Common Issues
Why is my postcode not being recognised?
A postcode may not be recognised if it is a new building and not yet recorded in the Royal Mail Postcode Address File (PAF).
In these situations, you can enter only the first part of the postcode (outcode) to bypass the error.
Why am I getting an 'Invalid area' error message?
When adding doors and windows, their dimensional areas must be less than or equal to the wall that they are attached to.
For instance, in a narrow hallway where the door is the full width of an end wall. The parent wall dimensions would still cover the full height from floor to ceiling, i.e. including the door area.
The Heat Load Calculator will automatically deduct areas of any doors or windows from wall areas to determine the net surface area for heat loss purposes.
Why does my result have a 'Heat transfer imbalance' warning?
When an imbalance in heat transfer within the building is detected, this will be displayed as a warning on the calculation result page.
The imbalance will only be present in the room heat load (heat emitter sizing) calculations. It will be factored out of the total space heating load, as this only includes heat loss to external surfaces.
An imbalance can occur from not accounting for one or more internal surfaces properly. Common reasons why this might happen include:
- Adding an internal door in one room, but not adding the same internal door to the adjacent room.
- Where adjoining rooms have significantly different ceiling heights, not accounting for the heat loss through the extra section of wall between the height differences.
Why is the sum of the room heat loads different to the total heat load?
This is by design and due to the fact that ventilation heat losses (through movement of air) will not always be to outside.
The Heat Load Calculator uses the Standard method for calculating design ventilation heat losses as per BS EN 12831-1:2017. This method proportions only half of the room ventilation heat loss to the total zone ventilation heat loss.
In summary, the total heat load will be approximately equal to the sum of 100% room fabric heat losses + 50% room ventilation heat losses.