The three main values produced by the Section J report are the insulation R-Values, the glazing values and the maximum wattage allowance. 

Insulation is measured as an R-Value. A high R-Value is better for an energy rating, until a certain point.

Glazing is measured by:

• U-Value measures the glazing or frame's ability to slow down the ambient temperature from outside to inside and vice versa. The lower the U-Value, the better the rating.
• SHGC-Value measures solar rays, directly from the sun. Warm climates benefit from a lower SGHC as it blocks the sun while cold climates benefit from a higher SHGC to welcome the sun in.

The lighting allowances only dictate the maximum watts allowed for each room. The architect, designer or electrician will still need to prepare a lighting plan that demonstrates the proposed lighting falls under the maximum watts per room we have specified. 

It is not uncommon to prepare a Section J report with the glazing results blowing out the budget dramatically. Having to provide a client with a report that specifies high-performance commercial double glazing is not ideal, and the NCC facade calculator does have limiting input parameters that we can adjust to improve the results. 

Because the project documentation is so advanced, usually at the building permit stage, reducing the glazing area to improve the results is not an option. This is where we recommend preparing a J1V3 assessment. Preparing 3D models in commercial energy analysis software allows us to run simulations to produce more accurate and favourable results. The results from the J1V3 assessment override Section J4 - Building fabric results.

As soon as the design is complete, send us the plans so we can do preliminary insulation and facade calculations. This will give you the knowledge that the commercial building project performs well. If it does not, it allows you to make improvements early on.

If the proposed building works are internal alterations only, we only need to prepare a Section J6 Lighting report. This report will ensure the new lighting design is compliant with the proposed building classification.

If the proposed building alterations include a new conditioned area (i.e. an office) that was previously an unconditioned space, the new internal walls enclosing the conditioned space will likely require insulation calculations as well as the J7 Lighting calculations.

Extension to existing commercial space will require full Section J calculations, however, the building owner may request partial compliance for the existing external walls, allowing them to remain unmodified. The existing roof will likely need to be upgraded though as there is usually access to the ceiling space. These requirements to upgrade the existing building fabric are always up to the discretion of the building surveyor.