Excellence in design for greater efficiencies

EDGE Experts encourage the construction sector to design and build green by serving as trusted and experienced advisors. EDGE Experts are able to: provide clients and professional teams with a greater understanding of bioclimatic design and green technologies through their skills, insights and thorough understanding of the EDGE software; provide a cost-benefit analysis of green concepts, systems and solutions that best match the client’s aspirations; and assist the client in imagining and realising an entirely green portfolio.

Energy efficiency simulation in the design of homes

Energy modelling has been shown to be one of the best-value tools in saving energy. Solid Green has now developed a solution that uses bespoke software and automation to provide architects with answers to all the most common questions on any residential project, to provide a solution that is energy efficient and thermally comfortable.

Sun Path Diagram

Results are quantified and presented for every room in the house, and the associated cost of heating and cooling is anticipated to give clients real metrics by which to make decisions. In this way, the cost of Energy Efficiency Simulation is radically reduced, while maintaining the quality of predictive information to the client.

Solid XA:Online

Solid XA was designed to allow specifiers to quickly and easily create and manage residential projects for SANS10400 XA Rational Assessment. The app is used to: input details for walls, glazing, roofs and floors; upload building plans; and enter client’s invoicing details. Through this easy-to-use system, multiple projects can be managed, and materials profiles can be saved for reuse later. Once all steps have been completed, the assessment is speedily performed by Solid Green.

To find out more about our services and products for residential projects, or to see how your residential project will perform before it’s built, reach out to us at hello@solidgreen.co.za.

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Chilufya Lombe, Director at Solid Green, says:

One of the most important aspects of passive design is fully understanding the local climate and making sure that the building is able to take advantage of the prevailing conditions. Solid Green has an extensive library of detailed weather data that are used to conduct simulations and analyse weather data.

1. Sunlight and Thermal Modelling

The area is characterised by high diurnal temperature swings for large percentages of the year. This large difference between maximum and minimum daily temperatures indicates that there is a lot of potential for using thermal mass for passive cooling. Low night time temperatures means the building fabric can store ‘coolth’ and release it during the day, greatly reducing the need for active cooling. Fig. 1.1 – 1.5 below illustrate the modelling for this building in these specific climatic conditions.

Sun Path Diagrams

Fig. 1.1 – 1.2 represents the path the sun follows with respect to the site location. This is often the easiest way to help design teams visualise the impact of the sun on the building. All shading elements as indicated on the tender drawings are captured in the actual building model; and self-shading from the building’s own form is also accounted for in the model. No adjacent buildings are present on site that can have overshadowing impact.

Sun Path Diagram, Fig. 1.1

Sun Path Diagram, Fig. 1.2

Temperature Distribution Charts

Fig. 1.3 – 1.5 show the temperature and humidity distribution for different months of the year. Every hour of the year is represented.

Temperature Distribution, Fig. 1.3

The percentage of hours above 26 °C is a good indicator of how much discomfort should be expected when using natural ventilation for cooling.

Temperature Distribution (Day), Fig. 1.4

With the correct treatment of the façade, night time temperatures should always be comfortable in this climate. It is also clear that winter temperatures can fall quite low and heating will be required in winter months.

Temperature Distribution (Night), Fig. 1.5

2. Passive Design Modelling

A baseline model was created using known design parameters and best-practice inputs for different building elements. This baseline was then used to test the impact of various passive design elements.

To truly optimise a building, a large number of combinations must be tested to ensure the interconnectivity between important design variables is fully assessed. Take glazing as an example: if the glazing specification is changed, then shading requirements, heating and cooling loads, thermal mass and natural ventilation requirements will also change. Fig. 2.1 illustrates how, with just a few options for various building elements, you can generate a large number of combinations to test.

Parametric Design Combinations

The most efficient set of solutions must be identified and assessed for accurate recommendations to be made. This is one of the big advantages of optimisation – you typically end up with a number of optimal solutions and have the choice to decide which solution best meets the design objectives.

Parametric Design Combinations, Fig. 2.1

3. Building Fabric Investigated

Thermal properties of standard materials were used directly from the extensive DesignBuilder materials database. The following tables represent various changes that can be implemented to achieve both the most energy efficient and thermally comfortable solution.

Glazing – options investigated, Fig. 3.1

Roof Insulation – options investigated, Fig. 3.2

External Walls – options investigated, Fig. 3.3

Ground Floor – options investigated, Fig. 3.4

4. Summary of Results

Based on the results generated from the above, recommendations were then made with regards to the best combination of building fabric. The initial design was over-insulated for this climate and led to the building not being able to cool down passively at night. The table below shows that the proposed changes not only reduce the buildings energy use for active cooling but also save the client money.

Best combination of building inputs:

Best Combination, Fig. 4.1

Fig. 4.2 shows the savings by means of the most effective combination of factors.

Overall Savings, Fig. 4.2

5. Conclusion

The baseline building can be improved by 30% overall in HVAC energy by optimising the building fabric. That represents 30% less energy to offset if the client would like to make the house carbon neutral. Reducing the cooling load effectively decreases the number of hours that the building will require active cooling. Although the overall heating has been increased, the energy consumption over a whole year has been decreased because heating is only required for two and a half months. These recommendations are therefore in line with the client’s objectives for an energy and cost efficient home.

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