Installing a woodburner in a SIPS house with MVHR

[pedragon]

Hi

 

Apologies if I have posted this in the wrong thread, as I'm not sure which is the most logical place to post.

 

We are trying to install a woodburner into a SIPS house. We have been told by a couple of installers that they need to put in an airbrick which we do not want to do on a SIPS house. We have MVHR that is connected to Solar PV with a battery storage, so chance of no air flow should be remote (if it all fails, we either put out the woodburner, or open a window or two for air flow).

We also have ASHP that runs UFH heating down stairs, so we don't have to use the woodburner if all power fails to MVHR.

We believe that the following would allow us to put in a woodburner and it take the 'fresh air' from the house, rather than a snorkel type connection to the stove as that will put an additional hole/cold bridge in the SIPS.

HETAS Risk Assessment and BS8303 allows for a stove to be installed without a permanent vent to the room

Although Document J of the building regs does recommend a 'non-closable' room vent in the wall as well as the direct air supply to the stove BS8303 now details a method by which you can see if the stove works well without this permanent vent to the room. Essentially it boils down to smoke testing the stove with the door open, all extraction units turned on, all windows and door closed. If once the risk assessment procedure has been carried out and the stove does not smoke into the room then it is deemed to pass. Its a bit more complicated than that, but your HETAS installer has access to the full procedure.

If the stove does smoke into the room then simply install one of our AirSmart devices which open a vent to the room only when the door of the stove is opened. You can choose a standalone model or a fully automated controller which will also adjust the burn rate of your stove and shut it down if its getting too hot.

It's from here...

https://www.stovesonline.co.uk/stoves-for-airtight-houses.html?srsltid=AfmBOorH3fCB3YvftCiKXuTS6zR6cpAxJAgDISJgrGbFcoALM9ZwCFc5

 

Firstly, are we correct in that we should be able to do this?

 

Secondly, if we are correct, can anyone suggest an installer that would do this under HETAS, as we would need to get this signed off for buildling control?

 

Many thanks,

 

Mike

[JohnMo]

It's simple, you need to install a stove that takes primarily and secondary air from outside. There are many models to choose from, but it's important it takes all air from outside.

 

Do not install a stove that takes room air. If you do you need to install an air brick which is bonkers in an airtight house. 

 

Do it correctly or don't bother would be my advice.  If you haven't planned to put in an air inlet pipe, it's time to start.

[Nickfromwales]

45 minutes ago, pedragon said:

We are trying to install a woodburner into a SIPS house. We have been told by a couple of installers that they need to put in an airbrick which we do not want to do on a SIPS house. We have MVHR that is connected to Solar PV with a battery storage, so chance of no air flow should be remote (if it all fails, we either put out the woodburner, or open a window or two for air flow).

We also have ASHP that runs UFH heating down stairs, so we don't have to use the woodburner if all power fails to MVHR.

We believe that the following would allow us to put in a woodburner and it take the 'fresh air' from the house, rather than a snorkel type connection to the stove as that will put an additional hole/cold bridge in the SIPS.

Oh, lordy! Where have you been getting advice from?

 

So..... IF your MVHR fan stopped spinning, there would still be a near-uninterrupted path for airflow through the MVHR system so that would allow the 'draw'. The MVHR doesn't close any valves or flaps, it's just a fan or pair of fans that are spinning or not.

 

"Open a window or two for airflow"?, "No". A HETAS design would require an uninterruptable supply of airflow, not simply rely on you deciding to monitor this by opening things or closing them, that would never pass any regs. What you would need is as above, a direct to air WBS that isn't reliant on the room not being sealed.

 

45 minutes ago, pedragon said:

HETAS Risk Assessment and BS8303 allows for a stove to be installed without a permanent vent to the room

In a leaky house, one that's not airtight, and not the house you are making? This caveat allows for a consideration that adventitious air for combustion would find its way into the room through all the gaps, nooks, and crannies (natural infiltration); if you have MVHR, then the house won't have any.....so can't be applied here.

 

Next, simply DO NOT DO THIS!! If you have an airtight house with MVHR then the heat output would be way above what the room it is in could ever dissipate, you'll just roast the room and have to leave it. A WBS has a place in a draughty bag-o-shit house, but not in any modern build with great insulation, airtightness, and MVHR (with subsequent minimal heat input requirement). This will become an expensive ornament.

[Nickfromwales]

If the house is open plan and 400m2 or above, I will retract 50% of that   

[saveasteading]

11 minutes ago, Nickfromwales said:

WBS has a place in a draughty bag-o-shit house

That phrase may stay in my mind.

[Nickfromwales]

1 minute ago, saveasteading said:

That phrase may stay in my mind.

Use it well, for we are the chosen messengers.

[nod]

Isn’t it 3kw and below don’t require any ventilation You shouldn’t need a stove any higher than 3

[JohnMo]

58 minutes ago, nod said:

Isn’t it 3kw and below don’t require any ventilation You shouldn’t need a stove any higher than 3

In a normal house (as @Nickfromwales put it a drafty bag - o - shit) you are correct, in an airtight one, you need room sealed and external air inlet. If you can justify or are required to have MVHR by building regs, you really need external air.

 

Plus you are not allowed to install said stove in a room where an extract terminal is present. As when you open door to reload the wood, combustion and flue gases could be drawn into room.

[saveasteading]

32 minutes ago, JohnMo said:

external air inlet.

It's easy to fit (just some ducting and a rainproof inlet,  and works very well and efficiently. Even if it wasn't the rule, I would now choose to do it.

[FarmerN]

We put a 3Kw wood burner in our 200sqm new build, with MVHR, GSHP and UFH

We do light it in winter for about 2-3 hours a night and I like it, you do have to leave the room door open, it soon gets HOT, the sort of temperatures everyone is trying to avoid at the moment!

Ours was planned from the start of the build so was  easy to put under floor ducts for an air supply coupled direct to the stove doing away with any question of an air brick.

As in post above you definitely need an air duct direct to outside coupled to the stove. 

It is impossible to justify on heating basis , it’s the aesthetics and nice to know we have the ultimate back up to a power failure. Fortunate enough to have a plentiful supply of home grown logs.