Sustainable Architecture and Environmental Impact

Sustainability Design Principles

On a global scale, architecture has over the years been found responsible for about 30 % of greenhouse gas emissions and 50% of waste deposits in landfills. To reverse this worrying trend, architects now pay much attention to environmental integrity of buildings. Good designs are seen to improve the quality of life of the occupants while at the same time minimising the negative effects on the dwellers and the environment. Sustainable architecture is achievable by implementation of the following principles.

Solar gain

Solar gain refers to the short wave radiation coming from the sun to heat up a building. The radiation can warm the building directly through a window or indirectly through the building fabric.

Heating

Solar gain is very beneficial for buildings in cooler climates. For hotter climates, solar gain should be minimised so as to avoid overheating of the building. However, the real setting is characterised with varying conditions throughout the day and the year. This means that, for a particular building, solar gain can be beneficial, say in the mornings and evenings and during winter, and be problematic, especially around midday and during summer. In my Black Friairs design proposal, Brise soleil has been fitted over the exterior windows. As can be seen from the excerpt below, much of the Western, South-Western and Southern side is covered with a glass facade. This design makes maximum use of the afternoon sun in Winter season.

During summer, the Brise soleil reflects direct, high level light and thus prevent the building from overheating. During winter, the Brise soleil is able to transmit low level light to the interior of the building.

Heat loss

To prevent heat loss during the cooler months and times, the Black Friairs Project involves use of the Trombe Wall. A Trombe Wall is a thermally massive wall with excellent absorption characteristics. Trombe walls are constructed behind a glazed facade to shield it from outside conditions. The space between the wall and the glazing allows sufficient air movement. Below is a diagrammatic illustration of the action of a trombe wall.

Solar radiation penetrates through the glazing and heats the wall. The wall emits long radiation which cannot pass through the glazing. The stored heat is slowly released into the adjacent spaces. Here is an excerpt of the West elevation of Black Friairs showing the glazing on the outside and the trombe wall on the interior.

Comfort and amenity

Thermal comfort is important in any building so that the occupants do not feel too hot or too cold. To ensure thermal comfort, my Black Friairs Project includes generally large rooms which ensure adequate air circulation even when the rooms are packed to capacity. Here is a sectional view clearly showing the occupants of Black Friairs operating in comfort.

Site location and Layout

Sun Path Analysis

Sun path analysis for any site is an important tool in determining the building orientation, spatial arrangement, window placement, and daylight access. Knowledge of the impact of the sun on a building helps the designer maximise the use of passive solar design features and therefore increase the energy efficiency of the building.

To assess the site of my Black Friairs Project, I used a combination of three tools - physical site visit, the SolarView online tool and the shading feature in SketchUp. The resulting sun diagrams provided a detailed overview of the path of the sun at different times of the year and day, as well as the effect of shadows cast by the buildings, trees and other landforms around the site. Below are simulations of the sun effect on the building between 9 am and 3 pm at Summer Solstice.

It is evident that the glazed facades of the main building receive adequate sunlight between 9 am and 3 pm. No significant shadow is cast on the glazing for the whole duration of this period.

The two images below show the effect of the sun at Equinox.

Like for the Summer Solstice, no significant shadow is cast on the glazed facades between 9 am and 3 pm.

Finally, the two images below depict the effect of the sun at Winter Solstice.

The sun may be at a low angle during this time, but it nevertheless shines on a fairly big section of the glazed facade for the better part of the day.

The Black Friairs main building can be said to be optimally located in relation to the sun’s path.

Sun Path analysis also helped in determining the orientation of my proposed Black Friairs development. The main requirement for this commercial development is passive heating during the winter months.

The ideal orientation for my Black Friairs Project is 20 degrees west of North.

Provision of adequate spacing to minimise overshadowing

Adequate spacing should be included between buildings to minimise overshadowing, especially in winter months when the sun is at a lower angle. The general solar criteria aims at ensuring over 70% of apartments in a building receive at least 2 hours of direct sunlight between 9 a.m. and 3.00 p.m., and that 50% of the main communal open spaces should receive 2 hours of direct sunlight between 9 p.m. and 3.00 p.m.

To minimise overshadowing, adequate space has been left between all buildings in my Black Friairs Project. The main is building is 4 storeys high. From the sun path analysis diagrams presented above, there is no significant shadow cast on the glazed facade of the building whether at summer solstice, fall equinox or winter solstice. There exists a tower to the south of the building. The tower is taller than the main building. To avoid overshadowing of the building, the tower is tapered towards the top. This way, its shadow is significantly reduced, especially during the winter months.

Solar Panel Implementation

Solar panels should seamlessly be incorporated into the design of buildings so that they don’t seem to be an eyesore to the occupants and the public. For the Black Friairs Project, nearly 100% of the roof area is well exposed to the sun throughout the year. No portion of the roof is significantly shadowed by other surrounding features. Solar panels can therefore be installed throughout the roof to tap renewable energy from the sun.

Prevailing wind consideration

Generally, the prevailing winds in my Black Friairs Project location blow from the South West to the North East for a better part of the year. For this reason, the entire South west face of the building has a glazed facade. The glass is permanently fixed and cannot be opened. This way, the occupants of the building are sheltered from the cold winds.

Both wind speed and wind direction were considered in designing the buildings for wind. The glass facade is strong enough to withstand the highest wind speeds expected. Sheltering by the glass facade was absolutely necessary considering there is no reliable shelter to the South West of the building. Most of the built up area is to the North of the building. There exists a large open field to the South West of Black Friairs. This exposes the building to fast wind speeds.

The Black Friairs project site includes a lot of open space between the buildings. This leaves the flower gardens and free communal spaces free from overshadowing by the tall buildings. The flower gardens will have adequate exposure to the sun all year round.

Building mass/form and orientation

Overshadowing impact of proposed building

As earlier mentioned, the tallest block within the Black Friairs site is tapered towards the top to minimize overshadowing of adjacent buildings. In addition, adequate space has been left between all blocks to increase access to natural sunlight as well as improve the aesthetics of the structures.

Compact Building form vs heat loss

The Black Friairs building exhibits a compact form. With a compact design, the surface area to volume ratio is kept at minimum. This increases the ability of the building in general to keep the heat gained from the sun for longer periods. Winter months will therefore be bearable. The occupants will never complain of extreme cold during the day.

Internal layout

Window orientation

Windows are basically used in buildings to let in natural sunlight and allow proper ventilation of the rooms. A single building can adopt several window design and sizes for different purposes. When the windows are shaded, the rooms will not get very hot during summer. With large overhangs, the heat from the sun is considerably blocked, thus reducing cooling costs.

Since the Black Friairs project site is in the Northern hemisphere, the south-facing windows will receive more natural light all year round. For the East facing windows, the morning sun will readily light up the room, but slight shadows prevail for the better part of the afternoon. For West facing windows, the afternoons can be well lit while the mornings can be a bit shadowy. Regarding solar gain, North and South facing windows absorb less heat because the sun does not shine perpendicularly through the windows. On the other hand, East and West facing windows allow more solar gain into the building because of their perpendicular orientation to the sun’s rays. For the Black Friairs Project, most North and South Facing windows have little or no overhangs - so as to maximize the entry of sunlight and heat into the building. For the East facing windows, the overhangs are strategically sized to prevent summer overheating but allow the winter sun to shine on the windows.

Partitioning of plan

Partitioning a building using masonry is rather permanent and cannot be quickly altered when need arises. Rigid partitioning is also a disadvantage when the building use changes. For instance, the main building in the Black Friairs project can be used for many different purposes, including offices, supermarket, gym, etc. When rigidly partitioned, the use will be very limited. To counter this, the Black Friairs Project has incorporated the multi-use concept for partitioning the main block. Acoustic movable walls are used in this case. With these, the users will quickly be able to transform a selection of smaller spaces into one large area to accommodate a larger group of people. As such, the building can be used for office purposes but be transformed to a hall when there is a larger function. Below is a sectional representation of the three floors of Black Friairs.

Partitions for spaces with high temperature difference

Kitchens generally have higher temperatures than all other rooms. If not properly partitioned, rooms adjacent to the kitchen may suffer from the high heat produced in the kitchen. The best method to prevent the kitchen heat from accessing adjacent rooms is through the use of cavity walls with cork panels between the double walls.

Zone heating system

It would be uneconomical to equally heat up all rooms in a building, including the unoccupied and the empty rooms. A sustainable approach is to create separate heating zones with individual heat control systems. The single zone heating system is the most popular. The thermostat is located in the specific room which needs heating. It measures the temperature of that particular room and regulates the temperatures accordingly through the thermostatic radiator valves.

Window design

Double Glazing

It is suspected that the numerous human activities around the Black Friairs Project location will allow unwanted noise into the rooms. Noise from road traffic and aeroplanes can be quite disturbing to the occupants, especially when in need of quiet working conditions. To counter this, all private offices are designed with triple-glazed windows to keep out the unwanted noise. The social areas have no need of soundproofing. For noise reduction, the appropriate air gap between the glasses is 150 mm.

On top of noise regulation, the multi-glazed windows help in thermal regulation. The sealed air gap is a poor conductor of heat. Therefore, during winter, heat in the rooms will not be easily lost to the outside. In summer, the double glass prevents excessive heat from accessing the interior of the rooms. This reduces over reliance on artificial heaters and air conditioners. For heat control, the appropriate gap is 12 mm.

Window thermal frames

Window frame materials affect the thermal resistance of windows. The best materials are vinyl, wood, fiberglass and some composite materials. For the Black Friairs Project, the windows for private offices have wooden frames. Other windows have vinyl framing. No windows in the entire development are made of aluminium or metal.

Window to floor ratio

The window to floor ratio of a building affects the heat gain and heat loss of the building. In general, the total window area should not be more than 25 % of the total floor area. For the Black Friairs project, the total window area is estimated to be about 22 % of the total floor area. This is an adequate window-to-floor ratio.

Opaque elements

Opaque elements are used in buildings to make them more energy efficient - that is to reduce the use of non-renewable energy sources such as coal, oil and natural gas. The facade walls and floors of buildings play a big role in thermal regulation of buildings. This depends on the material they are constructed of. The heat transfer coefficient helps explain the heat transfer phenomena across different elements. It is defined as the heat flux which crosses a unit area of a given element per unit of time, per unit of temperature difference between the interior and exterior environments.

Different facade solutions have different heat transfer coefficients. Below is a summary of the heat transfer coefficients for different facade materials:

From the figures, straw bales single walls have the best thermal behaviour. Raw Earth Single wall, Stone Masonry Single Wall, and Solid Brick Single walls have the worst thermal performance. The others are intermediate. For the Black Frairs Project, the facade walls are a combination of Masonry brick with the air-box partially filled with thermal isolation and Masonry lightweight concrete blocks with the air-box partially filled with thermal isolation

Airtightness and ventilation

Ventilation strategy

The Black Friairs project has incorporated both natural ventilation systems and mechanical ventilation systems. For the natural ventilation systems, three strategies have been employed.

Single sided strategy - Some of the rooms have windows on only one side. Air gets into the room and exits the room through the same openings.

Cross ventilation strategy - This is achieved by the use of windows on both sides of the rooms. When both windows are open, a current of air passes through the room in the direction of the wind. To optimise the airflow, the windows facing the wind should be opened slightly.

Stack ventilation strategy - For the top most rooms in the building, ventilations are added to the roof in addition to the ventilations on the walls. Warm air rises to the top of the room, creating a slight vacuum. Cold air from outside flows into the vacuum, thus achieving a natural airflow.

For all basements, mechanical ventilation is used to drive out stale air and replace it with fresh air. The Black Friairs project uses a combination of ceiling fans and pressure systems.

Airtight construction

An energy efficient building should have no infiltration when the ventilators are closed. Airtightness of a building is measured by air permeability, which is the air leakage rate per hour per square metre of envelope area at a test reference pressure differential of 50 Pascal. Whenever infiltration occurs when ventilations are closed, a corresponding exfiltration follows somewhere in the building. For instance, during winter, exfiltration can cause condensation on the walls which ultimately leads to moulds and rots. Airtightness is achieved by proper installation of vapour barriers. Exterior air barrier systems involve the use of sheathing membrane, sealed sheathing, and liquid applied membrane. Interior air barrier systems involve use of sealed polyethylene, airtight drywall. All joints within the building should be made airtight by following proper design guidelines as illustrated below:

Air barrier at roof/parapet

Air Barrier at window seal

Air barrier at podium/below grade

Conservatories and atria

My Black Friairs Project incorporates a fairly big atrium in the main block. An atrium is a large glassed area on a building which allows direct sunlight to enter.

The atrium is located between the indoor and outdoor, and thus has a great environmental implication. It also gives the occupants a greater feeling of space and light. The atrium provides a shelter from the external environment but still offers a magnificent visual link with that environment. The halls adjacent to the atrium are ideal for restaurants, where friends wine and dine as they enjoy the explicit outside views. The atrium acts as a buffer space between the interior and exterior of the building. During winter months, the building feels warmer. During summer, the occupants are shielded from the overly high outside temperatures. To achieve optimum results, solar protection material should be used in the glass facade of the atrium. Overheating can result when the glazing is installed without solar protection.

Heating system and controls

Sustainable heating systems in buildings

My Black Friairs Project has incorporated 1 major sustainable heating system - i.e. Solar Power. Some rooms in the main block are fitted with hydronic collectors, which heat liquid to raise the room temperatures. I have also designed for use of solar heating air systems which work in a similar manner to the HVAC system.

Part 2

Passivhaus, CfSH and BREEAM

Passivhaus is the new leading international energy efficient design standard for buildings. Passivhaus aims at construction of buildings with high levels of comfort, lower energy bills, improved indoor air quality and reduced carbon footprint. Passivhaus homes must be ventilated using a mechanical system that pre-heats ventilation air by making use of the heat from stale air as it escapes the house. Strict airtightness must also be observed to prevent the escape of heat.

CfSH is the Code for Sustainable Homes, which is used to ensure that new homes comply to sustainability principles of design. BREEAM is likewise a leading sustainability assessment method for buildings. One notable project that presents a clear use and understanding of the above three principles is the National College for High Speed Rail. Below is an outline of the major design features that make this building highly sustainable:

Strong focus on energy reduction

Highly efficient heating and ventilation systems - combination of highly efficient gas fired plant, ASHP providing Low Temperature Hot Water and Combined Heat and Power.

Underfloor heating to reception areas

Low flush toilets

Water monitoring systems

Leak detection systems

Rainwater harvesting system

Native hedgegrows and wild flowers area

Vegetated swale

References

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Paterson, N. BREEAM and the Code for Sustainable Homes on the London 2012 Olympic Park.

Reeder, L. (2012). Guide to green building rating systems. Hoboken, N.J: Wiley.

Reyes, C., Baraona Pohl, E., & Pirillo, C. (2007). Architecture sustainable. Alboraya, Valencia, Spain: Editorial Pencil.

Thompson, C. (1984). A review of building airtightness and ventilation standards. Bracknell: Air Infiltration Centre.

U.S. Green Building Council. (2010). Green building design and construction. Washington, DC.

United States. Dept. of Energy. (2016). Micro-inverter solar panel mounting. Washington, D.C.