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Measuring House Volume for an EPC

When completing a domestic energy assessment in order to provide an EPC (Energy Performance Certificate) for a home, the first thing you need to do is measure exactly how much space needs to be heated.  In other words you have to measure the volume of the dwelling.

Although many domestic energy assessors will also offer a floor plan service, especially if they are working for estate agents, in truth an EPC has no need for measuring the size of individual rooms in a house. 

The exact dimensions required are the macro dimensions, the overall size of the house.  The plan that is drawn up by the assessor for the EPC will have rooms marked on it but the exact measurement of each individual room is unnecessary.

In detached houses and easily accessible semi-detached houses the accessor will measure the dimensions of the house on the exterior.  For flats, maisonettes and terraced homes the measurements will be taken on the inside.  The method used has to be selected in the software so the calculations are automatically adjusted. 

Every nook and cranny has to be considered, as long as there is floor space it is measured.  This is why you’ll see assessors measuring bay windows carefully, as every area has to be included, no matter how small.  This is why you won’t find a domestic energy assessor who doesn’t know the formula for finding out the square root of a trapezium!  It’s ½ (A+B) x h if you’re interested?

If you have a cut out for your porch, or your unheated garage is part of the main property then these will have to be removed from the calculations.  Any upstairs floorspace above a garage may have to be treated as an extension as its floor make up is different to other parts of the house.

Speaking of extensions, all of these are measured separately, after all they were probably subject to different building regulations.

Finally, the easy part, measuring the ceiling height.  Times them all together to get the total volume that you have to heat, then on with the rest of the EPC.  Thank goodness for laser measures!

What is an Energy Performance Certificate (EPC)

When you want to sell your house or if you’re a landlord who wants to rent out a property you’re told that you need an EPC.  Sometimes you might be asked for your property’s EPC rating.

But what is an EPC?  How is it calculated?  What does it tell you?  What is an EPC rating?

What is an EPC?

Quite simply, an Energy Performance Certificate shows how energy efficient a building is, how efficient it could be and how to get from one to the other.

How is an EPC calculated?

A domestic energy assessor, the person qualified to produce an EPC for your property, is taking into account three main things:

  • The size of your property.  The first thing an assessor will do is to measure the volume of your property.  This shows them the exact amount of space that needs to be heated.
  • How you heat your property.  Do you have a gas boiler?  If so, how efficient is it?  If not, what energy source do you use to heat your home?  What emits the heat? (underfloor, radiators) How do you control that heat? (timer, TRVs, room thermostat)
  • How do you keep that heat and energy  inside your property?  In other words, once you heat up your property, how easy is it for the heat to escape?  Do you have decent loft, wall insulation?  Double glazing?  Draught proofing?

What does it tell you?

Your EPC will tell you how efficient your property is and how efficient it could be.  It will also have a list of measures which would improve the property’s energy efficiency.

For example, if the property has cavity walls which have not been insulated, it will show how much more efficient the installation of the insulation would make it.

What is an EPC Rating?

The EPC will give you two scores out of 100 for your property.  These scores correspond to a letter rating system from A-G (with A being the most energy efficient.)

The first score shows you the current EPC rating of the house, the second score shows the EPC rating should all of the energy efficiency measures be installed.