# Stack/wind pressure and flow networks.

Hello my first post,

I'm wondering if there is anyone about who could advise on the calculations involved in determining flow networks for natural ventilation. I'm studying a distance learning masters in sustainable design and there is something for this assignment I'm just not getting.

I've been through

A Guide to Energy Efficient Ventilation, Martin W Liddament – AVIC

Air Infiltration Calculation Techniques - An Applications Guide, Martin W. Liddament – AVIC

2009 ASHRAE® Handbook Fundamentals

Ventilation for Acceptable Indoor Air Quality, ASHRAEE standard 62.1

And several other presentations, book and publications.

and in part of this I found a couple of Discussions here that have helped but not fully covered what I need.

If anyone can help I'll go into more detail but the basic layout is below. Obviously I don't want to solution calculated for me as that would be cheating but just people to bounce off would be nice.

Views: 225

### Replies to This Discussion

Pascals for stack has been discussed to death here

Wind is pretty easy to find & if need be I would recommend googleing Bernoulli's principle on wind

Unfortunately just looking at the diagram without some context it is hard to know what you need help with

https://www.linkedin.com/groups/6942179/6942179-6030115404729307139           'm not sure this is what your exactly looking for Daniel but it should direct you to the right area.

I asked this question to Colin Genge really one of best minds regarding this in the business. Anyone can theorize but measuring is why most of us are here. If your going to measure one thing against another do it the same way every time. This escapes some in our industry...Anyway take the time to read what he wrote on set-up and join his group. Best of luck and share what you come up with.

Daniel,

I'm assuming you're trying to predict the airflows through the different openings W1, ... ? It is very unclear from the drawing. You're probably aware, but solving the problem requires calculating the pressure differentials at each opening, as they vary with height and temperature difference. The airflow is then simplified as an orifice flow, typically with flow and pressure coefficients that characterize the size and shape of the opening. Wind is trickier, but is generally treated similarly. I know the relevant equations are in the Liddament books, but can't remember specifically where.

So I wanted to start with a basic who can help then go into more detail later.
But yes find the air flows through the openings and area of the openings.

I've approached it now as airflow/m^2 of opening then used air rates per person (EN 13770:2004) to specify a target rate for winter and summer and size the openings from that.

This hasn't been the most precise and consistent course and assignment I've ever carried out.

My tutor got back to me and while areas don't quite feel right a little to much assumptions and things not quite adding up in the examples I'm slowly moving on.
We have a certain amount of freedom to manipulate the design so to simplify things I've closed off L1 as suggested by the tutor.
The thing that got me was having calculated the stack pressure based on the lowest opening and then added the wind how do I determine the flow networks.

The examples have the flow rates calculated end to end so combining the pressures W3 and L2 for the air flow right through the building. Treating each floor as individual zones.
Now the assignment is only meant to represent very early calculation estimates so I guess this is ok, personally I'd then move to use CFD software after the heavily simplified systems for better predictions.

## Forum Discussions

### Mini split installation location

Started by Jan Green in HVAC. Last reply by David Butler 11 hours ago.

### Insulation touches underside of roof in home with no soffit or soffit venting.

Started by John Carton in General Forum. Last reply by John White yesterday.

### Think of the house as a really big duct

Started by Frank Spevak in HVAC. Last reply by John White on Friday.

### Mini split air conditioners and ceiling fans

Started by Beverly Lerch in General Forum. Last reply by Beverly Lerch on Thursday.

### Condensation on ceiling and walls of master bedroom

Started by Jerry Needham in General Forum. Last reply by John Nicholas on Thursday.

28 members

151 members

52 members

26 members

8 members

## Latest Activity

Don Fugler replied to Don Fugler's discussion Choosing a range hood in the group Kitchen Ventilation
"There is a scientific paper that Tom Phillips cited where the researchers are looking at the…"
22 minutes ago
David Byrnes's video was featured

### Should the Attic Floor Insulation Be Removed When Doing Spray Foam?

Spray foam insulation contractors and homeowners alike have debated this questions over many years and since spray foam first gained popularity
3 hours ago
mosan, Shine Facility Services and Todd Hensel joined Home Energy Pros Forum
5 hours ago
John White posted a blog post

### Why Fall Is the Best Season to Replace Your Old HVAC System

8 hours ago
"I'm not sure if I'm making myself clear. You don't want to 'squeeze' the…"
11 hours ago
Jim Gunshinan posted a blog post

### More "Buzz" from ACEEE Summer Study—Grow Homes

Joe Clark and Martha Wudka of Evergreen Economics did a study in which "getting into the weeds (or…See More
17 hours ago
"I agre that the south wall would be shaded for the warmer summer months, but it won't look…"
19 hours ago
"I'll check on electrical.  Good point.  "
19 hours ago
"Thank you for that.  I wanted to put it on the west wall since there isn't much chance of…"
19 hours ago
"Hi Jan, actually, I said you'd be find putting it on the west wall since you wanted a larger…"
20 hours ago
Brett Little posted an event

### Using Pearl Certification to Bridge the gap between home energy and value - Free CE Webinar at Webinar Online

October 3, 2018 from 12pm to 1:15pm
In this webinar, “The Power of the Pearl Connection”, Pearl Certification’s Cynthia Adams, CEO and…See More
22 hours ago
"Being a Flip you must consider the install cost. At least get a bid for a PTAC unit like the ones…"
23 hours ago
"South Wall. It will have the highest load needed for cooling/heating. the shade from the tree could…"
yesterday
"I would add where is the power coming from? the south wall proposed might have easier access for…"
yesterday
"Soffit vents can be used for intake, but they are not the only means of intake. If you have a…"
yesterday

### Why One Room Is Hotter Than Others

"If the temperature difference between your bedroom and your living room feels like walking from a…"
Friday
"First: Mini split are a great option. Second:vI agree with David that installing on the south…"
Friday
Pearl Home Certification's blog post was featured

### What Sustains US

Friday
"Thanks for sharing this helpful information. Want to read more on duct cleaning pros and cons.…"
Friday
"Thank you, thank you!  I appreciate your insights.  I agree with the idea that installing…"
Thursday