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Best window seal for portable air conditioner UK

Updated: 20 October 2026

The best window seal for a portable air conditioner in the UK is the one that names your window and has review text that belongs to that listing. A 4.0 from thousands of reviews can be a parent count copied onto three lengths. This short list is from the twelve amazon.co.uk rows in our [air conditioner window seal comparison](/hub/cooling/air-conditioner-window-seal), with prices from 19 October 2026. Peter F. used those listings and the review notes. Nobody ran a lab test. A qualifying purchase can earn a commission at no extra cost to you. The picks assume a hinged window and a cloth kit, rather than a cut acrylic sheet.

The best window seal for a portable air conditioner in the UK is the one that names your window and has review text that belongs to that listing.

Our top picks

Derwit Derwit 4 m casement window seal

Best overall

Derwit Derwit 4 m casement window seal
6.7/10about £17.99
View offer
DREO DREO 400 cm window seal

Rank 2

DREO DREO 400 cm window seal
7.3/10about £19.99
View offer
Machine-YA Machine-YA 300 cm window seal

Best value

Machine-YA Machine-YA 300 cm window seal
7.2/10about £16.38
View offer
On this page
  1. 1.How to read these stars
  2. 2.A casement zip kit with its own reviews
  3. 3.The £7.99 sheet and the dear shared file
  4. 4.When none of these is the pick

How to read these stars

Read the review file before the average. Three MOEGFY ASINs show 4.0 from 4,220 and the same text. Two OWYR ASINs show 4.1 from 101 and the same text, both dated 23 April 2026 in this export. Those are two pools, not five tests. A comment that names 400 cm is not a test of the about £29.99 300 cm cloth. DREO's 4.2 from 85 and Machine-YA's 4.0 from 817 belong to those listings. Small is not false, and shared is not large. LYUNIT's 4.1 sits next to glue that perishes around 30°C, so a high average does not mean the tape survived a heatwave. If you have not measured, start with the buying guide.

A casement zip kit with its own reviews

If you will not cut acrylic, the top pick is the DREO DR-HPA039 at about £19.99. The 400 cm version is for casement windows, and sliding windows are not compatible. The 85 reviews are this ASIN's. The same file has a tear almost at once and a size line of 4 m × 4 m, which is not a 400 cm strip. Derwit at about £17.99 says most outward casements, with 4.4 from 32 reviews of its own. That small file is why it is not the top pick. Outward versus inward is on the casement page. The best value is Machine-YA at about £16.38, 4.0 from 817, for side-hung and bottom-hung windows, not sliders. Use it when three sides stay under 300 cm.
Derwit Derwit 4 m casement window seal

Testsieger

Derwit Derwit 4 m casement window seal
6.7/10about £17.99
View offer

The £7.99 sheet and the dear shared file

The BTSAE at about £7.99 is a 114 × 113 cm sheet you cut, with a drawstring for a hose up to 15 cm. Amazon.co.uk shows 2.0 from 18 reviews. Most texts say the tape sticks to the frame and not the fabric, so the hose pulls the sheet down. Skip it if the sheet has to stay up while the unit runs. OWYR asks about £25.99 for either length, with one shared 4.1 from 101. That text praises top-hinged windows and also says the zips will not stay closed. LYUNIT at about £16.99 has 1,266 reviews of its own and does not name the window. VOLIKRA at about £15.99 uses a drawstring, with adhesive failures from a few days to about six weeks.

When none of these is the pick

Leave this set for a vertical sash or a horizontal slider. Hook tape in a sash runner gets chewed when you shut the window. A rigid panel is the other exit when the casement will run through a hot spell and you can measure the opening. Aircon Revolution's September 2026 guide treats a rigid panel as the tighter seal and fabric as the removable one that still leaks. That argument is on the fabric versus rigid page. None of these cloths is a lock. Electrovision says the window is not secure while the seal is in use, so take the cloth down when you need the sash locked. Best in this folder means a casement is named, sliding is excluded, and the reviews are not a copy of another length.

Common questions

Which kit should you buy for a casement if you will not cut acrylic?
In this set the top pick is the DREO 400 cm kit at about £19.99, because the listing says casement, says not for sliding windows, and has 4.2 from 85 reviews of its own. Derwit at about £17.99 is the one whose title says most outward casements, on 4.4 from 32 reviews. Use Derwit if that wording matches the window and you accept the small file. Use Machine-YA at about £16.38 if the perimeter is under 300 cm.
Is the £7.99 sheet a false economy?
It is, if you need it to stay up. The BTSAE is 2.0 from 18 reviews, and most of the texts say the tape holds the frame and not the sheet, so the hose pulls it down. A minority kept it with extra hook-and-loop or through a few hot days. That is not the same product as a 400 cm zip strip. Spending about £7.99 twice, once on the sheet and again on tape that still fails, is the false economy.
Is DREO's 4.2 more meaningful than MOEGFY's 4.0 from 4,220?
DREO's 85 reviews are on that ASIN. The MOEGFY 4,220 is one pool shared by three ASINs in this export, including comments that name 400 cm. A larger number is not a larger test of the length in the title. DREO's file is small, and it still tells you about a tear and about glue left after wind.
Who should skip OWYR at £25.99?
Skip it if you wanted either a long review file or a price under £20. Both OWYR lengths show the same 4.1 from 101 and the same text. The shared reviews include zips that will not stay shut and a cantilever uPVC window that would not take the cloth. A top-hinged window and a dual hose are the case the praise describes.
Does best mean the tape will not fail?
No. LYUNIT, EGNBU, Derwit, Machine-YA, and the shared MOEGFY text all include adhesive complaints, from damp nights to a heatwave around 30°C. The top pick still has a wind-and-glue report. Check the frame after the first hot afternoon, and keep spare hook tape if the included strip lets go.
When is a rigid panel the better choice?
When the same casement will run for a long hot spell and you can measure the opening and cut a panel that is not ordinary glass. Fabric is the choice when you must take everything down, or the opening is an awkward hinge. A panel is outside this twelve-row set. A sash is outside both the fabric kits that exclude sliders and a casement-shaped panel.

Related pages

How to fit a window seal

Air conditioner window seal

Choosing a portable air conditioner window seal kit

Casement window seal for a portable air conditioner

Fabric window seal vs acrylic panel for portable AC

Sources

Public UK sources from the research digest, used for this page on 20 October 2026. Prices, stars, and review counts are the amazon.co.uk figures in the 19 October 2026 snapshot. NHS and GOV.UK pages do not recommend these kits.

  1. NHS: heatwave, how to cope in hot weather (retrieved 19 October 2026)
  2. GOV.UK: beat the heat, keep cool at home (retrieved 19 October 2026)
  3. Consumer Rights Act 2015, section 9 (retrieved 19 October 2026)
  4. GOV.UK: product safety advice for businesses (retrieved 19 October 2026)
  5. GOV.UK: reporting product safety issues (retrieved 19 October 2026)
  6. Aircon Revolution: window seal kits for portable air conditioners (retrieved 19 October 2026)
  7. Ideal Home: portable air conditioner window kits (retrieved 19 October 2026)
  8. Appliances Direct: how to install home air conditioning (retrieved 19 October 2026)