3xSVP or 1xSVP + 2xAAV

[Mr Blobby]

So our M and E are suggesting 3 SVP all internal venting out through the roof.  In a passive house I would have thought that one venting and the other two soil pipes capped with an AAV in the warm loft would reduce cold draughts. 

Which option is best?  Does it really matter?

[Conor]

We went for AAVs. One in concealed cistern and other in cupboard. No issues so far and BCO happy.

[Russell griffiths]

Just the one on the end of the run. 

[Temp]

+1 Many BCO want one open vent on the furthest stack from the sewer in the road and everything else can be AAV.

 

Got a feeling the rules actually say you can have less than one open vent per house on an estate/group of houses but plan for the above. 

[Mr Blobby]

So for an update, my M and E consultants have reacted with absolute horror to my suggestion that AAVs can be used on the internal soil pipes.  They say AAVs are a really bad idea and I must not use them.   Which is odd because that doesn't seem to be the experience of members on this forum. 

 

But then my M and E people are also pushing back on my request for cooling the slab.  And they insist serpentine UFH layout is better than counterflow.  And they don't want to specify IVAR manifolds because they say they're rubbish; They want to use mixing sets that go no lower than 25c.  I welcome their advice but its not always great and I suspect they do things the way they have always done it and get very few clients who ever disagree with them.

 

So, M and E are pushing back pretty hard on my AAV suggestion for the two internal soil pipes.  The head stack furthest from the sewer connection will be venting (and outside) so no BCO issues. 

 

If I do decide to vent the internal soil pipes then that requires of course a hole in the (aluminium) roof for each of the two pipes.  Surely a hole in the roof presents a greater risk from failure (and more initial construction cost) than the risk from a £25 AAV failing. 

Am I missing something here?  Are my M and E guys right in in objecting to AAVs or are they being obstinate and ignoring the bigger picture?

 

It seems like members here on this forum have no AAV issues, contrary to my M and E advice that they are rubbish and guaranteed to fail.  What should I do?  Should I stick to my guns and insist on two AAVs in the loft or accept my M and E advide to put two holes in the roof to vent the two internal soil pipes?

 

 

 

Edited April 1, 2022 by Mr Blobby

[Russdl]

1 hour ago, Mr Blobby said:

Should I stick to my guns and insist on two AAVs in the loft

I would. We have two AAV’s in the loft and before they were properly sealed in place it was pretty obvious that they weren’t. Since being properly sealed, no issues.
 

If one fails I don’t think it will be too long before we notice that it’s failed, replaced it and carry on. 

[Russell griffiths]

@Mr Blobby time to get a company used to dealing with low energy houses. 

I purposely changed my manifold to the Ivar as it had the lowest temperature mixing valve. 

[Beckside]

I have four bathrooms all with WC, shower, sink and one with a bath. I have one 110 AAV in a roof void. The only penetration through the fabric of the building above dpc is for the boiler flue. We are on a septic tank not the mains. It all works fine at the moment.

[Mr Blobby]

56 minutes ago, Russell griffiths said:

@Mr Blobby time to get a company used to dealing with low energy houses. 

I purposely changed my manifold to the Ivar as it had the lowest temperature mixing valve. 

 

Yes, I'm pretty certain my M and E consultants' specifications are unduly influenced by third party heating companies who want to maximise profit from a lazy installation.  No cooling, no counterflow loops, no IVAR manifolds?  I'll go elsewhere thank you.

 

The M and E heating specification should be vendor (ie installer) independant. It isnt.  I think anyone who engages M and E consultants should be wary of the independance of their adivice and conflicts of interest.  Its a bit shit really.

 

 

Edited April 1, 2022 by Mr Blobby
typos

[PeterW]

1 hour ago, Mr Blobby said:

The M and E heating specification should be vendor (ie installer) independant. It isnt.  I think anyone who engages M and E consultants should be wary of the independance of their adivice and conflicts of interest.  Its a bit shit really.

So as an M&E consultant, I can tell you a lot are independent and aren’t swayed by suppliers. We even ran a black list of products we wouldn’t recommend based on previous client feedback when the product didn’t deliver. 
 

There is also an element of client responsibility in all of this - if you don’t give your consultant a proper list of requirements for how you will use / live in the house; don’t give makes or manufactures of showers, taps and other connected appliances; and change your mind 3 times about what heating controls you want, then it’s down to you when it doesn’t all hang together. 
 

We were once presented with a thermostat that didn’t work, and client wanted “these in every room”… no labels, no boxes, no clue as to manufacturer as it had half the bits missing and yet they were “disappointed” that we couldn’t identify it so they could have them … There are hundreds of thermostats out there and yet we were supposed to guess what this was …

 

And that is the reason why we don’t work with end clients any more !!! 

[Beckside]

Sorry to say I agree with the OP, when I wanted to use weather comp and no mixers on the manifolds for my UFH. It was virtually impossible to find an ‘heating engineer ‘ that had even heard of it let alone had experience of this type of set up. I spoke to a lot of companies and consultants and not one had any knowledge or real life experience of utilising weather comp controlled heating systems. Yet this has been common practice in continental Europe for several decades. We are literally decades behind on integrated heating/cooling systems and their efficient control. I used a Viessman W200 system boiler which can control two mixed and one unmixed heating circuit. All software resident on the boiler with touchscreen and Wi-Fi connectivity.  It controls to motorised mixing valves to control flow temps to the ufh based on outside temp. No internal thermostats, it works incredibly well.  I think you have worked out what to do, find another ME with low energy experience.

[Mr Blobby]

5 hours ago, PeterW said:

if you don’t give your consultant a proper list of requirements for how you will use / live in the house; don’t give makes or manufactures of showers, taps and other connected appliances; and change your mind 3 times about what heating controls you want, then it’s down to you when it doesn’t all hang together. 
 

 

 

I'm sure there are lots of shitty clients just as there are really good M and E consultants.  I can assure you however that bad M and E does not mean bad client.  Quite the opposite.  To summarise...

 

My passive house architect got the M and E team on board early to ensure proper service voids and plant room etc go into the design.  M and E have the PHPP model hence the M and E team know this is a low energy build and what heating load to expect.

The M and E team have been supplied with a full list of all plumbing requirements including all sanitaryware and taps, showers.  Designs done at single local bathroom showroom etc and liasing with M and E.

M and E team have met with KNX designer to finalise all the lighting and electrics.

Full kitchen spec including appliances supplied.

Solar PV specification including battery and locations for installs etc all done.  Meters, connections, all agreed.

Car chagers included in spec etc.

 

Every single detailed requirement and design from my side has been supplied in full to my M and E team.  No changes, no messing about.

 

The problem is that, for example (and there are many), when my M and E team tell me that the heating company only do serpentine UFH layouts because they are better than counterflow layouts (despite my objections) then I am left to conclude that the M and E team are more interested in what their business partners want than listening to their clients. When they tell me they won't specify an IVAR manifold because the same heating installer doesn't like them, then again, this is the M and E team ignoring their client for no good reason other than to try and set me up with a pretty crappy heting installer they work with.

 

The M and E team appear to be guided by their own commercial relationships, not by best practice design or serving their clients best interests.  It happens.

 

 

... back to my original question, @PeterW, as an M and E guy,  should I avoid using AAVs and vent outside on all three soil pipes?

 

 

Edited April 1, 2022 by Mr Blobby

[PeterW]

I know this is no consolation but we would love clients like you ..!! 😀

 

And are they consultants or designers .? That can be a bit difference and I agree, they are not being the best !!

[Mr Blobby]

4 minutes ago, PeterW said:

I know this is no consolation but we would love clients like you ..!! 😀

 

And are they consultants or designers .? That can be a bit difference and I agree, they are not being the best !!

 

I think we overlapped....

 

... back to my original question, @PeterW, as an M and E guy,  should I avoid using AAVs and vent outside on all three soil pipes?

[PeterW]

I would AAV 2 internally and one external to keep BCO happy. Usually pick the one least visible for external. 
 

These are decent ones - better than the Floplast ones https://www.screwfix.com/p/mcalpine-vp100e-push-fit-air-admittance-valve/236HP

[Mr Blobby]

On 01/04/2022 at 23:09, PeterW said:

I would AAV 2 internally and one external to keep BCO happy. Usually pick the one least visible for external. 
 

These are decent ones - better than the Floplast ones https://www.screwfix.com/p/mcalpine-vp100e-push-fit-air-admittance-valve/236HP

 

Thanks for the link.

 

The external pipe will be against the kitchen wall that is at the boundary to next door, so not visible anywhere, and to bring it inside would mean boxing it throught the kitchen which would be awful. 

Why M and E think running it internally and venting it through a hole in the roof is a good idea is beyond me!

 

Edited April 3, 2022 by Mr Blobby