Q1. With diagrams describe the ways that the human body gains or loses heat to its environment. Explain how these mechanisms work. (20 marks) Before highlighting the impact the environment has on the human body, individuals taken into consideration that the human body is able to produce heat without influential factors such as the environment or the temperature. The foods consumed by humans are transformed into metabolism also known as energy. Throughout the digestion process the human body gives off heat. Scientific research has identified that 80% of energy attain by eating food is dispersed as heat whereas the other 20% energy can be consider as beneficial. There are two (2) types of the metabolic processes within the human body: • . Muscular Metabolism: Muscular Metabolism is also known as the total distribution of energy that our bodies allocate whilst in an active environment. At this point of time our bodies are bodies deconstruct the consumed foods and digest them into energy. In active environment our bodies’ heat levels increase because they’re over working to produce sufficient energy in comparison to an inactive environment where our bodies are still and relaxed. • Basal Metabolism: Basal Metabolism is also known as the total distribution of energy that our bodies allocate while relaxing or resting whereby the digestive system is inactive. The human body can gain and/or lose heat depending on the environment. The environment affects our bodies through the following processes examined below. • Evaporation – The human body heat levels can be lost from both respiration and perspiration. Respiration is process where “Breathing” disperses all the hot oxygen/air and tries cool down and relax the body. Whereas, perspiration is process where the body releases water also known as “Sweat” releasing all the trapped heat from the active body. • Evaporation is defined as the transformation of water from liquid to gas. High levels of humidity in the environment limiting evaporation from allowing the body to cool down and give off heat. Due to the decreased levels of evaporation water vapour becomes absent through the lungs and skin impacting breathing and humidity levels. • Conduction – The human body can either gain and/or loses depending on its interaction with various surfaces and objects. Heat levels vary due to the certain materials conductivity level. Transfer of heat is minimal within conduction as the human body is generally cloistered clothes and shoes. A good example of losing heat is when some individual walk around bare foot on a tiled or concreted surfaces this will be lead heat lose and cold feet. In comparison to carpet, tiles and concrete surfaces generally don’t absorb any heat because of their low conductivity level. • Convection – The motions and movements of air currents that our bodies are subjected to help generate heat. Whilst the human body is also subjected to persistent outside cool air which helps cool us down, our body’s reach certain limit whereby the energy becomes lost and can no longer be recovered. This loss of energy from our bodies become inaccessible. This cool air that replaces high temperatures (heat) within our bodies is triggered by winds and/or mechanical fans that may be present and increase convection onto the human body. Where the temperatures are seen to be high, convective cooling becomes inexistent amongst the human body and the body temperature increases due to the excessive heat temperatures • Radiation – Unlike convection and conduction heat can transfer and does not need any contact between the human body and the surface. During radiation, heat is discontinued by infrared radiation. Heat may be radiated to and from the body to either cool down of heat up the human body although this is dependent on the surfaces and surroundings of the atmosphere. Fire and/or sun exposure is a perfect example where the human body heat levels increase, whereas snow or cold walls of a home will cool and cause heat loss in the human body. Heat loss has been researched and identified to occur in the following percentages: - Radiation – 45% - Convection – 30% - Evaporation – 25% Q2. For an uninsulated brick veneer house in Sydney in winter describe the main paths of heat loss to the outside air. (Hint: Use a diagram showing a section through the building) (20 marks) The main purpose of a building is to allow for cool temperatures in summer and warm temperatures during winter for residents. During the winter season, a brick veneer home encounters a higher level of heat loss through the external walls, in Sydney locations. Furthermore, these heat loss paths have been identified in through the following: • Ceiling (25% - 35%) – It has been discovered that ceilings/roofs of homes discharge nearly 25-35% of heat to the outside air. In saying that, it also has been discovered that the roof/ceiling is also the most susceptible section within the house to heat discharge. The reason why the ceiling is more vulnerable to heat losses is because the heat has the tendency of rising whilst the course of convection begins to take place during winter. Convection is the course whereby movements of groups of molecules inside fluids are hotter which causes denser materials to sink into the house and less denser materials to raise in cold conditions due to the physics behind gravity. Brief Comparison: Throughout the summer, the roof of a dwelling draws an extra 25-35% of heat compared to the other seasons. In comparison to the rest of the house, the ceiling is the most exposed to the sun, resulting in a greater solar heat being generated. In order to stabilise radiant heat gained and lost, insulation is fitted commonly between joists in the ceiling. • Walls (15% - 25%) - It has been discovered that brick veneer walls of homes discharge nearly 15-25% of heat to the outside air. It is highly recommended to all residents that their homes should be appropriately insulated. Insulating a home safeguards tenants from the freezing outdoor weather which external brick suffers from. If walls are not insulated correctly residents may experience a chilly household because the external bricks become cold and grip all the heat flow from the home. Brief Comparison: A percentage rating of 15-25% is evidently applicable during the season of summer where the bricks used for the structure attract the heat. Where insulation is integrated within the walls of the structure, a reduction of heat flow will take place due to the absorption using this material. • Air Leakage (15% - 25%) - It has been discovered that air leakages discharge nearly 15-25% of heat to the outside air. Throughout the winter season, the cold air travels through the brick work and ultimately finds its way through windows/doors and any sort of holes and/or gaps within the home which provides a pathway for heat to escape the house. Bedrooms that don’t have any direct sunlight will also “drain” solar heating out of the structure. They must built out of lightweight materials or can be heated erratically. The cave effect will take place when tall mass walls within shaded area absorb up heat and ultimately discharge out of the building. Brief Comparison: Summer is known for its extreme temperatures which affects our building infrastructure. The walls situated within our homes absorb a heat gain rating of approximately 5-25% in contrast to the winter season of approximately 15-25% heat loss. Within the scorching summer seasons our homes are susceptible to strong sunlight which enter our homes and are absorb within the walls. This absorption increases the heat temperature whilst reducing air leakage within our homes. • Windows (10% - 20%) - It has been discovered that the windows within a home discharges nearly 15-25% of heat to the outside air. Heat loss/gain is vital throughout windows because of their low thermal resistance which the sun penetrates. Convection allows heat to be loss through a window. Heated air still has the ability to come into with cooled glass at the top end of the window, even if a curtain was to be installed. Once the air is cooled it becomes thicker and increases. The cooled air is substituted with hotter air close to the roof/ceiling and convection is made apparent. Brief Comparison: A percentage rating of 10-20% is evidently applicable during the season of summer. A gyprock formed or prefabricated pelmet is used to prevent heated air reaching the top end of a window. Windows which are shadowed by pelmets do not only effective in the winter but also highly effective during summer. Even though heat can still access the home, the air will limited to its travel path and wont able to travel behind the curtain and throughout the rest of the room. Another way of reflecting heat away from a window is with the use of light-coloured backings which are highly useful. All curtains around the windows must be shut to minimize heat exiting the home during cold winter nights and to minimize entering during the hot summer days. • Floor (10% - 20%) - The floor within the house has been identified to release approximately 10-20 percent of heat to the outside air. Un- insulated floors are susceptible to losing heat through the perimeter during winter, precisely when heat storage is needed. Brief Comparison: A percentage rating of 10-20% is evidently applicable during the season of summer where the floor used attract the heat. Where insulation is integrated within the floors of the structure, the heat inflow will increase within the floor safeguarding the floor from the cold. Many flooring systems include conduction (i.e. carpet) that assists in preserve heat in the floor. Q3. Do a quick calculation of the thermal conductance (U value) across a cavity wall consisting of: • •Outer skin 110mm brickwork (South facing, exposed aspect) • •30mm cavity • •Inner skin of 90mm studwork The necessary data can found in module 5. Compare this with the worked example of an insulated brick veneer wall in the worked example. Show your working. Discuss whether or not cavity brickwork is a thermally efficient wall for housing in Australia. (20 marks) Data/Notes: • Thermal conductivity of brickwork = 1.22 W/m.oC • Thermal resistance of 10mm plasterboard = 0.06 m2.oC/W U = 1/Rt Brickwork Thermal Conductivity = 1.22 W/m.oC (Thermal conductivity is given in the notes) Resistivity - Kb = 1/1.22 = 0.09 m2.oC/W External Resistance From Table 2: the external conductance fo = 81.20 W/m2.oC; the internal conductance fi = 8.12 W/m2.oC Ro = 1/fo = 1/81.20 = 0.0123m2.oC/W Internal Resistance Ri = 1/fi = 1/8.12 = 0.123m2.oC/W Cavity Resistance 30mm Cavity (not shown on table 3) 30mm = 0.152m2.oC/W (Based on interpolate) Worked interpolate example; 20mm = 0.151 30mm = x 40mm = 0.153 0.153 - 0.151 = 0.002 0.153 - x = 0.153 - x / 0.002 = 10/20 x = 0.153 - (0.002 x ½) x = 0.153 - 0.001 x = 0.152. Plasterboard Resistance Thermal Resistance of 10mm Plasterboard = 0.06 m2.oC/W (Thermal Resistance is given within the notes) Rp = 0.06 m2.oC/W Insulation Resistance Insulation Resistance found from Worked Example Diagram. Rinsul = 2.5 m2.oC/W Total Thermal Resistance Rt = 0.09 + 0.0123 + 0.123 + 0.152 + 0.06 + 2.5 =2.9373m2.oC/W Therefore: U = 1/Rtotal U = 1/ 2.9373 U = 0.34m2.oC/W Q4. Describe some strategies for passive solar cooling in hot dry climates. (Hint: Use diagrams) (20 marks) Passive solar design is identified as the use of the sun's energy (radiation) for the heating and cooling of living areas within a building. Passive solar design concentrates on taking advantage of the natural energy and air created by exposure to the sun. Passive solar design when constructing a building is crucial to preventing high electricity bills and greenhouse emissions caused by the use of Air-conditioners. Passive solar design looks at the following practices required to achieve maximum efficiency and effectiveness when designing and constructing a building: • Thermal Mass. • Bulk Insulation. • Equator – facing glazing (North in Australia). In passive solar building design, windows, walls, and floors are made to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer. Thermal Mass Thermal mass is the ability of a material to absorb and store heat energy. A lot of heat energy is needed to change the temperature of high-density materials such as concrete, bricks and tiles: these materials have high heat storage capacity and are therefore said to have high thermal mass. Lightweight materials such as timber have low thermal mass. Thermal mass can be broken down and identified into two aspects; Artificial Thermal Mass – The following materials within a building have been identified to store large amounts of heat storage within and are vital to incorporate to help achieve thermal mass. Artificial thermal mass is concentrated and arisen from the external temperatures and weather (sunlight etc.). - Concrete Flooring: The concrete floor slab of the structure must have a high reflectance (i.e. light-coloured) if heavyweight walls and a low reflectance (i.e. dark-coloured) if the walls are lightweight. Having bright coloured floors will redirect solar heat to high mass walls where the walls will store that heat. If the slabs isn’t insulated correctly the heat will escape through the perimeter especially during winter. Whenever heat needs to be stored the whole slab needs to be correctly insulated around its boundary. - Masonry Walls: Any room which is attracting a lot of direct sunlight must have a large wall surface area. The room must also contain large/high windows to increase the penetration of sunlight into the room. All high windows are recommended to have insulated window shutters to minimise heat loss which occur at night. Rooms which do not have any direct sunlight will drain out the solar heating of the structure. Rooms without direct sunlight should incorporate lightweight construction features and should be heated on occasion. - Rock Bins: Rock bin storage utilizes waste space under the building. They can be used on a steeply sloping side where the basement space would be under-utilised. The system uses two rock stores. In summer, excess heat is channelled from the building into Rock Store 1. Air is blown through Rock Store 2 and into the building to cool the occupants. In winter, air is blown through Rock Store 1 and into the building to warm the occupants. The Rock Store 2 is replenished by drawing air in from the exterior on winter nights. - Roof Ponds: Roof ponds can be specified and incorporated within a house to help increase the thermal mass of a building. The system is very effective because water is a very good thermal mass material and the roof collects the most solar radiation of any surface. At night times, the pond can be covered to prevent re-radiation of the stored heat back out into space. Natural Thermal Mass – Natural thermal mass is identified as the process of using earth’s natural environment and habitats to help heat and cool a building during winter and summer. - Slab on ground: Slab-on-ground construction is now the industry standard in Sydney. It has replaced timber flooring. Although concrete slabs provide excellent thermal mass and a ready base for further construction activities, the method has problems with termite control and damp proofing. - Earth Sheltered houses: Provided the building is sited so that glazing faces the equator (north in Australia), an earth-sheltered house can also gain benefit from passive solar heating in winter. Rooms must be kept shallow to ensure adequate natural day lighting. In comparison to slab-on-ground construction, waterproofing and drainage of the building is even more difficult. The structure of the building must be reinforced to support the weight of the earth above. Ventilation can also be a problem since the building is low in the ground and cross - ventilation is almost impossible to achieve. - Earth Berming: Structures can be positioned against an earth embankment. The embankment alleviates temperatures within the building because ground temperature don’t fluctuate much through the yearly seasons - Ground Coupled Plenums: An air plenum can be installed underneath the structure to assist in cooling the building down. Air travels into the plenum, it is then cooled by interaction with the earth beneath the structure. As the collected air goes into the building, the building is then heated. The heat will then rise and discharge from the windows situated at the top of the structure. Bulk Insulation Insulation acts as a barrier to heat flow and is essential for keeping a building warm in winter whilst cool in summer. It can also help with weatherproofing and soundproofing. A well-insulated and well-designed building provides year-round comfort, cutting cooling and heating bills by up to half and reducing greenhouse gas emissions. Climatic conditions determine the appropriate level of insulation as well as the most appropriate type to choose — bulk, reflective or composite. The most economical time to install insulation is during construction. Bulk insulation is typically installed in ceilings, walls and can be found in the floor. It works by restricting the transfer of heat between the inside and outside of a building. The millions of air pockets in glasswool and polyester insulation helps restrict the transfer of heat through the insulation batt. When insulation is installed within the walls, ceiling and floor, bulk insulation helps to prevent and reduce the hot air in the roof space or from the outside of the house from entering into the habitable living areas of the house. In cold weather, bulk insulation ensures that the heated air inside the home doesn’t escape unhindered through the walls and up into the ceiling space. Installing a thicker or higher R-Value bulk insulation will increase the amount of thermal protection, i.e. less heat will escape during the night and in the colder months of the year, and less heat will penetrate from outside in the hotter summer months. Equator – Facing Glazing Shading of your house and outdoor spaces reduces summer temperatures, improves comfort and saves energy. Direct sun can generate the same heat as a single bar radiator over each square meter of a surface. Effective shading — which can include eaves, window awnings, shutters, pergolas and plantings — can block up to 90% of this heat. Shading of glass to reduce unwanted heat gain is critical, as unprotected glass is often the greatest source of heat gain in a house. However, poorly designed fixed shading can block winter sun. The most effective shading and glazing of a building are identified below. Orientation Natural sunlight can be the worst enemy of any house owner as it can create unnecessary heat in a room if reflecting on a window, wall or roof. For this reason it should be known that natural sunlight light rises in the East and sets in the west on the North hand side. Therefore in understanding this, the orientation of the building is critical. The orientation of the building must consider the following; - Number of windows and positioning of windows to allow sunlight within. (Cross-ventilation) - Location of habitable rooms to ensure they receive natural lighting and air. - Insidious trees will help provide shading to the building. - Incorporating eaves/pergolas to help reduce sunlight. Glazing Double-glazing commercial framed windows provide a great form of installation that insures heat does not escape through windows whilst reducing the amount of heat that enters the windows. Double Glazing is universally known to dramatically reduce heat transmission through the glass window. The common and most significant advantages that doubles glazing provides are: • In the summertime, double-glazing prevents most of the sun's heat radiating into the building. • In the wintertime, the energy that was created on the inside of the property does not go to waste and stays within the building. • Double-glazing has an all year round of excellent sound insulation but is most effective with heat installation. Skylights are another option of glazing as they are an excellent source of natural light, perhaps admitting more than three times as much light as a vertical window of the same size, and can improve natural ventilation. However, they can be a major source of unwanted heat gain in summer and heat loss in winter. Awnings, Pergolas and Eaves Incorporating awnings, pergolas and/or eaves within a building will help reduce unnecessary lighting from heating the inside of the building. Although it may be efficient to incorporate as much sunlight within a building as possible, too much sunlight will increase the het flow within the building and cause hot temperatures. The three possible shading options help provide shading to windows which helps keep the interior of the house at a comfortable temperature. Windows are responsible for much of the heat that's transferred in and out of a home, and strategically placed shading controls will help to ensure that sunlight enters through windows during winter, whilst providing shade from the sun during summer. Well-placed shading controls can have a very significant effect on the climate control costs of a house. Q5. Describe how a solar pergola can be designed to manage the entry of direct sunlight into a building in a location like Sydney. (20 marks) It has been noted that the installation of pergolas is the most effective way to regulate sunray courses into a home. The shelter/shading given by the pergola assist in improving internal building temperature. Installing a pergola on the northern side of a home during summer minimizes sunlight from the windows and walls of the house. Generally the height of pergolas are increased during the winter to provide sunlight access from beneath the pergola because winter sun is position much lower in the sky. Installing additional pergola accessories such as angle blades will assist in lessening altitude summer sunlight while still providing the low winter sunlight to enter the blades and onto the building. Prior to installing any of the angle blades they must have custom design to ensure the width and thickness are made correctly to provide the appropriate shading effect. The angle blades must overlap approximately 25% to work correctly. There is a variety of pergolas systems which can be used to assist in providing weather protection and brilliant shading one of the being solar powered pergolas. Although, it must be noted that even though solar powered pergolas are effective in reducing sunlight and energy within the home, the pergolas aren’t translucent and therefore block out the sunlight from entering within the pergola even during the winter season. This is not efficient in allowing sunlight into the house. References • Cole, G. 2002. Residential passive solar design. Environment design guide, GEN 12. Australian Institute of Architects. [ONLINE] Available at: www.environmentdesignguide.com.au [Accessed 10 April 2017]. • Department of the Environment, Water, Heritage and the Arts (DEWHA). 2008. Energy use in the Australian residential sector 1986–2020. Canberra. [ONLINE] Available at: www.energyrating.gov.au [Accessed 11 April 2017]. • Insulation Council of Australia and New Zealand (ICANZ). 2007. Insulation handbook, Part 1: Thermal performance total R-value calculation for typical buildings. [ONLINE] Available at: www.insulation.com.au [Accessed 10 April 2017]. • Luther, M. 2007. Air leakage in buildings: review of international literature and standards. Environment design guide, TEC 23. Australian Institute of Architects, [ONLINE] Available at: www.environmentdesignguide.com.au [Accessed 11 April 2017]. • Sustainable Energy Authority Victoria (SEAV). 2006. Energy smart housing manual. Sustainability Victoria. [ONLINE] Available at: www.aprbuildingservices.com.au [Accessed 10 April 2017]. • Turner, L. 2004. Home insulation buyers guide. ReNew, 88. [ONLINE] Available at: http://renew.org.au. [Accessed 12 April 2017]. • Mosher, M & McGee, C. Insulation | YourHome. 2017. Insulation. [ONLINE] Available at: http://www.yourhome.gov.au/passive-design/insulation. [Accessed 15 April 2017]. • Reardon, C. 2013. Thermal mass | YourHome. 2013. Thermal mass | YourHome. [ONLINE] Available at: http://www.yourhome.gov.au/passive-design/thermal-mass. [Accessed 15 April 2017].