EPCs – What Do Assessors Do During a Survey?

EPC Orpington

Nowadays, most people are aware of what an EPC is, but they still aren’t aware of what an assessor needs to do and see when they visit their property.   EPC Orpington explains all the things an assessor considers during an assessment.

Age of House and Type

If we know the year that the house and any extensions were built in, then we can get a good idea of the energy efficiency measures the house originally had in place.  These assumptions are based on the building regulations present at the time. 

For example a house built in Orpington in the 1950s usually has cavity wall which was not originally filled and a loft space that was not insulated as a matter of course.

The build type generally tells us where heat can escape from.  If we are considering a flat then they could be surrounded on all sides by other dwellings which are also heated.  This makes some flats particularly energy efficient, whilst some detached houses are particularly inefficient.


This is the most time consuming part of the survey, your assessor is effectively measuring the volume of the property.  The reason for this is to work out how much space has to be heated.

EPC Orpington will also consider conservatories at this point.  Conservatories which do not have a separating door are considered energy inefficient.


The type of wall is important as it tells us what to look for insulation wise and what to recommend.  Cavity wall insulation is relatively cheap or free to get installed, whereas solid wall insulation can cost thousands of pounds and be a huge job to complete.

If it’s a cavity wall then we check to see if the cavity has been filled retrospectively by looking for drill marks on the external wall. 


For the most part we simply put our head in the loft to check for insulation.  If insulation is present we measure the depth.  A depth of 270 mm is recommended for traditional insulation.

It’s worth remembering that if you crush insulation down under floorboards, it’s only as effective to the depth you’ve crushed it to.


Are they solid concrete or suspended timber?  Have they been retrofitted with insulation?


We consider the glazing you have.  Obviously single glazing is the least efficient but this is followed by double glazing fitted before 2002, which is less efficient than glazing fitted afterwards.

If it was fitted before 2002 then we need to know what the frame is made out of, PVC is the most efficient.  If it’s PVC we consider the gap between the panes, anything of 16 mm or higher is considered best.

At this point we also count the number of doors to the open air the property has and whether any of these have certificates for insulation.  We also look at draught proofing.

Lighting and Ventilation

We count all of the light fittings in the house and look to see whether they have low energy or LED bulbs in place.

Next, we see if any mechanical ventilation systems or cooling systems have been fitted in the property.  We also examine fireplaces to establish whether they are open and whether warm air can escape.


We check out the boiler or any other means that you use to heat your home.  An assessor will consider each main heating system (if you have more than one) as well as any secondary means of heating you may have (open fires, electric heaters etc).

How the heat is distributed is also important, whether that be by radiators or underfloor.  High consideration is also place on how that heat is controlled.  Do you have a timer to ensure it only comes on when needed?  Do you have a room thermostat to control temperature?  Do you have TRVs to control temperature in individual rooms?

Hot Water

How do you heat your water?  Which heating system do you use?

If you have a non-combi boiler then we take a look at the hot water cylinder, we consider its size, whether it has been insulated, what type of insulation it has and does it have a thermostat?

How many rooms are supplied with hot water is the next thing that EPC Orpington considers.  Do these rooms have baths, showers or both?

It is at this stage where we consider newer water heating technologies and whether the property has them.  These include solar water hating, flue gas heat recovery systems and waste water heat recovery systems.

Other Technology

Solar photovoltaic panels are considered here and whether the house has a wind turbine.  We also consider whether the latter would be suitable (usually only recommended if the property is in a rural setting).

We look at the electric meter to establish the type and whether cheap electricity tariffs are available.  We also look at the gas meter, the presence of one is relevant if the property doesn’t use gas.

Other useful info

Lastly, EPC Orpington considers any other factors which may affect the overall result.  This could be the use of more obscure methods and fuels to heat the property and whether it has a swimming pool or anything else that would use an inordinate amount of energy.

If you need any of these points clarifying please call EPC Orpington at any time.  If you have a survey booked in, feel free to ask your assessor any questions on the day too.