Good morning!
I read your article Thermal bridges in energy certificates with interest.
I agree with your remark regarding the adopted dimensions, however, I have doubts about the entry “The first problem arises in the pattern itself (1.14). It's easy to see, that it does not mention point-type thermal bridges. ” The provision in the Regulation reads “heat transfer coefficient of the i-th partition between the space
heated and external side, calculated in the case of non-transparent partitions according to the PN EN ISO standard 6946, in the case of windows, skylights and doors are accepted according to the Technical Approval or according to the product standard
PN-EN 14351-1; in relation to metal and glass curtain walls according to the Technical Approval or according to the product standard PN-EN ISO13830, and in the case of a floor on the ground, taken as U_g _r and calculated as in point. 3.2.4.”
However, in the PN EN ISO standard 6946 in point 4 The rules were posted “Finally, it takes into account, if necessary, poprawki dotyczące współczynnika przenikania ciepła zgodnie z załącznikiem D, taking into account leaks in the insulation, mechanical fasteners penetrating the insulation layers and the dampness of the roofs
reversed as a result of precipitation.”.
So, counting U according to the standard 6946 I have to consider the influence of point bridges (the sheets from the building physics portal are useful, which you describe in the What to count tab and they take into account all the cases described in the standard 6946).
To sum up. I think, that the influence of point thermal bridges in the formula
1.14 has been included.
Yours sincerely
I warmly welcome.
While reading your article, the following thought came to me at the outset, which I would like to highlight. I will quote:
“The first problem arises in the pattern itself (1.14). It's easy to see, that it does not mention point-type thermal bridges. I will try to look at the consequences of this omission. Traditional sandwich walls are connected with steel connectors - anchors. Let's assume, that there are 4pcs. anchors per 1m2. Let us assume the cross-section of a single anchor 25mm2. Anchor material - steel (or stainless steel).”
I do not agree with the statement, that the formula does not take into account point bridges.
Well, in my opinion, it takes into account and I will try to prove it to you in a moment.
So, point thermal bridges should be taken into account when calculating the thermal conductivity coefficient in accordance with PN-EN ISO 6946:2008.
Norma says, that when calculating the thermal conductivity coefficient, we should take into account the correction due to leakage ∆U. This value includes, among others. correction element due to mechanical fasteners (Annex D – Corrections to thermal transmittance).
Based on this, I believe, that MI rightly does not provide in the formula for the transmission heat loss coefficient, losses due to point bridges, because if they occur in a building partition, they should be taken into account when calculating the thermal conductivity coefficient - this is our Ui which appears in the formula.
Application: listing the point bridges in this formula would be duplicating the same values.
I am at the stage of expanding my knowledge in the field of building physics and I would love to hear your views on my comments.
greetings