Each One Said Something: Does Everyone Ever Need Fresh Air?
If you've ever researched or designed a direct (HVAC) ventilation system for an office or home, you've certainly fallen into the metric "matrix" when it comes to fresh air flow per person.
Some people say it's a good idea
- "Just 15 m/h/person That's enough! "
- Another said, "These are the only ones "Yes 20 m/h/person Yeah! "
- Not even a few engineers have got the pin "Get it 30 m/h/person Just make sure! "
So what's the right number? Why is there such a huge disparity between the recommendations?
In fact, There's no one fixed number that applies to all buildings. And if you just multiply a fixed number by the number of people, you're probably designing a lack (or an excess) of fresh air for your space.
Why Is Not Fun With Human Heads Yet Enough?
The most common mistake many people make is to assume that Human beings are the only source of pollution The fact that air pollution in a closed space comes from the 2 main group:
1. Human-based pollution sources
When we are living and working in the room, our bodies constantly arise:
- Air CO2 from the respiratory system.
- Steam and sweat.
- Body odor and the bioeffluents (biological organic compounds arise from skin, breath).
2 Building - based pollution sources
Even if there's no one in the roomThe air is still being continuously polluted by:
- Volatile organic compound (VOCs) emanating from wall paints, floor coatings.
- Formaldehyde It's liberated from industrial wood, furniture, furniture shelves.
- Chemicals from curtains, carpeting, cleaners.
- The musty smell of the air.
If you only count fresh air by number, you're completely missing out on the fresh air you need to dilute the pollution that's accumulated in your furniture!
What's the ASHRAE 62.1 Green Hat Thinking About?
For this reason, the world's prestigious ventilation standards -- typically ASHRAE 62.1 (USA) or Vietnamese Standards TCVN 5687:2010 Never use a single number per capita.
ASHRAE 62.1 applied Ventilation Rate Procedure with the combination formula:
Total fresh gas flow = {Flow by number of people} + {Flow by area}
- Human gas supply (Rp): Provide adequate O2 and control the concentration CO2, body odor.
- Gas supply to space (Ra): Dilute pollutants arising from building materials and furniture per $m^2$ floor.
Example Effect: Same People But Different Fresh Air Flow!
Let's see 2 the following office case to see the marked difference when applying the standard formula:
Comments: Although the total output is equal at 2 But the properties of space are completely different. If you use a single coefficient for every space, you're very likely to get:
- Fresh air in the conference room Leads to drowsiness, hypoxia, skyrocketing levels of CO_2 $over 1000 ppm.
- Fresh air in a large office It's a waste of power air conditioning and electricity bills every month.
Lessons for Investors and Designers
- Stop applying empirical numbers emotionally: The numbers 15, 20 or 30 m3/h/ng who are just the estimated averages usage and room area before the traffic is closed.
- Fresh Air vs. Load Equilibrium air conditioning: The more fresh air to supply, the cleaner the air, but the more energy to use air conditioning (to cool/cool that fresh air). Accurate and sufficient calculation is key to operating cost savings.
- Consider Demand Controlled Ventilation (DCV): Use room CO2 sensors to automatically adjust fresh air supply fans to the actual number of people at each time.
Supplying fresh air is not merely "blowing outside air into the room," but the scientific calculation problem between human health, spatial quality and energy efficiency.
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