FAQ

Here is a page dedicated to questions frequently asked by our customers.

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Celotex boards are CE marked yet many competitors aren't - why?

CE marking confirms that our products fully comply with BS EN 13165 and that key performance characteristics have been verified through independent type testing. This is a very clear method of confirming that delivered products match your actual specification. Competitors that don't CE mark cannot match this level of transparency.


Celotex Position on the TIMSA/BBA U-value Competency Scheme

The TIMSA/BBA U-value competency scheme is being run to attempt to regulate the calculation of U-values with a view to improving their accuracy. Any scheme to govern the calculation of U-values should be inclusive of all areas of the construction industry and cover those calculations carried out both by individuals and on-line software applications.

The TIMSA/BBA scheme does not currently enjoy this level of coverage and although Celotex applaud the sentiment behind its creation, we will continue to offer the same level of high quality U-value calculations through our Celotex Technical Centre and on-line U-value calculator outside of that scheme.

Celotex supports the principle of ensuring that a U-value should be calculated to a high degree of accuracy.  All Celotex Technical Centre staff are trained to carry out calculations in accordance with BR443 ‘Conventions for U-value calculations’ and our on-line U-value calculator also follows the same conventions. Celotex also has staff within its Celotex Technical Centre who have gained qualifications to become On-construction Assessors for the production of SAP and EPC's for new build properties.

The level of staff training ensures that Celotex U-value calculations, SAP and EPC’s comply with the requirements of the Building Regulations for England and Wales, Scotland and Northern Ireland.


Can Celotex be exposed to the ground?

We advise that when used in ground floors, Celotex must always be above the damp proof membrane (DPM ).


Can Celotex be used as a cavity fire barrier?

No, where cavity fire barriers are required by national building regulations, they should be installed in line with the manufacturer's instructions.


Can Celotex be used below the damp proof course in a masonry cavity wall detail?

Celotex CG5000 and CW4000 can be used below the damp proof course in a masonry cavity wall detail.
 
When the products bridge the damp proof course (dpc) in walls, dampness from the ground will not pass through to the inner leaf provided the wall is detailed in accordance with the requirements and provisions of the national building regulations.
 
The insulation boards should be supported clear of the ground on the first row of wall ties and a clear cavity should be maintained between the insulation and the outer leaf.
 
Please refer to BBA Certificate 94/3080 for more information.
 
Where it is desirable to back fill the cavity below DPC level with a weak mix of concrete, this is acceptable as long as the outer face of the insulation is protected with a polythene membrane or material of similar moisture resistance and durability.


Can Celotex boards be installed on top of a liquid dpm?

Yes, providing that the liquid dpm (damp proof membrane) has been applied correctly in line with the manufacturer's instructions and is therefore fully cured before laying the Celotex boards.


Can Celotex boards be recycled at the end of their period of use?

Yes, the technology exists. However, with typical building life in excess of 50 years and our foam boards having been launched in the late 1970s, there is insufficient feed-stock available to make any commercial recycling venture viable at present. Nonetheless, Celotex boards can be safely disposed of.


Can I insulate between and over my flat roof joists?

Insulating between and over flat roof joists is not an accepted method of construction. When insulating between roof joists there must be a minimum 50mm ventilated cavity above the insulation.


Can I recess electric cables into Celotex?

No. Electrical cables should not be channelled into Celotex as that would reduce the performance of the Celotex.

Cables can penetrate through Celotex and if cables are laid between two layers of Celotex they should be oversized to cope with any increase in operating temperature.

Celotex has no detrimental effect on the cable sheathing.


Can I recess my downlighters into Celotex?

No. Downlighters should not be recessed into insulated ceilings as they penetrate the vapour control layer (VCL) and act like a flue, drawing warm moist air into the roofspace where it condenses and drips back out of the fitting, possibly causing a fire risk.

If downlighters are to be used, they should be fitted in a false ceiling below the structural ceiling.


Do Celotex boards contain any recycled materials?

Yes. Where boards contain glass fibre core reinforcement, it is made from recycled waste glass. About 90% of the aluminium in our foil facers comes from recyclable sources. Polyester polyols used in our boards can be produced from waste sources such as PET bottles used for fizzy drinks.


Do Celotex boards contain any unique 'ingredients'?

Yes. An exclusive feature in some of our boards is the incorporation of long-strand reinforcing glass fibres within the PIR foam core. This aids dimensional stability and further improves behaviour when exposed to a fire.


Do you need a VCL with Celotex Rafter-Gold / control of condensation without a VCL?

Celotex Rafter-Gold allows the insulation of a pitched roof without the need to raise the roof height and does not require a vapour control layer.

Whilst a vapour control layer is not required, it is important that there is a “well-sealed ceiling”. This means that any gaps or cracks in the existing ceiling should be made good – to minimise vapour transport into the construction by convection.

More information on Celotex Rafter-Gold can be found by visiting www.celotex.co.uk/rafter-gold.


Does Celotex operate a quality control system?

Yes. The company is quality assured to BS EN ISO 9001, confirming a robust and fully audited factory production control system.


Does the Celotex manufacturing process use a lot of energy?

The embodied energy arising from our manufacturing process is extremely low because the chemical reaction is exothermic.

Our latest cardboard packing line requires considerably less process energy than shrink wrapping and doesn't use oil-based plastics.

To see the Celotex manufacuturing process please click here


Have you got an ISO 14001 Certificate?

Yes, to download Celotex' ISO 14001 certificate please click here


How can I avoid cold bridging?

Cold bridging is caused when an element with low thermal performance penetrates an insulated element of a building, for example a concrete balcony cantilevering through an external wall.

Celotex TB4000 is designed to provide simple solutions to overcome localised thermal bridges, with boards available from just 12mm thick.


How is polyisocyanurate foam board made?

It is made by a lamination process, formed between aluminium foil facings that are glued together in a continuous laminator, where the 'adhesive' is a mixture of MDI and polyol. An added blowing agent causes this adhesive to expand into foam that hardens and is cut into manageable board sizes.

To see the Celotex manufacturing process please click here


How to avoid condensation risks?

What is condensation?

Condensation is a process where water vapour contained within the atmosphere condenses into water.

Condensation can form on visible surfaces, such as the inside of walls. This is known as surface condensation.

It is possible for condensation to form within the structure of a building and this is known as interstitial condensation. For example it may form on the roof timbers or within the structure of a wall.

How does condensation happen?

When warm air containing water vapour is lowered in temperature, the moisture within the air will condense into water. This will commonly occur where the air touches a cold surface.

As standards of thermal insulation have improved over the years, the risks of condensation have grown.

For example, if you have a great deal of loft insulation then you will notice that your loft will now be very cold in winter. This increases the risk of harmful condensation forming on the underside of your roofing felt.

Interstitial condensation can occur within roofs, walls and floors unless precautions are taken to minimise the risks.

What is the impact of condensation?

Condensation can cause damp spots and mould growth to occur on the inside of walls and ceilings. Over long periods of time condensation can degrade the structure of the building, leading to costly repair work or even structural failure.
 
How to avoid it?

Building regulations require designers to minimise the risks of harmful condensation and follow the guidelines laid down in BS 5250:2002 Code of practice for control of condensation in buildings.

Condensation in buildings is controlled with a variety of methods.

  • Vapour Control Layers

A vapour control layer is a material with a high resistance to the passage of water vapour. This might be a foil faced insulation board (like Celotex) or a polythene membrane.

The principle is to prevent moisture in the air from reaching the cold side of the insulation, where it could meet a cold surface and condense.

  • Ventilation

In some constructions a ventilated cavity may need to be provided on the cold side of the insulation. Any water vapour that does manage to reach this area is quickly dissipated before it can condense. An example would be a pitched roof with a traditional sarking felt – where ventilation must be provided.

Ventilation may also be provided within the property itself, to control the amount of water vapour present in air. For example extractor fans in bathrooms and kitchens.

  • Good Design

The risk of condensation may also be minimised by good building design. Carefully considering where to place layers of thermal insulation and following good building practice. For example, placing thermal insulation to the outside of a steel frame wall creates a warm frame construction and reduces the risk of condensation forming on the steel studs.
 
How can Celotex help?
As experts in thermal insulation, Celotex can offer advice and guidance on condensation issues. Our technical team can provide condensation risk analyses and guidance on complying with building regulations.


If the weather is cold, can I still install Celotex Boards?

Celotex insulation boards should not be installed when the temperature is at or below 4ºC and falling.


Is Celotex board packaging environmentally friendly?

We only offer shrink-wrap packaging on products requiring protection from rain while stored on site. Most boards feature banded cardboard packaging, which is easily recycled, and is biodegradable, minimising pollution from careless disposal.

Please see our sustainability statement for more details


Is Celotex of limited combustibility?

Celotex is classed as combustible when tested in accordance with BS476 and has a class 1 surface spread of flame when tested to the same standard.

For premium fire performance please see ourCelotex FR5000 and products


Is Celotex suitable below a raft slab?

We do not recommend the use of Celotex beneath a raft foundation.


Is Celotex suitable for a fully filled cavity?

Celotex offers both full fill and partial fill solutions for masonry cavity walls. Celotex CF5000 is designed for full fill cavity applications. Celotex CW4000 and Celotex CG5000 are designed for partial fill cavity wall applications. More information on our cavity wall solutions can be found on the relevant product pages of our website. Where a partial fill product has been specified a minimum 50mm clear cavity would typically be required. A 25mm clear cavity may be suitable in some circumstances, but where the wall is subject to NHBC Standards or is in a severe exposure zone then a 50mm minimum clear cavity must be provided. For more information please refer to our BBA Certificate for Partial Fill Masonry Cavity Walls. 


Is Celotex suitable for inverted roofs?

Celotex is not suitable for use in inverted roofs (protected membranes) as it must remain dry at all times.

Refer to our Applications page for more information on roofing.


Is Celotex suitable to use underneath tiles?

Celotex is not suitable directly below floor tiles. A screed is required to spread the load and prevent movement between the tiles.


Is PIR foam environmentally friendly?

PIR foam is an extremely effective insulant. Used appropriately, it will contribute to significant reductions in energy consumption and carbon dioxide emissions.

That is good for the environment.

Please see our Sustainability Statement in the 'Literature' pages for more details.


Is PIR foam expensive?

It is more expensive off the shelf than cheaper insulants like mineral fibre loft insulation, but usually the same price as a polyurethane board. However, PIR boards reduce the usable space loss in buildings.

They also require less costly mechanical fixings and don't need supporting materials to hold them in place.


What are polyisocyanurate (PIR) foams used for?

Rigid polyisocyanurate (PIR) insulation products are highly effective and lightweight. Their excellent thermal conductivity, high strength to weight ratio, combined with great manufacturing versatility provides a large variety of products which makes PIR insulation products the optimum choice for most construction insulation applications.


What are the key properties of polyisocyanurate foam board?

  • It's lightweight, providing minimised additional loading to structures
  • It's efficient: thickness for thickness there's no more efficient insulant
  • Is easy to cut and fit
  • It's difficult to ignite
  • It's durable and gives reliable energy savings throughout a building's normal lifetime
  • It is safe to use, emits no noxious/hazardous fumes and can be safely disposed of or recycled

What are the Target U-Values for England, Wales and Scotland?

Target U-values for floors, walls and roofs can vary depending upon the nature of the project. Key factors that affect compliance are whether the building is domestic or non domestic and whether the project relates to a new or existing building. In addition, different performance targets now apply in England, Scotland and Wales. The requirements of the building regulations are laid out in the following documents: England: Approved Document L. Wales: Approved Document L (Wales). Scotland: Scottish Technical Handbook - Section 6. Celotex has produced a comprehensive guide to the building regulations in each region. Further guidance on elemental U values can also be found in the Celotex Handy Guide. 

For special requests, contact the Celotex Technical Centre


What can I do if I have excessive glazing?

You are allowed 25% of the floor area as glazing plus any windows covered by the proposal if applicable.

It is possible to compensate for excessive glazing by overinsulating in the walls, roof and floor. Contact the Celotex Technical Centre for more information.


What do I need for a SAP calculation?

For a SAP ( Standard Assessment Procedure) calculation, all details of a new dwelling are required: areas and U values of each element minus window areas; window areas; U value of glazing and orientation; details of the central heating system and controls (including method of providing hot water and storage if applicable); number of flues and intermittent extractor fans and so on.


What is a Predicted Energy Assessment?

Predicted Energy Assessment (PEA). This is the predicted SAP Rating and Environmental Impact (CO2) rating from the SAP calculations that should have been completed at the design stage, to check whether they comply with Building Regulations. Predicted Energy Assessments do not have a Recommendation Report like full Energy Performance Certificates


What is a VCL?

A vapour control layer (VCL) is a layer within the construction that has a high resistance to the passage of water vapour. A polythene membrane would be a classic example. The job of the VCL is to prevent water vapour migrating into the insulated construction where it could lead to interstitial condensation.


What is a warm roof?

When discussing pitched roofs, the normal usage is that where insulation is positioned at the line of the sloping rafters then this is defined as a warm roof. 


What is an Energy Performance Certificate?

Energy Performance Certificates (EPCs) are now required, by law, on all new homes. EPCs became mandatory in October 2008 on all buildings, whenever they are built, sold or rented out.

An EPC is a measure of the energy efficiency of a building as well as the environmental impact as measured by CO2 emissions. The EPC provides 'A' to 'G' ratings for the building, with 'A' being the most energy efficient and 'G' being the least efficient. To date, most buildings will be either a 'D' or 'E' rating , with those built to the 2006 building regulations typically achieving a 'B' rating.

An EPC will provide a Recommendation Report that offers advice and suggestions on how to further improve energy efficiency. This will ultimately have a positive impact on reducing CO2 emissions.

Read more about SAP and EPC's


What is cold roof?

When discussing pitched roofs, the normal usage is that where insulation is positioned at the line of the horizontal ceiling joists then this is referred to as a cold roof.


What is Part L?

Approved Document L provides guidance on complying with the building regulations in respect of Conservation of Fuel and Power.

Approved Documents cover England and Wales. Guidance for Scotland is provided in the Scottish Technical Handbook.


What is polyisocyanurate (PIR) foam?

Polyisocyanurate (PIR) is an improved type of rigid polyurethane.

The production process creates strong isocyanurate linkages in the molecular structure. Chemical breakdown of the foam occurs at higher temperatures than PUR, so it is much more difficult to ignite.

True polyisocyanurate foam contains about 50% or more isocyanurate linkages.

To see the Advantages of PIR please click here.


What is the Company's sustainability policy?

It is the policy of Celotex Limited that the Company will at all times pursue strategies within its operations, product development and commercial activities to assess and minimise negative impacts on the environment whilst adhering to the principles of sustainable development, and to expect similar environmental standards from its suppliers and contractors.

For our Sustainability Statement or to view our BRE Environmental Profiles, please refer to the Sustainability page.


What is the difference between FR,CG4000 and FR, CG5000?

Due to our recent technology breakthrough in achieving a super low lambda of 0.021W/mK, our FR and CG products have been re-branded to reflect these results.

This is the only difference between the products which will help you to achieve better U-values.

Celotex FR5000

Celotex CG5000


What is the difference between PIR and PUR foams in a fire?

Rigid PIR differs from PUR in that it is produced using an excess of the MDI component. In the presence of an appropriate catalyst the excess MDI reacts with itself to form isocyanurate which is characterised by greater heat stability. The resultant PIR insulation products exhibit increased fire performance and reduced combustibility and higher working temperature limits compared to PUR and when incorporated into building products, can meet some of the most demanding fire performance requirements such as those currently stipulated for some applications by the insurance industry.


What is the GWP of Celotex?

All Celotex products have 'low' global warming potential (GWP). The definition of 'low' is less than five as set out by government and is referenced through industry publications such as the Code for Sustainable Homes. 


What is the life expectancy of Celotex?

Celotex is expected to remain efficient for the life of the building, and the Lambda values published have been prematurely aged in accordance with British Standards.


What is the recommended PPE with rigid insulation?


What is the specific heat capacity of PIR insulation?

The specific heat capacity cp states how much heat energy is required to increase the temperature of 1kg mass of a material by 1K. Specific heat capacity cp is measured in J/(kg·K).

More heat energy is required to raise the temperature by 1K of a material with a greater heat capacity. And inversely, less energy is required to produce a 1K increase in temperature in materials with lower heat capacities.

Calculated values of specific heat capacity cp of various materials
Material Specific heat capacity cp = J/(kg·K)

  • Rigid polyurethane foam (PUR/PIR) 1400 – 1500
  • Wood-fibre insulation boards 1400
  • Mineral wool 1030
  • Wood and wood-based materials 1600
  • Plasterboard 1000
  • Aluminium 880
  • Other metals 380 – 460
  • Air (ρ=1.25 kg/m³) 1000
  • Water 4190

What rigid insulation is recommended for underfloor heating applications?

Celotex recommends the use of Celotex FI5000 for all underfloor heating applications. FI5000 has been specifically designed for flooring applications and combines increased compressive strength, best in class thermal performance and an innovative composite facer that allows screed and concrete to be installed directly on to the product. FI5000 provides increased resistance to trafficking associated with the installation of underfloor systems to provide a robust solution offering high performance insulation and excellent dimensional stability.

Can Celotex GA4000 insulation be used in underfloor heating applications?

Yes. If GA4000 is chosen for use in underfloor applications extra care must be taken to protect the insulation from trafficking as it is not as resistant to the rigours associated with the installation of such systems as FI5000.Protective boarding should be used to minimise the effect of trafficking especially in doorways and walkways. It is also recommended that the time between the installation of GA4000 and pouring of screed should be kept to an absolute minimum as this will reduce the opportunity for trafficking to take place.

What if I want to use insulation layers in an underfloor heating application?

Where possible a single layer of Celotex insulation should be used. If two layer systems are required the boards should not be bonded together and both layers should be protected from trafficking. More information on flooring applications can be found in the Celotex Flooring Specification Guide


Where can I buy Celotex?

Celotex is very well known throughout the construction industry and is supported by a nationwide network of leading distributors and builders merchants.

Visit our Stockists page to find your nearest stockists.


Where can I find out more about Celotex' environmental policy?

To download our comprehensive Environmental Information Sheet and our Sustainability Statement, please refer to our Sustainability page.


Who makes polyisocyanurate foams (PIR)?

Most manufacturers of PUR boards can produce polyisocyanurate-modified foams.

However, Celotex is able to make very high 'index' foams in laminated board form, satisfying the ISO definition (over 400 index).

High Index foams satisfy the requirements of major fire insurers, so ensure you specify 'PIR foam to ISO standards'.


Who staffs the Celotex Technical Centre?

The CTC is staffed by experienced technical professionals and has justly earned a very high reputation for the speed and depth of assistance available.

We can provide U-value calculations for all product applications, SAP ratings and EPCs for dwellings and advice on any aspect of product selection, including compliance with building regulations.

Contact the Celotex Technical Centre today.


Why is there a polythene membrane between the Celotex and screed?

A polythene membrane on top of insulation below a screed or concrete oversight performs three tasks: it acts as a vapour control layer (VCL); it prevents migration of the screed / concrete which can force the boards apart leaving cold spots in the floor; and it prevents a reaction between the wet screed / concrete and the foil facer where small volumes of gases given off can weaken the screed/concrete. Celotex FI5000 features an innovative composite facer that when taped and sealed performs these functions without the requirement of a separate polythene VCL.

More information on flooring applications can be found in the Celotex Flooring Specification Guide


Why would I choose Celotex over seemingly cheaper insulants?

There are many different reasons, but perhaps the most compelling one is our boards' low thermal conductivity - the exceptionally slow rate at which heat passes through them. This facilitates relatively thinner, lighter, less costly roof, wall and floor constructions that easily meet tough modern insulation legislation standards.

We’d like to make finding the answers to your questions as simple as possible, and want to help you use our website with ease.

Take a look at our collection of questions. If your query cannot be answered on this page, please contact the Celotex Technical Centre on 01473 820850

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