Dissatissfied people - Comfort

[John73]

Hi,
Does anyone know how IES assessed the number of people dissatisfied?
Which aspects IES take into account?(eg temperature, humidity air velocity)

Thank you.

[PCully]

Hi,

I've done a little digging into this and here is a response previously sent out by my colleagues Terence and Liam that gives a little more information on Comfort in VE Vista:

Percentage of persons dissatisfied (PPD) and Predicted mean vote (PMV) both come from the work of Professor Ole Fanger.

Basically PVM is calculated from the bodies heat balance equation: heat production - heat loss from convection, radiation, respiration, sweating etc.

Fanger defined PMV as "the difference between the internal heat production and the heat loss to the actual environment for a man kept at the comfort values for skin temperature and sweat production at the actual activity level".

PPD is calculated from PMV using the equation:

PPD = 100-95*exp(-0.03353*PMV^4 - 0.2179*PMV^2)

IES uses Fanger's equations so you can find many resources on the web, e.g.

http://www.healthyheating.com/solutions.htm

Hope that helps you a bit
Phil

[John73]

Thank you for your answer.
I think it will help me in my project.

Regards

[jessica]

thus this model cannot be used on natural ventilation??, fanger studies apply on HVAC, how does the IES find the PPD in case of natural ventilation?