Faculty the use of central heating or air

Faculty for the Built EnvironmentDepartment of Conservation and Built HeritageBLH 3421  Traditional Building MaterialsRebecca Briscoe 485096(M)B.Sc Year 3 2017-18 TABLE OF CONTENTSINTRODUCTION_________________________________________________________CLIENT BACKGROUND__________________________________________________CLIENT REQUIREMENTS_________________________________________________ATMOSPHERIC AND COMFORT CONDITIONS____________________________RECOMMENDATIONS AND REASONING_________________________________ INTRODUCTION The client proposed in the brief is a family of four, including two teenagers, who currently live in Rovaniemi, Finland, and are looking to move to Qala, Malta, in the upcoming year. Their current house is a traditional Finnish wooden house with a slate roof. They have requested that their new house in Qala is also constructed out of traditional materials, as well as offering ideal atmospheric comfort conditions both in the Winter and Summer months. They insist on achieving this ideal using natural heating and cooling system, without the use of central heating or air conditioning. Within this report I will be recommending the appropriate construction materials and explaining why I believe they are the best option, as well as recommending design principles like building orientation and specific design features, required to satisfy the client brief.    CLIENT BACKGROUND Rovaniemi is a municipal city in Finland with a subarctic climate typical of Nordic countries. According to the Köppen climate classifications, Rovaniemi’s climate is classified as Dfb, which refers to a humid continental climate, generally characterized by large temperature discrepancies, short, warm summers and long, drastically cold winters. The temperatures in Rovaniemi are highest in July, rising to an approximate maximum of 20°C and lowest in the months of January and February, reaching temperature of around -14 °C. The average, annual relative humidity is of 80% with November being the most humid and June the least. Rovaniemi also experiences a great deal of rainfall and snowfall with the rain and snow periods lasting an average of 8 months.Rovaniemi’s location near the arctic circle, combined with frequent overcast skies, results in polar days during the summer months and polar nights during winter months. This means that Rovaniemi experiences days lasting over 24 hours during summer and nights lasting more than 24 hours during winter. Seeing as Rovaniemi’s climate is so distinct and unlike that of most other countries, it requires architecture that responds to these particular conditions. Finnish traditional architecture has therefore developed in such a way that it caters for this specific climate and offers the best living conditions all year round. Locally available materials, timber in particular, play an important role in the character of traditional architecture. Timber is generally prefered to stone or any other building material, seeing as it is readily available, lightweight and relatively easy to transport and work with.Apart from it being readily available, wood’s particular properties make it the ideal construction material, especially when paired with the ideal atmospheric conditions. Wood is exceptionally strong in relation to its light weight and is a poor heat conductor making it the ideal construction material in cold climates like Rovaniemi’s.   Wood is reasonably cheap and easily shaped and assembled allowing for a variety of architecture solution. It is also an ecological material: it is renewable and recyclable. Unlike any other construction material, wood is a living material. Just like any living organism, it is able to store heat within its mass when external conditions require so and release heat when it gets too warm. Wood is also able to regulate the ideal moisture content within a building resulting in an improved indoor air quality. In extreme climatic conditions, particularly very low temperatures, the construction material alone is obviously not sufficient to obtain the optimum conditions, and additional heating systems like wood burning stoves are required. One of the most attractive features of traditional Finnish architecture is the slate roofing. Slate is a metamorphic rock derived from the sedimentary rock shale via metamorphism. It’s high density means it is durable and waterproof, making it the ideal material for roofing. Slate can be cut into thin slabs, is fire-resistant, highly resistant to temperature fluctuations and is not affected by fungus and mold, meaning it requires minimal maintenance. It’s main negative characteristics are its fragility if stepped on, it’s weight and its complicated and expensive installation.    CLIENT REQUIREMENTS As specified in the brief, the Finnish family have chosen to move to Qala, the easternmost village in Gozo, Malta. Qala, meaning ‘harbour’, is surrounded by coastline, boasting amazing views of the neighbouring islands. They have decided to build their house on a promontory overlooking the sea similar to the plot of land identified in figures 1 and 2. One of the client’s requests was that of constructing their new house out of traditional materials. Maltese traditional architecture is a combination of local vernacular and modern architecture and is characterized by the predominant use of limestone, a honey coloured sedimentary rock composed primarily of calcium carbonate. Maltese geology consists of two types of limestone; globigerina and the harder coralline limestone. Globigerina limestone exists as two types of building stone, ‘franka’ and ‘soll’, both readily available all over the Maltese islands. ‘Soll’ has a higher concentration of non-carbonates which obstruct large pores, resulting in a lower porosity and a higher amount of small pores. Malta’s aggressive environment, high in airborne salts, particularly sodium chloride and sulfates, deteriorate ‘soll’, whereas the stronger ‘franka’ tends to resist this deterioration. It is for this reason that ‘franka’ is used for construction and not ‘soll’.On the other hand, the harder coralline limestone exists in two forms; lower coralline or ‘zonqor’ and upper coralline or ‘qawwi ta’ fuq’, found commonly to the North and on Gozo. Being the most crystalline stone, lower coralline is the hardest stone and is resistant to erosion. Upper coralline is the youngest rock, and is therefore found on high land in Malta and Gozo. It is a hard yet porous rock with a white or grey tint. It is mainly used as the building material for important buildings as well as for road surfaces and concrete mixes. Compared to ‘franka’, upper and lower coralline limestone are denser, harder rock, which are difficult to quarry and also more expensive. Whereas the Finnish use slate to cover their roofs and protect their interior from rain, Maltese used to use layers of ‘xahx’, ‘deffun’, a mixture of ground porcelain, lime and water. Nowadays, modern waterproofing materials like membrane are used instead. In comparison to Finland’s climate, Malta’s climate is a lot less extreme. Malta’s mediterranean climate, classified as Csa by Köppen, is characterized by hot summers and mild winters. Temperatures reach an average of 35° C during the summer months as a result of the hot and dry Sirocco winds originating from the African Sahara and drop to an average of 15° C in January. The highest levels of precipitation happen from November to February, but minimal to no precipitation occurs during the spring and summer seasons. Humidity in Malta is quite similar to that in Finland, with an average humidity of 76%.Given malta is not in the same geographical region as Finland, daylight hours are not as drastic. Sunshine duration hours vary from an average of 9 hours of daylight during winter to an average of 14 hours during summer.ATMOSPHERIC AND COMFORT CONDITIONS Given the proposed site is a promontory overlooking the sea and isolated from other residences, construction should be such that it takes into consideration the atmospheric conditions and orientation of the site. It being close to the sea, the greatest threat any building material will face is atmospheric salinity. Airborne salinity refers to the presence of salt in the atmosphere, both in the gaseous and solid state. The concentration of salinity in the atmosphere due to a marine climate depends on a number of variables, including distance from the coast and wind direction and velocity amongst others.In this particular case, one can assume that levels of atmospheric salinity are relatively high, given the proposed site overlooks the sea. The presence of salt in the air leads to two phenomena; efflorescence and subflorescence. Efflorescence is a layer of salt crystals that is deposited onto a surface when water evaporates from the surface. The greyish-white deposit itself is not harmful to the surface, however, once diluted with water, the salt dissolves and is absorbed by the material. Most porous building material carry the diluted salt through the material pores, known as capillary action. Once the diluted salt is in the pores, the water content evaporates resulting in re-crystallization of the salt within the pores, known as subflorescence. This inflicts large hydrostatic pressures within the material pores leading to scaling and cracking.Apart from taking precautionary steps with regards to the atmospheric conditions of the site, comfort conditions should also me considered. As specified by the client, the new house in Qala should be constructed such that natural heating and cooling systems are sufficient to achieve atmospheric comfort all year round. This can be achieved through design that takes advantage of the site’s location, climate and chosen building material to minimise the requirement of energy powered heating or cooling systems.The most appropriate building materials, house orientation and design features for this specific client and site will be discussed in the following section.   RECOMMENDATIONS AND REASONING One of the client’s requirements was that of using traditional building materials. A two storey traditional Maltese farmhouse with a verandah and rooms overlooking a central courtyard is being suggested.A central courtyard is being suggested because it allows warm air from inside the house to rise, and be replaced by cool air, creating a breeze inside the house. Windows on the courtyard walls should therefore be larger in span to further encourage this process.   A verandah is suggested on the western facade. It provides a sheltered outside area, where the Finnish family can enjoy warm summer days, sheltered from strong winds and the scorching summer sun.  Based on the orientation chosen, a recessed top storey is being suggested in order to allow sunlight to reach rooms on the northern side of the house, providing natural heating during colder months. As seen in diagram … the dimension and position of windows should be such that they allow the winter sun to heat the inside of the house, but block the summer sun. Landscaping could also be used as a shielding device from both strong winds and the sun, as well as acting as a protective barrier against winds carrying airborne salinity.  Structure – Interior and Exterior Walls’Franka’ is being suggested as the main building material for both internal and external walls. Globigerina is cut from local quarries all over the island and transported as block units of dimensions of approximately 20″ by 10″, by 6″ depth. ‘Franka’ is being favoured over timber because it is readily available, unlike timber, as well as for its structural capabilities and inherent properties. In general, limestone serves as a construction material because it is easy to work with, durable under dry conditions and when exposed to minimal thermal expansion, fire-resistant and good in compression. The load bearing capabilities of the masonry wall depend on the compressive strength of the units, on the infill mortar being used, and on the workmanship. In order to achieve the best possible compressive strength, the horizontal bed joints should be entirely filled with mortar, the infill mortar should not exceed a thickness of 0.5″, and the units should be well wetted in order to reduce the surface’s suction rate. Adding lime to the mortar will also help it retaining water resulting in a stronger mortar and therefore a stronger wall.   There are, however downsides to using ‘franka’. ‘Franka’ is a relatively soft stone, and is therefore prone to weathering, a process that affects both its appearance and structural capabilities. ‘Franks’ is porous and permeable, meaning that it absorbs and transfers moisture within its interconnected pores. When salts crystallize within the pore spaces, the forces created pry the grains apart, resulting in deterioration through erosion, crumbling, spalling and other weathering processes. The most prominent effect of weathering is the loss of detail, and therefore, using quarry-faced units is ideal in order to reduce the visibility of weathering. It takes a long period of wetting and drying cycles for weathering to actually become visible, but should still be taken seriously and prevented. Making sure that grout is well consolidated and making use of grout admixtures, like chemical, additives designed to reduce its water content, also reduces the number of voids in the grout, making it less porous. If the clients decide to plaster the exterior, then Lime Plastering is recommended seeing as it allows evaporation and reduces the risk of trapped moisture in the limestone walls.Other physical characteristics like implementing overhanging copings, eaves and flashings, as well as the landscaping can be used to minimize the effect of atmospheric salinity on external surfaces.Applying a damp proof course is being suggested in order to prevent rising damp through capillary action in the base of the stone.The mortar used should be a lime based mortar consisting of a mix of water, an aggregate like sand, and lime, making the mortar more waterproof and less prone to shrinkage cracking.Single leaf interior walls and double leaf cavity external walls are being suggested. The air cavity between the exterior walls act as an insulating layer, minimizing heat transfer, soundproofing and reducing the formation of condensation inside the house. Other non-traditional insulants like foamed insulants could also be used for increased insulation. Given internal walls are also built out of limestone, the thickness of the interior wall absorbs heat from the inside warm air during warmer months. During winter months, walls that are exposed to direct sunlight throughout the day, absorb heat and store it as solar heat energy. As the temperature drops, the stored heat is released into the house. Therefore, the limestone walls act as a form of temperature regulation system; they heat up the interior or absorb heat from the interior atmosphere as required to keep the ideal atmospheric temperature. This phenomena is a result of the thermal mass of materials like limestone.Fair faced or plastered interior walls are being suggested for easier upkeep.   RoofingFor the construction of the roof, it is recommended to use traditional timber beams and stone slabs or ‘xorok’, giving the specific rooms an authentic look. Stone arches can also be used when a larger span is desired. Timber is being suggested for the roof structure because of it is light and able to resist tensile loads, resulting in its ability to bend without breaking.When purchasing the structural beams to be installed, it is fundamental to make sure that the beams are graded, structural beams with no visible defects, like knots and warped grains; spiral and cross grains. When it comes to choosing the wood species, it is likely that the available kind are softwood beams. Even though the name may suggest so, soft woods can bear just as much load as hardwood. Hardwood’s higher density makes it more long-lasting, but increases its weight which is not ideal for use in suspended beams. The Maltese equivalent of the Finnish slate roof is the use of ‘deffun’. ‘Deffun’ is a mixture of ground porcelain, lime and water which is tamped down (imballat) onto the roof, forming a waterproof layer. ‘Deffun’ is being suggested over slate or any other waterproofing material because it not only prevents water from penetrating the roof structure but also provides a cooling effect through the evaporation of trapped moisture. The roof should also be painted in a light, reflective colour in order to reflect sunlight and reduce heat absorption through the roof.  GlazingWith regards to apertures, i recommend installing timber doors and window louvers, making sure to apply the required protective coating and flashing. I also recommend the use of double glaze glass which allows light to pass through but reduces heat transfer. Because of the need for a low cooling load, it is important to avoid oversized south-facing windows and ensure that south-facing windows are properly shielded from direct sunlight in order to prevent overheating. Louvers are therefore ideal seeing as the horizontal slats are such that they permit light and air, but obstruct rain and direct sunlight. Hanging thick curtains could also be used to block out the hot summer sun and prevent heat from escaping the interior during colder months.The greatest disadvantage to using timber louvers, however, is the deteriorating effect of moisture on wood. Wood is a hygroscopic material, meaning that it absorbs moisture through the cell walls and cell cavities, and expands or contracts depending on its new moisture content. Wood movement is responsible for most of the defects in woodwork and can be prevented by treating the wood elements.  FlooringAs flooring material I recommend using porcelain tiles. Porcelain is a type of ceramic characterized by its durability, resistance to water, low maintenance requirements and long lifespan. Porcelain tiles are smooth and cold to the touch, making them ideal for the warm summer months. During the colder months, however, rugs and carpets could be laid out to prevent heat from escaping through the floor.   REFERENCES


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