A ventilation/ exhaust fan is a more economical option compared to a hood. I had decided to get am exhaust fan on top of a ventilation hood as since it will be quite warm for the wet kitchen. It uses less electricity and is less noisy compared to the ventilation hood so it can be left on during food preparation.
One of the problems was that I had space constraint on the wall for the opening for the fan. The cfm of the fan increases when the fan size increases.
I tried calculating the minimum cfm for my kitchen and used the reference here.
There is also another online cfm calculator here.
How many cfm does my kitchen hood & ventilation fan need to be?
1. Based on heat output
- I’m using an induction so it is given in watt. Is it relevant here since induction has less heat output compared to gas? Anyway I will just convert…
- 3200Watt= 3.2 kWh= 10919BTU
- 109CFM
2. Based on hob size
- Linear foot on range against a wall= 1.67 feet
- Minimum 167CFM
3. Based on kitchen size
- It needs to cycle 15 times an hour
- 10ft by 9ft by 9ft= 810 cubic feet
- 810 X 15/60 = Minimum 203CFM
4. Add more based on duct work
Kitchen hood ducting
- 1 elbow bend= 25CFM
- 4.5 feet duct= 4.5 CFM
Calculate
Kitchen hood= Compare No 1, 2 and 3 and take the highest reading and add the duct work (No 4).
Exhaust fan= Only based on kitchen size
I will need a minimum of 233CFM for my kitchen hood and 203CFM for my exhaust fan.
This calculation takes into account of closing the wet kitchen sliding door.
Which ventilation fan design?
I choose a basic fan design that looks like this
How many diameters?
All of 6 inch ventilation fan I had come across had a CFM of less than 200.
I had decided to go with an 8 inch ventilation fan that requires a cut out size of 10 inch by 10 inch.
Ventilation fan brand
| Brand A | Brand B | Brand C | |
| Capacity | 260CFM | 318CFM | 318 CFM |
| Fan Speed | 1180RPM | 1205RPM | 1109-1301RPM |
| Motor | 25W | 17W | 14.9- 18.3W |
| Noise level | 49dB | 37dB | 37dB |
| Electric consumption in 24 hours | RM 0.13 | RM 0.09 | RM 0.09 |
| Price | RM 54.90 | RM 99.90 | RM 95.00 |
| Fan colour | White | Grey | Grey |
| Manufacturer Warranty | 3 years | 1 year | 1 year |
Let’s decide…
- My table fan is brand A and ceiling fan is brand B.
- I have excluded brand A as it is louder, not as energy efficient and has a lower cfm.
- I suspect that brand B and C are manufactured in the same factory as they have the same specs but different colour.
- I chose brand B as I am more familiar with that brand