DECODING THE ROLE OF INSULATED PLASTERBOARD THICKNESS IN ENERGY EFFICIENCY*

Insulated plasterboard is a game-changer for many builders, offering faster installation, cost reduction, and most importantly, improved thermal insulation performance. However, not all builders know what thickness of insulated plasterboard should be used, what it entails, and whether the 'thicker is always better' rule actually makes sense. In this article, we will attempt to answer what thicknesses of insulated plasterboard are required by building regulations in the UK, what requirements we should meet when choosing insulated plasterboard, and what we should avoid.

 

Table of contents

  • DECODING THE ROLE OF INSULATED PLASTERBOARD THICKNESS IN ENERGY EFFICIENCY
  • WHAT IS INSULATED PLASTERBOARD?
  • IMPORTANCE OF CHOOSING THE RIGHT THICKNESS
  • HOW THICK SHOULD THE INSULATION BOARD BE?
  • TYPES OF INSULATION BOARD AND THEIR THICKNESS OPTIONS
  • WHAT IS THE MOST EFFICIENT INSULATED PLASTERBOARD?
  • INSULATED PLASTERBOARD THICKNESS CALCULATOR
  • CONCLUSION

 

WHAT IS INSULATED PLASTERBOARD?

Insulated plasterboard is a two-component insulation product consisting of an insulating core and a standard plasterboard sheet. It has a wide range of applications in interior finishes of buildings when external wall insulation is not possible. An excellent example of using insulated plasterboard is a building that does not have a permit to insulate the masonry wall from the outside. After installation, thermal plasterboard can be used as a finished surface ready for further finishing through taping jointing or plastering with multi finish plaster.
Many people in the UK claim that insulated plasterboard can save up to 60% of the costs associated with insulating and finishing interior walls compared to traditional methods. The cost of finishing one square metre of the wall using insulated plasterboard is around £28, which, compared to the traditional method costing £65, provides incredible savings of around £37 per square metre. This gives savings of around £1665 for a 20m2 room.

 

IMPORTANCE OF CHOOSING THE RIGHT THICKNESS

When it comes to using insulated plasterboard for your building project, choosing the right thickness is crucial. While thicker plasterboard may seem like the obvious choice for better insulation, it's not always the case. Building regulations in the UK have specific requirements for the minimum insulation value, which means that going too thick may not provide any additional benefits, but can actually end up being wasteful and unnecessary.

On the other hand, choosing a plasterboard that is too thin can result in inadequate insulation, leading to energy inefficiency and higher heating bills. Additionally, the thickness of the plasterboard can also affect other aspects of the building project, such as weight load and fire resistance.

 

HOW THICK SHOULD THE INSULATION BOARD BE?

Referring to the current building regulations, the u-value for walls should be 0.28WmK. Only the thickness of insulated plasterboard of around 62.5mm can meet this requirement. This means that the minimum thickness of insulated plasterboard should be 62.5mm, which is offered by manufacturers such as Xtratherm with their XT/TL or SR/TB products, as well as Kingspan with their K118 product. When choosing the thickness of insulated plasterboard, it is important to keep in mind that the greatest savings come from the first 10cm of insulation. Anything beyond that can be considered an unnecessary cost. This is illustrated perfectly in the chart below. 


In conclusion, the most optimal thicknesses for insulated plasterboard are:

 62.5mm, 64.5mm, 67.5mm, 69.5mm, 72.5mm, 74.5mm, 77.5mm, 79.5mm, 82.5mm, 84.5mm, 87.5mm, 92.5mm, 99.5mm, and 102.5mm. The thickness of 122.5mm is becoming increasingly rare.

 

TYPES OF INSULATION BOARD AND THEIR THICKNESS OPTIONS

When it comes to application you can choose from standard insulated plasterboard commonly used on walls and ceilings and moisture resistant insulated plasterboard for wet rooms, bathrooms and shower rooms. 

STANDARD INSULATED PLASTERBOARD

A standard insulated plasterboard comprises standard Drywall Plasterboard pre-bonded to thermal insulation core.

MOISTURE RESISTANT PLASTERBOARD

Moisture resistant insulated plasterboard is backed with rigid polyisocyanurate foam insulation and two vapour barriers which are specially designed to use in wall lining and internal wall partitions. These boards are mostly used where both high thermal performance and high moisture resistance is required.

When it comes to thermal plasterboard performance you can choose from Phenolic, EPS (Expanded PolyStyrene), XPS (EXtruded PolyStyrene) and PIR (PolyIsocyanuRate) insulation core.

PHENOLIC FOAM PLASTERBOARD

Phenolic plasterboard is a premium performance insulation with a fibre-free rigid thermoset phenolic core. It provides a level of performance that is unrivalled in the world of rigid thermoset insulation materials with a thermal conductivity of just 0.018 W/mK across all thicknesses. It is a top-class three-in-one product for internal wall insulation used as mechanically fixed and adhesively bonded 'dot and dab' insulated plasterboard. For example, Kingspan K118 range is a high-efficiency phenolic insulation core with a certified thermal conductivity (lambda value) of 0.018W/mK factory bonded to 12.5mm premium plasterboard. Kooltherm K118 (previously Kingspan K18 and K17) provides high-levels of insulation, dry-lining and vapour control layer in one easily applicable 2400mm x 1200mm (8x4) insulating sheets.

PIR INSULATED PLASTERBOARD

Pir core wall panel is an insulated plasterboard combined of polyisocyanurate (PIR) rigid insulation foam core bonded to 9.5mm or 12.5mm tapered edge plasterboard that is suitable for internal applications, fixed with adhesive dot and dab direct bonding.

EXPANDED POLYSTYRENE EPS INSULATED PLASTERBOARD

EPS Insulated Plasterboard is a cost-effective way of improving thermal efficiency in both wall and roof applications. Made from expanded polystyrene foam insulation bonded to 12.5mm thick plasterboard, this insulation solution can be used for both new build and refurbishment projects.

EXTRUDED POLYSTYRENE XPS INSULATED PLASTERBOARD

XPS Laminates are fabricated by bonding a sheet of XPS insulation, a close-celled extruded polystyrene board made from melting plastic resins that are then extruded through a die and expanded during the cooling process, to tapered edge plasterboard.

 


WHAT IS THE MOST EFFICIENT INSULATED PLASTERBOARD?

The most efficient and best insulated plasterboard currently available is Xtratherm with its SR/TB sheet composed of a phenolic foam core. The second best and well-known product is Kingspan K118. Similarly to Xtratherm, it has a phenolic core which provides the best thermal insulation results, allowing for the use of the thinnest insulation and thus saving space.

 

INSULATED PLASTERBOARD THICKNESS CALCULATOR

The Insulated Plasterboard Thickness Calculator is a tool used to determine the ideal thickness of insulated plasterboard needed for a particular project. It takes into account several factors such as the type of wall, the desired insulation level, and the U-value required by building regulations.

To use the calculator, one needs to input the relevant information such as the type of wall construction, the thickness of existing insulation, and the desired U-value. The calculator then generates a list of recommended insulated plasterboard thicknesses that would meet the specified U-value requirement.

This tool is particularly useful in ensuring that the correct thickness of insulated plasterboard is chosen to meet building regulations, optimize thermal performance and minimize unnecessary costs. It is important to note that the calculator is a guide, and it is always advisable to consult with a professional to ensure that the correct thickness is chosen for a specific project.
Below we provide links to online calculators


CONCLUSION

In conclusion, insulated plasterboard is a highly effective solution for both insulation and interior wall finishing. Choosing the right thickness is crucial to achieve optimal thermal insulation and cost savings, with the most efficient options being between 62.5mm and 102.5mm. Xtratherm XT/TL Insulated Plasterboard and Kingspan K118 are two of the top-performing products on the market, thanks to their phenolic foam core. Additionally, using an online calculator can be a helpful tool to determine the appropriate thickness for your specific project. By selecting the right product and thickness, you can improve the energy efficiency of your building, reduce your environmental impact, and save money in the long run.

 

Related articles:

HOW TO INSTALL INSULATED PLASTERBOARD?

MANAGING MOISTURE: DO YOU NEED A VAPOUR BARRIER WITH INSULATED PLASTERBOARD?

5 BENEFITS OF INSULATED PLASTERBOARD

 

 

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