Hello all of you,
Can anyone share his/ her knowledge that how to do fresh air calculation
for a naturally ventilated building for IEQ pre - requisite. Any
suggestions or example ,would be highly appreciated.
Thanking you all in advance!
Ms. Sadaf Alam
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Sadaf,
I did this on a LEED platinum project a while back. I recall that we had
to invoke a couple of clauses in ASHRAE 62.1 to allow us to use thermal
modelling with CO2 as the metric (at the time 62.1 only had a very basic
natural ventilation rule of thumb such as minimum distance between
occupants and openings). IES was used for the analysis, but you could
use any thermal modelling program that incorporates network air flow
(e.g. E+, TAS, IDA).
Without being able to get access to the latest 62.1 I can't help further
- sorry.
You might have trouble meeting ASHRAE 55, depending on your climate.
Hope this helps.
Chris
Sadaf,
ASHRAE 62 has three paths of compliance:
1. The Ventilation Rate Procedure (VRP) is a prescriptive option which
means looking up airflow rates in the tables and doing some calculations.
This is the most common path but would normally apply to mechanically
ventilated buildings.
2. The Indoor Air Quality (IAQ) procedure is performance based which
requires a Mass Balance Analyses (can be done through modeling). There was
a recent article about this in the June ASHRAE Journal if you are a member.
This can apply to natural or mechanically ventilated buildings.
3. The Natural Ventilation Procedure (NVP) which states specific
requirements for opening areas.
I believe LEED generally requires you to follow the VRP or NVP but my LEED
2009 says you can show compliance with "acceptable engineering calculations
or multi-nodal bulk airflow simulation" which I think means following the
IAQ procedure.
Aaron Smith, P.Eng