CIBSE Loads - very small heating load

ApacheCalc – Heat loss/gain calculations using CIBSE procedures to determine design heating/cooling loads.
ApacheLoads – Design heating/cooling loads calculations using ASHRAE Heat Balance Method.
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CIBSE Loads - very small heating load

Postby jm2000 » Mon Apr 10, 2017 10:07 am


I'm sure this has been asked before, but I have searched through the posts and I cant find an answer.

I have completed a CIBSE Load calculation run to determine cooling and heating loads. I seem to be getting very low heating loads about 25 w/m2, i would have expected this to be around the 70-80 mark for a new building. I know that internal gains such as lighting, people and equipment are not effecting this as per the IES notes. The U-values are fine, I have checked them. Air changes set to 0.25 ACH.

My heating is set to a 9-5pm heating profile, but I don't think that should effect this as this is a peak load at an instant in time. Cooling set to a constant time profile and 24 C set point.

So I am at a loss as to why the answer is so low, I know I need to add a bit of pre heat, factor of safety etc, but I am wondering is there something I am missing?? or has something been removed for the heating load because of a gain from elsewhere.

Any help appreciated.


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Re: CIBSE Loads - very small heating load

Postby Wasted Energy » Tue Apr 11, 2017 8:20 am


New build to current UK Building Regs?

Then 25 W/m2 is about right - particularly if you have not allowed for an fresh air aux vent loads in the room.

We size residential heating on 35 W/m2, allowing for mech vent load to Part F.


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