Thermal Bridging

[Daithi]

Hi,

I'm simulating an existing building and have entered a wall construction. I have calculated psi values (W/mK) for specific junctions and wish to enter them. I note there is a Building Regulations section in the construction database which deals with Thermal Bridging Coefficient (W/m2K). I have found some supporting documentation describing this section (Apache Construction Database 6.3, Section 4, p11), and wish to confirm my understanding.

1. Is the Thermal Bridge Coefficient the psi-value averaged over the area of the building element. (I have a wall of 0.75m x 4.5m with a linear thermal bridge of 0.6477 W/mK which applies to one of the long sides, ie 4.5m. Is the Thermal Bridge Coefficient then 0.6477/0.75 = 0.8636 W/m2K?)

2. Is the Thermal Bridge Coefficient value inputted into this section added to the U-value and the total used in thermal simulations to work out heat loss, etc, through the building element, or is it just entered to ensure a Building Regulation threshold hasn't been breached?

Any help much appreciated.

Kind regards,

Daithi.

[ZapBran]

I'm pretty sure that the main IES Apache doesn't handle bridging coefficients at all. That bit in the constructions interface only applies a correction factor to the uvalue for the UK Part L building regs document as a post process after the calcs have been done.
Maybe someone from IES could clarify?

[Daithi]

Hi ZapBran,

Thanks for your feedback. I think you're right.

I carried out some test simulations with and without thermal bridging coefficients and there was no difference in the annual energy requirement. I then adjusted the construction build-up to achieve a U-value that reflected the original U-value + the thermal bridging coefficient and the annual energy requirement was noticeably higher. I think that's the way I'll deal with it.

It's a pity IES doesn't deal with thermal bridging by adding the coefficient to the U-value pre-process, it seems like such an easy function to programme. Perhaps I'll post this on the wish list.

Thanks again,

Daithi.

[PCully]

Hi,

Just to confirm (I think you both already have) the Thermal Bridging is only for the UK Compliance regs and not use dint he energy calcs. You need to account for this manually in the Constructions you define.

I think it is on the development plan to improve the Thermal Bridging interface for Apache simulations but I don't have a fixed date for when this will be implemented. Sorry if that dialog caused you confusion or got your hopes up

Phil

[Daithi]

Thanks Phil!

Daithi.

[manexi_users]

Hi everybody,

I read differents topics about the thermal bridges in VE, and i would like to know if the right method to include them in our projects is still to integrate them in each wall by degrading the U value ?

Also, PCully, you said on 2011 that : "I think it is on the development plan to improve the Thermal Bridging interface for Apache simulations but I don't have a fixed date for when this will be implemented.". Is it still available ? And, could you confirm that the most efficiency solution to integrate thermal bridges in VE projects is this one i described above ?

Thanks everyone !

Aymeric

[RossThompson87]

Hi guys,

I am just jumping in on an old thread, as we are now finding more and more demand for thermal bridging assessments.

"I think it is on the development plan to improve the Thermal Bridging interface for Apache simulations but I don't have a fixed date for when this will be implemented.".

With regards to the above, does IES already have some code for working out the lengths of all the junctions from the ModelIT geometry?
I think there must be something used in the SBEM calculations, as junction length is not an input.

Could this be made transparent, so we can see the lengths assumed?

Can the same mechanism be applied to Apache calcs or even DSM? Very strange that the simpler software like SAP and SBEM has more capability than DSM.

Ross