Hello All,
I've been advised to input a 5m3/hm2 air infiltration rate. Considering that the pressure in IES is set @50 P, what's the best way to convert this to ach? CIBSE TM23 recommends to multiply times the surface-volume ratio, but result seems to high.
Could anybody give me an advise on this?
THANKS!
Infiltration rate in ACH
-
VirtualEngineer
- VE Beginner
- Posts: 22
- Joined: Mon Jan 05, 2015 11:10 am
Re: Infiltration rate in ACH
Hi
I realise this was posted a while ago, but thought I'd add to it as I'd be interested to see what method everyone uses.
I usually use the tables given in CIBSE Guide A Section 4.6 which are based on empirical values for air infiltration rate. These give a relatively good idea of the infiltration rate for different types of building with various height/area combinations.
For converting from air pressure test values at 50 Pa to ACH, Figure 4.15 (CIBSE Guide A Section 4.6) gives a conversion factor relative to volume of enclosed space.
VEng
I realise this was posted a while ago, but thought I'd add to it as I'd be interested to see what method everyone uses.
I usually use the tables given in CIBSE Guide A Section 4.6 which are based on empirical values for air infiltration rate. These give a relatively good idea of the infiltration rate for different types of building with various height/area combinations.
For converting from air pressure test values at 50 Pa to ACH, Figure 4.15 (CIBSE Guide A Section 4.6) gives a conversion factor relative to volume of enclosed space.
VEng
-
Complex Potential
- VE Expert
- Posts: 467
- Joined: Wed Jan 09, 2013 11:57 am
- Location: Bristol, UK
Re: Infiltration rate in ACH
I'm assuming that this is for the purposes of carrying out a heating load calculation?
I'll tell you what I tell the mechanical engineers where I work. It's not the modellers job to decide on what infiltration rate should be. The person responsible for the mechanical design should be making that call.
Pointing at a pressure test target and telling you to use that frankly shows a lack of understanding.
Think about it this way, you could have two identical buildings, one in a city centre completely sheltered from the wind and the other near a cliff edge by the sea, totally exposed to the elements. If they both achieve 5 m3/m2.h @ 50pa in test conditions, does that mean they are going to have the same heating requirement?
Just food for thought.
I'll tell you what I tell the mechanical engineers where I work. It's not the modellers job to decide on what infiltration rate should be. The person responsible for the mechanical design should be making that call.
Pointing at a pressure test target and telling you to use that frankly shows a lack of understanding.
Think about it this way, you could have two identical buildings, one in a city centre completely sheltered from the wind and the other near a cliff edge by the sea, totally exposed to the elements. If they both achieve 5 m3/m2.h @ 50pa in test conditions, does that mean they are going to have the same heating requirement?
Just food for thought.
-
Wasted Energy
- VE Graduate
- Posts: 93
- Joined: Thu Sep 10, 2015 5:58 am
- Location: UK NW
Re: Infiltration rate in ACH
All
The BSRIA guide for calculating heating loads refers to the use of the TM 23 value. It is usually a small value when expressed as ach, less than 0.1.
You can actually find this value calculated for you as ach in the Building Details tab of the Set Building & System Data in the SBEM/DSM module, because this is the default option for Part L compliance.
The reality is that new buildings are pretty air tight, even at the seaside, and mechanical fresh air loads are far more significant than infiltration losses
W
The BSRIA guide for calculating heating loads refers to the use of the TM 23 value. It is usually a small value when expressed as ach, less than 0.1.
You can actually find this value calculated for you as ach in the Building Details tab of the Set Building & System Data in the SBEM/DSM module, because this is the default option for Part L compliance.
The reality is that new buildings are pretty air tight, even at the seaside, and mechanical fresh air loads are far more significant than infiltration losses
W