Naco Window Glass Broken? Sizes, Acrylic Blades and How to Replace

The question behind this page

"One of my naco window glass blades cracked. What size do I buy, and is acrylic a good replacement or should I stick with glass?"

Key Takeaways

• Most residential naco blades are 6 inches (152 mm) wide. Some newer louvre systems also use 4-inch (102 mm) blades.
• Thickness is usually 5 mm or 6 mm and length depends on the window, so measure an unbroken blade from the same row before ordering.
• Clear acrylic weighs less than half as much as glass and does not break into jagged shards, but it scratches more easily and does not belong next to a stove.
• Polycarbonate is the toughest, but it scratches more easily than acrylic and needs a UV-protected face towards the sun.
• No blade material makes a naco window secure. Blades slide out of their clips, so the grille matters more.
• UMAKE's 5 mm acrylic naco blades are from RM11.50 (clear, 6 x 16 in), in 14 lengths from 16 to 28 inches, clear, white or black.

What a naco window is

A naco window is a louvre window, also called a jalousie window: a row of horizontal glass slats held at both ends by clips. Turn the handle and every slat tilts together, like a set of blinds.

"Naco" started as a brand name. HAHN, the German louvre maker, still sells a louvre window called "type NACO". In Malaysia the word now means any louvre window, spelled naco, nako or "tingkap nako". Some Malaysian glass suppliers also call clear obscure glass, the textured glass that blurs the view, "NACO glass". If a glass shop asks "clear or naco?", that is what they mean.

You still see these windows on many older terrace houses, in kitchens, bathrooms, stairwells and back rooms, because they keep air moving in a hot, humid climate. The trade-off is well known: louvres seal poorly against drafts and driving rain, and the slats can be removed quietly from outside. That is why most Malaysian houses with naco windows also have a metal grille.

Why naco blades crack and fall out

A naco blade is a narrow strip of glass held only at its ends, so it is more fragile than a framed pane. The usual causes:

• Impact: a ball, a broom handle, a child leaning on an open blade, a slammed door.
• Tired clips: old clips lose their grip, the blade creeps sideways each time the window opens, and eventually one end drops out.
• Forcing the handle: a stiff linkage or a misaligned blade can crack glass at the clip.
• Wind on open blades: long blades left open in a storm take a lot of load at the ends.

Ordinary (annealed) glass breaks into large, jagged shards, and from window height they land on a sink, a staircase or a floor people walk on barefoot. That is the main reason people look at acrylic instead.

Standard naco window glass sizes in Malaysia

No single size fits every naco window, but the patterns are clear:

• Width: 6 inches / 152 mm is the common size. HAHN's NACO window is built around a 152 mm louvre, and Breezway's Malaysian selection guide lists 152 mm and 102 mm blades.
• Thickness: usually 5 mm or 6 mm. Manufacturer specs for modern systems call for 6 mm glass, and Malaysian suppliers also stock 5 mm. UMAKE's acrylic blades are 5 mm, so check what your clips hold.
• Length: set by the window width, and usually quoted in inches in older homes. UMAKE's 14 standard lengths:

Inches	mm (approx.)	Inches	mm (approx.)
16	406	22	559
16.5	419	23	584
17	432	24	610
18	457	25	635
19	483	26	660
20	508	27	686
21	533	28	711

Malaysia has a standard for these windows, MS 1057:1995 (Specification for adjustable louvre windows), covering materials, performance and dimensions. It is sold through the Department of Standards Malaysia, so measure your own window rather than trusting a number online. If you buy glass, remember that tempered glass cannot be cut once tempered, so it must be ordered at the exact length. Acrylic can be cut to any length.

How to measure your naco blade

Work in millimetres. A 3 mm error matters on a part that sits in a clip.

1. Find an unbroken blade in the same row. Blades in one bay are normally the same length. Open the window so the blades lie flat and measure one end to end. This is your most reliable number.
2. Measure the width across the short side: expect about 152 mm or 102 mm.
3. Measure the thickness with a caliper, or a steel rule held against the edge. 5 mm and 6 mm look alike.
4. If every blade is gone, measure from the inside back of one clip to the inside back of the opposite clip, then subtract about 2 to 3 mm so the blade is not jammed tight.
5. Check the clip pocket for play. A pocket made for 6 mm may let a 5 mm blade rattle.
6. Count the blades, plus a spare if another one looks chipped.

Why the gap matters for acrylic: the Plexiglas datasheet gives acrylic a thermal expansion coefficient about eight times that of plate glass. On a 24-inch (610 mm) blade, a 30°C swing from cool night to afternoon sun works out to roughly 1.3 mm of growth for acrylic and under 0.2 mm for glass. A blade cut too tight can bow.

Acrylic vs glass vs polycarbonate for naco blades

An honest comparison, using manufacturer data where it exists (clear sheet):

Property	Glass (annealed)	Acrylic (PMMA)	Polycarbonate (PC)
Clarity	Clear (obscure "naco glass" also sold)	92% light transmittance	Up to about 90%
Weight	Heaviest (about 2.5 g/cm³)	Less than half of glass	Less than half of glass
Impact strength	Lowest; jagged shards	Higher than all glass types, including tempered	Highest; "practically unbreakable"
Scratch resistance	Best (Mohs about 6)	Scratches more easily than glass; light scratches polish out	Scratches most easily unless coated; cannot be polished back
UV / yellowing	Does not yellow	Very stable: no significant discoloration in 20-year outdoor tests	Can yellow; needs a UV-protected face towards the sun
Heat and fire	Does not burn	Service up to about 93°C, softens above about 127°C, combustible	Service -40°C to 120°C; better fire ratings than acrylic
Heat movement	Very little	About 8x glass; leave end clearance	Similar to acrylic
Cleaning	Any glass cleaner	Mild soap and water; no window sprays	Mild soap and water; no abrasives
Security	The same for all three: blades slide out of the clips. Security comes from the grille.
Cost	Widely stocked; ask your local glass shop	UMAKE from RM11.50 per blade	Usually dearer; one US distributor says about 35% more than acrylic

For most homes acrylic is the practical middle choice: much tougher than glass, clearer than polycarbonate, stable in the sun and easy to cut. Polycarbonate only earns its place where blades get hit hard and often, and only as a UV-protected grade fitted the right way round. For more on grades and thickness, see how to choose acrylic sheet in Malaysia.

When acrylic makes sense, and when it doesn't

Good places for acrylic blades

• Children's rooms and play areas, where balls and leaning kids are a given.
• Stairwells and landings, where a falling glass blade would hit people below.
• Bathrooms and laundry areas. Acrylic handles humidity, and a white blade gives privacy while letting light in.
• Windows that keep losing blades. A lighter blade is easier on tired clips and will not shatter if it drops.
• DIY fitting. Less than half the weight of glass, and no razor-sharp broken edges.

Where acrylic is the wrong choice

• Beside a gas stove or wok burner. The maker rates the sheet for continuous service up to about 93°C, says it softens above about 127°C, calls it combustible and advises keeping it away from intense heat or flame. Keep glass behind the stove.
• Surfaces scrubbed often. Scouring pads and dusty rags will haze acrylic.
• Very long blades in windy spots. Acrylic is far less stiff than glass and, per the datasheet, can creep under long-term load. If a long 5 mm blade feels springy or rattles, it is the wrong fit.
• As a security fix. Any naco blade can be slid out. Fix the grille first.

How to fit a new blade into the clips safely

Clip designs vary by brand and age, so look at how yours holds the blade before forcing anything. Most are U-shaped pockets at each end, often with a small tab that stops the blade sliding out sideways.

1. Protect yourself: gloves and safety glasses. Tape across the cracks of a broken blade still in place.
2. Open the louvres so the blades lie flat.
3. Remove the old blade. Ease any retaining tab open with flat-nose pliers or a small screwdriver, slide the blade out lengthwise, and pick out fragments left in the clips.
4. Peel the protective film off the acrylic, if it has one.
5. Slide the new blade in lengthwise until it sits evenly in both clips, with a similar small gap at each end.
6. Close the tab lightly. It should stop sliding, not pinch the blade.
7. Test: open and close the window a few times. The blade should move with the others and overlap evenly when shut.

If a 5 mm blade rattles in a clip made for 6 mm glass, a thin rubber packer can take up the gap. Test any sealant or glue first: the manufacturer warns that some sealants and gasket materials can craze acrylic.

How to order naco blades from UMAKE

We cut these blades from 5 mm Grade A acrylic at our factory in Balakong, Selangor, and ship across Malaysia. On the acrylic naco window panel page you choose:

• Size: 14 standard sizes, all 6 inches wide, 16 to 28 inches long, or the Custom Size option for an instant price on your own dimensions.
• Colour: transparent, white or black. The listing describes white as a privacy finish that still lets soft daylight in; black screens the view. WhatsApp us if you need to know how much light the white passes.
• Quantity: priced per blade, with 5% off at 20 or more.

Prices on the live page when this guide was checked:

Size	Transparent	White or black
6 x 16 in	RM11.50	RM13.50
6 x 24 in	RM18.00	RM20.00
6 x 28 in	RM25.00	RM27.00

Other lengths fall in between, and the page updates as you pick. Production takes 2 to 5 working days plus 1 to 7 working days for delivery, and orders over RM200 ship free within the Klang Valley.

Need a different width or thickness? Our clear acrylic sheet comes in 1, 3 and 5 mm and can be custom cut; see acrylic sheet cut to size in Malaysia for how that works, and what can be laser cut for thickness limits. Unsure of your size? WhatsApp a photo and your measurements to wa.me/60179290938 (Mon to Sat, 8am to 5pm) and we will confirm before cutting.

Cleaning acrylic naco blades

Most acrylic blades are ruined by the glass spray under the sink. The Plexiglas care guide says to wash with plenty of non-abrasive soap or detergent and water, use a soft, grit-free cloth, and not to use window sprays or kitchen scouring compounds. Ammonia-based glass cleaners can cloud the surface.

• Rinse or dust off grit first. Wiping dry grit is what scratches acrylic.
• Wash with a few drops of dishwashing liquid in lukewarm water and a soft microfibre cloth.
• Rinse, then blot dry with a damp chamois or clean soft cloth.
• Skip paper towels, scouring pads, alcohol-based sprays and solvents like thinner or acetone.

Light scratches can often be reduced with a plastic polish made for acrylic. Polycarbonate cannot be polished back to clear.

Products

Frequently Asked Questions

What is the standard naco window glass size in Malaysia?

Most residential naco blades are 6 inches (152 mm) wide and 5 or 6 mm thick. Length varies with the window; UMAKE stocks 14 lengths from 16 to 28 inches. Measure an unbroken blade from the same row before ordering.

Can I replace naco glass with acrylic?

Yes. A 5 mm acrylic blade slides into standard naco clips like a glass blade, weighs less than half as much and does not break into jagged shards. Avoid it beside a stove, and check the fit if your clips were made for 6 mm glass.

Will a 5 mm acrylic blade fit a clip made for 6 mm glass?

It usually goes in but may rattle. Try one blade first. A thin rubber packer can take up a small gap; avoid solvent sealants, which can craze acrylic.

Is acrylic or polycarbonate better for naco windows?

For most homes, acrylic. It is clearer, more scratch-resistant and stable in the sun. Polycarbonate is tougher but scratches more easily, can yellow without a UV-protected face, and usually costs more.

How much does a naco window blade cost at UMAKE?

From RM11.50 for a clear 6 x 16 inch blade. Clear 6 x 24 inch was RM18.00 and clear 6 x 28 inch RM25.00, with white or black RM2.00 more. Orders of 20 or more get 5% off.

Does acrylic make my naco window more secure?

No. Any naco blade can be slid out of its clips. A fixed grille is what keeps intruders out.