The external wall of a house is constructed of two masonry (brick or block) walls, with a cavity (gap) of at least 50mm between. Metal ties join the two walls together.
Frequently Asked Questions
Cavity Wall Insulation
How is cavity wall insulation installed?
The cavity wall is injected with insulating material by drilling holes in the external wall, through the mortar joint. Holes are generally of 22-25mm diameter and are ‘made good’ after injection. Each hole is injected in turn, starting at the bottom.
Is my house suitable?
Before the installation, the installing firm will undertake an assessment of your property to confirm that it is suitable for insulation. This assessment may be undertaken by a surveyor or the Technician before installation.
Do I have to do anything before the installation?
The drilling process does create some vibration – so it would be wise to remove ornaments, particularly on external walls, for their safety and your peace of mind.
The Technician will need access to all walls, so he will need to get inside attached garages, lean-to sheds, conservatories etc. The insulation can only be really effective if all walls are done. If you have a wall right on the boundary, you may like to mention to your neighbour, that the Technician will need to go onto their property.
Are all the systems of insulation the same?
There are several different types of insulation:
- Bonded bead (white polystyrene beads)
- Glass wool (Yellow or white in colour)
- Rock wool (Grey/brown in colour)
Note: both glass wool and rock wool are known as ‘mineral wool’.
All systems of CWI have been tested, assessed and approved by the British Board of Agrément or the British Standards Institution. All are suitable for their purpose.
All systems have a similar insulation value.
How do I know the walls are full?
Each system has a defined pattern of holes, which has been tested to verify that it results in a complete fill. Most systems have an automatic cut out, which actuates when the adjacent wall area is full. There is tolerance in the injection pattern so that the material will flow past the next injection hole.
What about the ventilators that are in the external wall?
Ventilators supplying combustion air to fuel burning appliances must be safeguarded. Similarly ventilators at ground level that ventilate below timber floors must be safeguarded. The Technician will investigate them to check they are already sleeved. If they are not, the Technician will remove them and seal around them to stop them being blocked by the insulation. Other vents, which may be redundant, such a cavity vents or vents that used to supply air to open fires in bedrooms may be closed off. The Technician should discuss these with you. Redundant airbricks may be filled.
How long will the insulation last?
For the life of the building – the British Board of Agrément say so.
Will my house be warmer?
Yes – if your heating is not controlled by a thermostat. However, if you have a thermostat, it will cut out the heating at the same temperature, so you may not notice the difference in the room with the thermostat. However, you should find that the temperature in other parts of your house improves, for example, the small bedroom on the corner.
With CWI, you should find that the house holds its temperature for longer, therefore the time between heating cycles may be longer. The result should be a more even temperature throughout the house and / or a reduced fuel bill.
If I am concerned after the installation – what should I do?
Talk to the installing firm and tell them of your worries. A contract exists between you and the installer, so they must be given the opportunity to investigate your worries.
They will help you.
What is the recommended thickness for loft insulation?
The current regulations under the EEC programme states that a minimum 270mm of loft insulation is required.
I use my loft for storage but need to get it insulated, can I do this?
Once the loft has been insulated to a minimum 270mm thickness the ceiling joists will no longer be visible making the roof space hazardous to anyone attempting to enter. However it is possible to arrange for additional joists and floor boarding to be fixed via a local joiner to help maintain your storage area. If you already have a boarded area of no more than a third of the loft area the installers will work around it and leave it uncovered.
I have electrical cables in loft. Will these be a hazard in anyway?
Apart from any cables feeding a shower unit they will not. A cable, which feeds a shower unit, is usually a 30amp. The installers will identify this and make sure this cable is not covered by the insulation by either laying the cable on top if there is enough flex or leaving a gap in the insulation around the cable to ensure it does not overheat.
I have sloping areas and flat roof areas within my property. Can these be insulated?
It is not always possible to do these areas. The reason being is that the timbers within these areas need to breathe and if loft insulation is fitted in these areas it can block the airflow off altogether. Access to these areas is usually minimal if at all existent. However every property has to be treated on an individual basis and the surveyor will make an assessment when visiting the property and advise accordingly.
My roof space is not big enough for an installer to stand up in. Will this be a problem?
It is very common that roof spaces are not big enough for anyone to stand up in. This is not usually a problem as the installers are usually working in a kneeling position on walkboards. Many companies within the industry work to a 1.4m height minimum for installers to gain access. It is very rare that a roof space is less than this.
I already have some insulation in the loft but it is not very thick, will this have to be removed or can it be topped up?
Any existing insulation can be left in the loft and an additional layer added to it to bring it up to the required minimum thickness. It does not matter how long the existing insulation has been in the loft it still retains its insulant value.
What is a draught?
Draughts are most commonly identified on windy days, when the external cold air penetrates the fabric of the building, thus displacing the warmer internal air causing noticeable discomfort. On non windy days where the internal pressure of the building is higher than the external pressure the warm air escapes through the fabric of the building causing heat loss, this is less noticeable but wastes valuable energy.
Where are the most common draughts found?
The most common place for draughts are around the frames of external wooden doors and windows. This is usually caused by either poorly fitted doors or windows, or seasonal variation. Other areas where draughts can be found are between the frames of doors and windows and the brickwork, also under the window sills. They can also be found where services or waste pipes come through the walls of the building draughts can be found.
How can I tell if there is a draught?
The easiest way to identify a draught is by wetting the back of your hand and passing it over the area where you suspect a draught may be, there should be a noticeable difference in temperature when a draught is felt. Alternatively draughts can be identified by a professional who may use a smoke pencil or match.
How long will draught proofing measures last that I have installed?
Providing that the draught proofing materials are installed in accordance with manufacturers instructions it would be realistic to achieve a life expectancy of between 5 – 10 years. However it would be recommended to look for products carrying the British Standard Kite Mark BS7386 these products can last up to twenty years.
What types of draught proofing materials are there available?
There is a wide and varied selection of draught proofing materials available. It would be recommended that you first look for products manufactured to BS7386. These will take into account seasonal gap variation and give you a long life expectancy, secondly ease of installation and finally ease of maintenance. There are products available that can even be painted or stained.
Will this affect my gas fire?
Most fuel burning appliances with more than 7kw output require permanent fixed ventilation; if you are unsure consult your Corgi registered gas installer before proceeding with your draught proofing installation.
External Wall Insulation
What exactly is external wall insulation?
Basically, a system of boards of thermally insulating material that are fixed to the building exterior and finished with a weather resistant, decorative render.
What quality standards are solid wall insulation systems subject to?
All manufacturers are independently audited and accredited to the ISO9001 Quality Management Standard, ensuring consistent monitoring of all manufacturing processes.
Why should I consider external wall insulation?
Up to 35% of heat lost from poorly insulated buildings escapes through the walls. External wall insulation significantly reduces this heat loss, leading to a reduction in annual fuels bills by as much as 25%. External Wall Insulation systems also protect the building structure, prevent deterioration, and overcome thermal bridging and condensation problems. Newbuild In a newbuild instance EWI systems are the most cost effective way of achieving the current & future thermal performance requirements for the building regulations, achieving an internal environment with low temperature fluctuations and low heating requirements.
What types of building are suitable for external wall insulation?
Virtually all common types of construction – new build (from steel frame to solid masonry) or refurbishment (traditional and non-traditional house types). Contact Manufacturer Technical Services for specific advice.
Is external wall insulation environmentally friendly?
Yes. A majority of solid wall insulation systems are manufactured and independently audited in accordance with ISO14001 Environmental Management Standard. External Wall Insulation systems incorporate insulation materials that are CFC and HCFC-free.
What about BBA certification?
External Wall Insulation systems, Renders and Decorative Masonry Coatings are covered by British Board of Agrément certification. A list of BBA certificates can be found in the BBA area of this website.