bad by the sounds of it!

Giving this a kick - surely more than just one GBF member has used Passivent-type unpowered stack ventilation systems? There must be much to say about it.

thanks borphin and mrsherbie

Did you follow recommendations about permanent air inlet, and what do you think of that in an 'airtight' house?

Any experience of making the vents openable/closeable, perhaps automatically controlled by humidistat? That wd have to open/close both inlet and exhaust ducts (in pairs) simultaneously.

That just leaves mrsherbie then, who's fitted Passivent to a (?) 'modern' house. Is Passivent really unknown to GBF members? That says something about it.

I like the idea of Passivent as no running costs, no noise and nothing to go wrong/maintain. BUT I dont like the idea of it being uncontrolled i.e. different vent rates depending if it is windy/hot/cold. It would be good if there was a way of auto control (not passive then!!!)

I like MVHR because of its ability to recover heat (cost) and its controllability. With clever design and reading the thread on MVHR without noise I am sure it is achievable to have a quiet system.

Yes, ours brand new/in progress, very traditional build/oak frame but warm roof, airtight, fully celotex wrapped etc. Predicted energy assessment=74%efficiency, 97%carbon.
I think it depends on your lifestyle and where you live, we have no neighbours and it is pindrop quiet here, hence my not wanting any fans or noise whatsoever. We are always home and very outdoorsy so doors/windows open. My folks have full MHRV(2units) and the bathrooms/mirrors DO steam up when you have a shower or run a bath, so the mhrv clearly does not work as well as elec fans, even though it is powered. So we are prepared to open a window slightly when we use these rooms anyway as we have oak beams running though them.

We have a new wood burning rayburn going in(we currently live with a 40's backboiler one) so need direct airflow for this anyway, which ironically is coming in low down through the wall in the kitchen in the form of an old fashioned airbrick!
The rayburn needs it, and the dog likes to lay in a draught so it has 2 purposes LOL! The stone floor is UFH so the draught wont be a problem.
Obviously we have window trickle vents.
But in such an insulated house we have been actively 'adding' draughts & airflow LOL!

We could not have mhrv anyway as we are all vaulted ceilings under the warm roof with no lofts to hide ducting. So running ducting up inside the roof was our only option. Also I didnt want ANY pipes or protrusions coming through my lovely roof for visual reasons.

Yes, we have been wary of building a tupperware box to live in! not our thing! but it really is not that hard to open windows!
People seem to be getting ridiculously obsessed about building a hermetically sealed box with everything 'fully controllable'?? why?? people used to live in caves!
All these cheaply made electrical 'gadgets' DO go wrong after a period, because as we all know nothing is built to last nowadays : (

And as we are building a 'house for life' and will never move from here, simplicity in design and a total lack of pretentious 'outdated or broken down by next week' gadgety junk has shone through as the long term best maintenance solution
: )

And your heating system turned off? Or accepting that you're throwing away all your heated air prob every 20mins and re-heating that much outside air 3 times an hour?

That's the size of it, a conundrum that MHRV 80% solves.

Question is, can a Passivent (or DIY equiv) system be automatically controlled so as to do that wasteful thing only when really necessary e.g. under humidistat control - bearing in mind that the control has to be of both inlet and outlet channel(s) simultaneously.

Just a thought about controlling a passive vent, could the windspeed and/or direction not be used to vary a venturi. SO the faster the wind blows through it, the less effective the venturi becomes, or in aeronautical terms, it stalls at a relatively slow speed. They may do this already.

Thing about using wind direction (not that I think it is really a simple solution for this), is that there is a very good correlation between wind speed, temperature and direction. But that is just getting flash and moving away from our beloved KISS.

I think Venturi are great, I want one under my car.

Unless it involves lots of complex and unreliable electronics, and/or is sold by salesmen that the double-glazing industry rejected as too sleazy, it can't possibly be of interest! B^>

Rgds

Damon

A neighbour has implemented something similar in his extension. Effectively, it's a series of vertical pipes inside the walls that take air from the house up to miniature stacks on the roof. I couldn't comment on whether it works yet, as he hasn't moved into the extension, but I can understand what it's intended to do.

I'll report back when the project is finished, but don't hold your breath - he's run out of money so it could be a year or two.

Posted By: fostertomclient is averse on principle to relying on electric fans for evermore

Amen to that, I'd rather have cold draughts - wear lambswool socks and cardies, although I appreciate some people might have a different view.

Peter

Posted By: Peter ClarkAmen to that, I'd rather have cold draughts - wear lambswool socks and cardies,

That's OK as long as you're using less fossil fuel for heating than would be consumed by the mechanical ventilation.

Posted By: Peter ClarkYou mean less extra than would be consumed by ventilation?

Yes, that would be a better way of putting it.

Could use wood?

It would be better if the wood was "sequestered" - in a house or something.

Posted By: fostertoma client of mine has asthma/allergies that make intake ductwork (incl prob heat exchanger) a no-no because nasties do accumulate and breed in ductwork

But there are no allergens etc outside in the street or in the fields? I'd have thought a pollen-filtered intake would be a yes-yes rather than a no-no.