Stove External Air Supply

gouch

Hello,

I am building block 2 storey house. I am considering installing a MHVR system. I am planning on putting in 2 stoves. A conventional chimney is built for both stoves. The chimneys are on internal walls.

I believe I need an external air supply to my stoves for efficiency/comfort reasons.

The finished floors are in, 6" of concrete.

I am thinking of getting out the consaw and digging a channel across each sitting room floor to the gable walls, installing a 4" sewage pipe, wrapping it in foil insulation, leaving it stick up in the center of the hearth, and leaving it outside in the plinth with a grill covering it. Then backfill the channel inside with cement.


Has anybody any experience is retrofitting this in their house.

Do I need air dampers on this external supply and where do they go.

Any help or tips would be greatly appreciated.

Gulliver

Gouch

I was told by a couple of fire/stove suppliers and by some HRV suppliers you need either an external air supply OR switch the HRV off when stove is in operation :eek:

I'm wondering about this too. Going for 2 inset fires and have put 4" sewer in 4" insulation to each already. Screed will be over them.

I don't think the fires I'm going for (Riva and Barbas) have an actual air inlet, at least it's not visible in the installation manuals I downloaded, so now I'm wondering what happens under the stove.

It's hateful to rip up your finished floor, and I assume you don't have underfloor heating.

Do you have a suspended ceiling? Is there any leeway to put the air duct up
(i.e. box it in) and along the ceiling cavity to external wall?

sas

gouch wrote: »

Do I need air dampers on this external supply and where do they go.

I'm building passive and the PHI are insisting that I use 2 dampers for my stove. 1 where the intake pipe comes out of the screed and 1 in the chimney where the chimney breaces the airtightness envelope (this being a complete balls to execute because it's a masonry chimney).

The valves are damn expensive and if I could avoid them at all I would.

I'm looking at €750 for 1 motorized 1 (i.e. the one in the attic because I'm not going up there everytime) and 1 manual model. These have to be imported from Germany and as I said, if I'd any choice they'd be left out.

gouch

Hi Gulliver,

No underfloor heating and I have photos to locate pipes, not many in the path anyway.

I am wondering about where the intake air comes from, are there any problems with where the external vents are placed, i.e. wind direction, height from footpath etc?

I will probably use the foil type insulation to wrap around the 4" pipe as it will give a high insulation value and be compact.

Hi sas,

Does the damper on the intake pipe go inline with the pipe. What size pipe did you use. How did you terminate the pipe outside. Did you have to consider wind/ other variables I am not aware of or does the draw on the chimney overcome everything??

I dont have any provision for a damper on the chimney either. I assumed the if the stove was room sealed them the chimney would not require to be sealed if not in use. This may only be necessary for passive standard??

I dont wan to go cutting up my floor only to discover I should have brought out the pipes in a different direction.

Mike2006

I have recently installed a room sealed stove with a back boiler in my house.
It was different for me because I just had to go out through the back of the external wall so no floor digging involved.

This is what I did:

I was unsure of the size of the external air supply duct on my stove at the time so I put a 6" duct through the back of the chimney breast to the outside. When I found out that the pipe was 4", I just put the 4" flexible stainless pipe through the 6" pipe to the outside and then sealed the inside of the 4"pipe to the inside wall using a combination of orcon and airtightness membrane tape. I sealed the outside again and placed a grille over the pipe ope.

Remember, there is no heat travelling through this pipe, just air TO the stove. The pipe is sealed again at the stove end with a jubilee clip and sealer so it is airtight at the 'house' end too. The door is sealed on the front of the stove so the outside air cannot get into the house. So why would there be a requirement for a damper/dampers. The only time a damper might be applicable would be when you have the door of the stove open to lean it or fill it with fuel...

Also, if you are taking the pipe across the floor within a 4" sewer pipe, then i would not see the need to insulate the outside of the pipe either as what would the purpose of the insulation be?? There is no heat in the pipe to be 'lost' and even if there were, I would prefer it to be 'lost' within my floor and radiate back up than to insulate it to the outside and 'free' it there...

If it were me, I would take the supply across the floor and through the external wall, no insulation or no damper. Seal the circumference of the pipe around the stove air inlet and where it breaks the fabric of the house. After that, the air will find its way to the stove. There are usually 2 dampers on the stoves anyway; one to control the flue and the other to control the air supply to the stove. At least, mine does anyway... These dampers are just a metal-to-metal 'seal' so they are not an airtight seal... You would not want an airtight seal in these locations anyway unless they were interlocked to the lighting of the stove...

Just my 2c worth.

Mike.

sas

gouch wrote: »

Does the damper on the intake pipe go inline with the pipe. What size pipe did you use. How did you terminate the pipe outside. Did you have to consider wind/ other variables I am not aware of or does the draw on the chimney overcome everything??

I dont have any provision for a damper on the chimney either. I assumed the if the stove was room sealed them the chimney would not require to be sealed if not in use. This may only be necessary for passive standard??

I dont wan to go cutting up my floor only to discover I should have brought out the pipes in a different direction.

The bottom line is that room sealed stoves are never really sealed.

Even if they were, you have a constant flow of cold air from the intake pipe, through the stove and up the chimney. This cold air draws heat out of the chimney structure and hence the house. It's a constant draw on the heat stored in the masonry elements at and around the chimney.

I'm very dubious as to how much of a difference it makes in reality, my end target is different however as I've already said.

The damper does go on the intake pipe, it basically replaces a 12inch section of the pipe. I used 4" sewer pipe. I've read the theory on the direction the pipe should be versus wind etc. but I completedly ignored it and ran the pipe the shortest direct route to the outside. Note: my roof isn't on yet so I could yet get bitten by this.

The pipe will cross under the drive way and rise in the shrubbery along the perimeter. I've seen a hood similar to chimney cowls (alot classier and no doubt alot more expensive) used to terminate these. For now it's a question to answer next year for me.

tails_naf

Gulliver, Mike,

Could you PM your room sealed stove supplier, as well as th inset stove?

I've only done a bit of shopping around, but a few places I've been to gvme ne fairly blank stares when I mentioned thins like HRV, room sealed, etc. So Ideally I'd like to deal with a supplier in the know....

reefray

sas wrote: »

The pipe will cross under the drive way and rise in the shrubbery along the perimeter. I've seen a hood similar to chimney cowls (alot classier and no doubt alot more expensive) used to terminate these. For now it's a question to answer next year for me.

sas

Can you PM me the detail of the hood you saw please. I will need one of these when I get to the finishing stages of our build.

Thanks
Ray

sas

reefray wrote: »

sas

Can you PM me the detail of the hood you saw please. I will need one of these when I get to the finishing stages of our build.

Thanks
Ray

Sorry Ray, didn't mean to get your hopes up. I saw one at the house of a supplier that I didn't do business with on something else. I'm not in a position to find out now where it was bought I'm afraid.

gouch

Hi all,

Can anybody give me more information about my options for the external air supply to the stove.


Would anybody recommend bringing a pipe up the side of my chimney breast up to the attic and using this as my air supply??

Are there any fires hazards to be considered when installing an air supply to the stove. Could fumes/flames ever go the wrong direction?

reefray

Would anybody recommend bringing a pipe up the side of my chimney breast up to the attic and using this as my air supply??

gouch, I wouldn't think it would be a problem on the external of the chimney breast.

sas, no worries. If you do come across them before next April/May let me know please.

windyboy

Hi,

I have left out ducts through gable walls for external air supply to room sealed stove. Can someone advise suppliers of a decent looking stainless steel grill/louvres that are well designed to prevent the driving rain from entering into the back of the stove.

Cheers,

Windyboy