Hi again,

After remedial first floor ts insulating,(with great results),one of the bedrooms is still getting too hot..and of course it's the one with the flue passing through. It happens when the stove is running; not when the ts is charged. The small landing remains cooler. The flue is boxed in and vented top and bottom,with 60mm clearance as it should be.

I thought a clever fan arrangement might work to redistribute the unwanted extra heat, and I had a mild eureka moment!

We have a flue thermostat which starts the back boiler circuit pump when the flue reaches a certain temperature. If i wire up a little fan to start when the pump kicks in, (and of course stop when the pump stops; when the flue has cooled enough),then i can have heat extraction from the boxed-in void when appropriate.

Of course,i must maintain my 60mm clearance between flue and combustibles, so the fan cant be within the boxed-in void. Perhaps a length of 50mm diameter stainless flexi pipe (i happen to have some lying around) could take the heat from the void, with the fan located on the cieling below,in the sitting room, above the wood stove, but 60mm+ from the flue. Not only will this put the unwanted extra bedroom heat where i want it, but help move and mix the radiant heat from the stove across the gf sitting room and open plan kitchen/dining area.(a bit like those stove-top heat driven fans).

Please tell me this is a good idea..or why it may not be! (maybe it's been done before). I used to sometimes have the most wonderful inventive ideas whilst drinking too many beers of an evening in my workshop...until the morning,when i saw my sketches and scribblings from the night before,and felt a bit silly! I don't do that any more. So,again,i hope I'm not missing something.

Any thoughts welcome

Thanks,

Jules

What is the flue boxed in with? Any possibility to change to some vermiculite board? Or fill the void with loose vermiculite?

Not familiar with the UK regs for this but vermiculite is classed as non-combustable and normally used for insulating chimneys.

The boxing in is plasterboard. I put vents top and bottom,one near the bedroom floor,the other near the cieling. This is what my bco recommended.

Steamy..surely the fan would pull the really hot air from around the flue (somewhere more useful)and draw in warm air from the bedroom, so not really cooling the inside flue temperature? The boxed in section in the bedroom is only 2.2m;and the total flue length is over 6m. Think of the effect of cold air outside,where the flue exits the roof. I understand about creasotes and tar build up in a flue,which is worst in un insulated single wall flue pipe.i guess all I'm trying to achieve is to remove excess heat to make the bedroom cooler. Yes,the other way to do it is to insulate the flue (in the boxing in), but then the heat is unused (except to make the flue temp in that area hotter-which shouldn't be neccessary). Many twin wall flues exit a building through a wall,with a long run , up beyond the roof ridge, without any problems. Ideally I'd like to use this heat, hence the fan idea.

Posted By: JulesbarnI put vents top and bottom,one near the bedroom floor,the other near the cieling. This is what my bco recommended.

You've effectively built a radiator in the corner of the bedroom!

Posted By: SteamyTeaThe reason that there is a thermostat on the flue is to keep the flue temperature high, so you probably don't want to cool the flue.

It's a twinwall flue so should be OK to cool the outside of the outer wall - otherwise there'd be no point.

Jules, I do agree with Steamy that it's worth gving it a go. It seems likely it will work.

Posted By: djh

Posted By: JulesbarnI put vents top and bottom,one near the bedroom floor,the other near the cieling. This is what my bco recommended.

You've effectively built a radiator in the corner of the bedroom!

A convector radiator at that !!
If you could put horizontal ducts on the vents, both to an area that needed heat (on the same floor) providing the distance was not too great the convection in the boxed chimney should carry the heat to the other place without a (noisy) fan

Otherwise as above give the fan a go or ask the manufactures if insulating the flue would cause problems. I suspect not because the flue is already insulated. When I had a twin wall s/s flue in the UK the spec. rated it as capable of withstanding multiple chimney fires over 1000 deg. so if yours is anything close to this I would not expect additional insulation would cause problems.

You're ventilating out heat through the trickle vents all the time, I'd suspect that that is a better target for saving heat than what you might recover from your flue during the time that the stove is lit.

Something like the FreshR might be a possibility.

If you have MVHR, I would be temped to put the "living room outlet" blowing into the top of the boxing in of the flue, and provide an air output from the bottom into the living room. Along with making the boxing in 100% airtight (including where the flue goes into the loft!) and adding a layer of insulated plasterboard to the outside of the boxing in.

Maybe have a close-able vent into the bedroom for when you do want the heat.

You could install a fan somewhere remote in an acoustically isolated box, and have it pulling via a duct...

gg