Developing A Net Zero Energy Home: Solutions And Challenges

Selection of Low Carbon Construction Materials

Construction sector being one of the oldest sector of the economy utilized a greater percentage of energy produced on earth. A  net zero carbon emission building is usually attained on the condition that the overall amount of energy utilized annually by a building is almost similar to the measure of renewable energy that a given house produces on its actual boundaries (Steg, 2008). This may be achieved mainly by the reduction of the use of fossil fuels and any processes that lead to the emission of greenhouse gases in the building of the house/construction materials, repairs, and maintenance of the home (Abrahamse, 2005). There are several technologies in zero carbon design as discussed in the report which include selection of materials which may be classified as low carbon emitting, using modern and more efficient construction methods, reducing consumption  by using appliances that save energy, supplementing power using renewable sources of energy and finally recycling or reusing various products (Ameli & Brandt, 2015). It is key to note that zero carbon emission homes utilize energy mostly national electrical grid system and should on other hand return almost a similar amount of power in most cases.

This report aims in identifying solutions of developing a net zero energy home by identifying the causes of carbon emission by having two buildings with different material selection; one named YH and the other one is RH. This will help us calculate the embodied carbon energy produced by both the houses and the cost of saving determined when we use renewable sources of energy (Van den Bergh, 2008). The report will conclude by giving possible solutions that will help in achieving a net zero energy home and the challenges encountered during this process.

This can be done using two options in the building sector. These include the use carbon sink and low carbon material. For this case, we will consider the use of low carbon materials.

Below are sources of embodied carbon:

Low carbon materials are manufactured mainly with material, which are usually recycled and hence reduce the total amount of embodied carbon. There are many examples of low carbon materials, which can be used as an alternative recently (Anderson & Shiers, 2009). These materials include: Blended Cements, fly ash blocks, mud blocks for masonry, rammed earth walls etc.

Innovative construction processes will involve an adjustment of several components of the building to output conditions that lead to net zero emissions. These will include changing the design of the building to consider the following factors: day lighting, envelope airtightness, optimizing microclimate and natural ventilation, radiant cooling, under floor air supply and reducing window to wall ratio (Balzani & Armaroli, 2010). Other factors include the orientation of the home. For example if for the case of a given home that the winds are from east-west direction, in order to achieve proper ventilation the building’s longer axis will on the north-south direction.

Innovative Construction Process

Rainwater collection have is a common practice that have been adopted all over the world. A tank is strategically placed to collect water from the roof and preserved for use in the house e.g. for toilet purpose.

Renewable energy is referred to as energy usually tapped from renewable resources, which occur naturally and infinitely replenished throughout .They, include sunlight energy, wind energy, tides, and waves. In the case of a home setting, the renewable sources of energy to be used are wind and sunlight (Bergh, 2008). Sunlight provides solar energy, which is normally, tapped automatically using a wide range of devices such as a solar heater, photovoltaic, concentrated solar power etc. (Balzani, 2010). Photovoltaic system works by making use of the photoelectric effect to convert light into electrical direct current. Wind power is harnessed by running turbines, which range from around 600KW to 5MW (Goswami, 2006). Other renewable sources of energy that can be used in a household setting include bio mass energy.

Recycle and Reuse

There are several materials in a building setting that can be recycled and reused. The two main components are water and building materials. Water may be purified to be used for agriculture, cleaning or flushing the toilet. Waste such as plastic bags can be reused after cleaning and hence reducing the amount of solid wastes (Borenstein, 2008). It is also important to separate solid wastes into various categories so waste material such as plastics can be recycled hence reducing the amount of carbon emissions

current house that need to be redesigned to get an improve RH that has net zero energy. My house is model 16 located in Melbourne. Below is the plan

YH detail construction material 

The materials for YH were defined in the energy plus software. My choice of material selection include:

1. Brick veneer
2. Wall insulation
3. Ceiling plasterboard
4. Ceiling insulation
5. Wall plasterboard
6. Carpet
7. Concrete slab
8. Ceramic floor in the wet areas
9. Door material

The image below shows how this materials were defined in energy plus software.

Materials used in the construction of RH consist of different layers as shown below:

• Floor carpeting consist concrete slab and carpet.
• Exterior walls consisted of brick veneer
• Wet areas ceramic finish.
• Roof constructed with roof tiles
• Door materials and window with single glazing.
• Interior ceiling with plasterboard finish.
• Interior walls plastered on both sides with an insulation in the middle.Details of YH heating/cooling, hot water, and appliances

Mechanical means of regulating the indoor air has to be considered in order to achieve the house thermal comfort. This means we will have to introduce air conditioners to aid in regulating the cooling and heating of the indoor air. YH has 5 occupants with a number of appliances.

 These appliances are listed below with their quantity and amount of energy emitted.

The RH is the building that has been redesigned to enhance its performance in meeting net zero energy. To achieve a clear results, a similar location has been used, same floor plan and the method of construction type used in YH.

Management of Operative Energy Consumption and Consumption Behaviour

Materials used in RH include wood for flooring purposes since it’s readily available in Australia and carbon content is always very low making it a better choice for design.

Material selection as defined in energy plus software

Selection of durable and sustainable resources will help in reducing the amount of carbon emission and reduce the cost of energy.

1. Update the electrical setting into more energy efficient devices.
2. The plumbing setup should be properly done to avoid any leakage that may lead into an increase in carbon emission.
3. Select a more efficient air conditioner.
4. Water management within the house is prime to enable conservation of water.

Below is the list of the selected materials of RH;

A number of processes are involved in this stage of choosing the right material that will minimize the emission of carbon. This stages include design and building, material selection, methods of construction and the construction results.

Materials that can be recycle in RH include the tiles and blocks. The small craters made during the construction can be filed using the pulverized blocks. Timber for window framing can also be recycled. The plasterboard can be recycled by grind and mixing with water to make a new plasterboard. Glass wool can also be recycled to be used as insulation material.

Reduction of energy consumption can be achieved by using appliances that are rated 5 star that are more effective and at the same time consume less energy. The wall should also be insulated to achieve natural thermal comfort instead of depending on air conditioner in regulating the indoor air quality. In addition, achieving cross ventilation in the design will help solve this problem and maximizing on the use of natural lighting will save on the cost of energy consumption through lighting (Construction Limited Company, 2010).

Use 5 star energy rated appliances in RH due to their less energy consumption rate. E.g. use LED bulbs instead of fluorescents.

The table below shows appliances used in RH.

In the case of a home setting, the renewable sources of energy to be used are wind and sunlight. Sunlight provides solar energy, which is normally, tapped automatically using a wide range of devices such as a solar heater, photovoltaic, concentrated solar power etc. (Balzani, 2010). Photovoltaic system works by making use of the photoelectric effect to convert light into electrical direct current. The sustainable on-site energy will help in saving bills (Council, 2007).

In addition, gravity tanks have been set on site to harvest the rainwater in RH to help in storage of water that can be used in to carry out various house activities (Dixit, et al., 2010).

Water harvesting   source: google images

Calculation of embodied energy

First, material usage of each component should be obtained by taking in consideration of the area of coverage and multiplying by the weight of the material to get total in kg. The results will then be multiplied by the embodied energy co efficient of the material to obtain the total carbon content in kgCO_2. The total carbon content of the house will therefore be obtained by adding the carbon content of all the materials.

Choice of Renewable Energy Systems

The house has an area is 187 m², wall heights assume 3000mm. The ceiling area is 190 m² and the windows opening area 16.8 m².

YH material with their embodied carbon

The total embodied carbon emitted by YJ in a period of 40 years is 103,470 KgCO2 or 103 tCO2. In a period of 1 year, the total amount of carbon emitted will be: 104/40= 2.657 tCO2

RH materials with their embodied carbon

The total carbon emitted in a period of 40 years is 574187 KgCO2 or 57.4 tCO2. In a period of 1 year, the carbon amount that will be emitted will: 58/40= 1.45 tCO2

Below is the conversion of carbon energy into embodied carbon

The formula used in the conversion is given:

1 MJ= 0.098 KgCO₂

Pouring of concrete to make floor slab = 644 MJ/m²*187=120428*0.098=11801.944 KgCO₂

Elevating the floor level= 294 MJ/m²*187= 54978*0.098= 5387.844 KgCO₂

Plasterboard roofing and ceiling = 272 MJ/m²*187= 50864*0.098=4984.672 KgCO₂

Brick wall made of cavity clay= 861 MJ/m²*136.5= 117526*0.098= 11518 KgCO₂

Internal walls with their finishes= 907 MJ/m²*138= 125166*0.098= 12266 KgCO₂

Therefore, the total amount of embodied carbon for YH will be:

45,958.46 KgCO₂= 46 tCO₂

The total amount of carbon to be emitted annually will be:

46/40= 1.15 tC

We will calculate the carbon emission that occurs due to maintenance. Repairs and the changes that occur in materials during their 40 years of life cycle

The calculation process has been extracted from the excel spreadsheet

YH Maintenance Embodied Carbon

Your House (YH) carbon emission for a period of 40yrs will be 130,521 KgCO2, otherwise it can be represented as 131 tCO2 and the amount emitted yearly will be: 131/40= 3.275 tCO2

RH Maintenance Embodied Carbon

Embodied carbon amount that will be emitted during the life cycle of the serving of RH building will be 45,021 KgCO₂ or 45 tCO₂. The amount of carbon emitted yearly will be:

45/40= 1.125 tCO₂

Estimation of carbon emission from wastes of your rebuilt/redesigned home

Identify the type of waste produced each day. The DOC table help to estimate the solid waste emission. The table below gives an overview of the waste generated in the Redesigned House (RH)

The formula for calculating embodied carbon emission of waste

[(Q x DOC/3) – R] x 18.9

= (131.4*1.47/3)-0.1314)*18.9= 1214.412 KgCO₂= 1.2144 tCO₂

Considering the emission factor of waste is 25%. Therefore:

0.8*0.25=0.2 tCO₂

Therefore, carbon emitted yearly will be:

1.2144+0.2= 1.415 tCO₂

Total emissions of CO₂ in 40 years is:

1.415*40= 56.6 tCO

The table below shows the appliances with their usage per day and their consumption rate.

Recycle and Reuse

YH Appliances showing their usage

Carbon emission for scope 2 and scope 3 with an efficient Factor of 1.22 KgCO₂/KWh for scope 2 and Efficient Factor is 0.08 KgCO₂/KWh for scope 3.

31043*1.22= 37872.46 KgCO₂

31043* 0.08= 2483.44 KgCO₂

The amount of carbon emission yearly for YH is calculated below:

37872.46+2483.44= 40355.9 KgCO2= 41 tCO₂

The RH will have appliances that are more efficient in saving energy.

Calculation for scope 2:

6945*1.22= 8472.9 KgCO₂

Calculation for scope 3:

6954*0.08= 556.32 KgCO₂

Total amount of carbon

8472.9 + 556.32 = 9029.22 KgCO2= 9 tC

The table below shows YH embodied energy for heating and cooling.

The table below shows RH embodied energy for heating and cooli

The results shows that there was a significant reduction in the amount of energy used heating and cooling by 66%. This means that the house will be able to save on money spent on electricity bills

Summarize the changes (reduction/increase percentage) in carbon emissions

The tables below gives a clear comparison of YH and RH of embodied carbon emitted based on the results obtained above.

The results obtained above proves that we can reduce carbon emission, when we use low carbon materials, more efficient appliances rated from 3- 4 star, installing a hot water system, having waste management system and less maintenance can be advantageous. 

The table below shows a comparison of carbon emission annually for YH and RH with the reduction perc

It is evident that we managed to reduce carbon emission in all the factored elements of construction, which resulted into a total reduction of carbon emission in our redesigned house.

In this section, we will analyze the implications of using sustainable energy resources of our RH using HOMER software.

In the Homer software, we will introduce the loadings resources, generators, connections, and batteries with its life span. To introduce loads based on the results of the energy plus software;

Electrical Load inp

Components

The detail intended to achieve a net zero home

• Grid system
• PV system

Defines the cost of installation, replacement and operation & Maintenance (O&M)

• Converter

Defines the cost of installation, replacement, operation & Maintenance (O&M) and the life time of the converter

• Storage

Battery is needed to store excess energy. Homer defines the cost of installation, replacement, operation & Maintenance (O&M) and the life time of the battery

RH need an addition of energy storage by using batteries. Homer defines the cost of installation, replacement, operation & Maintenance (O&M) and the life time of the battery

• Wind Turbine

Designing On-Site Renewable Energy Supply using HOMER

Homer defines the cost of installation, replacement, operation & Maintenance (O&M) and the life time of the wind turbine include the hub height

Resources

Renewable energy resources that will enhance the Redesigned House in achieving net zero emission

• Solar resource

• Wind resource

Defines the average wind spend in m/s for every month

Project detail

• Economic
• Cost Summary
• Cash flow
• Compare Economics
• Electrical
• Renewable Penetration
• Generic flat plate PV

Emission

Results shows 40 years of life service gives a net cost of $45,931.

. The electrical productions by the PV scheme are 36.8 kWh per day, and the house load is about 11 kWh daily. Therefore, there is excessive electrical energy of approximately 25.8 KWh in a single day (36.8- 11= 25.8 KWh) that can be sold for profit. The electricity fee at Melbourne is $0.10 per KW. Thus, a benefit of $2.58 is present per day, that is 25.8 KWh/day* 0.1= $2.58.

The table I below provides all the comprehensive data about the charge

	Day ($)	Year	40 years
		($)	($)
Initial	1.26	458.75	18350
Capital
Income	2.58	941.7	37668
Benefit	1.32	482.95	19318

Therefore, by fixing the schemes and selling the excessive power for over forty years, a profit of $19318 is gained.

To analyze the reimbursement time for the preliminary cost of executing the systems the formula below is adopted;

Payback period (year) = Total Original Investment/ Total Pay (year)

Profit time= 18350/941.7=19.4 years.

Thus, the initial investment capital is attained after 19.4 years.

Achieve a house with ne zero energy is very hard without using to days energy and more so keeping in mind the expectation of the occupants. To achieve this, you must have the right setting the right building and the right teams that will make this dream come true.  However, it is very difficult to come up with a building with net zero energy of more than four stories. Most of the construction material such as PV is always very expensive (Lewis, 2007). Achieving the best orientation for the building is also a problem since when this approach is well achieved it can save up to 50% of the cooling and heating energy. The most critical issue is the selection of materials for construction. This is the most difficult part since safety of the building should also be considered. However, to achieve almost net zero energy, green materials and recycled should be a priority and readily available on site (Ameli & Brandt, 2015).

References

Abrahamse, W., Steg, L., Vlek, C. and Rothengatter, T., 2005. A review of intervention studies aimed at household energy conservation. Journal of environmental psychology, 25(3), pp.273-291.

Ameli, N. and Brandt, N., 2015. Determinants of households’ investment in energy efficiency and renewable: evidence from the OECD survey on household environmental behavior and attitudes. Environmental Research Letters, 10(4), p.044015. 

Anderson, J. and Shiers, D., 2009. Green guide to specification. John Wiley & Sons.

Balzani, V., & Armaroli, N. 2010. Energy for a sustainable world: from the oil age to a sun-powered future. John Wiley & Sons.

Borenstein, S., 2008. The market value and cost of solar photovoltaic electricity production.

Construction, L.C., 2010. Innovation and Growth Team. HM Government: London, UK.

Dixit, M. K., Fernández-Solís, J. L., Lavy, S., & Culp, C. H. 2010. Identification of parameters for embodied energy measurement: A literature review. Energy and Buildings, 42(8), 1238-1247.

Emissions, B.Z., 2013. Zero Carbon Australia Buildings Plan. Melbourne: Melbourne Energy Institute, University of Melbourne.

Goswami, Y. 2004. Transitioning to a Renewable energy Future. Refocus, 5(2), 60.

Hui, S. C. 2010. Zero energy and zero carbon buildings: myths and facts. In Proceedings of the International Conference on Intelligent Systems, Structures and Facilities (ISSF2010): Intelligent Infrastructure and Buildings. Asian Institute of Intelligent Buildings (AIIB). 

Khan, K. H., Rasul, M. G., & Khan, M. M. K. 2004. Energy conservation in buildings: cogeneration and cogeneration coupled with thermal energy storage. Applied Energy, 77(1), 15-34.

Lewis, N.S., 2007. Powering the planet. MRS bulletin, 32(10), pp.808-820. 

Martchek, K. J. 2000. The importance of recycling to the environmental profile of metal products. Recycling of Metals and Engineered Materials, 19-28 

Steg, L., 2008. Promoting household energy conservation. Energy policy, 36(12), pp.4449-4453.

Van den Bergh, J.C., 2008. Environmental regulation of households: An empirical review of economic and psychological factors. Ecological Economics, 66(4), pp.559-574.