Greetings

First of all......

* As we upgrade and build new....

  I think it is time to eliminate atmospherically vented appliances from the breathing zones of our homes

* I realize that the effects of wind and mechanical equipment can and often do overwhelm Stack Effect.

 

My current favorite online resources for visualizing "Stack Effect" are.....

*John Straube's Article

http://www.buildingscience.com/documents/digests/bsd-014-air-flow-c...

 

*John Klote's Article

http://fire.nist.gov/bfrlpubs/fire91/PDF/f91013.pdf

 

*Bud Poll's Worksheet

http://myenergyworkshop.homestead.com/hot-air.html

 

I plan to post some Illustrations and see if you folks agree with my current thinking about the location of Neutral Pressure Planes

Meanwhile...

Does anyone else have suggestions for online links concerning  "Stack Effect"?

Views: 5604

Reply to This

Replies to This Discussion

Concerning the Klote Article

No need to brush up on Calculus or Fortran....

Just try to follow the Illustrations and concepts

Hi John, glad to see the topic back at the top.  Your comment that atmospherically vented appliances need to be eliminated is correct and I would take the additional step and say that all auditors should have serious reservations about performing or recommending any wx work where these high risk appliances are in use. 

I have left my worksheet up but have newer pages in progress that will be added soon. 

I'll be following.

Bud

Good morning, great discussion. I have a question here in Chicago we have mostly atmospherically vented furnaces and boilers. When I look up at the chimneys some have no rain hat, some have a flat top with a grate around the perimeter(like chicken wire), and some have the standard b-vent top approved for combustion appliances. my question is what are the the  differences between each of these in overall stack affect on a house? I'm trying to resize photos will have them up later. Thank you in advance

Hi randy, I'll give this a try.  There can actually be several "stack effects" taking place in one house at the same time and they will each have their own pressure distribution and NPP.  A house that is rather open will have one.  Seal off the air flow between two floors and now you have two different stacks, each with a high and low and its own NPP.  Then look at your chimneys.  Each can be filled with different temperature air/gasses from cold to hot and each can have different exposure to outside temperatures.  The chase way around the chimney or vent pipes can have their own pressures which even though we will probably seal them, an initial complaint might be related to their air flow. 

As for the caps you mentioned, they would restrict the air flow through that path just a bit and thus a slight change in the total exfiltration of the house.  The result would be a slight shift in the NPP, less exfiltration and the NPP would move down slightly. As for one vs the other in regards to the house stack effect, probably no difference.

Bud

Hi Randy, thanks for the question

Hi Bud, thanks for your answer

I agree that there may be several chambers & flues(tubes) & Neutral Pressure Planes in a house.

 

This is just a Simple example of a theoretic "tight" house with only one open window.

My thinking is that the Neutral Pressure Plane would be near the middle of the only open window.

I say "near" based on the John Klote Paper.

The Klote Paper explains that the NPP is actually slightly below the center of the opening.

This is true for heating and cooling seasons.

I "think" that the pressure difference between Inside and outside will be Approx 1 Pascal at the floor and Aprox. 7 Pascals at the peak.

 

This Illustration is for the Cooling Season

the NPP is virtually in the same place as for the Heating Season

the pressures at the floor and peak are the same

only now....

Cold air is flowing OUT at the bottom and

Warm air is flowing IN at the top

Hi John,

In the heating season the pressure will be +7pa at the top and -1pa at the bottom, wrto (with reference to outside).  In the cooling season (just happens to be the same ▲T) it will be -7pa at the top and +1pa at the bottom, again wrto.  One of the keys to understanding how this comes about is introducing that outside pressure.  Our readings are wrto, but exactly what is that pressure.  We always think of it as 14.7 psi (101325pa) and most (myself included) never paid attention to the rate at which it changes (approx. 3.5pa per foot) as we go up or down in elevation.  My worksheet that John posted above goes into detail illustrating the pressure increments on the outside in cold air and then on the inside in warm (lighter) air.  It is the difference between those two columns of air that produces the total ▲T we call stack effect, in this case 8pa.  The next step is following the adjustment process that creates the NPP and ultimately determined the above and below pressures.

Making this connection between the atmospheric pressures outside and house the pressures inside has really helped me understand and predict air flow in many other applications.  Here are a few:  Attic venting, chimney draft, unintended duct drafting when not in use, convective heat transfer, and even predicting how tight a house is without running a BD (just an estimate for now).

Some may ask, "why do we need this new information?"  One of the answers is our new tighter approach to homes.  On a leaky home, opening a window might barely move the existing NPP.  But on a tight home, it could cause a swing of 10pa or more depending upon the outside temperature. 

One more detail that we will need to go over is that we cannot see this change in pressure between upstairs and downstairs with out trusty manometers.  A two story house from the ceiling at the top to the basement floor could have as much as 100 Pascals difference in pressure.  Seems like that is something they should have told us at training :).

Bud

Howdy Bud,

I totally agree that it helps to "Introduce" the outside pressure.

I know that it has helped me (Thank you Bud)

I actually have the outside pressures on my Drawings ....

I have turned them off for these early Illustrations.

I was just trying to keep things simple (and less cluttered) at first.

......And more like the John Klote example.

 

I think You and I are saying the same thing ... just with different words.

I will be adding the Outside Pressures in future Illustrations.

 

John

Except in this example the Delta-T is -35 and so the Delta-P would be -4 Pa.

Just like a Cold Climatist ..... assuming that "your" stack effect is the "positive" effect

And those who live in a hot climate experience "reverse stack effect"   ;--)

 

 

We all know that the Southland is "backwards". That's why we invaded it in 1861 and whooped it good.

RSS

Latest Activity

Michael Dunseith posted a status
yesterday
CEE posted a blog post
Friday
Sean Lintow Sr replied to Chris Bellanca's discussion Overheating garage
"There are only two methods - block the heat before it gets in & exhaust what gets in Blocking -…"
Friday
John White posted photos
Friday
John White posted a blog post
Friday
Rob Madden posted a discussion

E&O Insurance

Any recommendations for a good E&O and general liability insurance carrier for energy…See More
Thursday
John Redmond added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Flir I7 Infrared Camera (Barely Used)

I have been away from this site for a while, so my apologies if this is supposed to be posted…See More
Thursday
John Redmond joined allen p tanner's group
Thumbnail

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
Thursday
Hannah Wood liked Quinn Korzeniecki's discussion Application Period for 2018 Energy Auditor (EA) and Quality Control Inspector (QCI) Pilots Now Open
Thursday
Quinn Korzeniecki posted a discussion

Application Period for 2018 Energy Auditor (EA) and Quality Control Inspector (QCI) Pilots Now Open

We need you!Applications are now being accepted to participate in the 2018 Energy Auditor (EA) and…See More
Thursday
Quinn Korzeniecki added a discussion to the group Building Performance Institute (BPI)
Thumbnail

Application Period for 2018 Energy Auditor (EA) and Quality Control Inspector (QCI) Pilots Now Open

We need you!Applications are now being accepted to participate in the 2018 Energy Auditor (EA) and…See More
Thursday
David Butler replied to Chris Bellanca's discussion Overheating garage
"Easy... insulate the attic ceiling. I'm not sure how much good it would do to air seal a…"
Thursday
Chris Bellanca posted a discussion

Overheating garage

Hi all, I'm looking for potential solutions to a problem at a client's house.  The south facing 2…See More
Thursday
Landon added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Brand new retrotec blower door system $3000

Hi, I’ve got a brand new blower door system from retrotec that I got 2 months ago, and never got…See More
Thursday
John Redmond posted discussions
Thursday
David Holtzclaw replied to David Holtzclaw's discussion GSHP for domestic hot water
"Thanks John & Bill. Bill your experience is one reason why I wanted a larger heat pump with…"
Thursday
Diane Chojnowski posted events
Wednesday
Rob commented on Bob Krell's group Healthy Indoors (IAQ)
"Hello, Has anyone tried custom filtering of window AC units? Specifically concerned with…"
Wednesday
Michael Dunseith's 2 photos were featured
Wednesday
Franco Oyuela commented on Perry Ning's blog post Warnings About Portable Air Conditioners
"Here are the top five benefits of owning a portable air conditioner: 1. Low Price – All…"
Wednesday

Photos

  • Add Photos
  • View All

© 2018   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service