How to treat ground contact walls?

[RossThompson87]

Hi I am working on a project that requires Part L compliance and an EPC.

The building is built into a slope so the ground level varies all over the place.

What is the correct way to model the parts of the walls that are ground contact?

Do they need to be obstructed with topographical shade to prevent the notional building applying 'impossible' glazing with daylight dimming?

Should earth be added to the construction build up?

Should I apply the ground contact adjustment under functional settings?

Do I need to adjust the adjacency setting to a temperature from a profile that represents the ground temperature (e.g. around 10degC all year round) ?


Is there any official guidance on this?

Thanks

Ross

[btysoe]

I've not found any official advise on this subject either but I have faced the same problem.

I did apply topographical shade around the building to prevent the glazing in the notional building. Both actual and notional buildings see this so it's not giving you an advantage rather making it a fair comparison. If it was an adjacent building it would be treated in this manner I believe.

I also applied the ground contact adjustment where the walls were completed submerged but not where they were only partially.

I'm not sure about the ground temp.

[RossThompson87]

Hi btysoe I did actually get this response over email:

My email:

Hi,
I am working on a project that requires Part L compliance and an EPC.
The building is built into a slope so the ground level varies all over the place.
What is the correct way to model the parts of the walls that are ground contact?
Do they need to be obstructed with topographical shade to prevent the notional building applying 'impossible' glazing with daylight dimming?
Should earth be added to the construction build up?
Should I apply the ground contact adjustment under functional settings?
Do I need to adjust the adjacency setting to a temperature from a profile that represents the ground temperature (e.g. around 10degC all year round) ?
Is there any official guidance on this?
Thanks

Ross

This is the response:

Thank you for your email.

The later of your suggestions is the most important. See the attached PDF.

If your floor is ground contact then you need to consider this and use the Ground Contact option in the floor construction to add the U-value correction layer.

For a visual representation, and also for taking site shading into account, you should try and represent the ground by drawing the slope and setting it to room type ‘Topographical shade’.

I hope this helps.

Unfortunately I can't attach the PDF that came, but it explains how to import an absolute profile that is constant 10 degC. And assign this as a surface condition.

There is also no way to check which surfaces have this applied! So you need a good memory.

Ross