Why load calculations matter before any ducted install
A zoned ducted system only works properly when the cooling and heating loads are known room by room. In Johannesburg and Pretoria, a lounge on the west side, a north facing bedroom, and a shaded study can all need very different airflow, even in the same house. If the equipment is chosen by guesswork, you usually end up with uneven temperatures, noisy dampers, short cycling, and higher power use.
Our load calculations give the design team a proper starting point for the equipment size, duct sizes, zone sizes, and thermostat placement. We look at how the building actually behaves through summer heat, winter mornings, afternoon sun, roof space temperatures, and the way the family or staff use each room. That is especially important for homes with double volume areas, glass-heavy facades, upstairs bedrooms, and offices with meeting rooms that fill up at different times of day.
The aim is simple: pick a system that can keep up on the hottest days without being oversized for the rest of the year. Oversizing is just as much of a problem as undersizing because it wastes energy and makes zoning harder to control.
What is included in an Airzone load assessment
We measure the building and collect the details needed to calculate sensible and latent loads, then map the zones to match the ducted layout. For retrofits, we also check what is already in the ceiling void, what can be reused, and where air leaks or poor return paths may be affecting performance.
- Room dimensions, ceiling heights and floor areas
- Window sizes, orientation and shading
- Construction type, roof exposure and insulation level
- Occupancy, appliance heat and internal gain allowances
- Zone grouping for bedrooms, living areas and office spaces
- Equipment capacity recommendation in kW and airflow in L/s
- Basic duct and diffuser sizing notes for the installation team
Where needed, we include notes for humid coastal conditions, enclosed patios, server rooms, north-facing glazing or solar gain from metal roofs. If the project is in Sandton, Randburg, Centurion or Pretoria East, we factor in the common site conditions we see in those areas, including bulkier roof spaces and mixed-use home office setups.
How we carry out the calculation process
The process is straightforward. We start with the site assessment, then the design team works through the building data and zone plan before the final recommendation is issued. If drawings are available, we use them. If not, we measure on site and record the rooms directly. Either way, the result is based on actual conditions, not a rough estimate.
- Step 1: Site visit and room-by-room measuring
- Step 2: Review of insulation, glazing and roof exposure
- Step 3: Load calculation for each room or zone
- Step 4: Equipment size, airflow and damper strategy
- Step 5: Final handover notes for installation or retrofit
For new builds, this is best done before ceilings are closed so duct routes, return air and service access can be planned properly. For retrofits, the calculation helps us work around limited ceiling depth, existing bulkheads and older wiring. It also helps avoid the common problem of over-sizing a unit to cover one difficult room when the rest of the building only needs moderate capacity.
Typical turnaround for Johannesburg and Pretoria projects
For standard homes and small offices, load calculations are usually completed within 2 to 4 working days after the site visit and all room details are confirmed. Larger homes, multi-storey properties, offices with several zones, or projects that need more than one design revision may take a little longer. We will tell you upfront if the brief needs extra time.
Urgent turnaround can sometimes be arranged for projects that are close to installation and need final equipment confirmation. That said, it is better to allow enough time for correct sizing rather than rush the figures and end up with a system that cannot be balanced properly. A day saved at the start can cost a lot more later if the wrong capacity is ordered.
We work across Johannesburg, Pretoria, Centurion, Sandton, Randburg and Pretoria East, with support for surrounding areas when the project is a fit. If there are municipal or body corporate rules on outdoor unit placement, ceiling access, condensate drainage or noise limits, we flag those early so the design can be set up properly.
Pricing approach and what affects the fee
Pricing is based on the size of the property, the number of zones, the level of detail required and whether the work is for a new build, retrofit or system upgrade. A simple home with a few rooms is priced differently from a large residence with multiple living spaces, studies and a pyjama lounge, because the calculation takes longer and the zone plan is more involved.
We keep the pricing practical and explain what is covered before we start. If the brief changes halfway through, for example if a room is added, the ceiling plan changes or the client wants to split a zone further, we update the scope first. That way there are no surprises at the end. It is also the right approach where load shedding backup planning, inverter limits or generator capacity need to be considered, since those factors can influence equipment choice.
In many cases, the load calculation fee is credited back or bundled into the broader design and installation package when Airzone handles the full project. Ask for a quotation by email and we will confirm what applies to your site.
Keeping the system accurate after installation
Load calculations are not only useful at the start of a project. Once the system is running, seasonal servicing and operational checks help confirm that the building still matches the design assumptions. If a family extends the kitchen, closes in a patio, adds more glass, or changes office use, the original loads can shift. Then the zoning may need a small reset.
As a rule, we suggest a check every 12 months on standard residential systems, and every 6 months for busier office sites or properties with heavy usage. Coastal humidity, dirty filters, and blocked return paths can change how the system behaves. In Gauteng, dust build-up and ceiling heat also affect performance, so regular maintenance keeps the readings closer to the original design.
- Annual review for most homes
- Six-monthly review for offices and high-use spaces
- Earlier check after renovations or room changes
- Filter and airflow inspection during servicing
Key facts
| Service area | Johannesburg, Sandton, Randburg, Pretoria, Centurion, Pretoria East |
|---|---|
| Typical turnaround | 2 to 4 working days after site visit and confirmed room data |
| Calculation basis | Room-by-room cooling and heating loads with zone airflow planning |
| Project types | Homes, offices, new builds, retrofits and system upgrades |
| Output format | Equipment size, airflow, zone notes and design recommendations |
| Review interval | Every 12 months for homes, every 6 months for busy offices |
