Doors

At the time of writing, the methodology for EPC assessments of existing dwellings is RDSAP 10. A significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2027. In addition, government consultations indicate future changes to the format of EPCs and minimum rating levels required for private rental properties. Approaches to improving EPC ratings will therefore change in the future.

Doors are an element of 'building fabric' and contribute in a small way to the overall heat loss of a property.

This in turn affects running costs and because EPC ratings are currently a cost-based metric, it affects the overall rating.

During an EPC assessment, energy assessors record the number of external doors present at the property.

Only external doors are effectively considered, or rather doors that are within heat loss walls. Internal doors within a property are not normally included. Also, the door from a flat to a heated corridor for example is not counted.

Qualifying doors that have a glazing content of 60% or more are recorded as windows in the assessment rather than doors.

It is therefore entirely possible for a property to be assessed as having no doors in the case where all doors are highly glazed or not counted.

In most cases, assessment against the 60% rule is easy to make by simply looking at a door. In cases where it is not clear, the procedure is as follows: Measure both the area of the whole door frame, and also a total of the area of glazing in the door. Divide the glazed area by the frame area and multiply by 100 and you arrive at the percentage proportion of glazing.

For each recorded door, the presence or absence of draughtproofing is also recorded.

Remember, assessments only record the presence of various elements, including doors, and no information is recorded about their condition.

Finally, an option is available to indicate that a door is 'insulated'. This requires documentary evidence of the overall u-value of the door, and this needs to be manually entered.

The RDSAP 10 Specification document advises about 'insulated' doors as follows:

"A door is counted as insulated only if documentary evidence is provided, which must include U-value or manufacturer reference enabling the assessor to ascertain the U-value from the manufacturer."

This would tend to indicate that any door that has clear documentary evidence of it's u-value, would be able to be declared as 'insulated' in an EPC assessment, and the u-value enterred manually.

At the time of writing, the methodology for producing EPCs for existing dwellings is RDSAP 10.

This methodology assumes the area of a door is 1.85m2 and there is no option to alter this.

Due in part to this, a pair of French doors is counted as two doors in an assessment.

The methodology also assumes the u-value of a door as follows by default (extract from the RDSAP 10 Specification document):

Age bands vary slightly between England & Wales, Scotland and NI, but for England & Wales where I am based, these represent:

Age band M is 2023 onwards

Age band L is 2012 to 2022

Age band K is 2007 to 2011

Age bands A-J is up to 2006

So for doors leading to outside space, the default u-value depends on the construction age-band of the property. The value ranges from 1.4 for modern dwellings to 3.0 W/m2K for older ones.

Corridors & stairwells in the table refer to flats, and they work a bit differently.

From some quick research, I believe the current maximum u-value allowed for new replacement doors in existing dwellings is 1.4 W/m2K.

This effectively fits in with the table above for age band M although I also believe this is better than the current new-build backstop which is 1.6, which is a bit odd, although I could understand new builds having 1.4 just through standardisation across the industry.

Consider the case where you may have an older house, say a 1950s terrace house. If you have brand new replacement doors fitted today then the u-value of those doors will be 1.4 W/m2K (or better) but the methodology would ordinarily assume a value of 3.0 instead, unless manually overridden, and supported with documentary evidence.

By way of comparison, I assessed a Passivhaus last year, constructed in 2015, which had doors with u-values of 0.82 W/m2K.

The following recommendations are available in the methodology relating to doors:

Draught proofing of windows or doors

This recommendation is considered when:

• The existing dwelling has single glazed windows or external doors which are not draught proofed.

It is triggered if:

• The existing dwelling has less than 100% draught proofing of windows and doors.

The rating provided with the recommendation applied includes:

• 100% draught proofing

Insulated doors

This recommendation is considered when:

• The existing dwelling is
  • a house, bungalow or park home or
  • a (flat or masionette) and (no corridor or more than one door) ie door directly to outside

It is triggered if:

• Door(s) directly to outside not insulated

The rating provided with the recommendation applied includes:

• Change doors directly to outside to insulated doors with u = 1.4 W/m2K

This second recommendation of course only applies to doors and not doors that have been recorded as windows. Separate recommendations apply for windows.. 

Also, recommendations appear on an EPC only if they improve the rating by at least 1 SAP point, or 0.5 SAP points in the case of cylinder insulation, draught proofing and low energy lighting.

What I find interesting is the recommendation for 'Insulated doors' and the applied rating including: Changing the doors to 'insulated doors' with a u-value of 1.4.

As all new standard replacement doors fitted today will have a u-value of 1.4, if you have an older property and have a new replacement door fitted today, it should be possible to obtain documentary evidence of the u-value of that door from the installation company, declare the door as 'insulated' in a fresh EPC assessment and manually override the u-value.

This would not in itself trigger a Smart Audit, although the difference in rating it could make would be very limited.

We'll try this in an exercise next to see what difference it could make.

Here are some indicative ratings from our Case Study 2 property. This is a 1950s mid-terrace house.

The baseline is with three standard doors, with no significant glazing component.

We then try those doors without draught proofing.

We then try the doors with draught proofing again and one by one declare them as 'insulated' and manually overide the u-value with 1.4 W/m2K.

Finally we try all three doors with a u-value of 0.82 which is the performance level of doors in a Passivhaus I assessed in the past.

For this 1950s property, by referring to the u-value table earlier on this page, we can see the methodology will ordinarily use a u-value of 3.0 W/m2K for doors in this property.

If we had replacement doors fitted today, and could provide documentary evidence from the supplier that their u=value was at worst: 1.4 W/m2K, then each door could potentially provide us with a rough additional rating value of 0.2 SAP points each.

Replacement doors might cost around £900 each so that's quite a lot of money to invest just for a rating gain.

If you've had your doors replaced recently however, and perhaps if you have documentary evidence avaiable of the u-value, this might help as another measure to increase your rating.

We actually had our doors replaced in 2020 at this property, and from research I believe the worst case u-value allowed at the time was 1.8 W/m2K but I don't think we have any documentary evidence available to prove that.

In our table above, the last line is for three doors with a u-value of 0.82 W/m2K. This is the thermal performance of doors I assessed at a Passivhaus last year. They were significant doors in every respect, and would cost much more than the standard doors fitted to our house. The EPC rating increase for this house would only be brought up to about 0.27 SAP points per door, showing that the investment in this one area results in diminishing returns in relation to cost invested.

As always, engage with a domestic energy assessor to learn what rating you might achieve before starting ay works. This will provide a far better level of certainty with your final rating outcome.

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