IN MALAYSIA'S hot and humid climate, keeping homes cool can be a daily challenge. Many people rely on fans, air conditioning and open windows to improve airflow.
The idea is that bulky materials, such as thick curtains or rugs, can trap heat and make rooms feel warmer. Something that may be uncomfortable in a tropical environment.
But is there any truth to this?
Verdict:
TRUE
Heavy household fabrics such as thick curtains, carpets, velvet upholstery and layered bedding can trap heat and restrict airflow in a room.
These materials absorb heat during the day, especially when exposed to sunlight, and release it slowly, making indoor spaces feel warmer even after sunset.
In contrast, lighter and breathable fabrics such as cotton, linen, silk or bamboo allow better airflow and do not retain as much heat.
For homes in tropical countries like Malaysia, interior experts often recommend using lighter fabrics, minimal layering and breathable textiles to help maintain a cooler indoor environment.
While heavy fabrics are not the sole cause of a warm house, they can contribute to heat retention and reduced ventilation, making indoor spaces feel less comfortable in hot weather.
That said, not all heavy curtains are created equal, and the relationship between curtains and room temperature is more nuanced than it might first appear.
The key distinction is between standard heavy curtains, which absorb and radiate heat, and blackout or thermal curtains, which are specifically engineered to do the opposite.
According to the US Department of Energy, medium to light-coloured curtains with a white, thermally reflective backing can reduce heat gain through windows during summer by as much as 33% by reflecting solar radiation back outside before it enters the room.
A 2019 study by the Lawrence Berkeley National Laboratory found that properly installed thermal curtains can reduce heat loss through single-pane windows by up to 40%, while even double-pane windows saw improvements of between 15% and 25%.
The science behind this lies in how these curtains are constructed. Standard heavy curtains, particularly those in dark colours with no special lining, absorb sunlight and convert it into heat, which then radiates into the room.
A dark, unlined velvet curtain can reach surface temperatures of up to 49°C in direct sun, effectively turning your window into a radiator.
Blackout and thermal curtains work differently. They are typically made with multiple layers including a decorative outer fabric, an insulating middle layer and a light-coloured or reflective backing that bounces solar radiation back through the window before it can become heat.
Blackout curtains with thermal properties have an insulation rating, known as an R-value, of between 2.9 and 3.7, compared to R-1 for standard curtains, according to the US Department of Energy.
Colour and installation also matter significantly. Curtains in dark colours facing the glass will absorb heat, while those with a white or off-white backing facing the window will reflect it.
Gaps at the top, sides or bottom of curtains can create convective drafts that draw hot air from the window into the room, negating any insulating benefit.
For Malaysians looking to keep their homes cooler without cranking up the air conditioning, the practical takeaway is straightforward: swap out unlined dark or heavy curtains on sun-facing windows for lighter alternatives or properly lined blackout curtains with a reflective backing, keep them closed during the hottest parts of the day and ensure they are installed to cover the window frame completely with no gaps.
Sources:
1. https://www.thefoxesden.co.nz/
2. https://www.
3. https://www.anatolico.co/
4. https://www.energy.gov/
5. https://www.deconovo.com/
6. https://www.curtarra.com/
7. https://sleepoutcurtains.com/
8. https://www.endesa.com/en/
