Foil and woodfibre..?

[larry]

Ok, bear with me here...

So I'm insulating a solid wall with wood fibre. Using 2x layers of 40mm flexi wood fibre between battens/counterbattens with 20mm rigid wood fibre on top to carry the lime plaster (method worked well in the other room I've just done).
I've got a section where there will be a radiator in front.
Would it make any sense at all to sandwich a section of foil based insulation behind the top wood fibre layer , behind the area of the radiator only, to improve heat from radiator into the room.

Risks, benefits and what am I missing and not understanding? Thanks.

 

[paulc]

If you have decent double (or even triple) glazed windows and have killed all the cold draughts, the radiator could be hung on an internal wall. I've done it here, and it has simplified the plumbing considerably. The rooms heat up just fine, and I don't notice any cold spots around the windows.

 

[larry]

If you have decent double (or even triple) glazed windows and have killed all the cold draughts, the radiator could be hung on an internal wall. I've done it here, and it has simplified the plumbing considerably. The rooms heat up just fine, and I don't notice any cold spots around the windows.

Thanks Paul.
I've done that in one of the upstairs rooms, but for this room under the windows is really the only place it can go.

 

[a twig]

I wouldn’t worry about the foil personally, a bit of heat going into the wall isn’t the end of the world and can help with moisture etc

 

[Zebra]

Interesting question. I have a similar set up - radiator on external wall insulated internally with wood fibre - and I don't know if I considered foil in the walls behind the radiators. I have a vague idea that I did consider something similar and didn't go for it because it seemed like I was overthinking things. If it was winter I would do an experiment for you, I would go outside and measure the external temperature of the wall to see if the heat loss is greater where the radiator is, which might suggest there might be some merit to the scheme. Otherwise, if the heat loss through the insulated walls is minimal anyway, certainly compared to windows and doors etc, then I can't think the foil would do anything and wouldn't be worth the loss in breathability.

 

[noj]

Doesn't foil only work if it's shiny side facing an air gap? Sandwiched between board it just conducts rather well...

 

[a twig]

Foil is just as heat reflective irrelevant of whether the shiny side is facing or not.

No chance of conduction when it is sandwiched between an insulating medium, conduction would only happen if the foil was attached to the radiator, but anything reflected from buried foil will have to go back through the insulation again so not much would come back out the other side

 

[malcolm]

You get radiated heat in the form of infra red and stuff like that. That's how the sun is hot in the summer. Then you have conduction through a wall which is to do with one hot bit of wall making the next bit hot.

Aluminium foil is great for radiated heat as it is reflective and just bounces all that infra red stuff off. It is poor for conductive heat transfer as it is quite conductive for heat.

I cannot imagine the benefit of sticking aluminium foil in the middle of a wall. There is no radiated heat only conductive heat in the middle of a wall. I must have missed something here.

 

[Lacan07]

The whole point of hanging a radiator under a window on an external wall is that the colder air / surface pushes the heat into the room and the gap between the wall and rad is critical to allowing that process.