Keeping The Heat In: The Effectiveness Of Thermal Boards In Building Insulation

London Terrace Home With Large Red Door

Energy Performance Certificates are required for every residential property in the UK.

They list the energy efficiency rating, with A being the highest, and G being the lowest, along with a numerical rating out of 100. They also list the current running hosts for heating, lighting and hot water usage and potential savings with the recommendations provided. This lets potential buyers and renters know how much they’ll be paying and can compare different properties.  

One of the recommendations is improving insulation levels throughout the home. These also provide the biggest savings. The majority of your bills goes towards heating and cooling, so the initial cost of insulation is recouped quite soon. Of the different insulation materials used, thermal boards have proven quite popular of late, as they are some of the best choices in keeping your home warm in winter and cool in the summer. Also, thermal boards are cost-efficient, easily and quickly installed and will last for decades. One of the newest and most efficient boards is the Kingspan Kooltherm K12, used as a framing board in wall insulation. 

What are Thermal Insulation Boards? 

Thermal Insulation Boards are polymer-based foam boards, with or without facer materials, and used to insulate internal walls, ceilings, roofs and floors in residential and commercial buildings. Different types are available, and better suited for different insulation applications.  

Types of Thermal Insulation Boards

There are five major types of insulation boards commonly used today. These include EPS, XPS, PUR, PIR and Phenolic boards. They differ mainly in the production process, the type of polymer, and most importantly how efficient they are in reducing heat loss. 

EPS Thermal Boards 

EPS Expanded Polystyrene is the cheapest thermal board, largely due to the lower thermal resistance, or what is known as R-value. The higher the R-value, the higher the insulating ability of the board. EPS is a lightweight board, with high compression strength, and is suitable for numerous applications. It doesn’t rot over time or attract pests and vermin. The downsides are that it can absorb water and is flammable if exposed. To solve these weaknesses, manufacturers add facer materials, which also benefits in providing a higher R-value. 

XPS Thermal Boards 

XPS or Extruded Polystyrene is another polystyrene foam, though made with a different production process. The resulting boards are denser and display better thermal properties than EPS. XPS has a higher R-value for the same thickness and is also less prone to absorbing liquids and more resistant when directly exposed to fire. This makes it a better option for areas with high exposure to water and heat.  

PUR and PIR Boards 

Polyurethane (PUR) and Polyisocyanurate (PIR) thermal boards are both made of rigid cell polyurethane foam, but PIR includes a larger portion of blowing agent, in this case, MDI or methylene diphenyl di-isocyanate. This adds several advantages. PUR boards are generally better than both EPS and XPS boards, with higher R-values, good resistance to fire and water, and high compression strength. PIR builds on these qualities, having a slighter higher R-value meaning thinner boards. PIR also is fire retardant, and won’t catch fire, is denser and stronger and can be used in heavy-duty applications both in commercial and residential buildings. The downsides are that it is more prone to absorb moisture, and comes at a higher cost.  

Phenolic Boards 

Phenolic insulation boards are the most effective rigid foam insulation boards currently available. They have the best thermal properties among all foam boards, making them suitable for a range of applications. Phenolic boards are used in roofing, wall and floor insulation, as well as exterior insulation projects. Phenolic foam is also commonly used for insulation purposes in piping, HVAC systems, in the food processing industry, cold rooms, hospitals, fire doors, fire-resistant panelling and more.  

Properties of Phenolic Boards 

Phenolic boards, like the Kingspan Kooltherm K12 wall framing board, have a high closed cell content and fine cell structure. The boards are produced in densities ranging from 3.5kg/m2 to 20kg/m2 with higher density boards having particularly good compression strength, meaning they’re also suitable in some flooring insulation. Phenolic boards have high heat resistance ratings of up to 120°C and the best performance in fires with low flame spread and negligible smoke emission. This makes phenolic boards the preferred choice over PUR/PIR insulation boards for fire resistance. It also provides better moisture resistance, meaning framing boards like the Kingspan Kooltherm K12 and the K5 external wallboard, wick away any water. The closed-cell structure has low water vapour permeance, and moisture buildup is non-existent. This helps to preserve supporting structures, like wooden frames and prevents mould or mildew from developing over time.  

The thermal resistance figures, or R-values, are the highest of any foam insulation board – almost double that of EPS boards, and around 20 per cent more than PIR thermal boards for the same thickness. Adding boards of greater thickness proportionately increases the thermal resistance. Thicknesses for framing boards range from 25 to 120mm, depending on the type of wall. Two boards of 25mm placed together will provide the same thermal shielding as a single 50mm board in optimal circumstances.  

Benefits of Phenolic Insulation Boards 

Phenolic boards like the Kingspan Kooltherm K12 and other boards in the Kooltherm range, comply with the latest British BS EN 13166 standard for thermal insulation products. These boards provide the least heat loss, meaning thinner boards can be used to achieve the same R-values. This is useful where space is limited, like encroaching on pavements, or in cases like listed buildings. Boards are lightweight, rigid and solid. They are used in many insulation scenarios, like insulating timber or steel frame walls, in external walls, in structural soffits, and also combined with plasterboard for interior wall insulation. Denser boards have also been used in floor insulation. Boards are easily cut to shape and installed.  

Phenolic boards achieve the best energy performance ratings in properties by reducing carbon emissions the most of any insulation type. In addition, the phenolic foam doesn’t contain ozone-depleting CFCs or HCFCs and is eligible for green product certification.  

The type of board you choose will depend on your needs, the scope of insulation and the areas involved. With stricter emissions and energy-efficiency codes, buyers are recommended to spend more in the short term, and reap the rewards of lower bills and less structural damage in the long run. Meanwhile, more comfort and warmth are a given.  

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