External Air Supply for Stove

BarneyMc

I already have a 4 inch pipe in my floor leading to the outside to supply air to a stove I hope to install some time (the house is roofed and ready for first fixes).

There are a few potential issues however:
1. I've since learned that it's better to have a T connection for this pipe so that air can be drawn from either side of the house, rather than just rely on one side.
2. The pipe is located about 700mm to the right hand side of where the stove will be. I know the flexible duct will connect the stove to this but it may be a cold bridge and/or messy connection.

Luckily I've slabs on the ground floor so I can still core down and install another 4 inch pipe. This time I could centre it so it is located directly below the stove.

I won't be able to put a T junction on it but I could simply have it finish once it reaches the bottom of the slab. There is a void between the slab and the ground which is vented in numerous locations around the house. This would surely provide it with a good 360 air supply.

Anyway I'd just like to know if I'm going too far with this and should just stick to the origianl pipe or would the 2nd pipe give me a much more robust solution?

ferryman35

This is something with which its very hard to get help on here...the airtight stove concept does not appear to be well developed in Ireland / UK yet!

The main reason for having a duct go from one side of the house to the other and tee-ing off that is to balance air pressures, so that you didn't have the fresh air inlet in a pressurised zone or a vacuum depending on how the wind is blowing around your house.

If you only have a single inlet on the duct (presumably 110mm pipe?), then you can carry this pipe out from the house into the yard / garden, and turn it up somewhere convenient - this eliminates the pressure effects from the building. Be sure to make the vertical standpipe high enough to keep unwanted visitors, debris or snow(!) from getting in and guard the top of it. Also advisable to lay the pipe with a slight fall & drain off any condensate that might get in.

I wouldn't worry about the thermal bridge effect from the flexi pipe connecting your stove to the duct , especially presuming the pipe is plastic.

I suppose coring down into the void would also work - (as long as you seal up the original duct) but I would also be looking out for unintended consequences. it 'feels' like a more robust solution to have the duct going all the way outside.

BryanF

Pick the air-tight stove
Read the accompanying specification
It should give a size, max length etc of pipe/external air requirement

Biggest issue IMO is fixing a location for the stove and sticking with it.

ferryman35

I've seen the specifications to specify the diameter but I haven't seem them to specify a length.

The best instructions I've seen for external air here are from Stanley, but usually they specify 4" pipe main duct with a 3" connection for the stove.

European stoves often use the area surrounding the stove to heat air which can be ducted off to another room if required

BarneyMc

ferryman35 wrote: »

This is something with which its very hard to get help on here...the airtight stove concept does not appear to be well developed in Ireland / UK yet!

The main reason for having a duct go from one side of the house to the other and tee-ing off that is to balance air pressures, so that you didn't have the fresh air inlet in a pressurised zone or a vacuum depending on how the wind is blowing around your house.

If you only have a single inlet on the duct (presumably 110mm pipe?), then you can carry this pipe out from the house into the yard / garden, and turn it up somewhere convenient - this eliminates the pressure effects from the building. Be sure to make the vertical standpipe high enough to keep unwanted visitors, debris or snow(!) from getting in and guard the top of it. Also advisable to lay the pipe with a slight fall & drain off any condensate that might get in.

I wouldn't worry about the thermal bridge effect from the flexi pipe connecting your stove to the duct , especially presuming the pipe is plastic.

I suppose coring down into the void would also work - (as long as you seal up the original duct) but I would also be looking out for unintended consequences. it 'feels' like a more robust solution to have the duct going all the way outside.

Big thanks for this pal.

I can see the option of coring down the neater option. My existing 4 inch duct comes out into a yard so I would have to bring it away from this and out into an open area.

If going with the under slab option I would have to make sure all vents remain open which should be done anyway but just comes with more of a risk. Anyway I'll look into this and hopefull it will work out.

BarneyMc

BryanF wrote: »

Pick the air-tight stove
Read the accompanying specification
It should give a size, max length etc of pipe/external air requirement

Biggest issue IMO is fixing a location for the stove and sticking with it.

I was hoping to leave this decision until a much later date! Anyway what's another decision to make I suppose? If anyone can recommend an air tight, wood burning, non-boiler, free standing stove then please PM me.

ht9zni1gs28crp

Is it really necessary the Stove? If all it is doing is space heating and/or visual isn't there other options?

We ditched ours as it wasn't necessary to satisfy Part L or Passive Certification.

BarneyMc

Kash Aggressive Pennant wrote: »

Is it really necessary the Stove? If all it is doing is space heating and/or visual isn't there other options?

We ditched ours as it wasn't necessary to satisfy Part L or Passive Certification.

Fair point I suppose. I live on a farm so have "free" wood. It will also cut down on the heat pump demand. Oh.... and the wife may not be too pleased either :cool:

I'm not going for passive by the way.

New Build 2015

BarneyMc wrote: »

Fair point I suppose. I live on a farm so have "free" wood. It will also cut down on the heat pump demand. Oh.... and the wife may not be too pleased either :cool:

I'm not going for passive by the way.

What verdict have you reached Barney? Have you sourced a supplier?

New Build 2015

Kash Aggressive Pennant wrote: »

Is it really necessary the Stove? If all it is doing is space heating and/or visual isn't there other options?

We ditched ours as it wasn't necessary to satisfy Part L or Passive Certification.

Did you go with another option or ditch completely?

BarneyMc

New Build 2015 wrote: »

What verdict have you reached Barney? Have you sourced a supplier?

I will go ahead with coring down through the ground floor slab and putting in a 4 inch Wavin pipe. Anyone know how to close off an exising hole in a suspended ground floor slab?

Regarding the stove I haven't looked into but a 4 inch pipe should leave it compatible with 99% of all stoves.

exaisle

I'm using a Hwam Vivaldi free-standing wood-burning stove....and a MHRV system, so an external air supply was required. I picked the Vivaldi because of its height but I'd generally recommend Hwam stoves from the point of view of efficiency and appearance. PM me for more details if needed.

I used a steel 4" pipe running under kitchen units and through the wall of the living room to supply fresh air to the stove.....I've had no problems whatsoever just having one air inlet and I suspect that putting a second in might be overkill.

One thing to note....you haven't said whether the pipe is metal or plastic and an earlier poster assumed it might be plastic..however...it should be metal, to avoid the possibility (however rare) of blow-back of hot ash.

I think the amount of air entering your stove will be governed more by how good a draught there is on the chimney/flue than how many inlet points there are. The stove itself will allow you to regulate air in, to a degree, but you should also include a damper to reduce the flow through the flue when required or you'll end up using more wood than you need to.

Hope this is of help. As an earlier poster said, there aren't very many airtight stoves around :-)

BarneyMc

exaisle wrote: »

I'm using a Hwam Vivaldi free-standing wood-burning stove....and a MHRV system, so an external air supply was required. I picked the Vivaldi because of its height but I'd generally recommend Hwam stoves from the point of view of efficiency and appearance. PM me for more details if needed.

Thanks, will look into but might go for something more traditional.

exaisle wrote: »

I used a steel 4" pipe running under kitchen units and through the wall of the living room to supply fresh air to the stove.....I've had no problems whatsoever just having one air inlet and I suspect that putting a second in might be overkill.

OK, maybe the need for a T junction is not needed. However I can bore down still and get air from under the ground floor slab so might just stick to this plan just in case.

exaisle wrote: »

One thing to note....you haven't said whether the pipe is metal or plastic and an earlier poster assumed it might be plastic..however...it should be metal, to avoid the possibility (however rare) of blow-back of hot ash.

Well the existing pipe is plastic. But I thought the plastic duct connects to the stove via another flexible piping? Surely that would mean the 4 inch duct would be ok being plastic?

exaisle wrote: »

I think the amount of air entering your stove will be governed more by how good a draught there is on the chimney/flue than how many inlet points there are. The stove itself will allow you to regulate air in, to a degree, but you should also include a damper to reduce the flow through the flue when required or you'll end up using more wood than you need to.

Hope this is of help. As an earlier poster said, there aren't very many airtight stoves around :-)

Yes I've heard a lot of stove retailers say 'airtight' alright!!!

cyfac

We have just installed a Boru carraig mor air supply inlet fitted to stove on its underside, 3 inch galvanised pipe fed to external south facing wall (south was recommended) hidden behind kitchen kick boards. Stove installer said while acknowledging air intake need, correct flue height is the most important factor

exaisle

OK, maybe the need for a T junction is not needed. However I can bore down still and get air from under the ground floor slab so might just stick to this plan just in case.

>>Why bother? You'll have ample air supply from the existing pipe...leave your slab alone and stop giving yourself extra work (and headache!) :-)

Well the existing pipe is plastic. But I thought the plastic duct connects to the stove via another flexible piping? Surely that would mean the 4 inch duct would be ok being plastic?

>>Id make sure that the pipe connecting the stove to the existing pipe was >>metal. The risk of blowback is minimal if you have a decent flue well set up but no harm being on the safe side.

BarneyMc

exaisle wrote: »

OK, maybe the need for a T junction is not needed. However I can bore down still and get air from under the ground floor slab so might just stick to this plan just in case.

>>Why bother? You'll have ample air supply from the existing pipe...leave your slab alone and stop giving yourself extra work (and headache!) :-)

Well the existing pipe is plastic. But I thought the plastic duct connects to the stove via another flexible piping? Surely that would mean the 4 inch duct would be ok being plastic?

>>Id make sure that the pipe connecting the stove to the existing pipe was >>metal. The risk of blowback is minimal if you have a decent flue well set up but no harm being on the safe side.

If I thought it would work I would leave it the way it is. I'm just afraid it may not. The existing pipe exits on the north side of the house and is very sheltered. It's my last chance to do this before floors, etc. go in.

cyfac

As i have said previously my pipe is exiting to the south the stove installers said it has to be either south or west so i think you may have to go with the T option

gooseygander

BarneyMc wrote: »

If I thought it would work I would leave it the way it is. I'm just afraid it may not. The existing pipe exits on the north side of the house and is very sheltered. It's my last chance to do this before floors, etc. go in.

Hi Barney, my thoughts are that your pipe may be Sheltered from wind and weather but not sheltered from air. Fires and stoves work off the drawing of air to fuel the fire not the blowing of wind, I would not worry or bother making to much of an effort to rectify it if it cannot be done easily.

moch

Hi, Just reading this thread now as I was looking for ideas on connecting a stove to external air supply pipe, I have installed a 4inch sewer (wavin) when building last year that the engineer said would be good enough. The pipe is approx 4 metres long and is on the east side of the house (shortest route). On the inside the pipe comes up through the floor at the chimney breast just slightly off centre.
I have ordered a boru double sided stove with external air supply that is now in stock so should be fitting next week. Does anyone know generally what pipe is fitted between the stove and connection in the floor?
Is there any opinions on the wavin pipe being exposed to heat?

893bet

moch wrote: »

Hi, Just reading this thread now as I was looking for ideas on connecting a stove to external air supply pipe, I have installed a 4inch sewer (wavin) when building last year that the engineer said would be good enough. The pipe is approx 4 metres long and is on the east side of the house (shortest route). On the inside the pipe comes up through the floor at the chimney breast just slightly off centre.
I have ordered a boru double sided stove with external air supply that is now in stock so should be fitting next week. Does anyone know generally what pipe is fitted between the stove and connection in the floor?
Is there any opinions on the wavin pipe being exposed to heat?

There will be a special connection kit to connect to the pipe in the floor.

BarneyMc

cyfac wrote: »

As i have said previously my pipe is exiting to the south the stove installers said it has to be either south or west so i think you may have to go with the T option

How? As I said earlier my ground floor slabs are in.

BarneyMc

gooseygander wrote: »

Hi Barney, my thoughts are that your pipe may be Sheltered from wind and weather but not sheltered from air. Fires and stoves work off the drawing of air to fuel the fire not the blowing of wind, I would not worry or bother making to much of an effort to rectify it if it cannot be done easily.

Yeah I never thought of the 'wind' factor initially. In a normal situation a stove doesn't rely on wind within a house - as you say it just draws air from the room. The only difference with the external air supply is that it has to draw the air through a 4 inch pipe first. I suppose this shouldn't make that much difference?

BarneyMc

893bet wrote: »

There will be a special connection kit to connect to the pipe in the floor.

Yes I was told the same. By the way is it easy to hide and insulate this pipe? Unfortunately mine appears about 2 and a half feet from where the stove will sit.

cyfac

Boru takes a 3inch diameter pipe i got mine threaded and screwed into air inlet with PTE tape my stove is on an internal wall on the other side is the kitchen i ran the pipe behind the kitchen presses kickback and out to the external wall Which means i can acesss if i need to