Celotex Technical FAQs

Celotex FF4000

Celotex recommends the use of FF4000 for all underfloor heating applications.

FF4000 has been specifically designed for use with underfloor heating and combines increased compressive strength with improved clip retaining properties.

FF4000 provides increased resistance to trafficking associated with the installation of underfloor systems to provide a robust system offering high performance insulation and excellent dimensional stability.

Celotex GA4000

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 FF4000.

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.

Layers

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.

the CTC is staffed by seasoned construction 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.

Just about anything...

• Car seats, dashboards and bumpers
• Soft furnishings. sanding blocks
• Thermal insulation boards, pipe insulation, refrigerator and deep freezer cabinets
• Shoe soles
• Adhesives for lamination
• Flotation tanks and safety equipment

The list just goes on and on...

• It's lightweight, providing minimised additional loading to structures
• It's efficient: thickness for thickness there's no more efficient insulant
• 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
  
  

Target U values for domestic buildings in England and Wales are 0.2 W/m2K in roofs insulated at rafter level, 0.16 W/m2 in roofs insulated at horizontal ceiling level, 0.3 W/m2K in walls and 0.22 W/m2K in floors.

In Scotland there is a two tier system according to the efficiency of the boiler.

For oil boilers with a minimum SEDBUK rating of 85%, natural gas boilers with a rating of 78% and LPG boilers with a rating of 80% the requirements are as above with the exception of flat roofs and floors where the requirement is 0.25 W/m2K.

For boilers below those ratings, the requirements are 0.18 W/m2K in roofs insulated at rafter level, 0.16 W/m2K in roofs insulated at horizontal ceiling level, 0.27 W/m2K in walls and 0.22 W/m2K in flat roofs and floors.

SEDBUK is the Seasonal Efficiency of Domestic Boilers in the UK.

For special requests, contact the Celotex Technical Centre.

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.

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.

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.

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.