Thermal bridges and wooden frames: insulation pub

[bham]

What is a thermal bridge?
It is a passage from cold to hot or vice versa and this passage is slowed down or facilitated depending on whether the "conductive" material is insulating or not.
To say that wood is insulating is a bit quick. Einstein could have said that everything is relative ... It is more than concrete, more than metal but less than rock wool of equal thickness.
So no, there is no thermal bridge only with metal, but with all materials !!!
To return to the above advert, you should know that the rafters placed on the roof in France often have, but it depends on the regions, a section of 8cm x 10cm, which is ridiculous from a thermal insulation point of view. Hence the possibility of covering these rafters from the inside with insufflated or non-blown insulation. Well, you have to put it in perspective, the chevron itself will not generate a very significant thermal bridge. Likewise in this case, the idea of ​​fixing placo in an attic should be abandoned by means of metal tabs fixed on the rafters, these also constituting thermal bridges.
But the ideal is indeed, in terms of insulation from the inside, to have a uniform insulating coating under rafters rather than between rafters.
I therefore refer you again to the calculator below, repeatedly mentioned to see for yourself that we can not say that the wood is insulating or not, it all depends on its thickness and density:
http://www.ideesmaison.com/15-facons-de ... -banc.html

Christophe has just written: "Besides if we think a little and following the very definition of a thermal bridge, in the attic it simply does not exist since the beams are covered by the roof ... am I wrong?"
Okay Christophe but don't forget that the roof is tiles fixed on slats or slates ... In short if I stay with the tiles, an under-roof screen separates the rafters from the slats / tiles and we provides an air gap of at least 2 cm for ventilation between screen and slats / tiles. This ventilation therefore constitutes a source of cold, not to mention that the screen is microperforated.

[bpval]

What is a thermal bridge?
Likewise in this case, the idea of ​​fixing placo in an attic should be abandoned by means of metal tabs fixed on the rafters, these also constituting thermal bridges.
.

Very true, and as many possibility of "dew point" to the right of the legs under the eaves with appearance of traces of humidity in cold weather and while insisting much ugly mushrooms that will have to re-upholster

Well then

Hello

[I Citro]

I have the impression that these rock wool suppliers say anything to sell their products ...

This is also my opinion.

And that makes me doubt their skills ...

In my opinion, thermal bridges do not come from wooden parts but from the air circulating around ...

[ThierrySan]

I understand better with this definition that we do not have quite the same conception of things:
http://fr.wikipedia.org/wiki/Pont_thermique

Indeed, I absolutely do not consider that a thermal bridge is a thinner section that can let out calories ...
I consider that a thermal bridge is a direct heat exchanger between the inside and the outside of a wall. For my part, an insulator is by no means a thermal bridge. Even less when it is very thick or when placed on other materials ...
In the first case, we can speak of a thermal bridge at infinity. And for my part, we are far from its original meaning ... Another deviation that can lead to big confusion !!!

It is necessary that the builders of habitats speak with scientific words ... And, I put it on the same side as the coefficient of performance of heat pumps!

In conclusion, it's a big bullshit, but it's only my opinion!

[bpval]

Hello

A thermal bridge is a discontinuity in an "isolated" set.

Example: as Wikipedia says

A ground floor facade wall with insulation
A floor that comes to rest on this wall
A front wall of the 1st with insulation

The entire facade has a thermal bridge at the point of the junction of the walls and the floor and runs horizontally all along the building at each level (or floor).

It is a part of the building that technically it is difficult to isolate.

In another post, "insulation from the outside" is mentioned and this technique is more expensive and more fragile to shocks and does not a priori have a thermal bridge over the entire facade, except at the level of the openings (windows and doors)

Hence the advantage of having double or triple glazing and pvc or aluminum frames with the incorporation of polyurethane or other

Anyone who wants to apply RT2005 standards (wikipedia) is getting ready
to endure a thousand sufferings. Calculations and parameters are pure empirical style

Hello

[bpval]

I understand better with this definition that we do not have quite the same conception of things:
http://fr.wikipedia.org/wiki/Pont_thermique

Indeed, I absolutely do not consider that a thermal bridge is a thinner section that can let out calories ...

In conclusion, it's a big bullshit, but it's only my opinion!

Imagine a car radiator
with even a very small leak

And equate it to a thermal bridge
And assesses the amount of energy that ultimately escapes fairly quickly

And make the parallel with the possible cost of the repair of your vehicle and the energy cost of the heating which fucks the camp outwards
A thermal bridge is a slightly cracked door


Hello

[Woodcutter]

[..] The guy who spawned the text neither knows much about thermal bridge

The two solutions he offers are valid

if he masters the laying techniques
better than the thermal bridge

Hello

Toutafé agree!
But on the other hand, it could offer less energy-consuming solutions and with a smaller overall environmental footprint!

[ThierrySan]

So, I continue on the thermal bridges ...

To respond to bpval, a leaky heater is a heater that loses calories by exchange of fluid between the system and the outside ... There, there is no notion of thermal bridge involved ...

An insulator is in no way a thermal bridge in my eyes ... Only metals play this role! If I take the example of your picture window, the aluminum of the support of your triple glazing is a thermal bridge between the interior and the exterior if it is only one block. On the other hand, you will notice that to break this thermal bridge, the interior and exterior supports are each separated by a kind of pvc or other joint ... Thus, no direct thermal transfer is diffused between the interior and the exterior of your habitat.

[bham]

So, I continue on the thermal bridges ...
An insulator is in no way a thermal bridge in my eyes ... Only metals play this role! .

Why are you stubborn?
Il it's not just metals which can constitute a thermal bridge but also concrete (external balcony which brings cold in the house, slab in contact with the external walls, ... etc) and by extension all the materials. Everything is just a notion of scale, thickness, density.
I think you have a bad understanding of what an insulator is. An insulator is insulating only compared to a standard, concrete is insulating, it takes just a meter thick to be as insulating as 2 cm of polystyrene (R = 0,55 approximately). Likewise, saying that wood is insulating does not mean anything, if you have a house with 3 cm planks, it will not be more insulating than a 25 cm concrete block house (R = 0,25 is the equivalent 1cm of polystyrene). It is, as I said above, the thickness which will make the difference and which will make a piece of wood that it is insulating (within the meaning of the standard in force) or not. Wood is therefore more insulating than concrete or metal but less than polystyrene.

Coming back to our 10cm rafters, their R = 0,83 cad the equivalent of 4cm of expanded polystyrene. So you can say that 10 cm of wood is insulating since it is as good as 4 cm of polystyrene. But except that 4 cm of poly .... it's not much in terms of insulation since the RT2005 requires, if I remember correctly, an R in wall insulation equal to 10 or 12 cm of polyst ....
So, this means that below this standard, your insulation is not effective enough, so it means that your insulation lets cold and hot pass to a degree that is not considered acceptable in terms of thermal insulation, that finally means that your insulation, insulating as it is, constitutes a thermal bridge in absolute terms, which has nothing to do with the importance of a thermal bridge as we 'hears about aluminum or concrete of course but it is one anyway.

[I Citro]

Nice presentation bham.
I too would have tended to approach the subject as thierrysan.

I will have just added concrete to metals for conductive materials ... and I would have been wrong since as you explain, concrete can be insulating if we put the thickness there .... we will then have d other perverse effects of non-breathing concrete ...
The question of using metal with large thicknesses does not arise for a simple question of ... budget!

I would remind you, however, that metal joinery with thermal break is far from being widespread.
We still find on the market joinery (steel but also aluminum) without thermal break or with a thermal break in the opening only instead of the "double break" ie in the sash and the frame.
I recently discovered super insulating joinery combining high-performance glazing with wooden joinery plus aluminum exterior cladding. These are very high-end ...