Building Water Performance
Australia is one of the largest polluters in the world. Achieving net zero energy homes in most countries like Australia has been a struggle with up to 1.5% greenhouse gas emission. A report released by the Australian government shows that 23% of greenhouse gas emission is as a result of the buildings energy demands (Iyer-Raniga & Wasiluk, 2007). Since 2002, there has been restriction on water consumption as a strategy to counter drought conditions. Therefore, the rapid enhancement of water and energy performance of the building sector can significantly add to the environmental, social and economic benefits across the country, timely reduce global energy use and promote environmental sustainability.
To analyze the 4 bedroom bungalow house case study to determine the building water performance, energy performance, and indoor thermal comfort that are among the key steps towards the sustainability of the built environment.
Water consumption rate can be challenging to achieve in a home setting due to different activities that require water to undertake. However, to achieve a sustainable design, it is a requirement to fulfill the water consumption targets to help in saving water for future use. An average family home is required to consume a target of 40%, however, this can vary depending on different climatic conditions.
Calculate the BASIX score of “water” of the original case study building, and analyze the reasons why the building fails to satisfy the BASIX PASS requirement
The BASIX report gives a score of 27% which is below the target of 40% water performance. This means that the building sustainability in terms of water consumption is poor and cannot sustain the test of time. Since the design has failed to meet the BASIX requirements, then it means that there are a number of parameters that the builders did not take into consideration to achieve a sustainable design. To comply with the BASIX standards, there are a number of measures that have to be taken, but in this case study some of those measures were not fulfilled, and that is what lead into the failure of the water performance of the building. Some of those reasons include:
- Lack of rainwater tanks and storm water tanks in the design was a big failure to meet the BASIX requirement.
- Use of WELS rated 3 star (>7.5 but <= 9 L/min) and 3 star toilet are not recommended for the project to pass the BASIX test.
- Indigenous species with low water use should have covered at least 80% of the site instead of the garden covering a larger percentage considering that it uses more water(Huizenga, et al., 2006).
- The design lacked hot water recirculation system that would have helped to regulate the hot water used throughout the development.
Solutions appropriate to improve the water performance of the building to achieve BASIX score of over 40%, 50% and 60%
- This building project will pass using WELS rated 7.5 – 9 litre/min showerhead, 4-star toilets and 3-star basin and kitchen taps.
- Upgrading to 5 star tap ware achieves another 1% and 6-7.5 litre/min showerhead achieves another 2%.
- Use rainwater tanks with 50 – 100% of roof draining to it connected to irrigation, clothes washing and toilet flushing.
- Keep landscaped areas to a minimum and use low water plants such as natives
Estimate the likely investment required for your developed three solutions
To achieve the target for water performance, it definitely means that the cost of the investment will increase with a significant amount of approximately $200 since the 5 star water fixtures are very expensive.
Compare the three solutions you developed and discuss the advantages and disadvantages of each solution.
Rainwater tanks are mainly used for storage of water that can be used in the wet areas such as kitchen, toilet and the excess water can be used in irrigating the landscaped areas. The solutions I have provided to improve the water performance is a kind of cycle or web whereby the components are connected to each other to minimize on the water consumption. In this case we have the primary component which is the rainwater tank which will supply water to the household water fixtures such as the toilet and kitchen during rainy season when there is enough water and there is basically no need to use water from Wollongong City Council. It therefore means that, for water to be used sparingly in the bathroom, the showerhead should spray water of around 8liters/min to save in consumption. On the other hand, the toilet should be 4 star, kitchen and basin taps should be 3 star to help on the building water performances. The excess water due to overflow can be used in the lawn areas and gardens.
Building Thermal Comfort
Rainwater tank
Advantages
- Helps in storing runoff water from the roof area
- Helps in supplying indoor cold water taps
Disadvantages
- More building investment due to installation requirements and maintenance
Keeping landscaped areas to minimum
Advantages
- Help in water conservation
Disadvantages
- Reduce the aesthetic of the environment
Water appliances
Advantages
- Reduce on water wastage
Disadvantages
- They are expensive hence increase the cost of construction
Achieving thermal comfort in a building is the most important requirement of a building not only as a BASIX compliance but also it is a standard requirement in most countries. It is important to take care of the cooling and heating loads to ensure that there is a balance of the energy to help keep the indoor temperature warm. Thermal comfort can be achieved on account of the location of the building, the size, orientation, form, glazing, ventilation and insulation.
The case study building failed to pass the BASIX comfort requirement due to a number of reasons assessed in the energy performance of the building. Such failures include
- Wall insulation: the internal wall shared between the two bedrooms and the garage lacks additional insulation. This means that energy transfer co efficient will increase, more heat will be lost from the bedrooms to the garage due to the difference in temperature experienced in the two spaces.
- Wall insulation: the incorporation of the cavity wall in the design lacks additional insulation which would have helped to reduce the U-value by 0.67, therefore, this measure is a significant source of maintaining the balance between heat loss and heat gain to achieve thermal comfort (Huizenga, et al., 2006). Significantly, the cavity wall need more insulation, without further detail on insulation, it will mean that glazing will be increased and this will eventually have a great impact on the windows, otherwise double glazing is recommended to achieve a more thermal comfort design. Lack of more insulation on the wall resulted in the design not complying with the BASIX requirement leading to fail.
- Ceiling insulation, it is important to insulate the building at the ceiling level, but in this case study, the ceiling did not account for the value of blanket and foil insulation to improve the indoor temperature.
- Shading from structures: All windows (W1, W2, W3, and W4) lacked shading devices to protect the indoor temperature from the direct solar radiation, this tampers with the quality of the indoor temperature leading to poor thermal comfort. This resulted into more heat transfer which gave a U-value of 6.7 and solar heat gain of 0.7.(Iyer-Raniga & Wasiluk, 2007) Windows have a great impact on indoor temperature due to the long wave radiation, solar radiation, and convention draft
- The recommended floor type for the design included a concrete slab on the ground, with this type of floor, there will be more heat gain and loss due to the difference I temperatures between the slab and concrete. This makes the concrete to loss more heat to ground leaving the floor to be very cold and uncomfortable.
- In addition, the larger percentage of the concrete slab on the ground did not have an in-slab heating system to help regulate the floor temperature while a small floor area of 35m2was suspended from the ground and it was made of AAC panel on frame which should be the other way round. The larger floor area can be suspended while the small area can be on the ground.
- The wall type used on the external walls is a cavity brick with no additional insulation, This reduce the potential of achieving thermal comfort, in addition, the internal walls shared with garage is not recommended, unless the wall is installed with foil to regulate the temperature.
On the other hand, there are certain strategies adopted in the design that helped to achieve the building thermal comfort. These achievements include
- Glazing: this is an architectural feature that gives the occupants a direct connection to the outdoor environment while at the same time reducing the energy lighting demands
- The glazed doors and windows used in the design help to reduce the total heating and cooling loads. Glazing has drastically been reduced on the windows facing north since there is always a high amount of solar radiation experienced on the north facing windows (Huizenga, et al., 2006). In addition, the windows facing north have smaller sizes compared to the windows on the east and west side where there is maximum glazing due to short wave radiation encountered on these windows
- Construction methods of the ceiling and roof type was a great move to help achieve thermal comfort. Flat ceiling and a pitched roof or Pitched or Skillion roof/Raked ceiling helps to increase the attic space for cooling the hot air that raises which eventually helps to cool the indoor temperature for the occupants comfort.
Appropriate technical options to improve the thermal comfort of the case study building to PASS the BASIX thermal comfort requirement
- Keep main living areas on the north side of the building to help maximize north faced glazing.
- Position garage, laundry, and similar ‘service rooms’ to west and or south.
- 20 – 40% of the buildings floor space should equal the amount of glazing – this is the most economical.
- Windows are approximately 90% of a home’s heat gain and 50% of a home’s heat loss, therefore aim to have: the majority of glazing on the north façade with up to 50% of the façade glazed o Up to 15% of the east and west elevations glazed, and 10% of the southern elevation glazed(Iyer-Raniga & Wasiluk, 2007).
- Fixed windows (not opening) tend to perform poorly particularly when placed high such as in voids or at the top of gables.
- Thermal mass acts like a temperature battery and helps to reduce drastic changes in temperature. Slab on ground with floor tiles and one or two internal brick walls in rooms with large amounts of glazing can help with thermal comfort.
- 450 – 900mm eaves (including gutter) are best for shading.
- Large eaves or an alfresco over sliding doors can block winter sun from the opening making the opening perform poorly due to heat loss.
- Insulate walls with R2.0 or R2.5 insulation and ceiling with R3.0 or R3.5 insulation and install ‘roof blanket’ under metal roofs or R3.5 – R4.0 insulation with sarking for tiled roofs(Iyer-Raniga & Wasiluk, 2007).
This gives a ‘target score’ according to the energy consumption of fixed appliances such as cooktops, hot water systems, air conditioners, ceiling fans, lighting etc. that are to be installed in the building
Step 1
calculate the BASIX score of “energy” of the original case study building, and analyses the reasons why the building fails to satisfy the BASIX PASS requirement (i.e. BASIX score of 50%); Energy targets are set to ensure that a home receive net zero energy. The BASIX report for the case study building energy performance gave a score of 21% which is below the energy target of 50%. This means that the reduction of greenhouse gases has not been achieved hence the building is unsustainable since heating and cooling loads have not been minimized. Some of the reasons why the building did not pass the BASIX requirement include
- The hot water system used was not the most efficient option, instead of using electric storage, solar energy could have been used because it is more efficient and environment friendly. In the long run more electric energy could have saved which could have lead into reduced greenhouse emission(Huizenga, et al., 2006).
- Ventilation approaches adopted were not the best to help in energy saving. The kitchen and bathroom could be naturally ventilated considering they are located on the exterior walls of the building. This could have saved the energy used in operating the individual fans.
- Lighting the living and dining room require energy efficient lamps since the spaces are continuously used and require fluorescent or LED lamps. Not having the dedicated fluorescent or LED fittings leads to more energy used(Huizenga, et al., 2006).
- Lack of a well-ventilated space for the refrigerator leads to accumulation of heat
Step 2
- In many cases designs will pass the energy targets by using typical 6-star gas instantaneous Hot water service, reverse cycle air conditioning, LED/Fluro lighting, gas cooktop and the installation of a clothesline(Iyer-Raniga & Wasiluk, 2007).
- If the design fails by under 5% of meeting the targets using some of the following may help:
- Well ventilated fridge space achieves 2%
- Utilize natural lighting and ventilation as much as possible.
Step 3
Estimate the likely investment required for your developed three solutions
The incorporation of the solutions will definitely mean additional cost to the developer of up to $300 to purchase the energy efficient fixtures.
Step 4
Compare the three solutions you developed and discuss the advantages and disadvantages of each solution.
The solutions proposed to comply with the BASIX requirements range from installing appliances with good rating to help in the management of energy saving to allowing enough space for appliances such as the fridge and making use of the natural light and ventilation to the maximum. This combination of outdoor environment to quality indoor appliances can greatly improve the BASIX energy requirements.
6 star appliances
Advantages
- Have a reduced energy consumption per minute
Disadvantages
- They are very expensive, this eventually increase the cost of the building
Well ventilated fridge space
Advantages
- Improve the quality of air in the kitchen
Disadvantage
- Require more space
Natural lighting and ventilation
Advantages
- Eco friendly to the indoor air quality
Disadvantages
- More fenestration to achieve outdoor air quality and light means that there will be more window, doors and skylights which will need glazing. Hence more spending to achieve this design measures
Building Sustainability Index (BASIX) is responsible to ensure that homes built in NSW are more considerate when it comes to water and energy efficiency strategies employed in the designs. The main aim is to reduce the amount of greenhouse gas emission in to the atmosphere and water conservation targets as seen in the case study building. Therefore, before any construction is done, it is important to submit the BASIX certificate of the development in order to help secure our environment for the future.
Considering the analysis done, there has been tremendous failure to ensure that the design meet the energy, water and thermal performance because of poor design decisions. It is important for all house to comply with the BASIX requirement by having components such as the rainwater tanks that will greatly help in rain harvesting with an average size of 4000 liters. The majority of the water will be supplied to the laundry and toilet while the rest can be used for irrigating the gardens.
References
Huizenga, C., Zhang, H., Mattelaer, P., Yu, T., Arens, E.A. and Lyons, P., 2006. Window performance for human thermal comfort.
Iyer-Raniga, U. and Wasiluk, K., 2007. Sustainability rating tools-a snapshot study. Environment Design Guide, pp.1-14.
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