Energy Modelling and Design
The house was modelling in both IES and Accurate. The NatHERS report I did for certification is attached. This does not really try to model the house performance, but just shows it's a least 7 stars. Due to AccuRate limitations, PCMs and building sealing cannot be accurately modelled.
Update 17/9/2016: We have just finished the first Winter. This is The model did not account for a large tree to the NW of the tree, which blocks Winter (and Summer) sun. Generally no heating was required even at night. Some nights were cold and we used a terrible 1kW electric heater for morning warm-up. This was run for about 2 hours per day over 20 days. It runs about 30% of the time when on. This is 4.3 MJ/m²/year (same as modelled figure). It appears the tree's shade (lack of solar gain) is 'cancelling out' the PCM and building sealing.
Accurate was good to test options: it's faster but less sophiscated compared to IES (or EnergyPlus, etc). The summary of modelling is:
- IES and FR5 results are significantly different.It is difficult to get to the bottom of why - I gave up quickly.
- Shading is important (Scenario 3 to 4)
- Ceiling fans are great
- Insulation (particularly floor) is good for heating
- Thermal mass is good (even in Brisbane).
- If you do all this the above, super windows and superheavyweight provide only minor benefits.
The detailed results are below:
And as HTML:
| Name | Note | Walls R_total |
Roof R_total |
Floor R_ttal |
Windows | Heat MJ/m² |
Cool MJ/m² |
Total MJ/m² |
Stars |
| 2 Bad windows | This is NCC minimum without shading | 2.8 | 4.1 | 0.0 | U7 SHGC 0.77 | 31 | 183 | 214 | ☆ |
| 3 Add shading | This is NCC minimum | 2.8 | 4.1 | 0.0 | U7 SHGC 0.77 | 31 | 148 | 179 | ★ |
| 4 Add deck shading | 2.8 | 4.1 | 0.0 | U7 SHGC 0.77 | 39 | 96 | 135 | ★★ | |
| 5 Add better windows | 2.8 | 4.1 | 0.0 | U5 SHGC .50 | 39 | 73 | 112 | ★★☆ | |
| 6 Add more insulation | 4.5 | 6.0 | 2.0 | U5 SHGC .50 | 11 | 70 | 81 | ★★★☆ | |
| 7 Add ceiling fans | 4.5 | 6.0 | 2.0 | U5 SHGC .50 | 12 | 43 | 55 | ★★★★☆ | |
| 9 Add movable shading lourves | 4.5 | 6.0 | 2.0 | U5 SHGC .50 | 5 | 46 | 51 | ★★★★★ | |
| 10 Add detailed east/west window shading | 4.5 | 6.0 | 2.0 | U5 SHGC .50 | 4 | 43 | 47 | ★★★★★ | |
| 11 Add lighted coloured roof and walls | 4.5 | 6.0 | 2.0 | U5 SHGC .50 | 4.3 | 41 | 45.3 | ★★★★★ | |
| 14 Add medium weight walls and floor | Final rating | 4.5 | 6.0 | 2.0 | U5 SHGC .50 | 4.7 | 39 | 43.7 | ★★★★★☆ |
| 12 Test only: Super windows | Gets worse - do not use | 4.5 | 6.0 | 2.0 | U2.7 SHGC0.64 | 0.7 | 48 | 48.7 | ★★★★★ |
