I recently bought a 2 storey corner lot house with windows and sliding doors facing east. The house is still empty as I'm waiting for design from ID, but I've tried sleeping on the 2nd floor a few times and found it to be unbearably hot. I bought a cheap temp and humidity sensor and placed it on the 2nd floor, and found that the 2nd floor temperature fluctuate between 32c and 35c. My house already has radiant barrier installed underneath the roof tiles. Recently I have also installed solar panels on the roof, and found that it helped to reduce the 2nd floor temperature by 1-2c (it now fluctuate between 30c and 33c).

Now I'm considering to add insulation on the attic, because I've read somewhere that for house in hot climate, most of the heat enters through the roof, which explains why adding solar panels helped to reduce the temperature a bit since it shades the roof from sun. The idea is to minimize heat transfer from attic to 2nd floor through the ceiling by adding thick insulation. So far I received quotation from TCL to add 100mm blow in cellulose on top of 2nd floor plaster ceiling for rm4 psf.

Basically my goal is to reduce my house temp as much as possible using passive cooling, so that when I add aircond later, they don't have to work that hard, thus saving more money. I've heard about turbine ventilators, which are common here, but from what I understand, it doesn't play well with aircond, since it will actually pull cold air out as well, so your aircond has to work harder to keep the room cold.

Has anyone done something similar before? Does it actually help to reduce house temp? Is the price of rm4 psf about right?

I had similar issues, I installed a solar ventilator and this improved the temperature for my situation. I think this is the least invasive method and quick to install. I got the one from verdant this was about 10 years ago

Interesting. Since the solar ventilator will vent air out, how does air enter the roof to replace the vented air? AFAIK roofs in Malaysia don't have soffit vents for air intake.

Yes, M'sia roof construction generally do not have soffit vents. But then the roofs are also not air tight, so there is a lot of air bleed to replace the air removed by the ventilator. There is actually fibre cement board with slots cut in specifically for soffit installation in M'sia. (Eg : UAC Duravent)

I would agree to using an insulation in the attic, but I would go for rock wool instead of blown-in. Reasons being it being a continuous mat instead of loose fill, does not need a specialist installer, easier to manage in the future if other local tradespeople have to deal with it.

I wouldn't focus on the cost at all because this is a "do once, last forever" deal.

I'm worried if I install solar ventilator without soffit vents, it will end up pulling air from 2nd floor through small cracks in ceiling, since the CFM of the solar ventilator is pretty high. I guess I need to add soffit vents and air seal the ceiling before proceeding.

I have cellulose in my house. previous one had rock wool. Cellulose works better cause it forms a layer in a short period of time so the entire area is closed up. Also done by TCL - they did a good job.

BUT if you can afford it go for 200mm not just 100mm. IMHO 100mm not enough.

Did you do air sealing before putting the insulation? Or TCL did it for you? I read online that insulation is only effective if you air seal cracks and holes as much as possible (especially around ceiling down lights). Otherwise heat transfer will still happen via convection, especially if there is difference in air pressure.

So far my plan is to do all of the following:
- Add temp/humidity sensor in every rooms (including attic) to measure difference before and after
- Air seal the 2nd floor ceiling
- Add cellulose insulation
- Add ventilation in attic to promote airflow in attic ONLY (I see people typically add vent in 2nd floor ceiling, but that nullifies benefit of insulation and air sealing)

My ceiling is closed near 100% - all plaster ceiling holes sealed. We use a central air ventilation system from airegard for fresh air. But that is not a must but it helps if your place is permanently a/c-ed. The heat transfer you talk about will be neglible for most circumstances. But still a good idea to keep unwanted houseguests out

You should absolutely vent the space under your roof tiles or use a tiling system that breaths so disperse the hot air too. Monier has a solution for that.

Oh nice, I was going to open another topic regarding fresh air. I'm considering it as well, but problem is HVAC knowledge is so limited in Malaysia so I don't know who to ask haha. If you don't mind answering:

1. Are you using the fresh air or ERV series?
2. Is it expensive to install? Airegard provide installation service or you find contractor yourself?
3. Is it expensive to maintain? I'm assuming you can't just hire any aircond maintenance guy.

install exhaust fan to improve ventilation inside ceiling space.
https://www.asphaltroofing.org/importance-p...roofing-system/

This post has been edited by keyser soze: Apr 2 2025, 05:37 PM

1. Fresh Air, no ERV when we did it.

2. Airegard installed it - not expensive.

3. Just make sure you can access the box with ease. I swap the filter (expensive! 1xx RM per filter) once every two years.

Tip: connect to a smart switch then you can control when you cycle the air and avoid times when its too hot. I cycle when temp is below 27° and otherwise on a schedule. You could even link it to a CO2 meter and cycle once the value too high.

WTA
by central air ventilation system, u mean multiple Fresh air units?

i am planning to do ducting for multiple areas using one unit.
which model is yours, is the circulation strong?

Same one unit can take care of the entire house for maybe 3k sqft+

Just adjust the ventilation according to what is needed - you can connect to a smart switch and if you like a CO2 monitor. then set a schedule (ideally when not too hot to save aircon money) and then set a trigger if CO2 exceeds your thrigger value to run until you are below. Last one is optional.

We use one unit with two suction and two inflow points spread out throughout the house. just make sure you factor in other suction points (toilet, kitchen) when you decide on the placement.