Home Energy Rating for existing homes: assessors must input permanent internal window coverings, and can enter how well each one fits

The short answer, by who you are

• You sell or install blinds, shutters or curtains. On a Home Energy Rating of an existing home, a permanent internal covering you fitted is an input the assessor must record. If they use Method 2, how you mounted it counts: the method classifies fit by the largest gap around the covering and the airflow through it. Side channels, a reveal mount with small gaps and a pelmet with a top all move a covering up the scale.
• You make, import or specify product. A covering is “more insulating” on this method only through one of three features: a bright metallic outside, layers separated by air with one layer of low through-airflow, or a solid non-metal layer thicker than 5 mm. Metal plantation shutters do not qualify on thickness, and are entered as venetian blinds.
• You own or rent out a home and are getting a rating. The assessor photographs each type of internal covering. Temporary coverings should not be modelled.

Read alongside our guides to the WincovER product ratings and window film’s WERS ratings. Neither scheme is mentioned in the Technical Note or the Guidance Note; this method has its own way of describing a covering.

What the assessor must record

The Home Energy Rating for existing homes is the expansion of NatHERS, the Nationwide House Energy Rating Scheme, to homes already built. Its Stage 2 began on 1 July 2026, since the release of Stage 1 of the expansion in July 2025, with assessor training and accreditation opening to all those interested in becoming an assessor. The rules an assessor follows are in the NatHERS Technical Note for existing homes, version 20260701, published by the federal Department of Climate Change, Energy, the Environment and Water. It describes the assessment as one of the building’s thermal performance, its energy-using fixed appliances and the renewable energy produced and stored on site, not the behaviour of the people who live in it.

Clause 8.11 is the one that matters to this trade: Assessors must input permanent internal window coverings where present, while temporary and non-permanent coverings should not be modelled. Where a window has more than one covering, only the layers that fully cover the window go in. The assessor picks the type from a fixed list.

1. Holland blindsroller
2. Venetian blindsincludes metal plantation shutters
3. Roman blinds
4. Vertical blinds
5. Honeycomb blindsmultiple layers separated by air and low through-airflow fabric
6. Plantation shuttersthick solid layers not made of metal
7. Open weave curtains
8. Close weave curtains
9. Heavy drapesmultiple layers separated by air and low through airflow lining

The Note does not say what makes a covering permanent; we found no definition in it or in the Guidance Note that goes with it (searched 9 October 2026). Pelmets, side channels and linings are not types on the list. They come in through the second method.

Two ways to enter a covering

Clause 8.13 gives the assessor a choice. Under Method 1 they enter only the type, and the software applies default values for that type. Under Method 2, the Assessor enters the type of window covering and also enters the 4 window covering characteristics that allow a more accurate rating. The choice is not always free: Where pelmets or any other improved window covering features are present, these must be entered using Method 2.

Method 1

Type only

• The assessor enters one of the nine typescl 8.13(i)
• The software applies default characteristic values for that typecl 8.13(i)
• Photos of each type of internal coveringevidence, p 39

Method 2

Type plus four characteristics

• Outside appearance: bright metallic, light, medium or darkcl 8.17, Table 13
• Light through the covering when fully closed: little to no light, some light, or a lot of lightcl 8.18, Table 14
• Insulative value: more insulating or less insulatingcl 8.19
• Fit: Loose fitting, Medium fitting, Close fitting or Fully enclosedcl 8.20 to 8.22, Table 16
• Required where pelmets or other improved features are present; photos must show the four characteristicscl 8.15; evidence, p 39

Outside appearance means the outward-facing surface of the covering. The Note warns that its “medium” is still quite light in tone, and that metallic coatings that are dull silver or darker count as medium, not bright metallic.

Fit is where the installer comes in

For Method 2, the assessor estimates fit from two things: the gaps between the covering and the nearest frame or wall at the top, sides and bottom, and the airflow through the covering itself. Table 16 of the Note sets the classes. Laid out as a grid, it reads like this.

Fit class by largest gap and airflow through the covering

Largest gap	High airflow	Restricted or medium	Low airflow
20 mm or more	Loose	Loose	Loose
Under 20 mm	Loose	Loose	Medium
Under 4 mm	Loose	Medium	Close
Under 1 mm	Loose	Close	Fully enclosed

Loose fitting

Venetian blinds, vertical blinds, mesh or lace curtains. Cellular blind (low through-airflow) with large edge gaps. Curtain on rod or rail not touching ceiling (top gap ≥ 20 mm).

Medium fitting

Plantation shutters (medium through-airflow) with small (< 4 mm) edge gaps. Reveal-mounted roller blind with small top and edge gaps.

Close fitting

Reveal-mounted pleated or cellular blind (low through-airflow) with very small edge gaps (gaps <4 mm).

Fully enclosed

Roller blinds (with block-out coating) with enclosed side channels. Cellular blinds with enclosed side channels. Curtains hanging to floor or sill with an enclosed pelmet and with block-out/thermal lining or coating (low through-airflow).

Two features in the Guidance Note for existing homes do most of the work at the top of the grid. On pelmets, it says They can improve the thermal performance of the window covering by reducing the top gap size provided they are mounted flush to the wall or window reveal and are enclosed on the top, front and sides. Its photographed counter-example is a pelmet not flush to the wall, with a top gap between 4 and 20 mm. On side channels:

“Side channels can be installed on roller blinds and cellular blinds which enclose the side edges of the window covering and effectively reduce the edge gaps to zero.”

One more rule favours the best-fitted layer. Where a window has several coverings, the assessor assesses fit only for the one that gives the best classification, or the one closest to the window if that is unclear (clause 8.22). The Guidance Note’s worked example is a white sheer curtain closest to the window with a lined heavy curtain in front, a pelmet flush to the wall and the curtain flush to the floor: it classes as Fully enclosed, assessed on the heavy curtain alone.

What counts as “more insulating”

Insulative value has two classes, and the Note sets out exactly what earns the better one. Everything else is “less insulating”.

Bright metallic outside

Counts: a bright metallic coated fabric

Does not: a brushed metallic venetian finish, or a darker or dull metallic coated fabric (both classed as medium)

Layers separated by air, one with low through-airflow

Counts: a cellular or honeycomb shade with enclosed air pockets and low through-airflow fabric; a heavy curtain with a separate densely woven lining making an enclosed air pocket

Does not: a pleated shade with no enclosed air pockets; a cellular shade in high through-airflow fabric; a lined roman blind with no significant air gap between its fabrics

A thick solid layer, not metal

Counts: timber plantation shutter louvres thicker than 5 mm

Does not: timber venetian slats under 5 mm; thick metal plantation shutter louvres

The Guidance Note even tells the assessor how to check a shutter: look for end caps on the louvres and tap one, because metal makes a sharp noise.

What changed, and when

The Technical Note has been reissued four times since its launch version, numbered 20250520. These are the points where the covering rules moved.

1. Version 20250520Launch version of the Technical Note for existing homes
2. Version 20250611Instruction added to model metal plantation shutters as venetian blinds
3. July 2025Stage 1 of the expansion to existing homes released
4. Version 20260109Clause 8.9: internal window coverings “must be modelled where present”; Method 1 applies “conservative” default values
5. 1 July 2026, version 20260701Stage 2 begins. Clause 8.11: assessors must input “permanent” coverings; temporary ones should not be modelled; “conservative” is gone from Method 1

The January 2026 version said Internal window coverings must be modelled where present. and described Method 1 as applying conservative default window covering characteristic values. The July version limits the rule to permanent coverings and calls the Method 1 values simply “default”. Its change log does not list either change; it does list a new section defining standard settings and default values, which says default values are typically worst-case values. The Note does not say whether the Method 1 values for coverings themselves changed. The Home Energy Rating news item on the July updates says the Technical and Guidance Notes were revised to streamline assessments, support comparability and clarify issues identified during Stage 1.

This is a method for existing homes. The Technical Note for new homes, version 20241023, which governs ratings used to show a new design meets the building code, has no section on internal window coverings; its shading section deals with eaves, neighbouring buildings, screens, glazed verandahs and protected trees. We have not read the software documentation, so we do not say how a new-home rating treats a blind or curtain.

What the same scheme tells households

The Home Energy Rating site’s Improving your rating page, last updated 24 June 2026, puts coverings among the quick wins for both the Home Energy Rating and the Star Rating:

“seal gaps around doors and windows, install shading and improve window coverings by using heavy curtains or cellular blinds.”

The scheme’s upgrade factsheets for single dwellings, one per climate zone, put numbers to it. Each upgrade is scored Low, Medium or High for cost, savings and effort. Savings are Low at 10% of annual bills or less, Medium up to 30% and High above 30%; cost is Medium between $1,000 and $4,000, not counting installation. The factsheets have a row for curtains and one for external shading; there is no row for internal blinds.

Our read

This section is opinion, built on the documents above.

For a blind business, the useful thing here is the vocabulary. “Energy-efficient blinds” means nothing to an assessor. Under 4 mm edge gaps, enclosed side channels, a pelmet with a top that sits flush, a low through-airflow fabric: those are things the method names and an assessor can see and photograph. On this method, a cellular blind with large edge gaps is Loose fitting, the same class as a venetian. The fabric did its part; the install did not. A business that measures and records its gaps at handover, and leaves the customer a note of the mounting, the channels and the lining, is giving the next assessor the evidence Method 2 asks for.

The other half is restraint. The same scheme’s factsheets score curtains Low for savings everywhere but the alpine zone, and external shading Low everywhere. That is the government’s own number, and it should cap the sales pitch. Sell fit, comfort and a covering the method can see. Do not sell a power bill cut the scheme itself does not claim. And the department could help everyone by saying what “permanent” means: the line between a curtain an assessor counts and one they ignore is now a single undefined word.

Sources

1. NatHERS Technical Note for existing homes, version 20260701, Department of Climate Change, Energy, the Environment and Water, July 2026, listed as the current document on the Technical Note page (read 9 October 2026): change log; clauses 2.16 and 2.19 to 2.21; clauses 8.11 to 8.23 and Tables 13 to 16 on internal and external window coverings; the windows and doors evidence requirements.
2. NatHERS for existing homes Technical Note, version 20260109, superseded (read 9 October 2026): change log back to the launch version 20250520, including the 20250611 entry on metal plantation shutters; clauses 8.9 and 8.10.
3. NatHERS Guidance Note for existing homes, version 20260701 (read 9 October 2026): section 8.4 and Tables 8-12 to 8-16, the pelmet and side-channel guidance, the worked examples and the shutter check.
4. NatHERS Technical Note for new homes, version 20241023 (read 9 October 2026): searched for internal window coverings; section 10 on shading.
5. Home Energy Rating Upgrade Factsheets, single dwellings, climate zones 1 to 8 (all eight PDFs read 9 October 2026): the windows and shading rows and the cost, savings and effort definitions.
6. Improving your rating, Home Energy Rating, last updated 24 June 2026 (read 9 October 2026).
7. Stage 2 of Home Energy Rating for existing homes begins, Home Energy Rating news, 1 July 2026 (read 9 October 2026).
8. Existing homes software and assessment method updates, Home Energy Rating news, 1 July 2026 (read 9 October 2026).

How we did this. We downloaded the current and the immediately previous Technical Note for existing homes, the current Guidance Note and the current Technical Note for new homes from the Home Energy Rating website, and compared the window covering clauses of the two existing-homes versions line by line. We searched every document for blind, curtain, pelmet, shutter, drape and covering. The fit grid rearranges Table 16 without adding to it; where a covering meets two of the table’s rows we show the higher class, which is our reading. The 7 of 8 count is ours, from the eight factsheets. We have not read the rating software or its documentation, so this story does not say how much any covering changes a rating, and we have not asked the department. We have no commercial relationship with any maker, importer or installer of window coverings.

Assess homes, or fit coverings, and read a clause differently? Tell us and we will check it at the source and log the outcome here.