 

Kingspan Kooltherm K5 External Wall Board

This board is designed for use in external walls, and offers excellent thermal performance with a thermal conductivity as low as 0.022 W/mK.

In the UK, the most common thickness used is 90mm and 100mm, and the cost varies depending on the supplier and quantity ordered.

Kooltherm K5 External Wall Board in the UK is around £50-70 per m2. It is available in various thicknesses ranging from 20mm to 70mm. Using Kooltherm Kingspan K5 a higher insulation value is achieved with a thinner board thickness than with other insulation materials (such as EPS, XPS and mineral wool). K5 is not cheap, but it is worth using because better insulation material means lower heating bills.

 

 

Overall, Kingspan's Kooltherm K-range offers a wide range of products for various applications, providing excellent thermal performance in slim profiles. The cost of each product can vary depending on the thickness and application, but they are generally considered to be premium products due to their superior insulation properties.

 

 

Kingspan TW50 Thermawall Cavity Wall Insulation Board

Kingspan TW50 Thermawall Cavity Wall Insulation Board is a high-performance cavity wall insulation board with a fibre-free rigid thermoset polyisocyanurate (PIR) core designed for partial fill masonry cavity walls.
It is commonly used for insulating walls and has a thermal conductivity (lambda) value of 0.022 W/mK.

The typical thickness range for TW50 is 40-100mm, with a cost per m2 ranging from £12-£20 depending on thickness. 

TW50 Kingspan is a lightweight, easy to handle and install cavity wall board which can be readily cut by bricklayer using a sharp knife.

This reflective, low emissivity aluminium foil surface improves the thermal resistance of any unventilated cavity adjacent to the TW50 board.

 

 

Kingspan Therma TP10 PIR Insulation

This is a general-purpose insulation board commonly used in walls, roofs, and floors. It has a low thermal conductivity and is available in thicknesses ranging from 25mm to 150mm. The price per m2 can vary depending on the thickness, but it typically ranges from £10-£25. The insulation core and facings of Kingspan Thermapitch TP10 resist attack by mould and microbial growth, and do not provide any food value to vermin.

TP10 PIR Board is chemically inert and safe to use manufactured with a blowing agent that has zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP). ThermaPitch TP10 Insulation Pitched Warm Roof Board is thermally efficient, as determined by using long-term thermal resistance values called R-Value.

 

Kingspan Thermawall TW55 PIR Insulation

Kingspan Thermawall TW55 PIR Rigid Fibre-Free Insulation Board is an insulation board with certified thermal conductivity of 0.022 W/mK used between studs or as an insulating sheathing material for steel and timber framing wall applications.
The typical thickness range for TW55 is 20-150mm, with a cost per m2 ranging from £20-£45 depending on thickness.

Kingspan Thermafloor TF70 PIR Insulation

Thermafloor TF70 PIR Insulation is a polyisocyanurate (PIR) fibre-free rigid insulation board with certified thermal conductivity of 0.022 W/mK used to insulate solid concrete, suspended ground floors and for use with underfloor heating systems.
It is typically used for insulating walls, floors, and roofs where a high level of thermal insulation is required. The typical thickness range for TF70 is 20-150mm, with a cost per m2 ranging from £18-£60 depending on thickness.

Kingspan Thermaroof TR24 Flat Roof Insulation Board

Kingspan Thermaroof TR24 is a high-performance flat roof insulation board suitable for use in built-up, single-ply, and green roof systems. It is made of rigid PIR foam insulation core faced with a coated glass tissue on one side and bitumen-coated glass tissue on the other side. The board provides excellent thermal insulation and helps to reduce heat loss in commercial and residential buildings. It is lightweight, easy to handle, and cut to fit around obstacles. The most commonly used thicknesses for this product in the UK are 100mm and 120mm. The price per m2 varies depending on the thickness and quantity purchased. 

Kingspan Thermaroof TR24 achieves a resistivity greater than 300 MNs/gm, when tested in accordance with BS EN : . Flat Roof Insulation Board TR24 should always be installed over a vapour control layer or sealed metal deck.

If correctly installed, Kingspan Thermaroof® TR24 can have an indefinite life.

 

Kingspan Thermaroof TR26 Flat Roof Board

Kingspan Thermaroof TR26 is a high-performance insulation board designed for use on flat roofs. The board is made of rigid polyisocyanurate (PIR) foam, which provides excellent thermal insulation. It has a low thermal conductivity, making it very effective at reducing heat loss from buildings.

The TR26 board is typically used in new construction or refurbishment projects and is suitable for use in a variety of flat roof applications, including mechanically fixed single-ply membrane systems, as well as built-up felt and mastic asphalt systems.

Common thicknesses for TR26 range from 25mm to 150mm, with prices per m2 varying depending on the thickness and supplier.

 

 

Kingspan Thermaroof TR27 Flat Roof PIR Board

Kingspan Thermaroof TR27 Flat Roof PIR Board is a PIR, flat-roof insulation board that is used on roofs waterproofed with fully-adhered, single-ply, partially-bonded, built-up felt, mastic asphalt or cold liquid applied waterproofing. It is made of a rigid PIR foam core with a composite foil facing on both sides.

The board is designed to be installed directly onto a flat roof deck, providing excellent thermal insulation and reducing heat loss. It is commonly used in commercial and industrial buildings, as well as in residential properties.

The thickness of the board can vary depending on the required insulation level, but it typically ranges from 25mm to 130mm. The cost per square metre of the Kingspan Thermaroof TR27 board can vary depending on the thickness and quantity purchased, but it generally ranges from £20 to £45.

 

Kingspan Thermaroof TR31 Plywood Flat Roof Insulation

Kingspan Thermaroof TR31 Plywood Flat Roof Insulation is a high-performance insulation board designed for use in flat roofs with a waterproof plywood deck. It features a thermoset fiber-free rigid insulation core, faced on both sides with a low-emissivity composite foil.

The insulation board provides excellent thermal insulation with a thermal conductivity of 0.022 W/mK.

The board is available in a range of thicknesses from 56mm to 126mm and is commonly used in commercial and industrial buildings.

 

 

 

 

Overall, Kingspan PIR offers a wider range of product options, including flat roof boards, pitched roof boards, cavity wall boards, and floor insulation boards.

Kingspan GreenGuard range offers 3 types of extruded polystyrene with different flooring loads in different grades called Greenguard - GG300, GG500 and GG700. Kingspan GG type of insulation material is formed with polystyrene polymer using an extrusion process. The XPS has a high R-value, good moisture resistance and high structural strength. Just like EPS, XPS is made of 98% air and just 2% plastic.
Rigid XPS Insulation (Kingspan Styrozone) is a fibre-free rigid extruded polystyrene (XPS) insulation board with high compressive strength (stress) for specialist applications such as basements, car parks, inverted roofs and heavy-duty commercial, industrial and cold store flooring.

Kingspan XPS foam boards are the most popular when it comes to high quality insulation for roofing, below grade applications, commercial and recreational vehicle insulation. This is because it features a closed-cell construction. XPS might need a slightly increased thickness to reach the same intended U-value, but can offer a more robust and flexible solution as it can be positioned above or below the DPM and is resilient if exposed to moisture. It is available for a variety of applications including sheathing, foundation, under slab, re-siding, commercial roofing, under road plaza deck and commercial walls. It also is suitable for use under high load pavement, such as floors. XPS is usually avoided in areas where materials with less density are needed or where the material, which is not produced below a certain density, is not applicable.
Kingspan XPS is aslo frequently used in basements as well as foundation walls. Closed cell insulation boards are also suitable for many demanding and varied insulation applications including flat roof applications given the minimal moisture absorption. In these environments, XPS provides proven performance. Panels are available in various thicknesses (30mm, 50mm, 80mm and 100mm), so you can tailor the efficiency to suit your requirements.

 

OPTIM-R E ROOFING SYSTEM

This is a vacuum insulated panel (VIP) system that provides outstanding thermal performance with a thickness of only 20mm. It is designed specifically for flat roofs and can help to reduce the overall thickness of the roofing system.

OPTIM-R E Roofing System from Kingspan has become popular for several reasons:

1.Outstanding thermal performance
The system is based on vacuum insulation panel (VIP) technology, which provides outstanding thermal performance with a thermal conductivity as low as 0.007 W/mK. This means it can achieve the required U-values with a much thinner insulation layer compared to traditional insulation materials.

2.Ultra-thin design
The system has a thickness of only 20mm, which means it takes up less space and allows for more headroom in buildings.

3.Resistant to moisture
The VIPs used in the system are resistant to moisture, which means they won't degrade over time or lose their insulating properties.

QUADCORE EVOLUTION ROOF PANELS

You will get efficient and thoughtful service from Langfang Clear Chemical.

These are insulated roof panels that feature Kingspan's QuadCore Technology, which provides excellent thermal performance and fire protection. They are also lightweight and easy to install.

QuadCore Evolution Roof Panels from Kingspan have become popular for several reasons:

1. Durability
The panels are made with high-quality materials that are designed to last for many years, making them a long-term investment for building owners.

2. Lightweight 
Despite their strength and durability, the panels are lightweight and easy to handle, which makes installation quicker and easier.

3. Aesthetics
QuadCore Evolution Roof Panels are available in a range of colours and finishes, which means they can be customised to suit a variety of architectural styles and design preferences.

 

TEK CLADDING PANELS

These are insulated cladding panels that are designed for use in both roofs and walls.
The TEK Cladding Panel comprises 142 mm or 172 mm thick Structural Insulated Panels (SIPs) connected with a unique jointing system.

The panels themselves consist of a high performance rigid urethane insulation core, sandwiched between two layers of Oriented Strand Board type 3 (OSB/3).

During manufacture, the insulation core of the TEK® Building System panels is autohesively bonded to the OSB/3 facings.
This process provides more reliable and superior adhesion than the secondary bonding process used in the manufacture of most other SIPS.
Kingspan TEK® Building System panels are a structural composite. This composite assembly provides stiffness, strength and predictable responses to applied loads.

 

The appropriate thickness of Kingspan insulation to use will depend on a variety of factors, such as the building regulations in your area, the type of building you are insulating, and the specific application of the insulation. Here are some common insulation thicknesses used in the UK and their typical applications:

Walls

70mm: This is a common thickness for insulation used in solid walls, where the insulation is applied to the outside of the wall (Kooltherm K5 Kingspan External Board)

90mm: This is a common thickness for insulation used in cavity walls, where the insulation is placed between the two layers of wall (Kingspan Kooltherm K106 Cavity Insulation Board)

92.5mm: This thickness is sometimes used for high-performance insulation in walls, where a higher level of thermal performance is required (Kingspan Kooltherm K118 Insulated Plasterboard)

100mm: This is a common thickness for insulation used in timber frame walls, where the insulation is placed between the studs (Kingspan Thermawall TW55 Insulation Board or Kingspan Kooltherm K112 Framing Board )

Floors

50mm: This is a common thickness for insulation used in suspended timber floors, where the insulation is placed between the floor joists (Kingspan Thermawall TW55 PIR Insulation)

100mm: This is a common thickness for insulation used in concrete floors, where the insulation is placed on top of the concrete slab (K103 Kingspan Kooltherm Floorboard)

150mm: This thickness is sometimes used for high-performance insulation in floors, where a higher level of thermal performance is required (Kingspan Thermafloor TF70 PIR Floor Insulation Board)

 

Roofs

100mm: This is a common thickness for insulation used in pitched roofs, where the insulation is placed between the rafters (Kingspan Kooltherm K107 Pitched Roof Insulation Board)

126mm: This thickness is sometimes used for high-performance insulation in roofs, where a higher level of thermal performance is required (Kingspan Thermaroof TR31 Plywood Flat Roof Insulation)

150mm: This is a common thickness for insulation used in flat roofs, where the insulation is placed on top of the roof deck (Kingspan GreenGuard GG300 R Extruded Polystyrene)

 

 

It's important to note that these are general guidelines, and the appropriate thickness of insulation for your building will depend on a range of factors. It's recommended that you consult with a professional insulation installer to determine the appropriate thickness of Kingspan insulation for your specific application.

 

Kingspan K7 and K107 are both rigid insulation boards designed for pitched roofs. The main difference between the two is their thermal conductivity values. K7 has a thermal conductivity value of 0.023W/mK, while K107 has a thermal conductivity value of 0.019 W/mK. This means that K107 offers better insulation performance than K7.
Kingspan K7 and K107 are not just a change in product name. They are two distinct insulation board products from Kingspan, designed for pitched roofs, with different thermal conductivity values. While both products offer insulation for pitched roofs, K107 has a better insulation performance than K7 due to its lower thermal conductivity value. It is important to select the right Kingspan insulation board for your construction project based on the specific requirements and building design.

Kingspan offers a range of insulation boards designed for various applications, including:

Kooltherm
A premium performance insulation board with a fiber-free rigid thermoset phenolic core.

Therma
A range of high-performance insulation boards suitable for walls, floors, and roofs.

KoolDuct
A pre-insulated ductwork system designed for HVAC applications.

TEK
An insulated panel system designed for roofs and walls.

OPTIM-R
A vacuum insulation panel with a microporous core that provides excellent thermal insulation.

 

Phenolic insulation and polyisocyanurate (PIR) insulation are both types of rigid foam insulation. The main difference between the two is their thermal conductivity values. Phenolic insulation has a lower thermal conductivity value than PIR insulation, which means it offers better insulation performance.

To provide an example of thermal conductivity values, a 100mm thick phenolic insulation board typically has a thermal conductivity value of around 0.018 W/mK, while a 100mm thick PIR insulation board typically has a thermal conductivity value of around 0.022 W/mK.

The savings and return on investment from using phenolic insulation versus PIR insulation will depend on various factors, such as the specific building design, location, and energy costs. However, generally speaking, phenolic insulation can provide greater energy efficiency and lower heating and cooling costs due to its superior insulation performance. While the initial cost of phenolic insulation may be higher than PIR insulation, the long-term savings on energy bills can provide a significant return on investment over time.

 

Kingspan also offers a range of insulated panel systems designed for walls and roofs. These panels consist of a rigid insulation core sandwiched between two metal facings. Kingspan insulated panels are quick and easy to install, making them a popular choice for commercial and industrial buildings.

Some of the most popular Kingspan insulated panel products include:

Kingspan KSRW
This panel is designed for use in roofs and walls, and features a polyisocyanurate (PIR) insulation core with a high-performance thermal conductivity of 0.022 W/mK.

It is available with a range of metal facings, and is suitable for use in both new build and refurbishment projects.

The average cost for this panel is around £60-£90 per square metre.

 

 

 

 

Kingspan Optimo
Optimo insulated metal wall panels deliver a flat, aesthetically appealing modern building envelope solution. The use of pearlescent micas or metallic colours can provide an even more dynamic finish to any project. Optimo has the same joint as KS Series panels and can integrate with a variety of profiles. It is available with a range of metal and plastic facings, and is suitable for use in a variety of building types, from commercial and industrial to residential. The average cost for this panel is around £70-£95 per square metre.

 

 

 

Some of the benefits of using Kingspan insulated panels include:

Excellent thermal performance: The high-performance insulation core of Kingspan panels provides excellent thermal efficiency, helping to reduce energy consumption and lower heating and cooling costs.

Speed and ease of installation: Kingspan panels are designed to be quick and easy to install, which can help to reduce construction times and labour costs.

Durability and longevity: Kingspan panels are designed to be robust and long-lasting, helping to ensure that they continue to provide effective insulation and weather protection for many years.

Aesthetics: Kingspan panels are available in a range of colours and finishes, allowing them to be tailored to suit the aesthetic requirements of different building projects.

Phenolic insulation is generally considered to be a safe and reliable insulation material. However, there have been some concerns raised about the use of phenolic insulation in high-temperature applications, where it may release toxic gases. 
It is important to use phenolic insulation in accordance with the manufacturer's instructions and to consult with a professional if you have any concerns.

There have been some cases where phenolic insulation has been incorrectly installed or used inappropriately, leading to issues such as moisture penetration or reduced insulation performance. It is important to ensure that phenolic insulation is installed correctly and in accordance with the manufacturer's instructions, and to monitor its performance over time to ensure that it continues to provide effective insulation.

There have been some reported cases of metal buildings experiencing corrosion and rusting issues after the installation of phenolic insulation. This is because some types of phenolic insulation contain acids that can cause corrosion of certain metals, particularly in humid or moist conditions.

In one example from the UK, a metal building that had been insulated with phenolic insulation was found to have extensive rust and corrosion issues within just a few years of installation. The metal cladding and roof panels had deteriorated significantly, leading to leaks and other structural problems. The building owner was forced to undertake extensive repairs and replacement work to address the issue.

To prevent these types of problems, it is important to choose phenolic insulation products that are specifically designed for use with metal buildings, and to ensure that the insulation is installed correctly and in accordance with the manufacturer's instructions. Regular inspections and maintenance can also help to identify and address any potential corrosion issues before they become major problems.

 

In conclusion, choosing the right Kingspan insulation board for construction requires careful consideration of a number of factors, including the type of application, the required thermal performance, and the available budget. It is important to select the right thickness and type of insulation for the specific application, and to ensure that it is installed correctly in accordance with the manufacturer's instructions. While there are some concerns regarding the use of phenolic insulation in high-temperature applications, Kingspan's range of insulated panel systems offer excellent thermal performance, durability, and ease of installation, making them a popular choice for a wide range of commercial, industrial, and residential building projects.

 

BIBLIOGRAPHY

• Kingspan. (n.d.). Insulation boards for pitched roofs. Retrieved from https://www.kingspan.com

• Kingspan. (n.d.). Insulated panel systems. Retrieved from https://www.kingspan.com

• Ecohome. (n.d.). Polyisocyanurate (PIR) rigid foam insulation. Retrieved from https://www.ecohome.net

• Walls and Ceilings. (, March 1). Phenolic vs. PIR. Retrieved from

  https://www.wconline.com/articles/-phenolic-vs-pir

 

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Best insulation boards

Spray foam insulation &#; is it really that good?

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Building regs part L changes. What is all about?

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How to install insulated plasterboard?

 

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This CPD, sponsored by Kingspan Insulation, looks at different types of insulation products for masonry cavity walls, how energy efficient they are and the cost implications of choosing one product over another for projects of varying sizes

Introduction

Achieving value for money is a fundamental ambition for any project team. Too often, however, this can lead to &#;value engineering&#; where cheaper, lower-performing materials are added into a project as a way of reducing costs. In addition to the obvious issues this raises for the overall quality and performance of the building, the differing properties of these products can also lead to costly changes in the design. 

New research from Currie & Brown has shown that when overall costs are considered, it can often be cheaper to install premium performance phenolic cavity wall insulation over cheaper, thicker materials such as glass mineral fibre insulation.

This CPD will examine various types of insulation products for masonry cavity walls, their energy efficiencies and the cost implications for choosing one product over another.

Cavity considerations

Masonry cavity wall approaches are the preferred method of housebuilding for many developers in the UK. The tightening of the Building Regulations and Standards relating to energy efficiency state that walls must be insulated to a high standard. For new homes, these requirements are covered within Approved Documents L1A to the Building Regulations (in England), (in Wales), and Section 6 (Energy) of the Building Standards (in Scotland).

To ensure compliance, it is a good idea to target an external wall U-value of 0.16 W/m²·K for properties in England and Wales and 0.15 W/m²·K in Scotland. A wide variety of cavity insulation products are available to achieve this. When specifying these items, it is important to consider what the thermal conductivity (lambda value) of the material is. This is the measure of how a material conducts heat. Materials with a low thermal conductivity value are more resistant to heat loss through conduction, meaning a reduced thickness of insulation can be used to achieve the same level of thermal performance.

Cheaper materials often have relatively high thermal conductivities. For example, the typical thermal conductivity of glass mineral fibre cavity wall insulation is between 0.032-0.037 W/m·K. In contrast, the latest phenolic insulation boards have a thermal conductivity of just 0.018 W/m·K. Therefore, while the insulation boards themselves are more expensive than lower-performing materials, they can enable the desired U-value to be reached using thinner insulation and thus creating a thinner overall external wall construction. This can have a significant impact on other areas of the construction, such as the size and cost of foundations. 

To understand how this may affect overall project costs, Kingspan Insulation commissioned construction consultancy Currie & Brown to carry out an analysis.

Scenarios

To assess how the choice of insulation could impact overall project costs, Currie & Brown developed scenarios for properties of three different scales:

• Large detached house
• Small detached house
• Mid-terraced house

Each property was modelled using SAP , the government&#;s standard assessment procedure to evaluate the energy rating of dwellings. The procedure considers various aspects of the energy expenditure that goes into heating a home including space heating, water heating, ventilation and lighting.

Each of the houses was designed to meet the requirements of Approved Document L1A Building Regulations (England) with an external wall U&#;value of 0.16 W/m2.K. Two external wall specifications were developed for each scenario, one with glass mineral fibre insulation and the other with premium performance phenolic insulation. The full specifications are shown in Table 1. 

The phenolic insulation board features a water-tight, vapour-open polypropylene fleece outer facing supported with a 10mm residual cavity, which protects against moisture penetration. The higher thermal conductivity of the glass mineral fibre insulation meant that the cavity depth had to be increased by 80mm relative to the phenolic construction to achieve the target U-value.

Table 1: Modelled specifications and overall external wall construction depth  Specification Thickness (mm)  Brick outer leaf (102.5mm)

• 100mm cavity including 90mm phenolic cavity wall insulation
• 100mm blockwork inner leaf

 302.5 Brick outer leaf (102.5mm)

• 180mm cavity fully filled with glass mineral fibre cavity wall insulation
• 100mm blockwork inner leaf

 382.5

Cost variables

A cost analysis was then conducted by an experienced residential quantity surveyor. In addition to the up-front cost of the insulation

and associated products, the analysis considered a wide range of variables related to the varied cavity width and external wall constructions. These included:

• Foundation length with associated effects on concrete, reinforcement, excavation, disposal and backfill quantities; 
• Length of external perimeter of foundations with implications for formwork area; 
• Length of external perimeter of the outer wall layer with implications for the area of brickwork in groundworks and external walls; 
• Width of cavity closers, trays and lintels; 
• Length of wall ties; 
• Length of roof rafters and joists; 
• Length of fascia boards and guttering; 
• Area of roof covering (including slates, membrane and battens);
• Foundation width. All options were modelled with a standard foundation width of 900mm with 750mm and 600mm options considered for the scenarios with 100mm cavities.  

In all scenarios, the internal area of the home was kept constant with the impact of varying cavity width seen entirely on the external footprint. The homes have timber roof structures finished with slate tiles. 

Foundations are 300mm deep in a 600mm trench. It was assumed that the thinner cavity for the phenolic insulation specification would allow a narrower foundation of 650mm compared with 900mm for the glass mineral fibre specification as shown in Figures 1 and 2. All costs within the analysis were based on costs current to the third quarter of .

Results

The analysis showed that while the cost of the glass mineral fibre insulation itself was less than the phenolic insulation, the increased cavity width with the glass mineral fibre specification raised the cost of all accessories as shown in Table 2.

Table 2: Costs for components with varying rates between scenarios  ComponentUnit Cavity width 100m  Cavity width 180mm  90mm phenolic cavity wall insualtion (inc tape)  m2  £32.50    180mm glass mineral fibre cavity wall insulation  m2    £14.00  Wall ties  m2  £3.33  £4.51  Closers  m2  £5.68  £6.43  Trays  m2  £2.66  £3.42  Lintels  m2  £10.92  £12.27

Furthermore, the glass mineral fibre construction added significantly to the scale of the build programme. In addition to more extensive foundations and associated groundworks, the need for wider cavities and thicker walls also led to an increase in the external wall areas as detailed in Table 3.

It was found that the use of glass mineral fibre saw an increase in length of the outside wall, width to the outside wall and cavity thickness in all three of the different domestic new-builds. Using glass mineral fibre also meant an increase in total external wall area (minus openings), external area (excluding gable ends) and external perimeter for the large and small detached houses. 

Table 3: Dimensions of each building type and scenario  DimensionLarge detached house  Small detached house  Mid-terraced house      100mm cavity  180mm cavity  100mm cavity  180mm cavity  100mm cavity  180mm cavity  Length to outside of wall (m)  9.6  9.76 (+0.16)  8.9  9.06 (+0.16)  7.98  8.14 (+0.16)  Width to outside of wall (m)  8.8  8.96 (+0.16)  5.25  5.41 (+0.16)  4.63  4.79 (+0.16)  Cavity thickness (m)  0.1  0.18 (+0.08)  0.1   0.18 (+0.08)  0.1  0.18 (+0.08)  Height to eaves (m)  4.73   4.65   4.73   Total external wall area minus openins (m2)  185.44  188.69 (+3.25)  156.22  159.86 (+3.64)  31.76  31.76 (-)  External area excl gable ends (m2)  167.65  170.9 (+3.25)  118.92  122.57 (+3.65)  31.76  31.76 (-)  External perimeter (m)  39.67  40.31 (+0.64)  28.3  28.94 (+0.64)  9.25  9.25 (-)

When all these factors were considered, the analysis showed that the overall cost for the large and small detached houses with the phenolic insulation specification and 600mm foundation was actually less than that of the glass mineral fibre specification with a 900mm foundation (as shown in Table 2). 

For the mid-terraced property, the cost differential was almost identical, with the phenolic construction costing just £4 more than the glass mineral fibre specification. The mid-terraced property performed differently due to the area of insulated external wall being significantly reduced because of the two-party walls.

In addition to these cost benefits, the reduced construction thickness of the phenolic insulation specification may also help to increase natural light levels within the space. Research from consultant Peutz BV has shown that by installing phenolic insulation over glass mineral fibre alternatives, external wall and window reveal depths can be reduced. This can help to improve daylight levels within a room. 

The research looked at a range of facade arrangements and found that the percentage improvement in the average daylight factor when using the phenolic construction over glass mineral fibre ranged between 10.6% and 63.2%. This can provide a healthier space for occupants and may make them more attractive and saleable to potential buyers.

Table 4: Summary of results  House type 100mm cavity phenolic insulation specification with 600mm foundation 180mm glass mineral fibre specification with 900mm foundation  Large detached  £53,993  £54,154 (+£161)  Small detached  £41,324  £41,744 (+£420)  Mid-terraced  £9,801  £9,797 (-£4)

A holistic view

With constant pressure on the bottom line, it is understandable that architects and project teams look to find cheaper solutions where possible &#; particularly when the material itself will not be visible to potential owners. The research from Currie & Brown shows, however, that selecting materials purely based on their shelf price can lead to unforeseen additional costs as well as compromises in design. By taking a more holistic look at how products such as insulation can impact other areas of a project, it may therefore be possible to specify more premium options and achieve improved performance and quality while still saving money overall.

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