Welcome to our blog post – Wall Construction & Insulation
It is down to the energy assessor to work out the construction of these walls and whether they have been insulated.
The EPC is a non-evasive survey. We will not drill holes in walls to check if a wall insulated. The software we use to create EPCs is based on building regulations. If we can not gain access to a building part to establish the construction, the software will revert back to the building regulations at the time the property is built. A cavity wall built in 1960 would be assumed by the software to have no insulation when it was constructed however a cavity wall built in 1983 would be assumed to have insulation.
It would be beneficial to let the energy assessor know when the house was built and the age of any extensions.
Cavity Wall Insulation:
Did you know, if you have had your cavity walls insulated since the property was built, we will need to see either visual evidence or certification?
Did you know, if you have had retro fit external or internal wall insulation carried out, we can only note this down if we can see it or you can provide us with correct documentation?
Here is an example of a Cavity Wall Insulation certificate. If the walls have been rendered over since the cavity walls were insulated, we will need to see this certificate to note that it has had insulation installed since it was built.
The energy assessor will also need to be provided with documentation if your property has had internal or external wall insulation added.
Internal Wall Insulation:
Internal wall insulation is different to dry lining the outer internal walls of your home. The diagram below demonstrates the make up of a solid wall that has internal wall insulation.
We would need to know the thickness of the insulation used and ideally the material used as some materials have better thermal values than others.
Evidence can either be noted down if we can access glimpses of the insulation or we would need letter headed documentation from your builder stating the completed works including the thickness of the insulation. If only parts of the property have been insulated we will need clarification of which walls have been retrofitted.
Internal wall insulation can be measured through small peep holes that may be present in the property – in the past we have managed to measure the insulation in a bathroom where the extract fan had not been screwed in properly so we could take it out to reveal behind the dry lined wall. Another example was inside a cupboard that went back to the original wall where the electric meters were still attached.
External Wall Insulation:
External wall insulation is very similar to internal wall insulation but is placed on the outside rather than the inside of a property. The thickness of external wall insulation tends to be slightly thicker than internal.
The insulated boards are hard for an energy assessor to notice as the builder will most likely have rendered or added weatherboarding on top to hide the panels. If there are any glimpses of the insulation please let your energy assessor know before or when they arrive. We will need to be able to hold a ruler up against the insulation to measure it.
If there are no glimpses and you are aware of the insulation, please have ready for your assessor, official documentation stating the works – architects plans with stated insulation or a letter headed document from your builder stating the completed works listing location of insulation and thickness.
If we do not have this information then we would not be able to state on the EPC software that the walls are insulated – this could make a big difference to your overall energy rating, especially if the house was built before the 1900s when thermal u-values were pretty much unheard of!
