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Bruce Frey
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Jesse Thompson
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Posts:59
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| 05/14/2009 12:18 PM |
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Wow, still no real air tightness standards. Amazing to see that this is still out of the conversation. We've got a really long way to go. The UK instituted this how long ago?
John Straube at U of Waterloo likes talking about how the Continuous Air Barrier standards (material, assembly, building) magically increase by a power of ten (0.004 cfm/ft2, 0.04 cfm/ft2, 0.4 cfm/ft2), when all that matters is that a building ends up air tight. It's not a real standard yet. Material tightness will always be incidental to the end goal, which is a predictable, field-tested building envelope.
0.4 cfm/ft2 for buildings isn't a terrible target to shoot for, if only the requirement wasn't continuously dodged by people claiming that their buildings are performing at that level because they used air tight materials which individually meet the 0.004 cfm/ft2 metric. |
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Jesse Thompson
Kaplan Thompson Architects
http://www.kaplanthompson.com/
Portland, ME
Beautiful, Sustainable, Attainable |
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Bruce Frey
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Posts:272
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| 05/14/2009 3:14 PM |
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You are right!....this is especially problematic for tall buildings in cold climates. The results of stack effect at the top and bottom of tall buildings due to infiltration/exfiltration are amazing. We started doing thermographic studies, the commercial building equivalent of a blower door tests and BMS pressure monitoring and as a matter of course in the mid 80s after a spate of crappy curtainwall jobs in the boom years of the late 70s/early 80s in the USA.
Bruce |
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cmkavala
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Posts:1384
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| 05/16/2009 7:26 PM |
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Bruce;
just a guess , since commercial buildigs require large amounts of fresh air, infiltration is not so much the problem with a positively pressurized building and exfiltration is hard to control with exhaust vents.
blower door testing may not prove very much ? |
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Chris Kavala
chris@southernsips dot com
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Bruce Frey
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| 05/17/2009 3:45 AM |
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Infiltration and exfiltration are big issues for glass curtainwall buildings since everythng basically relies on gaskets and sealants.
For a major project with a custom curtainwall system, we do laboratory tests for static (using a pressure chamber) and dynamic (using an aero engine) structural, air and water tests before fabrication begins. The test chamber may be 2 stories high by 30' or so wide. We have also done coldwall tests to check thermal performance.
During the (early) course of installation, we will randomly select a few areas and do field pressure and water tests. We will build a pressure chamber on-site and enclose 2 or 3 window units for testing. This is our "blower door" test...basically to confirm that the acutal installation matches the design and lab results.
If we use a manufacturer's "standard" system (i.e., one that has been previoulsy used and tested), we may forgo lab tests, but we usually will do field tests, especially if taller than 30 stories.
Ideally, we have a tight building and we can maintain a slight positive pressure with minmal fan hp. I have also seen leaky buildings that were not possible to pressurize. Stack effect caused by a leaky wall in a tall building in the north can be very ugly. I have seen exterior doors that are almost impossible to open....ground floor elevator doors that won't close, etc.
Tight is always good.
Bruce |
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cmkavala
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| 05/17/2009 7:15 AM |
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Bruce;
there is no way to stop exfiltration going out thru exuast fans, dampers are for incomimg air only, as soon as you positivley pressurize a building it will blow out thru the exhaust ducting
Testing wall systems are great as long as it is in a "reality" type situation. A tight curtain wall in a room serves no purpose if there is a 4" hole thru the wall right next to it |
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Chris Kavala
chris@southernsips dot com
1-877-321-SIPS |
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Bruce Frey
Registered Users
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Posts:272
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| 05/17/2009 1:25 PM |
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Posted By cmkavala on 05/17/2009 7:15 AM
Bruce;
there is no way to stop exfiltration going out thru exuast fans, dampers are for incomimg air only, as soon as you positivley pressurize a building it will blow out thru the exhaust ducting
.................... A tight curtain wall in a room serves no purpose if there is a 4" hole thru the wall right next to it
We don't let people poke holes in our facades. These are large buildings that have centralized air supply and return systems that can be tuned with balancing dampers, motorized dampers and frequency drives.
Bruce
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cmkavala
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| 05/17/2009 1:33 PM |
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Point missed, the larger the building the worse they are:
Elevator shafts, multiple doors opening constantantly, etc., a tight curtain wall is the least of infiltration/exfiltration problems |
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Chris Kavala
chris@southernsips dot com
1-877-321-SIPS |
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Bruce Frey
Registered Users
Basic Member
Posts:272
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| 05/19/2009 3:25 AM |
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Posted By cmkavala on 05/17/2009 1:33 PM
Point missed, the larger the building the worse they are:
Elevator shafts, multiple doors opening constantantly, etc., a tight curtain wall is the least of infiltration/exfiltration problems
Sorry, I did miss your point.
In the past 52 years, my company has developed ±120 Million square feet of mostly large office buildings. ±76 Million sf of the properties we operate are Energy Star rated. Based on our experience, I respectfully disagree.
Bruce
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