Room In Roof

At the time of writing, the methodology for EPC assessments of existing dwellings is RDSAP 9.94. This updates to RDSAP 10 on 15th June 2025 and a significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2026. In addition, government consulations indicate future changes to the format of EPCs and minimum rating levels required for priate rental properties. Methods for improving EPC ratings may therefore change in the future.

This is where a room or even a whole upper 'storey' in a property is located within what would otherwise be a pitched roof and loft space.

It could be that these rooms were either built into the property in this way originally, or it could be that they were formed via a 'loft conversion'.

Here's a nice example, located in the centre of Lacock in Wiltshire:

We'll add some content here about this subject shortly, but the main issues are with the level of insulation present and the documentary evidence required if work has been carried out since the property (or building part) was originally constructed.

The definition of Room In Roof is met when:

• 50% or more of the length of walls that face the eaves have an internal height that is less than 1.8m at what is often called the 'Common Wall'. Gable end walls and party walls are excluded from this 'length' consideration.
• A fixed staircase enables access and one is able to walk down that staircase facing forwards. A fixed step ladder would not fulfill this requirement.

If 50% or more of eaves facing walls have an internal height of 1.8m or more, then the storey is considered in the assessment as a normal storey, not a Room-in-Roof.

Once a room-in-roof has been identified, a construction dateband must be assigned to it in the EPC assessment.

Guidance instructs that this dateband must be the same as the building part that the room-in-roof is part of, unless documentary evidence is made available to prove otherwise. This is described in RDSAP 9.94 Convention 3.13 as follows:

"Age band for roof room: Same as the bulding part unless evidence proves otherwise. Evidence includes documentary evidence (e.g. planning applications), dated photographs of the property concerned validating date of construction (the evidence might establish the earliest possible date of construction if roof room is absent in the photograph)."

Therefore, if the Room-In-Roof was created after the original construction of the building part, but documentary evidence is not available to prove this, then within the EPC assessment it must be recorded with the same databand as the building part it is part of. This can lead to a reduction in the final EPC rating.

Energy assessors need to abide by the rules and conventions, firstly to ensure that EPCs are accurate, but also because some EPCs are audited. If an EPC fails such an audit due to a lack of evidence to support the information recorded, then there are consequences for the assessor's accreditation. Decent assessors will be keen to retain their professional accreditation and will not want to record a room-in-roof date incorrectly.

It would therefore be wise for property owners with a room-in-roof to research as much as they can about their property and obtain as much documentary evidence about the room in roof as possible. This is best done before calling an energy assesor to conduct an EPC, and it would be best to make the evidence available to the energy assessor via email before any visit to find out in advance whether the asssessor thinks the evidence is sufficient.

In the next table, I model the presence of a simple Room In Roof on my own house (under RDSAP 9.94) to see the effect that different datebands (England & Wales) have on the EPC rating. This is the property we cover in our Case Study 2 page. For the Room In Roof, I declare the floor arear to be the same as that of the first floor of the building. I also add 2 to the counts of habitable and heated habitable rooms, and 1 to the number of storeys. I then change the construction dateband of the room in roof and see what difference it makes to the EPC rating:

So, you can see how the EPC rating varies, depending on the construction dateband of the Room in roof. The older the dateband is, the worse the EPC rating. This is due to the lower building regulations in those earlier datebands.

For the worst case situation with this property, if I had a room in room constructed very recently, say since 2012, but I did not have any documentary evidence to prove that it complied with bulding regulations at that time, then an assessor would have to delcare the dateband of the room in roof to be the same as that of the main building. This would lead to an 11 point reduction in the EPC rating with this particular property.

These indicative figures only apply to my property. Always consult a local domestic energy assessor to consider your property before making any decisions.

A recommendation for room in roof insulation can appear on an EPC for an existing dwelling.

The criteria are:

• The property has been declared as having a room in roof
• Any part of the roof rooms <100mm insulation or U value >0.5

The EPC rating expressed when this recommendation has been included is based on the insulation being improved such that: the U values of all room in the roof elements are improved to a U value of 0.18.

Work in progress....

An update in methodology to RDSAP10 on the 15th June 2025 will lead to changes in the way that a Room In Roof is assesssed.

This in turn may lead to slightly different EPC ratings for properties with particular types of room-in-roof if they were re-assessed unde rhte new methodology.

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