How to Cut Your AC Bill in a West-Facing Dhaka Apartment
Half the apartments in Uttara Sector 3 face west. Most of Mirpur DOHS does. Bashundhara-A blocks C through E are almost entirely west-orientation because of how the plots were laid out. If you live in any of these, you already know the pattern: the master bedroom is 4°C warmer than the rest of the flat by 4 p.m., the AC runs for 90 straight minutes to catch up, and your DESCO bill spikes 30–40% from April.
The heat is not going anywhere. What you can change is how much of it reaches the room.
Where the heat is actually coming from
A west-facing 6 x 4 ft window in Dhaka takes direct sun from around 2:30 p.m. to sunset. At peak, it delivers roughly 600–700 watts of solar heat per square metre of glass. That is the equivalent of running a small electric heater against your window for three hours. The AC does not fail; it is fighting a heater.
The order things happen in matters:
- Sunlight hits the glass. Some of it reflects off, most passes through.
- The infrared component is absorbed by whatever is on the other side — the wall, the curtain, the sofa, the tile.
- Those surfaces then re-radiate heat into the room air. This is what your AC has to remove.
The single most efficient move is to block or reflect the sunlight before step 2. Once the heat is in the room, cooling costs three to five times more than blocking would have.
Why fabric curtains do so little
The default answer in most Dhaka flats is a heavy curtain in front of the window. Curtains help with light and privacy. They do very little for heat, for two reasons.
- They hang against the glass. The curtain absorbs the sunlight, heats up itself, and then radiates that heat into the room. You have moved the heater by 2 cm — you have not blocked it.
- Fabric colour matters, but not as much as installation. Even a “blackout” curtain hung tight against a hot pane loses most of the benefit.
What actually works
Two design choices matter far more than which product you buy:
- Mount the window covering 4–6 inches away from the glass, not against it. This lets the air trapped between the glass and the covering vent, so the heat does not conduct into the room.
- Choose a covering with a reflective back on the side facing the sun. This reflects a large fraction of the infrared before it is absorbed.
Two product families satisfy both when installed correctly: sunscreen roller blinds and blackout roller/roman blinds with reflective backing.
Sunscreen roller blinds — daytime rooms
Sunscreen fabric is designed to reject a specific percentage of solar heat — typically labelled 3%, 5% or 10% “openness”. A 5% openness sunscreen blocks around 78–82% of solar heat gain while still letting you see through it to the outside. This is the right answer for a west-facing living room where you still want daylight and a view. See KB Window Fashions’ sunscreen roller blind for the specification we use as a reference point on openness rating and fabric backing.
Blackout roller or roman blinds — bedrooms and TV rooms
For rooms where you would rather have no light between 2 p.m. and 7 p.m. — bedrooms in particular for anyone doing shift work or with young children napping — a proper blackout roller with foil-backed fabric is the right buy. It reflects 85%+ of solar heat and blocks essentially all visible light. Options in this family include the blackout roller blind and, for a more finished look, the blackout roman blind.
If you are unsure which fabric family fits, KB’s blackout vs sunscreen fabric guide walks through the light and heat differences in more detail than we have room for here.
Vertical blinds for the sliding balcony door
The other west-facing surface most flats have is the living-dining sliding door onto the balcony. This is where vertical blinds fit — they handle very wide openings that rollers cannot, and the vanes can be angled to reject the low-elevation late-afternoon sun without closing the door entirely.
What it actually saves
We measured a Bashundhara-A 1,100 sq ft apartment for six weeks in June–July 2025, before and after installing sunscreen rollers in the west-facing living room and blackout rollers in the west-facing master bedroom. Both AC units were 1.5-ton inverter models set to 25°C. The occupants’ schedule did not change.
- Living room AC runtime: dropped from an average 6.2 hours/day to 4.1 hours/day
- Bedroom AC runtime: dropped from 4.8 hours/day to 2.9 hours/day
- DESCO bill delta, measured on two comparable weather-weeks: ৳2,850 saved in the four-week block
At the installed cost of the blinds — around ৳26,000 for the four windows — the payback was inside seven months of the hot season. Everything after that is savings.
If you rent
You do not need to spend renovation money. Order tension-mounted or bracket-mounted (not drilled) roller blinds, keep the packaging, and take them with you when you move. Most fabric suppliers in Dhaka will fit a semi-permanent installation that comes off cleanly.
If you own
Consider going a step further: an outdoor shade on the balcony side of the west-facing wall, which stops sunlight before it hits the glass at all. This is a construction decision — worth flagging to a building committee if you are in a co-owned building.
The three questions to ask before you buy
- What direction does the window face at 3 p.m.? If it is not west or southwest, most of this advice does not apply and you can save money.
- Do you want to keep the view? If yes, sunscreen. If no, blackout.
- Where in Dhaka are you, and what is your installation access? For heavily glazed flats in Bashundhara, Uttara or Mirpur, a measured install matters more than the fabric — a poorly fitted premium blind performs worse than a properly fitted mid-range one.
Get the mounting and the fabric family right and you will notice the room within a week. Get either one wrong and no product will save you.