Cavity Wall Insulation Frequently Asked Questions

General | Cavity Wall Insulation | Loft Insulation

What is cavity wall insulation?

Cavity wall insulation is generally a mineral wool made out of either treated glass or rock fibres which can be blown into the wall cavity of many homes. It creates the same quilt-like insulating effect as loft insulation.

How will the insulation be installed?

A Mark Group technician will arrive at your home and perform a pre-installation check. Remember to ask them for their identification cards.
Firstly, the trained technician will drill a series of 22mm-25mm holes in the external wall mortar in-between the bricks of your home.Using the machine in the van the technician will then inject the insulation into the cavity through the drilled holes.
All this takes between two to three hours (for a three bedroom semi detached house).

Do I have to do anything before the installation?

All surveyed visits are left with a guide to help you prepare
The drilling does create some vibration – it would be wise to remove ornaments, particularly on external walls, for safety and peace of mind.
The technician will need to gain access to all walls, so he will need to get inside any attached garages, lean-to-sheds, conservatories etc. If you have a wall right on a boundary you may like to mention to your neighbour that the technician will need to go onto their property to complete the installation.

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 your home for safety purposes.

Is there much mess?

The drilling process inevitably creates a little dust. The technician will go around the outside of your home at the end of the installation and clean up. We also believe it wise to remove vehicles from any driveway near to where drilling will take place. In return this will give the technician better access for equipment and tools.
It is important to note however, the conditions and nature of our weather can at times hamper even the most determined attempts.
Please, take the time to speak with our staff and be sure that you are happy with the finished product.

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

This is usually a length of bristle brush. If the neighbour’s house were to be insulated at the same time, or has already been insulated, the cavity barrier will not be needed.

What about the external wall ventilators?

Ventilators supplying combustion air to fuel burning appliances and those at ground level that ventilate below timber floors must be safeguarded.
The technician will check that any ventilators are protected as part of our safety inspection. Other vents, which may be redundant, such as cavity vents or vents that are in bedrooms may be closed off.
The technician should discuss these with you, so if you have any questions please ask.

What about filling and finishing the drill holes?

The technician will fill all the injection holes with mortar that closely matches the existing colour and texture.
On some older properties or weathered facades it may take several months for the newness of the mortar to blend, but these holes are very small and they will blend as the weather effects them.
On pebbledash finishes, they will apply pebbles to the surface to match the existing finish, as close as possible.
Normally, where you have a painted wall we 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.

When will I receive the guarantee?

The guarantee you will receive is called a “CIGA” (Cavity Insulation Guarantee Agency) which guarantees workmanship and materials for 25 years.
We will apply for it on your behalf and it will be sent to you direct from CIGA. It can take up to 8 weeks for this to be delivered to you after installation.

Will my house be warmer?

Insulation dramatically reduces heat loss through the insulated wall therefore you will be able to achieve the same temperature in your home by turning your thermostat down by a little.
Your property should still achieve the desired warmth because the house will retain its temperature for longer.

If I am concerned after the installation - what should I do?

Talk to Mark Group (the installer) to discuss your concerns and allow us an opportunity to investigate your worries. Most concerns can be resolved swiftly and efficiently so please do not hesitate to speak to a member of their customer services team. Contact details will be left with you at the point of survey and installation.