Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



widget @ surfing-waves.com


Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




  1.  
    Hi,

    My new build has three AAVs on the 3 SVPs rising up the house, and also a HepvO waste on the condensate drain from the boiler....
    These seem like good solutions.

    However, I'm now wondering about the effect they may have on the air-tightness.
    during the test, when the house is de-pressurised, I'd expect them to seal nicely, but when pressurised, i would have thought that air would blow out through them. I haven't got the AAVs yet, but the HepvO needs very little pressure to let air out.

    Does anyone have experience of air tests with AAVs or HepvO? was the pressure air change rate worse than the de-pressure?

    for the HepvO, I could put a trap in as well, and fill it with water, but for the AAV, I don't think there's much I can do....

    Thanks,

    James
    •  
      CommentAuthordjh
    • CommentTimeJun 5th 2017
     
    Yes, I have both AAVs on my soil pipes and a HepvO on the condensate drain from my MVHR.
    These vents & traps should be sealed for the test, if necessary.

    In my case we sealed the HepvO but two of the AAVs were inaccessible for sealing and so led to a somewhat greater leakage during pressurisation. The average result was still 0.42 ACH though, so I didn't feel any great urge to break open the enclosures around the valves to improve the result further. The depressurisation result was 0.33 ACH and the pressurisation result 0.51 ACH
  2.  
    Hi djh,

    Thanks for the info - really useful.

    However, I'm not so worried about the test, as much as air leakage over the life of the house (actual performance vs. measured performance).

    Surely sealing them for the test is kind of "cheating"? as they're not normally sealed?

    Everything else being equal, your numbers (which are really impressive!) suggest that in operation, around half the leakiness of your house is down to AAVs.

    Anyone else? is it standard practise to seal these up when testing? Is there anything else that gets sealed up during testing that's normally not sealed?

    Cheers,

    James
    •  
      CommentAuthordjh
    • CommentTimeJun 5th 2017
     
    The AAVs and HepvO aren't subject to pressure differentials in the way that a door or window seal is. Just the difference between the pressure inside the house and the pressure in the drains. It's not like the wind blows directly on them. So I don't think there's much leakage through them, except when there's supposed to be.

    What can be sealed during testing depends on whether it's a Part L test or a Passivhaus test. See

    https://www.attma.org/wp-content/uploads/2016/09/ATTMA-TSL1-Issue-3-Rev-0-2016.09.09.pdf
    http://www.passivhaus.org.uk/filelibrary/Primers/Passivhaus-Airtightness-Guide.pdf

    Personally, I think taping up trickle vents or any other vent that has a closing mechanism is wrong.
    • CommentAuthortony
    • CommentTimeJun 5th 2017
     
    I have had a lot of trouble with AAV in storms jamming open, won't use them, love hepVO

    I also hate internal SVP especially draughty boxing in.
    • CommentAuthorDarylP
    • CommentTimeJun 5th 2017
     
    @jamesheath, if your ATT engineer de-pressurises your dwelling, then the HepVos will be fine.
    However, if he/she pressurises the dwelling, they will leak....
    We mostly de-pressurise, as it makes it easier to hear/see leaks.
    Good luck :smile:
    •  
      CommentAuthordjh
    • CommentTimeJun 5th 2017 edited
     
    Posted By: DarylP@jamesheath, if your ATT engineer de-pressurises your dwelling, then the HepVos will be fine.
    However, if he/she pressurises the dwelling, they will leak....
    We mostly de-pressurise, as it makes it easier to hear/see leaks.
    Good luck:smile:

    Both are required in the passivhaus test.
    •  
      CommentAuthordjh
    • CommentTimeJun 5th 2017
     
    Posted By: tonyI have had a lot of trouble with AAV in storms jamming open, won't use them, love hepVO

    Haven't noticed any problems so far, but they're not very old yet. Thanks for the heads up to keep an eye on them.

    I also hate internal SVP especially draughty boxing in.

    Why would the boxing in be draughty?

    Do you have another solution to the thermal bridge that an externally-vented internal soil stack represents?
    • CommentAuthortony
    • CommentTimeJun 5th 2017
     
    Every svp I have ever seen is draughty inside the boxing, hole into the loft, open perps in corners, leaky unplastered blocks, holes in the slab especiallly with suspended floors, first floor voids are notorious for bring draughty and these draughts get into the svp boxing.
    • CommentAuthorgoodevans
    • CommentTimeJun 6th 2017
     
    The draughty boxing is a result of incorrect detailing at the air barrier or no air barrier (but will give a easy vertical channel to distribute the infiltrated air).

    I am planning an internal SVP so I should ensure good sealing at the air barrier(s) and if against an external wall ensure the air barrier is contiguous behind the pipe before boxing in. In these circumstances I presume that there will be at least one boxed SPV won't be draughty.
    • CommentAuthorgoodevans
    • CommentTimeJun 6th 2017 edited
     
    Tony - can you comment further on your preference for HepvO.

    As far as I can see it solves the issue of loosing the trap water due to storm, evaporation or syphoning due to bad design.

    But presumably it can 'burp' each time there is a pressure variation between the drain and the house. If they leak with less than 50Pa back pressure (5mm head) then on windy days all the plugholes could be burping all day. EDIT - I see that one end of the silicon is not connected - unless there are foreign bodies in the HepvO no back pressure will result in drain gas entering.

    On the other hand when the wife drops something down the plughole I could claim that it's gone as there is no trap. That'll save me a couple of mucky jobs a year.
    • CommentAuthorgoodevans
    • CommentTimeJun 6th 2017
     
    Does a HepvO really allow the pipe runs to be relaxed - is each plughole considered to be vented - will the BCO sign off if the strict guidance is not followed?
  3.  
    Thanks for all the comments.

    I don't think I've quite got to the bottom of this though.

    I really don't care about the pressure test TBH - my take on the pressure test is that it's there to ensure the performance of the house, not to get an artificially good figure.

    Therefore my concern is the leak of air through the AAVs in normal use. I guess what I'm interested in is whether they open at 50Pa in the drain (my guess is yes) and how often that happens.

    I can see wind outside the house creating 50Pa pressure differences all the time, largely by dropping the external pressure, but would the drains often drop below the house pressure (obviously they may occasionally, the whole point of the AAV is to relieve that pressure difference).

    For instance, has anyone ever heard an AAV "sucking" on a really windy day?
    •  
      CommentAuthordjh
    • CommentTimeJun 6th 2017
     
    The whole point of my AAVs is to avoid the soil stacks penetrating the airtightness barrier. The only place my soil stacks penetrate the airtightness barrier is at the bottom, where they are sealed to the slab and then pass through 100 mm+ concrete so there's not much chance of a draught there. My SVP is entirely outside the house (it's a length of rainwater downpipe, with a mesh cover on the top).

    And my first floor void is entirely within the airtightness barrier.

    Just because most houses are not built properly doesn't seem a good reason not to follow best practice when you can.
    •  
      CommentAuthordjh
    • CommentTimeJun 6th 2017 edited
     
    James,

    I agree about the purpose of an airtightness test. I would think there's something severely wrong with an AAV if it doesn't open when there's a delta P of 50 Pa. Other than allowing waste water to flow through it*, its main purpose is to relieve pressure differences caused by flushing water down the drains elsewhere in the house.

    I think the air pressure in a well-built house pretty much matches the average pressure outside and doesn't follow every gust. Ditto for the sewage system, although I expect it's influenced a bit more. It's been pretty windy today and I can just see the water in the toilet bowls moving a little sometimes; they'll be damped by the AAVs of course.

    But there's much less air going through the AAVs than through our ventilation system and even through infiltration. I don't really understand your concern, or see any alternative to be honest.

    I've never heard any noise from our AAVs.

    The technical info for the HepvO is reproduced at http://www.leapltd.co.nz/uploads/files/HepVo_Aust1.pdf BTW. I'm sure there are other copies around.

    * edit: I was thinking of the HepvO at this point, not a conventional Durgo-type AAV. Clearly a Durgo isn't intended to ever encounter water!
    • CommentAuthorMike1
    • CommentTimeJun 6th 2017
     
    Not directly relevant to the question, but don't forget that Building Regs require an open vent pipe (without an AAV) at or near the head of each main drain run - which may or may not apply to your house, depending where it is on the local sewer and the requirements of the BCO. Though to avoid air-tightness issues that could be a separate external stack just for ventilation.

    The idea is that this allows sewer gasses to escape and avoids pressure build-up in the sewer. I guess that this pressure-evening wouldn't be enough to counteract variations in pressure in the house, but there would be some sort of interplay going on...
  4.  
    Posted By: Mike1Not directly relevant to the question, but don't forget that Building Regs require an open vent pipe (without an AAV) at or near the head of each main drain run - which may or may not apply to your house, depending where it is on the local sewer and the requirements of the BCO. Though to avoid air-tightness issues that could be a separate external stack just for ventilation.

    The idea is that this allows sewer gasses to escape and avoids pressure build-up in the sewer. I guess that this pressure-evening wouldn't be enough to counteract variations in pressure in the house, but there would be some sort of interplay going on...


    Yes, I have a sewage treatment plant and the external stack is 600mm high and next to the the treatment plant. I have only AAVs inside the house.
    •  
      CommentAuthordjh
    • CommentTimeJun 7th 2017 edited
     
    Posted By: Mike1Not directly relevant to the question, but don't forget that Building Regs require an open vent pipe (without an AAV) at or near the head of each main drain run - which may or may not apply to your house, depending where it is on the local sewer and the requirements of the BCO. Though to avoid air-tightness issues that could be a separate external stack just for ventilation.

    Exactly:
    Posted By: djhMy SVP is entirely outside the house (it's a length of rainwater downpipe, with a mesh cover on the top).
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press