Again, I edited my last (last para) just too late!

Maybe the effect of insulating the flue suggested by Finny has somthing to do with his point? it is somthing that i planned to do anyway, but having read all above, it sounds like room sealed or nothing

Posted By: Viking HouseHow do you stop the stove from being a cold radiator in the morning because cold air drops down the chimney at night?
The room with the stove is always the coldest room in the house when the stove isn't lighting.
People don't close chimney-roof valves before they go to bed because the stove is still smoking, and they don't set their alarm for 2 0'Clock to get up to close the valve either.

I was in a Passive House at 9 0'Clock one cold morning, the room with the sealed stove was 15 degrees while the rest of the house was 20 degrees, the stove was 8 degrees and acted as a cold radiator.

As our only space heating for the entire home, i would think in the coldest months that it would be lit most of the time and with little effort and good quility logs i should be able to keep it alite through the night, as with the existing old broken fire she just requires a bit of tenderness in the morning and she away also the more modern fires are usually so full of cast iron or ceramic that they hold heat for hours even if the do go out in the middle of the night.

Forgive me as I have only quickly read the posts on this thread but any air passing over the top of the flue will cause a drop in pressure. Exacly the same as air accelerating over the top surface of an aircraft wing does. Hence the wing is pushed up. The air passing over the flue would do the same. On very calm days dont light your stove!!!!! I cant explain that one......
My BCO told me recently that elbows are not needed anymore. My flue is vertical and works a treat, cough, cough.

if you don't have a properly engineered air intake, your fire will draw cold air along from the floor and give occupants nice cold feet. If you engineer a air vent close or behind the fire( stove) then this effect is cured.
Frank

Or.. if air is drawn through the building on its way to supplying the stove it will be available to the occupants to extract some oxygen, If its path is directly to the stove it won't. Even the cleverest stove cannot seperate oxygen from air before it enters the firebox.. As mentioned previously a 5 Kw stove will move around 10-15 cubic metres of air per hour. Recommended air changes in a building per hour are at least 1. It must follow that a well installed appliance, lit or unlit will contribute to this.
I admit that if you are building today other options are available to you. Desirable even. I would happily see an airtight envelope with MHRV with either a well sized and installed heat pump (where low carbon electricity is readily available and locally efficient) or a wood fired heating system where well seasoned sustainably managed firewood is available.
This scenario however only applies to a small minority of properties currently and to convert many existing ones is prohibitively expensive and sometimes more energy intensive than simply starting again from scratch.

I think in your circumstances I would be tempted to install 5Kw or under, then test. If you were happy to have a vent with direct air feed, I would install it. Ultimately, it will be up to your installer or Building control officer, they will have to be satisfied that your installation is compliant. Speak to them first.

Posted By: finnyI think in your circumstances I would be tempted to install 5Kw or under, then test. If you were happy to have a vent with direct air feed, I would install it. Ultimately, it will be up to your installer or Building control officer, they will have to be satisfied that your installation is compliant. Speak to them first.

Thanks Finny, you have been a real help

What are the dangers of starving the fire of air? will it just go out? or somthing more sinister? will co2 be an issue?

Yes if you starve a fire of air it will go out. This would be obvious, less obvious is a fire that burns well intermittently, you might often have a window ajar or trickle vents open, which would allow adequate air to feed the fire, someone could then shut windows/vents when the fire is already lit which would cause it to smoulder potentially spilling carbon monoxide into the room. As tony says above, CO has no smell and it's effect are similar to that of drinking in the early stages of poisoning, as is the next stage of headaches, drowsiness and falling asleep. Ultimately it can prove fatal, and sadly does sometimes. It really is worth having a competent installer who understands all the implications of what they are doing and who has the experience and skills to ensure your installation is both efficient and safe. They will as a matter of course install an approved CO alarm, a legal requirement.

Just our own experience.

Sub 5kw wood burner (Morso 'Badger') We fitted the external air kit was we wanted to ensure sufficient combustion air when we built our reasonably airtight home.

The outdoor air kit is a 5" flexi pipe. The internal room vent on the stove remains closed. We get a great draw (flue extends 1 metre over ridge line) and great fire.

The house being very well insulated means that it is easy to over heat. Much more than 2 or 3 hours burining can do it. Downside is that it can act as 'the mother of all cold bridges' when not lit in cold weather. We like having a fire and the real lift it can give so are willing to live with that particular downside.

In terms of not having an external air duct we have tried running with the outdoor duct closed and interior open. Could feel air being drawn over the floors, and noticed rapid drop in internal air quality, reduction in fore combustion, only solved by opening a window. In short, you need that extarnal air source.

"we need a double fronted fire, as it services two rooms"

We have a double fronted fire but wish now that I just went for a single sided (with 2nd room just seeing the rear of the fire. Double sided isn't as clean burning as you can't get the 'cleanburn' feature - at least not in the Stovax range that I bought.
Ours doesn't pump out as much heat as some smaller single sided stoves that I've seen.
The windows tend to need cleaning more as well as the airwash doesn't work as well.

All depends if you need to feed from both rooms of course. Our decision was purely on aesthetics. It does look nice right enough.

That’s a definite problem solved, by the GBF just purchased a "Romotop stomboli" (see post above for details) from www.arada.co.uk the real bonus is they are getting rid of all Romotop stock as they have lost franchise and we picked up a new £2000 fire for £1000 delivered they have 2 left if anyone else is interested?

sorry

Well spotted Tom. just assumed .co.uk should have put www.arada.uk.com

<blockquote><cite>Posted By: Viking House</cite>If you build a Passive House with a 15kWh/m2.annum heating demand and use a stove to deliver the heat then the amount of kWh's used is usually closer to 30kWh/m2.annum, this is because of the cooling effect of the chimney which cools down the stove at night, people don't close the valves before going to bed because the stove is still smoking.</blockquote>

What about a thermal mass stove of some type. Fast, clean burn, then shut down baffles keeping the heat in?

Posted By: finny What about a thermal mass stove of some type. Fast, clean burn, then shut down baffles keeping the heat in?

Where are the baffles? On the stove? If so then half the heat from the thermal mass goes up the chimney.
Other options would bo to put the stove in the sunroom and have an external quality door between the sunroom and the house that you can close when you go to bed or when the stove isn't lighting.
or Put the stove outside the house, cover it with insulation and pipe in the heat.
or climb up on the roof and stuff the chimney with a binbag part filled with rockwool when the stove isn't lighting, say in Nov and March!