Gas appliances and air tightness.

[BarumMike]

We have an Aga and three gas appliances.  They draw air from the room unlike the gas boiler which has an external air vent.  On a windy yesterday, thinking about what air leaks I could seal up I listened to the wind whistling in the unlit gas fire in my room.  So my question:- In a house with internal gas appliances which cannot be directly connected to the outside where do I draw the line in chasing air tightness when I need air leaks to avoid carbon monoxide poisoning?  I appreciate there is no simple answer to this question. Are there any clever solutions to this issue?  Is this such a big issue that the objective is to remove all such appliances?  The house is large, old, leaky and listed so that getting near a Passivhaus standard so that the whole house is warm is a forlorn hope.  Having regional heating sources has helped us survive the winters!

[Iceverge]

We had an airtightness of 0.32ACH which was bout 4900mm2 of open area over 600m2 of envelope. A glance at some ventilation charts suggests 550mm2 per kW of installed appliance so even in our house we would be able to have a 8.9kW appliance. 

 

A CO detector is still a good idea in case of a blocked flue etc but I wouldn't worry in the slightest about the ventilation in your case. 

[JohnMo]

You need to stay on the correct side of allowing air in for combustion, otherwise its a path for trouble etc...

 

If you really want to make a difference, you may need to dump those appliances that use room air, as this air needs to come from somewhere

[Marvin]

Surely your Gassafe engineer will advise you when inspecting the equipment and location!

 

A CO detector is, I think, obligatory, as is an unobstructed air supply (usually an air brick through the external wall). 

 

Also the gas AGA instructions for your model of AGA will list installations requirements.

 

Good luck

 

M

[SimonD]

A Gas Safe engineer will have knowledge of the ventilation requirements of each appliance within specific locations which take into account the volume of the room and the heat input of each appliance. Some, like cookers also require an openable window in the same room.

[BarumMike]

There is no way I am putting an air brick in the wall of each room with a gas appliance!  Apart from the fact that the house is plenty leaky enough already, the wall is at least 24 inches of stone.  When a plumber put in a toilet in a new bathroom, he wrecked two diamond core drills before getting in a specialist contractor..    I am not worried that the appliances are not getting enough oxygen.  I am worried that I and the missus are getting too much fresh oxygen on cold breezy days!  But a CO detector is a good idea.

 

 

[BarumMike]

PS If that sounds unappreciative it wasn't meant to be.  I am very impressed how much time people give to this forum.  Its just that I know our place is a long way on the safe side of the CO risk spectrum.

[Marvin]

Hi @BarumMike

 

The problem here is defining the air entering your existing kitchen now, I'm sure it's plenty, but how much? If you improve the air tightness will what is left be enough? Not that this gives you an answer, it just defines the problem. (hopefully)

[SimonD]

5 hours ago, BarumMike said:

There is no way I am putting an air brick in the wall of each room with a gas appliance!  Apart from the fact that the house is plenty leaky enough already, the wall is at least 24 inches of stone.  When a plumber put in a toilet in a new bathroom, he wrecked two diamond core drills before getting in a specialist contractor..    I am not worried that the appliances are not getting enough oxygen.  I am worried that I and the missus are getting too much fresh oxygen on cold breezy days!  But a CO detector is a good idea.

 

 

 

Nobody said you needed to put a load of holes in the wall, someone just needs to do the calcs. How do you know if the appliances are getting enough air? Usual calculation for what is called adventitious ventilation - e.g. leaky house - is assumed 7kW and equivalent to 35cm2 open area.

 

The reason for the ventilation is in part to ensure you have enough air to breathe and the appliance has enough air to breath so that it combusts the gas properly - if it doesn't then things can get even more dangerous.

 

 

4 hours ago, BarumMike said:

Its just that I know our place is a long way on the safe side of the CO risk spectrum.

 

As above, you clearly don't know this and are just guessing, nor do you know the answer to your original OP. 😉 A Gas Safe engineer would be able to do the calcs in less than 20 minutes - so a cost of probably less than £60 and then at least you're not left guessing any more.

[Nickfromwales]

1 hour ago, SimonD said:

 

Nobody said you needed to put a load of holes in the wall, someone just needs to do the calcs. How do you know if the appliances are getting enough air? Usual calculation for what is called adventitious ventilation - e.g. leaky house - is assumed 7kW and equivalent to 35cm2 open area.

 

The reason for the ventilation is in part to ensure you have enough air to breathe and the appliance has enough air to breath so that it combusts the gas properly - if it doesn't then things can get even more dangerous.

 

 

 

As above, you clearly don't know this and are just guessing, nor do you know the answer to your original OP. 😉 A Gas Safe engineer would be able to do the calcs in less than 20 minutes - so a cost of probably less than £60 and then at least you're not left guessing any more.

Spot on  

 

All gas-burning appliances need to be lit simultaneously, with all internal and external doors shut and all windows closed. Then each open flue appliance needs to have a smoke match lit and then the spillage viewed in each room / space. ONLY then, and after the written side has been also been complied with, can you state anything other than "I don't know" ( because you don't know  ).

 

Why not change these fires to room sealed / balanced flues? Are they all on outside walls?

[BarumMike]

11 hours ago, Nickfromwales said:

Spot on  

 

All gas-burning appliances need to be lit simultaneously, with all internal and external doors shut and all windows closed. Then each open flue appliance needs to have a smoke match lit and then the spillage viewed in each room / space. ONLY then, and after the written side has been also been complied with, can you state anything other than "I don't know" ( because you don't know  ).

 

Why not change these fires to room sealed / balanced flues? Are they all on outside walls?

I take the point that I can't say with authority until a formal test has been done. All apart from the Aga are against inside walls in old fireplaces.  Hence my assumption that increased air supply would require holes in walls.  Only one is in a room with a ground level suspended floor which could be vented.  Apart from the size and leakiness of the house, the other reason for my assumption that we are not nearly at risk of insufficient air supply is that all three fires were installed by a meticulous gas engineer who did not raise the question of additional venting and have been regularly serviced by gas engineers.  

 

The messages I take away are:-

1. As we continue on the journey of dealing with draughts etc, I need to pause when significant change has been made and recheck the adequacy of air supply to the appliances.

2. That journey strengthens the case for CO alarms.

3. That having an open flue appliance working in a room may (should?) contribute to increasing air leaks elsewhere in the house and make those areas cooler.

4. And so a longer term aim might be to find alternative ways of achieving individual room heating - ?smart TRVs, electric heaters, directing insulation efforts to rooms where the ambition is to remove a gas appliance.

 

Does that sound about right?  And are others further down this journey in an old large and expensive to heat house and have solutions/experience to share?

Edited March 15, 2023 by BarumMike

[JohnMo]

2 minutes ago, BarumMike said:

That journey strengthens the case for CO alarms.

So does the law, I believe 

[Marvin]

15 minutes ago, BarumMike said:

That journey strengthens the case for CO alarms

I though CO alarms were mandatory, er.., or not in Scotland?

[Nickfromwales]

9 minutes ago, Marvin said:

I though CO alarms were mandatory, er.., or not in Scotland?

In a new electrical installation, but no policeman is going to put cuffs on to anyone with gas fries with no alarms in an existing dwelling / install. However, if a GSR'd engineer attends site, they really shouldn't undertake any works unless they've at least included this addition / upgrade in their fees. There are some things you just do NOT step around because "you can".

On a previous major renovation I insisted that the client accepted my costs for replacing every existing smoke / heat detector in the house, even though they appeared to be working, as they just looked dusty and tired. When I explained why and the minimal costs they agreed and thanked me for my diligence.

Some things are just a good idea, regardless of regs etc