Energy in Buildings Haroon Junaidi Energy consumption in

Energy in Buildings Haroon Junaidi

Energy consumption in Buildings • Buildings consume up to 40% of the produced energy in US/UK. • 30 % Portion of energy in buildings used inefficiently or unnecessarily 1 • One sixth of all water pumped out of natural flows are consumed in buildings. One quarter of all virgin wood harvested ends up in buildings. And this does not account for all the interior wood furniture • Combined percentage of U. S. greenhouse gas emissions generated by commercial buildings (17 percent) and industrial facilities (28 percent): 45 percent 2 • In Bangkok, a new office building uses 80% less energy than a comparable building, while the ING bank headquarters in Amsterdam uses ten percent the energy of its predecessor. • The Canadian outdoor company Mountain Equipment Coop recently built a new retail outlet that used 50% recycled material by weight. And the Vancouver Island Technology Park diverted 90% of construction from the landfill. The impacts of these projects illustrate the solutions exist in all regions of the planet. 1. U. S. Environmental Protection Agency, ENERGY STAR program. “Useful Facts and Figures. ” No date referenced. 1 June 2007 http: //www. energystar. gov/index. cfm? c=energy_awareness. bus_energy_use 2. Inventory of U. S. Greenhouse Gas and Sinks: 1990 -2005. “USEPA #430 -R-07 -002, Table 2 -16: U. S. Greenhouse Gas Emissions by Economic Sector and Gas with Electricity-Related Emissions. ” April 2007. 14 June 2007 <http: //www. epa. gov/climatechange/emissions/usinventoryreport. html>.

Energy Loss in Buildings • Walls: The majority of heat loss from a building occurs through the walls, as the largest surface area. This is dependent on building material, wall construction and level of insulation. • Roof: Approximately 25% of heat loss from a building is through the roof. This is dependent on roofing construction, roofing material and insulation. • Windows: Between 10 -20% of energy loss from a building is through windows. This is dependent on type, material, draughtproofing and glazing. • Doors: Approximately 15% of energy loss from a building is through doors, as a large opening.

Retro-fitting Considerations • Traditional buildings require approximately twice the amount of ventilation of modern buildings; moisture moves through traditional buildings until it evaporates. • Modern, impermeable building products obstruct this process with the aim of keeping moisture out, which works in modern buildings specifically designed to keep moisture out, but is damaging in traditional buildings that require higher levels of ventilation. • The introduction of modern materials and methods (such as u-PVC and doubleglazing) in traditional buildings is counter-productive because they restrict air flow, trapping moisture inside, accelerating decay

Thermal Inertia • A measure of the responsiveness of a material to variations in temperature. The term is used in building industry. • In remote sensing it is measured by diurnal changes in temperature. Materials with a high heat capacity display high thermal inertia, consequently such materials will show small changes in temperature through the diurnal cycle. • Thus buildings with high thermal inertia tend to even out the ambient thermal changes and require less energy to bring the internal temperature in the comfort range Mud, which was the choice of material for dwellings in rural areas in third world provide high thermal inertia and thus reduce the need of heating or cooling •

Thermal Inertia If the right materials are used it is possible to even out the extremes of temperature of the external environment through a combination of high thermal mass, low thermal conductivity and high thermal inertia. The graph below shows how the peaks of the highs and lows are evened out to a more constant internal temperature Source: http: //www. ecademy. com/node. php? id=143919

Historic Building Codes • Building codes have a long history. What is generally accepted as the first building code was in the Code of Hammurabi which specified: – 229. If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death. – 230. If it kills the son of the owner, the son of that builder shall be put to death. – 231. If it kills a slave of the owner, then he shall pay, slave for slave, to the owner of the house. – 232. If it ruins goods, he shall make compensation for all that has been ruined, and inasmuch as he did not construct properly this house which he built and it fell, he shall re-erect the house from his own means. – 233. If a builder builds a house for someone, even though he has not yet completed it; if then the walls seem toppling, the builder must make the walls solid from his own means.

DEC and EPC • The Scottish Building Standards Agency (SBSA) is responsible for delivering the Scottish building standards system • Every time a dwelling is either purchased or rented by a new occupant, it is a legal requirement to provide that occupant with an energy performance certificate (EPC) • DEC (Display Energy Certificate) to be displayed in buildings larger than 250 m² that are occupied by a public authority EPC (Energy Performance Certificate) to be displayed in commercial buildings larger than 250 m² that (a) are frequently visited by public and (b) where an EPC has previously been produced on the sale, rent or construction of that building • The energy performance of existing buildings of any size that undergoes major renovations to be upgraded in order to meet minimum energy performance requirements. Currently, there is a threshold of 1, 000 m² • Minimum energy performance requirements to be set in respect of technical building systems, e. g. boilers, air-conditioning units etc

DEC and EPC • The Energy Performance Certificate (EPC) is part of a series of measures being introduced across Europe to reflect legislation which will help cut buildings’ carbon emissions and tackle climate change. • Display Energy Certificates (DECs) show the actual energy usage of a building, the Operational Rating, and help the public see the energy efficiency of a building. This is renewed on an annual basis

DEC and EPC • For public buildings a DEC (Display Energy Certificate) will be required, for other commercial property, an EPC is required • The differences between the two certificates is distinct. A Commercial EPC is similar to a domestic type, whoever the energy assessment method used is wholly different. • A Display Energy Certificate (DEC) carries an Asset Rating and an Operational Rating • Display Energy Certificates are valid for 1 year and must be renewed annually. • Commercial EPC's are valid for 10 years. If the property is resold during this time a new EPC will be required.

Building Standards in Scotland • To improve the design, building standards then places a number of constraints and backstops on the design of the actual dwelling. These include: – Maximum average U-values for the main building elements. – Maximum air leakage rates. – Limiting heat losses through non-repeating thermal bridges (Standard 6. 2) – Discourage inappropriate trade-offs, such as using renewable energy generation to compensate for poor levels of insulation

Zero Energy Buildings • If a building has a net Carbon emissions of zero annually it is termed as a Zero energy building. Although there are several varying definitions of Zero Energy Buildings • Buildings consume up to 40% of the produced energy in US/UK. • Huts, tents, yurts, mud houses are all zero energy building out of necessity because of the inaccessibility to electricity in the third world • Zero energy Buildings produce their own energy through wind energy from a nearby site or through solar energy and efficient glazing and HVAC systems. • In the December 2006 Pre-Budget Report, then UK Government announced their 'ambition' that all new homes will be 'zero-carbon' by 2016 (i. e. built to zerocarbon building standards). To encourage this, an exemption from Stamp duty land tax is to be granted, lasting until 2012, for all new zero-carbon homes up to £ 500, 000 in value. http: //www. bbc. co. uk/programmes/p 01 k 6 stl •

Draught-Proofing-I • Research shows that up to half of all heat loss in buildings can be due to unintended air leakage and uncontrolled ventilation • Insulation levels have increased substantially over the last few decades, but heated air is still escaping and can be pinpointed as a major source of energy loss. • Uncontrolled ventilation also lets moisture to escape and sometimes get trapped by walls resulting in with it which results in damp, mildew, rot and condensation • The climate of the UK does not expose us to extremes in temperatures but we are exposed to extremes in wind pressure, especially in coastal areas. • While insulation is central to low energy construction, air and wind-tightness must also be central to an energy efficient design strategy to reduce unnecessary heat loss. • The current UK building regulations allow for a hole the size of a 20 p in every square metre of the building fabric - this leads to all sorts of problems.

Draught-Proofing-II • Traditional buildings may be over-ventilated and draught-proofing is one of the best and least intrusive ways of improving comfort, reducing heat loss and also reducing noise and dust ingress. Windows, doors, letter boxes, loft hatches and even cat flaps can let cold air in, so can all be improved by draught-proofing. • If carried out carefully, many draught-proofing measures are compatible with the principles of building conservation because they are typically reversible with few lasting consequences and no loss of historic fabric. • Draught-proofing may require prior Listed Building Consent, but is a solution welcomed to improve energy conservation in traditional buildings with original or traditional windows. Using existing shutters can also help cut down heat loss through windows.

HVAC • As much as half of the energy used in your home goes to heating and cooling. • Using programmable thermostats, that would help control the heating in the vacant periods for the dwelling. • Ducts that move air to-and-from a forced air furnace, central air conditioner, or heat pump are often big energy wasters. Sealing and insulating ducts can improve the efficiency of your heating and cooling system by as much as 20 percent — and sometimes much more • The use of Heat pumps can reduce the heating cost by up to three times. • Heat pumps can be used for both heating and cooling. Some of the Newly designed heat pumps have the COP between 3 -6. • A COP of 3 implies for every 1 unit of energy (k. Wh) given to the compressor 3 Kwh of heat is returned. Heat pumps can be ground source or air sourced. • At depths of 3 meters from the surface, even at Northern latitudes, temperatures of 10 -15 °C can be expected. This makes a consistent heat source for heat pumps

Air Heat Recovery System

Thermal Conductivity “k” • Thermal resistance, usually denoted by “k”, is a measure of the permeability of a material for heat. While thermal resistance “R” is the measure of permeability of heat transfer • The thermal conductivity of an object can change sometimes if it has the ability to hold moisture • Objects that are good conductors of electricity are also good conductors of heat • The total Thermal resistance depends upon the materials as well the thickness • Thermal resistance of object that are placed perpendicular to the direction of heat transfer can be added directly

Thermal Resistance Analogy • Thermal resistance is analogous to electric resistance. Resistance in series can be added • When thermal resistances occur in series, they can be directly added. So when heat flows through two components each with a resistance of 1 °C/W, the total resistance is 2 °C/W Air Tiles Wall Air

Thermal Resistance for different building materials Cementitious foam m. K/(W) 9– 18 Perlite loose-fill 12 Wood panels, such as sheathing 11 Vermiculite loose-fill 10 – 11 Vermiculite 10 Straw bale 7 Softwood (most) 6. 3 Wood chips and other loose-fill wood products 4. 6 Snow 4. 6 Hardwood (most) 3. 0 Brick 0. 76 Glass 0. 61 Poured concrete 0. 36

U-Value • To simplify the estimation of heat loss, U-values are used instead of thermal resistance. In contrast to thermal resistance, U-value is the measure of permeability of heat loss from a given area from an object taking material thickness into account. • Although they are both measure of heat permeability but U-value is different from thermal conductivity “k”, which only deals with conduction inside materials. • In U-values both conduction and convection across the object is taken into account • U-values are generally available for building materials and help engineers estimate what the total heat loss

Typical U-Values

Glass for Buildings The properties for glass required are: – – – – Optical clarity Flatness Maintain thermal inertia i. e. retain heat in winters, and block heat in summers Block noise Transmissivity (τ) Absorbtance (α) Thermal Resistance

Types of Glasses • There are several types of glass. The glass used in modern buildings have to follow the safety standards. • Three types of Glass relevant to energy conservation and renewable energy are: – Toughened Glass – Glazing Glass – Low Iron Glass

Glass properties • Glass is most often used where it needs to hold its own weight without bowing. • In some cases it has to hold additional weight, for example glass stairs • Toughened Glass or Tempered Glass is used in a variety of application and has great mechanical strength compared to ordinary glass. Moreover toughened glass is will usually shatter in small, square pieces when broken • Tempered glass is manufactured through a process of extreme heating and rapid cooling, making it harder than normal glass due to residual stresses • Lethal injuries can be caused by broken glass and thus British Standards for safety glazing ensure that the glass used in building breaks safely • Most solar energy based applications used to generate electricity or heat use specialized glass with greater transmittance than ordinary soda lime glass (window glass). This glass is more commonly known as Low Iron Glass

IGU –Insulated Glass Units • Double and Triple glaze window significantly reduce the overall U values of the structure • High glazing area can provide not only allows adequate light but also heat • Thermal performance is also improved by replacing the air between the panes with a heavy gas that is more viscous than oxygen and nitrogen. Higher viscosity reduces movement and thus convective heat transfer. – – U-values of Windows Plastic & Metal ( U-value =2. 2 ) Wooden Frame Glazing U-values = 2. 0 While most double glazed windows have U-Value =1. 6 Triple Glazed windows are available with U-value = 0. 7

BIPV • Much less expensive compared to conventional PV • Solar Tiles/ Solar Shingles available now can be used instead of normal roof slate • For flat roof due to “Thin film technology” cheap, flexible and modular solar panels available. These are integrated to a flexible roofing membrane and thus not only cater for roofing materials but also provide electricity • Skylights and windows can be replaced by semi transparent PV modules • Whole Facades of building can be covered by PV module to give it a futuristic look and also provide substantial amount of energy • If BIPV is incorporated in the design phase it will save additional money for material and labour that will be required in case of retrofitting

Investigate “smart glass” technology

Thermal Bridging In a building that is not properly insulated, thermal bridges represent low comparative losses (usually below 20%) as total losses via the walls and roof are very high (about >1 W/m 2 K). However, when the walls and roof are very well insulated, the percentage of loss due to thermal bridges becomes high (more than 30%) but general losses are very low (less than 0. 3 W/m 2 K). That is why in low energy consuming buildings, it is important to have very high thermal resistances for walls and roofs to have low heat losses via the junctions

Thermal Bridging • A Thermal Bridge is a thermally conductive material which penetrates or bypasses an insulation system; such as a metal fastener, concrete beam, slab or column • Heat will flow the easiest path from the heated space to the outside - the path with the least resistance. And this will not necessarily be the path perpendicular to the surfaces. Very often heat will "short circuit" through an element which has a much higher conductivity than surrounding material, which can be described as a thermal bridge. • Typical effects of thermal bridges are: – Decreased interior surface temperatures; in the worst cases this can result condensation problems, particularly at corners. – Significantly increased heat losses. – Cold areas in buildings

Thermal bridge caused by structural beam below balcony window Courtesy: REN Solutions

Insulation Material – Blankets - Batts or Rolls: Rock wool and Fiberglas. – Loose-Fill (blown-in) or Spray-applied materials: Rock wool, fibreglass, cellulose, and polyurethane foam – Rigid Insulators: Extruded polystyrene foam (XPS) Expanded polystyrene foam (EPS or bead board) Polyurethane foam Polyisocyanurate foam – Reflective Materials: Foil-faced paper Foil-faced polyethylene bubbles Foil-faced plastic film Foil-faced cardboard

Influence of Microclimate on Building Design • The micro climate is the variations in localised climate around a building. • The microclimate has a very important impact on both the energy and environmental performance of a building. • An ideal site for the designing an energy efficient home would be one that has full solar access and protection from the harsh elements of nature.

What is a microclimate? The Meteorological Glossary defines a microclimate as: 'the physical state of the atmosphere close to a very small area of the earth's surface, often in relation to living matter such as crops or insects. In contrast to climate, microclimate generally pertains to a short period of time. '

Natural Microclimates • The treetops of a high, dense forest can form an almost unbroken surface, which acts in a similar way to the ground. During the day the tree tops absorb solar radiation, resulting in high temperatures at canopy level. The temperatures decrease downwards, owing to the shading effect of the trees. • Thus, the forest floor is generally cooler than the canopy and the surrounding countryside. In the Summer this temperature difference can be as much as 5 degrees Celsius. At night forests retain their heat and are generally warmer than their surroundings.

Urban Microclimate • The most common microclimate that man has created is the 'urban heat island'. This is used to describe how a city is relatively warmer than the surrounding rural areas. • This can be observed on infrared satellite images in the Summer - major cities can be spotted as darker areas compared to the rest of the country.

Causes for Urban Microclimate • Major towns and cities contain little of the natural environment. In the heart of the city it is rare to see any trees, and the commercial environment consists mainly of concrete. Concrete absorbs heat and re-radiates it slowly much like an electric storage heater. • In rural areas the trees use heat in the process of transpiration, and heat is also used in evaporation from streams and rivers. • High concentrations of pollution cause fog to linger longer than in the countryside. In particularly stagnant conditions 'smog' can form, causing health problems for certain groups, which are at risk

Effect of Micro Climates • A consequence of urban heat islands is the increased energy required for air conditioning and refrigeration in cities that are in comparatively hot climates. The Heat Island Group estimates that the heat island effect costs Los Angeles about US$100 million per year in energy. • Conversely, those that are in cold climates such as Moscow, Russia would have less demand for heating. However, through the implementation of heat island reduction strategies, significant annual net energy savings have been calculated for northern locations such as Chicago, Salt Lake City, and Toronto

• http: //www. bbc. co. uk/weather/features/und erstanding/microclimates. shtml