Air vent for wood stove - advice needed please.

[Oxbow16]

Hi all

 

I'll be having a 6kW wood stove installed soon.  It's an old house, so we get the first 5kW for free and only need to provide air for the remaining 1kW.  From what I've read, this needs to be 23mm x 23mm for square, or 26mm diameter if round.  We don't want any large grill faces or anything like that.  Would prefer it to be visually as unnoticeable as possible.  Can't do anything with the window, as that's being replaced in the future.  

 

So...

 

- Would it be best to do one hole to spec, or several little holes? 

- Can anyone work out what size the little holes would need to be if doing a few?  Or is that as simple as dividing 26 by the number of holes?

- My installer said it would be enough to just have the holes lined...  Any ideas what's best to use?

- How to make the holes rodent mouse proof?

 

Also, I've read several times how random the nominal rating of stoves is...  How 5kW stoves can be largely different in physical size, have different sized fire boxes and therefore different fuel loading capacities, have different ranges (the Arada Ecoburn is rated 1.5 - 9Kw, whereas the Clearview Pioneer is rated 1kW - 5kW)), and yet all be rated as nominal 5kW.  And on top of that, how the testing of stoves is very artificial and easily manipulated to reach a desired rating.  With all that in mind - and forgetting HETAS, regs, etc for a moment - how much real life need is there for an air vent with a 6kW stove installed?  For the record, the stove is a Woodwarm Fireview 6kW (5.8kW nominal to be precise).

 

Many thanks

 

(PS - We'd love to have a direct air feed but for several reasons it's just not possible.)

 

[ProDave]

That's not the way the regs work.  Under 5kW you don't need to provide an air vent but above you do.  It is certainly a wise thing to provide regardless.

 

And I always understood the air vent should equal the area of the flue pipe.

[wozza]

Why can you not have a direct air feed ?

 

Is this an option?   Leaflet Efficience Pf 2014 (calameo.com)

 

Edited January 25, 2021 by wozza

[PeterW]

1 hour ago, ProDave said:

And I always understood the air vent should equal the area of the flue pipe.

 Not exactly ... you need a minimum area which is about the size of a 50p piece per kW. 

[ProDave]

1 hour ago, PeterW said:

 Not exactly ... you need a minimum area which is about the size of a 50p piece per kW. 

Is it different in Scotland?

 

I recall our last house we had a 5kW stove, and being "5kW or greater" it needed an air supply and it was BC that told us the area of the air supply should be >= the area of the stove flue pipe.

[PeterW]

Regs have always been done via calculation in all areas from memory. 
 

From the ScotRegs 3.16 you have this

 

a permanent air entry opening or openings with a total free area of 550mm2 for each kW of combustion appliance rated output more than 5kW. (A combustion appliance with an output rating of not more than 5kW has no minimum requirement, unless stated by the appliance manufacturer).

 

The diameter of a 50p piece is 27.5mm, so around the same area. 

[Oxbow16]

Many thanks for the replies.  

 

RE direct air feed.  The walls are thick, the floor is solid, the stove will be in a recess which is not on an external wall...  There was just too much involved in getting air to it.  It's too late now anyhow as I don't think the Woodwarm Fireview can have a direct air feed, and we've already ordered.  

 

5 hours ago, ProDave said:

That's not the way the regs work.  Under 5kW you don't need to provide an air vent but above you do.  It is certainly a wise thing to provide regardless.

 

 

I appreciate that's not how the regs work.  Going above the speed limit is not have road law works either, but I'm sure we've all been guilty   I guess my point and question was that regs aside, what would the down side be of no air vent?  And how necessary is it (again, practically speaking) when it would seem that nominal output ratings are to a large extent seemingly arbitrary.  Don't get me wrong, if I were sticking a huge stove in way above the 5kW mark, then I wouldn't be asking at all.  But this is only 0.8kW above a threshold that sees other stoves - capable of more output - below the threshold.  A HETAS installer will be doing the work and so the hole(s) will be needed for sign off, I know, but how necessary they are?  I'm not so sure...  

 

5 hours ago, Oxbow16 said:

- Would it be best to do one hole to spec, or several little holes? 

- Can anyone work out what size the little holes would need to be if doing a few?  Or is that as simple as dividing 26 by the number of holes?

- My installer said it would be enough to just have the holes lined...  Any ideas what's best to use?

- How to make the holes rodent mouse proof?

 

Any thoughts on these aspects would be most appreciated.

 

Thanks again.  You guys have been a great help over the last few months.