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MVHR ducting to outside


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2 minutes ago, Nickfromwales said:

I prefer that to terminals in a gable.

I did originally consider the NW gable, the bit you can see and my only gable, but it was a long run and the roof was just easier.

No inline filters yet, but I may add them (in the attic) in due course.

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21 hours ago, James H said:

I am  sorry I don't see why there has to be a fire collar around a pipe that is going out side.

 

It was our BC who asked. The whole section of wall that had a brick skin was fire stopped  (red bags in photo) . Don't ask me why, or if its really needed but if it meant giving me brownie points with BC it was worth it

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Sorry for delay in replying to jsharris and others.

The MVHR system was designed by Green building store, in Yorkshire,they commissioned it, and I installed it.  They had the posibility to put the in and out lets in other locations.  I did ask them if they needed to be further apart, and they said not for my instillation.

Which is for 110m2 with a PAUL Focus 200. 

The out side wall is not finished it still has to be clad (swan larch), the back of the building is facing North and open aspect as it is a straight wall, yes there are various pipes there none of which interfere with the ventilation. Both pipes have a fall to the outside so that any condensation will drip out side and not build up inside.  There is a lot of space around the pipes and in this case I think there is no real risk of air mixing.

 

I went for a system designed by t Green building store because:

1. I knew not much about it.

2. it had to be done right first time.

3. the price was not a problem as I have spent around £200 on the heating (one panel heater) for the whole house (which is working up to now since mid December)

4.Other company's when talked to  were a little bit vague about every thing as though they only wanted the sale.

5. Having the system commissioned by a professional meant all the figures could be passed on for SAP cert.

 

We are very happy with the system as it makes the house very agreeable to live in, our main living area 19-20c and the other rooms all above 18c most of the time.

Drying cloths takes no time in the utility room and no damp or musty smells on our cloths, as we used to have in our last house (200 year old stone cottage).

 

I will post a photo of the back of the house which I will hope makes it clearer (in another post as it will be from my phone).

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They do look very, very close together in those photos, far closer than any guidance I've ever read anywhere suggests.  There's bound to be a degree of cross contamination with them arranged like that, I think, the question really is how much that may be and whether it will prove to be a nuisance at times.

 

The worst case will probably be a still day, when the extract is dealing with smells from the kitchen (or worse) which then get partially sucked back in to the fresh air intake and distributed around the whole house.  If you rarely get still days you might get away with it, but it's not really an example of good practice, and I would have thought that the designer should have known a lot better than to place them that close together.

 

Mind you, if you're in an area where there is always a breeze it may not matter too much.

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3 hours ago, Moira Niedzwiecka said:

What kind of external vent grilles are best?

With a cowl or not?

Is it necessary to have an insect mesh?

Ideally not a cowl as it would restrict air flow a bit. I wanted stainless steel bullnose cowls which look good but because they slot onto the end of the duct I thought the restriction would be too great. I used a 300mm square grill with an insect screen behind which has an airflow greater than the cross sectional area of the duct.

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If fitting grilles with mesh screens you just need to bear in mind the need to clean the intake one.  I find ours regularly gets clogged up with cobwebs and the fluffy floating seed stuff (Old Man's Beard?) and so needs cleaning around once a month or so at the time of year when all these seeds are floating around.  It's one reason I'm looking at repositioning it down to a more accessible location and fitting a bigger screen that I hope will be easier to clean and not need cleaning to often.

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1 hour ago, Moira Niedzwiecka said:

Like those Peter.

Where did you get the grilles from?

I have been searching the net but not found anything as nice.

They're aluminium and I got them from Ironmongery Direct, but it was several years ago and unfortunately they don't appear to stock them any longer.

SDSLondon still do them but they are more expensive.

https://www.sdslondon.co.uk/zig-zag-pattern-vents.html

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  • 1 month later...

@Moira Niedzwiecka

Hi Moira, the grilles are flat. I cut some cedar battens, I think 20mm square, and made a frame which I attached to the cladding around the duct pipe. I screwed the grille to the frame. The grille, 300mm square, needs to be set away from the end of the duct, 125mm diameter, to allow the airflow into the duct. The total cross sectional area of the holes in the grille must be larger than the cross sectional area of the duct.

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