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Frequently asked questions about Cavity Wall and Loft Insulation

Cavity Wall Insulation

What is a cavity wall?

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.

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.

How long does it take?

Cavity Wall Insulation normally takes around two hours to install, but the time does depend on the size of the house and other factors, such as access.

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.

Is there much mess?

The drilling process inevitably creates a little dust, which will be cleared at the completion of the job. It may be wise to remove vehicles from the drive and things close to the walls. This will also give the Technician better access for equipment and tools.

Does the Technician have to come into the house?

The Technician must undertake checks before and after installation, including any heating appliances, so it is essential that they have access inside the property.

My house is semi-detached, how do they stop insulation going into my neighbour’s cavity?

Assuming your neighbour’s house is not already insulated, the Technician will insert a cavity barrier at the party wall line. This is usually a length of bristle brush. Of course, if the neighbour’s house were to be insulated at the same time, the cavity barrier would not be needed.

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)
  • Urea formaldehyde foam (white foam)

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.

Except for Urea Formaldehyde foam, the systems can be used in all parts of the UK.

All systems have a similar insulation value.

Are the Technicians trained?

All Technicians (team leaders) undergo training by the system supplier and the installing firm to ensure they are competent in CWI and carry a training card. Please feel free to ask to see the training card.

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.

Is the insulation ‘dense’?

No, as the insulation is contained within a masonry wall, it doesn’t need to be ‘dense’. For insulation and other purposes, a light density is better. Before installation, the Technician will undertake a quality test to ensure the insulation will go into the wall at the right density. He will also note the amount of material used, to know that sufficient insulation has been installed.

Note: Drilling a hole in the outer wall and testing the cavity fill with a rod or pencil will not provide any meaningful information.

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.

What about filling the holes?

The Technician will fill all the injection holes with mortar to match the existing as closely as possible. He will use a mix that closely matches the existing colour and texture. On pebbledash finishes, he will apply pebbles to the surface to match the existing finish. After weathering, the holes are difficult to see.

But my house has painted areas?

Normally, the installing firm will not paint the injection holes. Unfortunately, even if the original paint is used, it may not match due to weathering. So it may be necessary for you to consider painting the area, after the mortar has dried.

You should discuss and agree what will be done, with the installing firm.

Do I apply for the CIGA 25 Year Guarantee?

No, the installer or the agent submits the Guarantee application. The Guarantee is posted to you within days of the application being received at CIGA. - Keep it safe

CIGA is non-profit distributing; its only function, is to stand as guarantor for the promises set out in the Guarantee. It has the resources to meet the promises made in the Guarantee.

All professional approved installing firms are members of CIGA and can apply for a CIGA Guarantee, for properties built with traditional cavity walls. You should insist on a CIGA Guarantee, since nothing else can give you the level of assurance to which you are entitled.

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.

Are there any maintenance or servicing requirements?

No, not to the Cavity Wall Insulation, but normal building maintenance is needed.

How long will the insulation last?

For the life of the building - the British Board of Agrément say so.

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.

If I have thermal breeze block on the inner leaf does this mean I do not need CWI?

If you have the recommended 50mm cavity width then your cavity is suitable for insulation and the insulation will improve the thermal performance of the external walls of the property.

When it rains or if water gets into the cavity will the insulation allow water through and cause damp?

All systems on the market that our registered installers use are tested and assessed and will not allow water to cross the wall construction via the insulation. Water which penetrates the outer leaf of the wall will drain down the cavity face of the outer leaf.

If I have a random stone construction can I have CWI?

Due to stone properties not having a regular cavity, it will require an installer to assess the individual property.

Loft Insulation

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.

How much heat is lost through the roof?

As much as 25% of heat is lost through a roof which is not adequately insulated.

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.

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 a cold water tank and pipework in my loft. Will these need to be insulated as well?

Yes they will. Any company who carries out loft insulation is responsible for insulating any tanks and pipework that are in the roof space to ensure they do not freeze come the winter period.

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 some lights within the ceiling (downlights) that protrude into the roof space. Will these cause any problems?

No. The installers will cut the insulation away from these leaving a gap of approximately 2” around the lights to prevent overheating.

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.

Will I have any problems with condensation in my loft if I have it insulated?

Providing there is sufficient ventilation existing within the roof space, condensation will not occur. The installers are responsible for leaving all areas of ventilation i.e eaves level etc clear of insulation to maintain the current airflow. However if at the time of survey it is noticed there is already signs of condensation then the surveyor will advise of appropriate measures that are available to help cure this.

My hatch is very small. Will the installers be able to get the insulation into my loft?

On rare occasions where the loft hatch is not big enough to get the insulation into the loft a new loft hatch can be created by the installing company at an additional cost.

I have quite a draught coming from my loft hatch. Can anything be done about this?

Yes. Upon completion of the work the installers will fit a draught excluder strip around the loft hatch providing it is made of timber.

Will there be much mess whilst the work is carried out?

Any mess created should be very minimal, as the installers will provide dustsheets to cover the areas of carpeting/flooring around the loft access areas to the door of entry to the property.

How long will the work take?

Anything between 30 minutes to an hour and half depending on the size of the property and the amount of insulation being installed.

Is there any funding available to help assist with the payment of loft insulation?

There are various grants available at the moment but they all have individual criteria’s. The installing company will advise accordingly if you are able to access any of these.

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