Blower door test: Determining the volume

sas

Hi,

Something I've pondered for a while now.

On my block build I assume I'll test twice
(a) at completion of airtightness work when there is scope to improve on weaknesses
(b) at full completion

At point A my ceiling slabs will not be in situ when tested.
At point B my ceiling slabs will be installed and plastered.

The PHI are telling me that my volume is that area enclosed by the finished surfaces i.e. the air in the cavity between my hollowcore and my slabs is excluded.

What's the convention? Do I use what will ultimately be the volume of my finished home when determining the result for point A?

No6

I think the weakness will arrive with the electrician and plumber!!. I would use the finished volume but I am not a pressure tester so I could be wrong.

fclauson

SAS
what do you reckon is the delta between the volumes as a percentage
is the ceiling void inside or outside the airtight layer
and if its say 20cm on a 2.5m room height then thats going to be 7.5% difference - you could do it for both vols and see what the figure is

Francis

sas

No6 wrote: »

I think the weakness will arrive with the electrician and plumber!!. I would use the finished volume but I am not a pressure tester so I could be wrong.

Yeah, that was where I'm landing i.e. finished volume. It's the smaller of the 2 and hence likely to give you the most pessimistic result.

The electrician and plumber will have completed their first fix and I do the first test.

sas

fclauson wrote: »

SAS
what do you reckon is the delta between the volumes as a percentage
is the ceiling void inside or outside the airtight layer
and if its say 20cm on a 2.5m room height then thats going to be 7.5% difference - you could do it for both vols and see what the figure is

Francis

No idea on the percentage.

Ceiling void is and always should be inside the airtightness layer.

The bigger the volume the better the result, hence the more pessimistic approach makes sense as long as it's your own home. If you're building someone elses home however.....

beyondpassive

Came across this before when testing a renovation that was struggling to get under 1. Being able to include crawl spaces within the thermal envelope would have helped our result.

EN13829:2001 is interchangable with ISO 9972:2006 is flawed as it is vague on certain matters. Measured Volume is one of them. The committee which is looking at revising the standard recognises this. See page 11 for their interpretation.

http://www.aivc.org/medias/pdf/Workshop062010/Session%204.2%20-%20Yoshino.pdf

Partitions and crosswalls, and suspended floors are included in the volume, so you would have to conclude that services cavities are also included. This is generally what is understood by envelop area

When alles did the final test he refered to a DIN standard listed by the Passivhaus institute which used the finish dimensions.(Din 4108 perhaps)

Discrepancies between both standards are sumariised here: http://www.inive.org/members_area/medias/pdf/Inive%5CBlowerdoor2007%5CeBolender.pdf

Hopefully alles can confirm his learned interpretation.

alles

Hello all,

A couple of things here:

- the contention by beyondpassive that the EN13829 is flawed is spot on, in that there are so many gaps and cracks in its scope. These really only become evident when you start testing and have to refer back to the document for guidance.

- In this regard, several national testing associations or regulatory bodies in the various countries that adhere to EN13829 as the national testing methodolgy have developed extensions to, or additions to, or clarifications of, certain aspects of EN13829 that cause them bother.

- In this regard again, the Passive house methodology comes out of Germany, and so I use as my guidance for Passive House testing, whatever it is that the Germans do. This may be based on PHI guidance/training manuals, or also the flib group, which is the main German airtightness testing association, which has a document on their website (www.flib.de) on testing to Method A (i.e. the Passive House required method) in which the volume question is treated.

IN that document it is clear - what you count is the visible air space conditioned volume of the building. No inside of partitions, no above suspended ceilings, no unheated basement areas (outside of the thermal envelope), no couple of centimeters between your finished wall layer and the airtightlayer behind it. In other words, (and I am making this definition up now on the fly, but I think it is accurate enough) if you can't see it in the usable state of the building, then you don't count it - it is the 'clear air volume'. You should be able to go into the building and take 'width * breath * height' of each of the spaces to be included and add these all up. <snip>

If you test a building before the final surfaces are available (which is usually the case in the first test) then you still report the result as if the final finished surfaces were present (i.e. a smaller volume than that which you see when performing this first test, where the layer visible is usually the airtightness layer itself). This answers the question posed by SAS in originally - YES.

There are a couple of snags - contentions even within the national groupings over what might be an acceptable volume and not: attic spaces reached by an airtight attic hatch inside the thermal envelope, maybe used to store items but only say a meter high or so - do you include these? I have spoken to testers from various countries, and our own on this and other points, and it turns out there is disagreement. <snip>

I am actually working on a discussion document which I will soon submit to the PHI to see can we have, at the end of the discussion process, a fully comprehensive EN13829 based standard (with all of the relevent extentions, additions and clarifications) for the Passive House test, on which there can then be no disagreement across country boundaries or within the airtightness community, be it designers/specifiers/testers.

Final thought however, despite whatever I might say or what you read here, the final say will be the certifiers for the Passive House cert. The rule of thumb must be: aim conservatively.

If in doubt, leave it out of your volume calculations.

Sas, I hope this has helped a fraction,

alles