Functional Requirements of Buildings

Orientation of a building is the placing of the building on the site, and the arrangement of its rooms, so that the sun, wind, rain and view are used to give comfort inside with the least artificial heating, cooling and lighting.

Factors for orientation

1. Sun path and solar radiation: In Nepal (about 27°N–30°N) the sun is in the southern sky. Long walls and large windows should face south for winter sun. East and west walls get low-angle sun, so keep openings there small.
2. Wind direction: Prevailing wind (in the Terai, mostly west-to-east in summer) should reach the main openings for cross ventilation. The building axis is kept at 0° to 30° to the wind, not parallel to it.
3. Rainfall: Driving rain direction decides where sheds, eaves and chhajja are needed.
4. Topography and view: Slope, drainage and a good view or privacy may change the best direction.
5. Climate zone: Hot-humid Terai needs shade and ventilation; cold hills need solar gain and compact form.
6. Surroundings: Nearby trees, buildings and noise sources can shade or block wind.

Factors for planning

• Aspect: Each room faces the direction suited to its use: kitchen east/north-east (morning sun, away from afternoon heat), bedroom south-east or south, living room south, store and toilet north or west.
• Prospect: View outward from the openings.
• Grouping: Rooms of the same use are placed together to shorten circulation.
• Roominess: Right sizes and proportions for the furniture and activities.
• Privacy: Bedrooms and toilets are hidden from the road and neighbours.
• Circulation: Short, direct passages and stairs with little wasted area.
• Furniture requirement and sanitation: Wall space for furniture; light, ventilation and clean water and drainage.
• Flexibility and economy: Space can be altered later, and the plan is compact so that the cost is low.
• Bye-laws: Setback, ground coverage, floor area ratio and height as per Nepal Building Code and municipal bye-laws.

        N
   [Store][Toilet]
 W [Kitchen][Dining] E
   [Living][Bedroom]
        S  (large windows)

Moisture movement is the passage of water, as liquid or vapour, through the pores, cracks and joints of building materials and components. It causes dampness, which weakens materials and spoils health and finishes.

Types and forces of movement

Capillary rise is greater in fine-pored material such as brick; it is large in clay and silt soil.

Remedial measures

1. Damp proof course (DPC) at plinth level (25 to 40 mm cement concrete 1:2:4 with waterproofing compound), and DPC at parapet and sills.
2. Surface treatment: waterproof cement plaster, water-repellent paint, pointing of joints.
3. Cavity walls to break the path of moisture.
4. Integral waterproofing: add compounds (Pudlo, Dr. Fixit) to concrete and mortar.
5. Membranes / tanking: bitumen, polythene sheet, or bituminous felt on basements.
6. Good site drainage: slope the ground away, apron around building, subsoil drains.
7. Roof treatment: slopes, flashings, brick-bat coba, proper gutters and downpipes.
8. Ventilation and vapour barrier: stop condensation by ventilation and by vapour barriers on the warm side.
9. Good materials: dense, well-burnt bricks and non-absorbent stones.

Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment (ASHRAE). A person feels neither too hot nor too cold, and wants no change in the surroundings.

Thermal factors affecting thermal comfort

• Air temperature (dry-bulb): the main factor. Comfort range about 21 to 27 °C.
• Mean radiant temperature: radiation from surrounding walls, roof and sun.
• Relative humidity: comfortable between 30 and 60 %. High humidity stops sweat evaporation.
• Air movement: moving air increases evaporation and convection; 0.1 to 0.5 m/s is comfortable.
• Clothing (clo value) and activity level (met value).
• Personal factors: age, sex, health, body build, and acclimatisation.

Thermal balance of the human body

The body keeps the core temperature near 37 °C. Metabolism produces heat (about 100 W at rest). The body is in balance when

$$M \pm R \pm C - E = 0$$

where $M$ is metabolic heat, $R$ is radiation, $C$ is convection and conduction, and $E$ is evaporation. In hot conditions, the skin blood vessels widen (vasodilation) and sweating gives cooling by evaporation. In cold conditions, vessels narrow (vasoconstriction), shivering raises metabolism, and heat loss is reduced.

 Metabolism (M) ----> BODY 37 C
                       |  |  |  |
          Radiation R--+  |  |  +--Evaporation E
          Convection C----+  +-- Respiration

Thermal preferences (ASHRAE 7-point scale)

The building should be designed to give a vote between -1 and +1 for most users. The comfort zone is shown on a bioclimatic chart (Olgyay or Givoni) using temperature and humidity. A fixed index, effective temperature (ET), combines temperature, humidity and air movement in one number: the temperature of still saturated air giving the same sensation.

Design should cut heat gain in summer (shade, insulation, ventilation) and keep heat in winter (insulation, solar gain), to hold the body in balance without strain.

Ventilation is the supply of fresh outdoor air to a space and the removal of stale air, without causing discomfort. Its functional requirements are:

1. Supply of oxygen: Occupants use about 0.5 m³/h of oxygen; fresh air keeps oxygen near 21 %.
2. Removal of carbon dioxide: CO₂ from breathing (about 0.02 m³/h per person) must be kept below about 0.1 %.
3. Control of odour, smoke and gases: Kitchen, toilet and body smells, fumes and dust are carried out.
4. Control of humidity: Removes vapour from cooking, bathing and breathing, and so stops condensation, dampness and mould.
5. Heat removal: Removes excess body, appliance and solar heat, giving a cooling effect on the body by air movement.
6. Thermal comfort: Gives air movement of 0.1 to 0.5 m/s without draught.
7. Prevention of airborne infection: Dilutes bacteria and virus load.
8. Adequate air change: Rate is fixed by use, such as 6 to 8 air changes per hour (ACH) for a living room and 15 to 20 ACH for a kitchen. The standard is given in the National Building Code.

Ventilation openings should be placed to give cross flow, with inlets low and on the windward side, and outlets high on the leeward side.

Air conditioning is the process of treating air to control its temperature, humidity, cleanliness and distribution together, to meet the needs of the occupants or of a process.

Four functions

1. Temperature control (heating or cooling).
2. Humidity control (humidifying or dehumidifying).
3. Air cleaning (filtering dust, pollen, bacteria).
4. Air distribution and circulation through ducts.

Main parts

• Compressor, condenser, expansion valve, evaporator (refrigeration cycle) for cooling.
• Air handling unit with blower, filter and coils.
• Ducts, diffusers and grilles.
• Thermostat and controls.

 Room air --> Filter --> Cooling coil --> Fan --> Duct --> Room
                          ^ refrigerant from outdoor unit

Types

• Comfort air conditioning: offices, homes, hospitals, cinemas.
• Industrial air conditioning: textile mills, laboratories, computer rooms.
• By system: window unit, split unit, packaged, central plant (chilled water).

Advantages and limits

Gives comfort in all seasons and a clean room. But the initial and running costs are high, it needs a sealed building with good insulation, and it needs regular maintenance. In Nepal, it is mainly used in hotels, hospitals, offices and malls.

Thermal comfort is a state where a person feels neither hot nor cold. Thermal performance of a building component is its ability to resist heat flow, measured by its U-value (transmittance, W/m²°C) or its thermal resistance $R$ (m²°C/W). A low U-value means better performance. For a composite element

$$U = \frac{1}{R_{si} + \sum \frac{t}{k} + R_{so}}$$

Insulation of exposed walls

1. Cavity wall: Two leaves with 50 mm air gap; the still air resists heat flow. Filling the gap with insulation (glass wool, thermocole, polyurethane foam) improves it further.
2. Insulating material on the wall: Boards of thermocole (EPS), cork or mineral wool fixed on the outer face (external insulation, best for thermal mass) or inner face.
3. Hollow blocks / AAC / fly-ash bricks: Walls built from low-conductivity units.
4. Thick walls and reflective surfaces: Light-coloured paint or lime wash reflects solar radiation.

 Out |brick|air gap|insulation|brick| In

Doors and windows

• Use double glazing (two glasses with 6 to 12 mm air space) or low-E coated glass.
• Use timber or uPVC frames instead of metal; metal conducts heat.
• Weather stripping to stop air leakage.
• Shading: chhajja, louvres, curtains, and trees on the east and west sides.
• Insulated, solid-core flush doors.

Roofs

Roof gets the maximum solar heat in plains.

1. Terracing / brick-bat coba on RCC slab, with lime concrete of 75 mm.
2. Insulation layer: Thermocole, glass wool or foam concrete on the slab, covered by waterproofing.
3. False ceiling with air space and insulation.
4. Ventilated double roof, or roof over the slab to give shade.
5. Reflective finish: white china mosaic or white paint.
6. Green roof or water spray / pond: evaporative cooling.

  Waterproofing + tiles
  Mud/lime concrete 75 mm
  Insulation (EPS)
  RCC slab

Moisture (dampness) in a building is the unwanted presence of water in its materials and spaces.

Effects of moisture

• Damp patches, peeling plaster and paint, stains and efflorescence (white salt deposit).
• Corrosion of reinforcement and steel, spalling of concrete.
• Rot and fungal attack of timber, and termite attack.
• Reduced strength, and cracks in masonry from expansion and contraction.
• Reduced thermal insulation, since wet materials conduct heat more.
• Unhealthy air; mould, breathing problems; and damaged floor coverings and furniture.
• Short circuits and electrical leakage.

Main sources of moisture

1. Rising damp from the ground by capillary action.
2. Rain penetration through walls, roof, joints and openings.
3. Condensation on cold surfaces from humid air.
4. Leakage from plumbing, drains, and sanitary fittings.
5. Construction moisture: water in concrete, mortar, plaster, and curing.
6. Hygroscopic materials: salts in bricks.
7. Poor drainage and surface water around the building.

Methods to stop moisture

Damp proofing should be planned at design stage; it costs far less than repair later.

Damp proofing is the provision of a barrier or treatment that stops or reduces the entry of moisture from the ground, or from other sources, into a building. The impervious layer used is called a damp proof course (DPC).

General methods

1. Membrane damp proofing (DPC): A continuous impervious layer is put at plinth level (and at other levels) across the full width of the wall. Materials: flexible (bitumen felt, polythene sheet, lead, copper), semi-rigid (mastic asphalt), rigid (cement concrete 1:2:4 40 mm thick, dense bricks, stone slab).
2. Integral damp proofing: Waterproofing compounds (pore fillers such as chalk or talc, or water repellents such as soap, alum, and Pudlo) are mixed into concrete or mortar to make it impervious.
3. Surface treatment: Waterproof plaster, or repellent coatings (silicones, bituminous paint, cement paint), on the wall surface; pointing of joints.
4. Cavity wall construction: An air gap in the wall cuts the path for moisture.
5. Guard (surface) drains and sub-soil drainage: Lower the water table and drain surface water away from walls; an apron round the plinth.
6. Pressure grouting / chemical injection: Cement grout or chemicals injected into the wall to form a barrier in existing buildings.
7. Electro-osmosis: Used for old buildings.
8. Tanking for basements: continuous waterproof membrane on floor and walls.

  Wall
  ======== DPC at 150 mm above ground
  Plinth
  ~~~~~~~~ ground level

Ventilation is the supply of fresh air to, and removal of stale air from, an enclosed space.

Types of ventilation

1. Natural ventilation: Uses wind pressure and stack (thermal) effect through openings.
   • Wind-driven (cross) ventilation: windows on windward and leeward sides.
   • Stack effect: warm air rises and leaves through high openings (ventilators, ridge, chimney), and cool air enters low.
2. Mechanical (forced) ventilation: Fans and ducts are used.
   • Extract (exhaust) system: fan removes air; used in kitchens, toilets.
   • Plenum / supply system: fan forces fresh air in.
   • Balanced system: both supply and exhaust fans.
3. Combined (mixed mode).

Mechanical ventilation is preferred where natural ventilation cannot give the needed rate: basements, large halls, interior rooms, kitchens, workshops.

Design methodology

1. Find the number of occupants and the use, then the required fresh-air rate (e.g. 25 to 30 m³/h per person) or the air change rate (ACH) from the code.
2. Required flow: $Q = \frac{V \times N}{3600}$ (m³/s), where $V$ is room volume and $N$ is ACH.
3. Natural: Wind flow $Q = E A V$ (m³/s), with $E$ effectiveness (0.5 to 0.6 for wind perpendicular to opening, 0.25 to 0.35 diagonal), $A$ open area, $V$ wind speed (m/s). Stack flow: $Q = C_d A \sqrt{2 g h \frac{T_i - T_o}{T_i}}$.
4. Fix opening areas (generally 15 to 20 % of floor area) and locate inlets low and outlets high, on opposite walls.
5. Mechanical: Choose fan capacity for $Q$, size ducts for 3 to 6 m/s, and select grilles.
6. Check the result against the Nepal National Building Code (NBC 206).

Thermal comfort is the state of mind in which a person is satisfied with the thermal environment around him or her, feeling neither hot nor cold.

Factors determining thermal comfort

1. Air temperature: the dry-bulb temperature of the air; comfort range roughly 21 to 27 °C.
2. Mean radiant temperature: heat radiated by walls, floor, ceiling and the sun. A hot ceiling makes people feel warm even in cool air.
3. Relative humidity: 30 to 60 % is acceptable. High humidity stops sweat from evaporating, and low humidity dries skin and throat.
4. Air velocity: Air movement increases heat loss by convection and evaporation. 0.1 to 0.5 m/s is comfortable; more than that causes draught.
5. Clothing insulation (clo): Heavy clothes keep heat in.
6. Metabolic rate / activity (met): Hard work produces more heat, so lower temperature is preferred.
7. Personal factors: age, sex, health, body size, acclimatisation, food, and the time spent in the space.
8. Other: floor surface temperature, vertical temperature difference, and the condition of the outside climate.

The first four are environmental factors (controlled by the designer), and the last three are personal factors. The combined effect of temperature, humidity and air motion is expressed by effective temperature. The designer controls the environmental factors through orientation, insulation, shading, ventilation and, if needed, air conditioning.

Energy Conscious Design (ECD) is the design of buildings that reduces the use of energy for heating, cooling, lighting and ventilation, while keeping comfort, by using the site, climate, form, materials and efficient systems.

Design considerations

1. Site and climate analysis: sun path, wind, temperature, rainfall, microclimate.
2. Orientation and layout: Long axis east-west, main openings facing south; compact form; living areas on the sun side and service areas on the cold side.
3. Building envelope: insulated walls and roofs, double glazing, light roof colour in hot zones, thermal mass in places with large day-night temperature swing.
4. Passive solar heating: south windows, Trombe wall, sunspace, greenhouse.
5. Passive cooling: shading, ventilation, courtyard, evaporative cooling, earth cooling.
6. Daylighting: skylights, light shelves, reduce artificial lighting.
7. Natural ventilation to avoid fans and AC.
8. Efficient equipment: LED lights, efficient appliances, solar water heaters, controls and sensors.
9. Renewable energy: solar PV, solar thermal, biogas.
10. Landscaping: trees for shade and wind control.
11. Materials: low embodied energy local materials (stone, mud, bamboo, stabilised earth blocks).

Renewable and non-renewable energy

Nepal has large hydropower potential (about 83,000 MW, of which about 42,000 MW is economically feasible), and imports all petroleum products and coal. The energy-conscious building therefore reduces national imports as well as the owner's bills.

Moisture

Moisture is water, in liquid or vapour form, present in building materials or air, which in excess causes dampness.

Sources of moisture in a building

1. Rising damp from the ground (capillary action).
2. Rain penetrating through walls, roof, windows.
3. Condensation of water vapour on cold surfaces.
4. Plumbing leakage from pipes, sanitary and drain lines.
5. Moisture left in materials from construction (concrete, mortar, plaster).
6. Poor surface drainage, ground water and high water table.
7. Hygroscopic action of salts present in bricks and sand.

Moisture control in the basement of an RCC building

Basement is below ground, so it faces ground water and hydrostatic pressure.

1. Site drainage: Surface water is diverted by sloped ground and drains. A sub-soil drain (perforated pipe in gravel) around the foundation lowers the water table.
2. Waterproof concrete: Dense M25 or higher concrete with a waterproofing admixture (crystalline or plasticiser), and water-stops at construction joints.
3. Tanking (membrane): Continuous waterproof membrane under the floor and up the walls.
   • External tanking (positive side): membrane of bitumen or APP sheet on the earth face, protected by brick or PCC.
   • Internal tanking (negative side): membrane and cement-sand plaster inside, with a counter wall.
4. Floor: PCC 1:3:6 on a layer of compacted hard core, then membrane, and then the RCC raft or floor slab with a screed.
5. Drained cavity: An inner skin with a cavity that drains to a sump, with a pump.
6. DPC at floor and wall junction, and at the ground level of the wall above.

 Ground    |  RCC wall  |Membrane| backfill
 level --- |            |        | 
           |  Floor slab        |
 ----------+====================+---
           PCC + membrane + hardcore
           [sub-soil drain]

Basement floor

A basement is the floor of a building that is partly or wholly below the ground level. Basements are used for parking, services, storage and sometimes for living. The basement floor is the lowest floor, usually a raft or slab resting on the ground, with a base of well-compacted hardcore and PCC.

Type of wall appropriate for basement

The wall faces earth pressure and ground water, so it must be strong and watertight. A reinforced concrete retaining wall (M25 or higher, 200 to 300 mm thick, with waterproofing admixture), cast monolithic with the raft, is the most suitable. Masonry walls (brick or stone in 1:4 cement mortar) are acceptable only for shallow, dry basements; the RCC wall can be designed for lateral pressure and hydrostatic pressure.

Waterproofing techniques

1. Integral waterproofing: Dense concrete with low water-cement ratio (below 0.45), plasticiser or crystalline admixture, and PVC water bars in construction joints.
2. Tanking (membrane waterproofing)
   • External (positive side) tanking: Membrane (bituminous coating, APP/SBS sheet, or HDPE) applied on the outside face of the wall and under the raft. This is the best way because water is stopped before it enters the wall. A protection board or brick wall guards the membrane during backfilling.
   • Internal (negative side) tanking: Used when the outside is not reachable. Waterproof cement plaster with crystalline coating, or mastic asphalt, is applied inside and held by an inner loading wall.
3. Cavity drain system: An inner skin separated by a cavity; leaking water flows to a sump and is pumped out.
4. Sub-soil drainage: A perforated pipe around the footing in graded gravel, leading to a sump.
5. Grouting: Cement or chemical injection in cracks and joints.
6. Surface treatment: Cement-sand 1:3 plaster with waterproofing compound, 20 mm thick, in two coats.

  GL ___                      ___
     |  | backfill           |  |
     |  | protection board   |  |
     |  | membrane           |  |
     |  | RCC wall           |  |
     |__|____________________|__|
     Basement floor: screed
                     membrane
                     PCC + hardcore
          sump [ ]   <- drain pipe

Given

• Inlet and outlet openings: 0.3 m × 0.3 m and 0.4 m × 0.4 m, so $A_1 = 0.0900\ \text{m}^2$ and $A_2 = 0.1600\ \text{m}^2$
• Wind speed $v = 4$ km/h $= 4/3.6 = 1.1111$ m/s, at 90° to the opening
• Coefficient of effectiveness $E = 0.68$ (already accounts for the wind direction; the room size does not enter the formula)

Formula

For wind-driven ventilation through two openings in series, the effective area is

$$A = \frac{A_1 A_2}{\sqrt{A_1^2 + A_2^2}}, \qquad Q = E\, A\, V$$

Calculation

$$\begin{aligned} A &= \frac{0.0900 \times 0.1600}{\sqrt{0.0900^2 + 0.1600^2}} = 0.07844\ \text{m}^2 \\ Q &= 0.68 \times 0.07844 \times 1.1111 = 0.05927\ \text{m}^3/\text{s} \end{aligned}$$

Answer: $Q = 0.0593$ m³/s $= 213.4$ m³/h.

Given

• Inlet and outlet openings: 0.36 m × 0.36 m and 0.4 m × 0.4 m, so $A_1 = 0.1296\ \text{m}^2$ and $A_2 = 0.1600\ \text{m}^2$
• Wind speed $v = 5$ km/h $= 5/3.6 = 1.3889$ m/s, at 45° to the opening
• Coefficient of effectiveness $E = 0.32$ (already accounts for the wind direction; the room size does not enter the formula)

Formula

For wind-driven ventilation through two openings in series, the effective area is

$$A = \frac{A_1 A_2}{\sqrt{A_1^2 + A_2^2}}, \qquad Q = E\, A\, V$$

Calculation

$$\begin{aligned} A &= \frac{0.1296 \times 0.1600}{\sqrt{0.1296^2 + 0.1600^2}} = 0.10071\ \text{m}^2 \\ Q &= 0.32 \times 0.10071 \times 1.3889 = 0.04476\ \text{m}^3/\text{s} \end{aligned}$$

Answer: $Q = 0.0448$ m³/s $= 161.1$ m³/h.

Thermal performance of a building is how well the building keeps indoor temperature comfortable with little energy, by controlling heat gain and loss through its envelope. It depends on U-value, solar gain, ventilation, and thermal mass.

The statement is correct. The two factors named control most of the heat exchange.

Geometric dimensions

• Surface-area-to-volume ratio: A compact shape (cube) has a smaller external area per unit volume, so heat loss in winter and gain in summer is less. Long, spread plans lose more.
• Orientation and aspect ratio: A building elongated along east-west with its long side facing south gets more winter sun and less low-angle east-west sun.
• Window size and position: Glass area gives solar gain and conduction loss. Overhang depth, roof height and room depth control shading and daylight.
• Ceiling height: High ceilings let hot air rise away from occupants and aid stack ventilation.
• Wall and roof thickness: Thick elements give more resistance ($R = t/k$) and time lag.

Material properties

• Thermal conductivity (k): Low k (AAC blocks, hollow bricks, insulation) reduces heat flow; high k (steel, glass, stone) increases it.
• Thermal mass (specific heat and density): Heavy materials (stone, mud, concrete) store heat and delay it (time lag), reducing temperature swing.
• Surface properties: Colour (absorptivity) and emissivity decide how much radiation is absorbed or reflected.

Thus a good design gives a compact geometry with right orientation and uses suitable materials. Neither alone is sufficient.

Solar control means using the sun's energy for heating in cold seasons and keeping it out in hot seasons.

Passive solar control

Uses building design and natural flows only, with no mechanical parts.

• Orientation and layout: Main openings face south.
• Direct gain: South windows let in winter sun to heat floor and walls (thermal mass).
• Trombe wall: A dark masonry wall behind glass absorbs heat and releases it into the room.
• Sunspace / greenhouse: attached glazed space.
• Shading devices: chhajja, louvres, pergolas, trees, to stop summer sun.
• Reflective roof colours, insulation, cavity walls to cut heat gain.
• Natural ventilation and evaporative cooling.

 Winter sun --> [glass] --> room, dark wall stores heat
 Summer sun --> blocked by overhang

Active solar control

Uses mechanical or electrical devices with collectors and a pump or fan.

• Solar water heater (flat-plate collector with circulating pump or thermosyphon tank).
• Solar air heater with fan to blow warm air into the rooms.
• Photovoltaic panels for electricity for lights, fans, and heat pumps.
• Motorised shades / louvres that follow the sun.
• Solar-powered absorption chillers for cooling.

Passive systems cost little and need almost no maintenance. Active systems give more control but cost more and need maintenance. Best design combines both.

Site selection is the choice of a plot that is best suited for the purpose of the building, comfort, safety and economy. The main criteria are:

1. Purpose and location: Near the users, work, school, market and hospital (residential); near roads and customers (commercial); away from habitation (industry).
2. Soil and ground condition: Firm soil with good bearing capacity. Avoid black cotton soil, filled ground, marshy land, or slopes liable to slide.
3. Topography and drainage: Gently sloping land with natural drainage. Avoid low pockets that collect water, and land near flood plains.
4. Water table: Low water table, to avoid damp and costly foundation work.
5. Services: Road access, water supply, electricity, sewer, telephone and internet.
6. Environment: Fresh air, no smoke, noise or odour from industries, and pleasant surroundings; good sun and wind exposure.
7. Safety: Away from flood, landslide, fault lines and fire hazards; follow earthquake zoning in Nepal.
8. Shape and size: Regular plot with right area for setback, and the possibility of future extension.
9. Legal matters: Clear ownership, land use zone, bye-laws, setback, and permits from the municipality.
10. Economy: Land cost and the cost of development, and the availability of labour and materials.

Functional requirements of ventilation

1. Supplies oxygen and removes carbon dioxide from breathing.
2. Removes odours, smoke, dust and harmful gases.
3. Controls humidity and prevents condensation and mould.
4. Removes excess heat to give thermal comfort.
5. Provides air movement for cooling the body.
6. Dilutes airborne germs.

Conditions where mechanical ventilation is preferred

• Interior rooms and basements with no external walls for openings.
• Large halls and theatres with many people where natural flow is not enough.
• Kitchens, toilets, laboratories with strong odours, fumes or vapour.
• Industrial buildings with heat, dust or toxic gases.
• Sites with calm wind, or high outdoor noise or pollution, where windows must stay closed.
• Multi-storey and tightly-sealed buildings, or where air conditioning is in use.
• Where the rate of air change must be controlled precisely, as in hospitals and clean rooms.

Ventilation requirement in the Nepal National Building Code

Yes. NBC 206 (Architectural Design Requirements) gives provisions for light and ventilation, such as:

• Habitable rooms must have window area not less than about 10 % of the floor area (about one-tenth) and the openable part at least half of that.
• Minimum clear height of rooms and ventilation shafts for bathrooms and toilets (WC) without outer walls.
• Kitchens must have exhaust or openings to outside.
• Basements and large public buildings require mechanical ventilation designed for specified air changes per hour.

The exact values should be taken from the current NBC 206 and municipal bye-laws.

Air change per hour (ACH)

Air change per hour is the number of times the whole volume of air in a room is replaced by fresh air in one hour.

$$ACH = \frac{Q}{V}$$

where $Q$ is the volume of air supplied or removed per hour (m³/h) and $V$ is the room volume (m³). For example, a 4 m × 5 m × 3 m room with a supply of 360 m³/h has $V = 60$ m³, so $ACH = 360/60 = 6$. Typical values: living rooms 3 to 6, kitchens 15 to 30, toilets 6 to 10, assembly halls 8 to 12.

Effective temperature (ET)

Effective temperature is an index that combines dry-bulb temperature, humidity and air movement into one number. It is the temperature of still, saturated air (100 % RH, no air movement) that gives the same feeling of warmth or cold as the actual conditions. It is read from the ET chart (Yaglou and Houghton) using dry-bulb and wet-bulb temperatures and air velocity. The comfort zone is about 20 to 27 °C ET for most people, with the preferred ET at 22 to 25 °C.

The thermal performance of a building is its capacity to keep the interior comfortable by controlling heat flow. Four basic factors are:

1. Climate and site: Air temperature, humidity, solar radiation, wind and rainfall decide the heating or cooling load. Site features such as slope, trees and neighbouring buildings change local exposure.
2. Orientation and building form (geometry): The direction of the building and its shape decide the solar gain and the exposed surface area. A compact form with long axis east-west reduces heat exchange.
3. Building envelope materials and construction: Conductivity, thickness, thermal mass, colour and reflectivity of walls, roof, floor, and glass. Resistance is $R = t/k$ and transmittance $U = 1/R_{total}$. Low U-value gives better performance. Heavy materials give time lag.
4. Openings and ventilation: The size, position and shading of windows control solar gain, daylight and air movement. Air leakage and natural ventilation affect both heat and humidity.

Other factors are internal heat gains (occupants, lights, appliances) and the use pattern.

Daylight factor

Daylight factor (DF) is the ratio of the illumination at a point inside a room (from the sky, not direct sun) to the simultaneous outdoor illumination on an unobstructed horizontal surface, given as a percentage.

$$DF = \frac{E_i}{E_o} \times 100\%$$

Factors affecting thermal performance

1. Climate (temperature, humidity, radiation, wind).
2. Orientation and building shape.
3. Properties of materials: conductivity, thermal mass, absorptivity.
4. Size, type and shading of openings.
5. Thickness and insulation of walls and roof.
6. Ventilation and air leakage.
7. Internal heat gains and surroundings (trees, buildings).

Types of natural ventilation

• Wind-driven (cross) ventilation: Wind creates positive pressure on the windward side and negative on the leeward, and air flows through the openings in between. Flow $Q = EAV$.
• Stack (thermal buoyancy) ventilation: Warm air, being lighter, rises and goes out at a high opening, while cool air enters low. The stronger the temperature difference and the height between openings, the greater the flow.
• Single-sided ventilation: Openings on one wall only; weak flow.
• Night ventilation: Cool night air flushes heat out of the thermal mass.

 cool in -> [room] -> warm out (high)
 wind -->  | window     window |  --> 

Educational building

A building used for teaching and learning: schools, colleges, universities, training centres, with classrooms, laboratories, libraries and offices.

Residential building

A building where people live and sleep: houses, flats, hostels, dormitories, hotels, and apartments. (NBC groups educational as one use class and residential as another.)

Essentials of air conditioning

1. Temperature control: Cooling in summer and heating in winter to hold about 22 to 26 °C.
2. Humidity control: Keep relative humidity about 40 to 60 % by humidifying or dehumidifying.
3. Air filtration / cleaning: Dust, pollen, smoke and bacteria are removed by filters.
4. Air circulation and distribution: A fan and ducts give uniform air movement, without draught.
5. Fresh air supply: A fraction of outside air is mixed with the recirculated air.
6. Refrigeration plant: compressor, condenser, expansion valve and evaporator for cooling.
7. Controls: thermostat and humidistat for automatic operation.
8. Insulated building and sealed openings: This reduces the load.
9. Proper load calculation and equipment sizing: considering occupants, lights, solar gain and fresh air.

Residential building

A building used for living and sleeping: houses, flats, apartments, hostels, hotels.

Institutional building

A building used for medical, educational, charitable or care purposes where people stay or attend: hospitals, schools, colleges, orphanages, sanatoriums, jails.

Types of mechanical ventilation

1. Extract (exhaust) system: Fans remove air from the room; fresh air comes in through openings. Used in kitchens, toilets, factories. It gives negative pressure.
2. Plenum (supply or positive-pressure) system: A fan forces filtered air in, and stale air leaves through openings. Used in hospital operating theatres, clean rooms.
3. Balanced (combined supply and extract) system: Both supply and exhaust fans; the pressure is balanced. Used in theatres, halls, basements.
4. Ducted system with air-handling unit: Central fan, filters and ducts to distribute air; can be combined with air conditioning.

 Extract:  out <-[fan]  room  <- air leaks in
 Plenum:   in ->[fan]   room  -> air leaks out
 Balanced: in ->[fan] room [fan]-> out

Given

• Inlet and outlet openings: 0.32 m × 0.32 m and 0.42 m × 0.42 m, so $A_1 = 0.1024\ \text{m}^2$ and $A_2 = 0.1764\ \text{m}^2$
• Wind speed $v = 5$ km/h $= 5/3.6 = 1.3889$ m/s, at 45° to the opening
• Coefficient of effectiveness $E = 0.33$ (already accounts for the wind direction; the room size does not enter the formula)

Formula

For wind-driven ventilation through two openings in series, the effective area is

$$A = \frac{A_1 A_2}{\sqrt{A_1^2 + A_2^2}}, \qquad Q = E\, A\, V$$

Calculation

$$\begin{aligned} A &= \frac{0.1024 \times 0.1764}{\sqrt{0.1024^2 + 0.1764^2}} = 0.08856\ \text{m}^2 \\ Q &= 0.33 \times 0.08856 \times 1.3889 = 0.04059\ \text{m}^3/\text{s} \end{aligned}$$

Answer: $Q = 0.0406$ m³/s $= 146.1$ m³/h.

Thermal comfort in buildings is the condition in which occupants are satisfied with the thermal environment (temperature, humidity, air movement and radiation) and want neither warmer nor cooler surroundings.

Classification

Thermal comfort is classified by the basis of assessment.

1. Subjective (psychological) comfort: The person's own feeling of the environment, from votes on the 7-point ASHRAE scale from -3 (cold) to +3 (hot). Example: students voting on the classroom temperature.
2. Physiological comfort: Based on the body's heat balance and on skin and core temperatures. When heat produced equals heat lost with little sweating or shivering, there is comfort. Example: a person resting at 24 °C needing no extra effort of the body.
3. Physical (environmental) comfort: Based on measurable parameters and indices such as dry-bulb temperature, effective temperature, and the comfort zone on the psychrometric chart. Example: ET of 22 to 25 °C is comfortable for sedentary work.

By season or condition

• Summer comfort: Needs cooling and ventilation; 24 to 28 °C with air movement.
• Winter comfort: Needs heating and insulation; 18 to 24 °C.

By model

• Static (heat balance) model: Fanger's PMV/PPD, assumes steady indoor conditions (air-conditioned rooms).
• Adaptive model: People adapt through clothing, windows and fans, so comfort range follows the outdoor temperature (naturally ventilated buildings, common in Nepal).

Understanding these helps the designer choose passive or active methods to meet the comfort needs of the users of the space.

Thermal comfort is the state of mind in which a person is satisfied with the thermal environment. It depends on air temperature, radiant temperature, humidity, air speed, clothing and activity. The comfort range is about 21 to 27 °C with 30 to 60 % relative humidity.

How to achieve thermal comfort

1. Select a site and orientation suited to the climate.
2. Use a good building form and layout (compact, shaded courtyard).
3. Provide a good envelope: insulated walls and roofs, suitable colours, double glazing.
4. Provide shading and ventilation.
5. Use heating or cooling devices where passive means are not sufficient.

Passive methods

Use natural energy flows without mechanical equipment.

• Passive heating: direct gain (south windows with thermal mass), Trombe wall, sunspace, insulation, compact form.
• Passive cooling: shading by chhajja, trees and louvres; cross and stack ventilation; courtyards and wind catchers; evaporative cooling with ponds and plants; earth-contact cooling; night ventilation; light-coloured, insulated roofs.

 Passive heating (winter)      Passive cooling (summer)
 sun-> [glass]|dark wall       shade ^  hot air out (high)
        warm air to room       cool air in (low) <- shaded yard

Active methods

Use energy-consuming equipment.

• Active heating: electric heaters, heat pumps, boilers with radiators, solar water or air collectors with pumps, gas or biomass heaters.
• Active cooling: fans, evaporative (desert) coolers, split and central air conditioning, chillers.
• Controls: thermostats, timers and sensors.

Comparison

Best practice is to use passive measures first to reduce loads, and add active systems only to cover the remainder.

Daylight factor (DF) is the ratio of the illuminance at a point on a working plane inside a room, due to the sky light (excluding direct sunlight), to the simultaneous illuminance on a horizontal plane outdoors from an unobstructed sky, expressed as a percentage.

$$DF = \frac{E_i}{E_o} \times 100\%$$

where $E_i$ is indoor illuminance (lux) and $E_o$ is outdoor illuminance (lux).

Components

$DF = SC + ERC + IRC$

• Sky component (SC): direct light from the sky through the window.
• Externally reflected component (ERC): light reflected from outside surfaces such as nearby buildings.
• Internally reflected component (IRC): light reflected from the room surfaces.

Points

• It is a measure of the adequacy of daylight, and it stays constant for a point in an overcast sky.
• It falls with distance from the window; the point near the window has a higher value.
• Recommended values: about 2 % for houses, 3 to 5 % for classrooms and offices, and 5 to 10 % for drawing rooms and workshops with fine work.
• Factors: window size and position, glass, obstructions, room finish colours.

Natural lighting

Illumination of interior spaces by the light of the sun and sky through windows, skylights and ventilators. It is free, changes in time, and gives good colour rendering. Design uses window area, orientation and light shelves.

Artificial lighting

Illumination from man-made sources (incandescent, fluorescent, CFL, LED lamps) used when daylight is insufficient or at night. It is controllable and constant but uses energy and costs money.

Daylight factor

Daylight factor (DF) is the ratio of the indoor illuminance at a point to the simultaneous outdoor illuminance on an unobstructed horizontal surface, as a percentage.

$$DF = \frac{E_i}{E_o} \times 100\%$$

 Sky (outdoor Eo)
      \  \  \
   ====[window]====
       \  \
        . point P  (indoor Ei)

Calculation

Given $DF = 2.0\%$ and $E_o = 7000$ lux.

$$E_i = \frac{DF \times E_o}{100} = \frac{2.0 \times 7000}{100} = 140\ \text{lux}$$

Answer: Internal illumination = 140 lux. (This is lower than the 300 lux usually needed in a classroom, so supplementary artificial lighting or larger windows would be needed.)

Thermal performance of building sections

Thermal performance is the ability of a wall, roof, floor or window to resist heat flow and keep indoor conditions comfortable. It depends on the conductivity ($k$) and thickness ($t$) of its layers, surface films, air gaps, thermal mass (time lag and decrement) and the colour of the surface. Good performance means low heat gain in summer and low heat loss in winter, giving comfort with less energy.

Transmittance

Thermal transmittance (U-value) is the rate of heat flow through one square metre of a building element for a temperature difference of 1 °C between the air on its two sides, in W/m²°C. It is the reciprocal of the total resistance.

$$U = \frac{1}{R_{total}} = \frac{1}{\frac{1}{f_i} + \sum \frac{t}{k} + \frac{1}{f_o}}$$

with $f_i$ and $f_o$ the internal and external surface conductances.

Calculation

Layers from inside to outside: inner surface film, 12 mm plaster, 110 mm brick, 25 mm thermocole, 25 mm cavity, 110 mm brick, 12 mm plaster, outer surface film.

$$\begin{aligned} R_{total} &= 0.1232 + 0.0167 + 0.0957 + 0.7353 + 0.9615 + 0.0957 + 0.0167 + 0.1000 = 2.1446\ \text{m}^2\text{°C/W} \\ U &= \frac{1}{2.1446} = 0.466\ \text{W/m}^2\text{°C} \end{aligned}$$

Answer: $U = 0.466$ W/m²°C.

Thermal gradient

The temperature drop across each layer is proportional to its resistance. For example, take inside 25 °C and outside 5 °C ($\Delta T = 20$ °C). Heat flux $q = U\Delta T = 0.466 \times 20 = 9.33$ W/m². Drop in each layer is $\Delta T_i = qR_i$:

 25C ‾\
       \___ brick  (gentle)
           \
            \  thermocole (steep)
             \
              \  cavity (steep)
               \___ brick, plaster
                   \ 5C
 in |P|B|Ins|Cav|B|P| out

The steepest falls are in the cavity and the thermocole, because they have the largest resistance.

Renewable and non-renewable sources

Renewable energy comes from sources that are naturally replaced in a short time: solar, hydro, wind, biomass and biogas, geothermal, tidal. Non-renewable energy comes from fixed stocks formed over millions of years: coal, oil, natural gas and uranium.

World scenario: About 80 % of world energy is still from fossil fuels (oil about 30 %, coal about 27 %, natural gas about 23 %). Renewables, including hydro, supply roughly 15 to 20 % of primary energy and about 30 % of electricity, and are growing fastest in solar PV and wind. Fossil fuels are limited and cause climate change, so countries move to renewables. Nepal gets most of its electricity from hydropower, and most household energy from firewood, with petroleum fully imported.

Trapping solar energy in buildings (energy efficient design)

1. Orientation and layout: Long axis east-west and living spaces facing south.
2. Direct gain: Large south windows; the sun heats floors and walls of high thermal mass (concrete, stone, adobe).
3. Trombe wall: Dark masonry wall behind a glass pane with vents; absorbs heat and sends it by convection and radiation.
4. Sunspace (attached greenhouse): Glazed space on the south side which collects heat and shares it with the rooms.
5. Roof collectors / solar air heaters and water heaters for hot water.
6. Roof pond or water wall to store heat.
7. Photovoltaic panels for electricity.
8. Insulation and weather sealing to keep the gained heat, and overhangs to avoid summer overheating.

 winter sun ->|glass| air gap |dark mass wall| room
                   vents top & bottom: warm air loop

Passive solar design

Passive solar design is the design of a building so that it collects, stores and distributes solar energy for heating (and rejects it for cooling) by the form, orientation and materials of the building itself, without mechanical equipment.

Importance

• Reduces energy for heating, cooling and lighting, and so saves money.
• Gives thermal and visual comfort.
• Has low maintenance and running cost, with no moving parts.
• Reduces use of fossil fuel, firewood and pollution; useful in Nepal's cold hills and mountains.
• Increases building life and value, and gives more daylight.

Setting layout plan of building

1. Place the building with its long axis east-west, so the long face looks south (within 15° of south).
2. Put living and working rooms, with large glazing, on the south side. Put stores, toilets, stairs and garages on the north as a buffer.
3. Keep east and west walls with few and small openings.
4. Use overhangs, chhajja, or deciduous trees on the south side to give shade in summer and let the low winter sun in.
5. Keep buildings spaced so that each is not shaded by the next one (sun angle at winter solstice).
6. Plant evergreen trees on the north-west side as wind-break against cold winds.

            N  (stores, toilets)
        +---------------+
   W    | bed |  kitchen|    E
        |---------------|
        | living (glass)|
        +---------------+
            S  sun -> 
          [tree, deciduous]

Common acoustic defects

1. Echo: Reflected sound arrives more than about 0.1 s after the direct sound, giving a repeated sound. Cured by absorbing surfaces on the reflecting walls.
2. Reverberation: Persistence of sound after the source stops because of repeated reflections. Too much reverberation lowers clarity. Cure: add absorbing materials to reduce reverberation time.
3. Sound foci (concentration): Concave surfaces focus sound at one point, making dead spots elsewhere. Avoid concave domes; use convex or absorbing finishes.
4. Dead spots: Areas with little sound. Use reflectors and avoid focusing.
5. Echelon effect: Repeating reflections from regularly-spaced steps or railings, giving a musical tone.
6. Resonance: Panels or air volumes vibrate at their natural frequency and amplify some tones. Use damping.
7. Sound shadow: Balconies shade the sound behind them.
8. Insufficient loudness and external noise.

Can a good sound insulator be a poor absorber?

Yes. Sound insulation depends on the mass and airtightness of the material, which reflect sound. Sound absorption depends on porosity, which lets sound enter and lose energy. A dense concrete wall or brick wall is an excellent insulator (high transmission loss), but its hard, smooth surface reflects almost all sound back into the room, so its absorption coefficient is very low (about 0.02 to 0.05). On the contrary, a mineral wool blanket absorbs well but, being light and porous, insulates poorly. So the two properties are not the same and may even be opposite.

Systems of sound insulation

Sound travels as airborne sound (voice, TV) and impact or structure-borne sound (footsteps). Insulation is by barriers.

Vertical barrier systems (walls and partitions)

1. Heavy, dense walls: thick brick, concrete (mass law: doubling mass gives about 5 to 6 dB more).
2. Cavity (double) walls with a gap of 50 mm or more, with no rigid ties, and the gap filled with sound-absorbing wool.
3. Staggered stud or double-stud partitions with separate frames.
4. Plastering on both faces to seal pores and gaps; sealing of all cracks and service holes.
5. Acoustic doors and double glazed windows with different glass thicknesses.

Horizontal barrier systems (floors and ceilings)

1. Heavy RCC slab (airborne sound).
2. Floating floor: floor finish on a resilient layer (rubber, cork, mineral wool) which is lifted off the slab and walls by a gap.
3. Resilient floor finishes: carpet, rubber, cork tiles to reduce impact noise.
4. Suspended (false) ceiling hung on resilient hangers, with absorbent material above it.

 Floating floor:
   finish
   screed
   resilient layer (wool)  <- edge strip at wall
   RCC slab

Four common acoustic defects are as follows.

1. Echo: When a reflected sound reaches the listener more than about 0.1 second (some textbooks say 1/15 s) after the direct sound, it is heard as a separate repetition. It occurs in large halls with parallel hard walls far from the source. Remedy: cover the reflecting surface with absorbent materials such as acoustic plaster, curtains or panels; make the walls irregular.
2. Reverberation: The sound persists in the room after the source has stopped because of multiple reflections. Excess reverberation makes speech unclear and music muddy. Optimum reverberation time is about 0.5 to 1 s for speech halls. Remedy: raise the absorption (carpets, curtains, acoustic ceiling, upholstered seats). Reverberation time by Sabine is $T = 0.16V/A$.
3. Sound foci and dead spots: Concave surfaces, such as domes and curved walls, concentrate reflected sound at some points (foci) and leave other places with very low sound (dead spots). Remedy: avoid concave surfaces, or cover them with absorbing material; use convex diffusers.
4. Resonance: Some objects or air spaces vibrate at the same frequency as the sound, increasing certain tones. Remedy: damp the panels with absorbent backing, and avoid hollow spaces of resonant size.

Other defects are echelon effect, sound shadow, and external noise.

Acoustics is the science of sound, covering its production, transmission, absorption and reception. In buildings, it deals with providing good hearing conditions and controlling noise.

Acoustic defects and remedies

Design of the hall should give uniform loudness, right reverberation time, and freedom from echo and noise.

Objective of floor insulation

An RCC slab is heavy and airtight, so it blocks airborne noise (voice, music) well. But it is a good conductor of impact (structure-borne) sound, such as footsteps, dragging of furniture or falling objects, and carries it to the room below, and through walls to other rooms. So floor insulation is provided mainly to reduce impact sound transmission, and also to improve the sealing around joints and add comfort.

Methods of horizontal sound insulation (floors and ceilings)

1. Floating floor: A screed or floor finish rests on a resilient layer (glass wool, rubber, cork, foam) laid over the slab; an edge strip separates the floor from the walls.
2. Resilient floor finish: Carpet, rubber, cork or vinyl tiles absorb impact.
3. Suspended ceiling with absorbent material, supported by resilient hangers below the slab.
4. Increasing the mass of the floor.

Methods of vertical sound insulation (walls and partitions)

1. Heavy walls (230 mm brick) plastered on both faces; use of dense blocks.
2. Cavity wall with absorbent filling and no rigid ties.
3. Double partitions with independent frames; resilient mounting.
4. Seal gaps; use acoustic doors and double-glazed windows.
5. Avoid back-to-back pipes and sockets.

Characteristics of audible sound

1. Frequency / pitch: Audible range is about 20 Hz to 20,000 Hz; speech is mostly 250 to 4000 Hz.
2. Intensity / loudness: Measured in decibels (dB), from 0 dB (threshold of hearing) to about 120 dB (pain). $L = 10\log_{10}(I/I_0)$ with $I_0 = 10^{-12}$ W/m².
3. Quality (timbre): The tone that tells apart two sounds of the same pitch and loudness; it depends on harmonics.
4. Velocity: About 343 m/s in air at 20 °C.
5. Wavelength: $\lambda = v/f$.
6. Sound is reflected, absorbed, transmitted and diffracted at surfaces.

Defects due to reflected sound

Echo, excessive reverberation, sound foci (from concave surfaces), dead spots, echelon effect, and resonance.

Methods of sound insulation

1. Site planning: Set the building back from noisy roads, use trees and earth mounds as barriers, and place quiet rooms away from noise.
2. Heavy and dense construction: Thick walls and slabs; mass law.
3. Cavity walls and double partitions with absorbent filling.
4. Floating floors, resilient finishes and suspended ceilings for impact sound.
5. Sealing cracks, gaps and service holes, and acoustic doors and windows with weather strips; double glazing.
6. Vibration isolation: Flexible mounts for machines and pipes.
7. Absorbent surfaces inside the room to reduce noise level.

How absorptive materials absorb sound

Sound absorbers are porous, soft or flexible. Absorption works by three mechanisms:

1. Porous absorption: Sound enters the connected pores of materials such as mineral wool, glass wool, acoustic tile, carpets and curtains. The air in the pores moves, and friction with the fibres changes the sound energy into a little heat.
2. Panel (membrane) absorption: Thin panels of plywood or hardboard over an air space vibrate when sound strikes them, and absorb mostly low frequencies by internal damping.
3. Cavity (Helmholtz) resonators: Perforated boards with an air space behind; air in the holes resonates and loses energy, mostly in a narrow band.

The absorption coefficient $\alpha$ is the fraction of incident sound absorbed (0 for a perfect reflector, 1 for an open window).

General considerations for noise control in buildings

1. Site selection and planning: Set back from highways, railways and airports. Put noisy zones away from quiet rooms. Use trees, fences and mounds as buffers.
2. Building layout: Group noisy and quiet spaces separately; a service core between.
3. Insulation: Heavy walls, floors, double glazing, sealed doors.
4. Absorption inside rooms using acoustic ceilings and carpets.
5. Control at the source: Silent machines, vibration mounts and enclosures for generators and pumps.
6. Services: Isolate ducts, pipes; lined ducts, silencers.
7. Legal regulation: Noise limits and horn restrictions.

Sound insulation is the prevention of the passage of sound from one space to another (or from outside to inside) by using barriers that reflect and block the sound energy. It gives privacy and a quiet environment.

Types of sound

• Airborne sound: voice, music, traffic; reaches the listener through air and structure.
• Impact (structure-borne) sound: footsteps, hammering; travels through the structure.

Principles

• Mass law: Heavier barriers insulate better; doubling the mass raises the sound reduction by about 5 to 6 dB.
• Airtightness: Gaps and cracks greatly reduce insulation.
• Isolation (decoupling): Separating the layers with an air gap or resilient material.
• Damping and absorption in the cavity.

Methods

1. Thick, dense walls and slabs; cavity walls with wool fill.
2. Floating floors, carpet and suspended ceilings.
3. Double-glazed windows and solid-core doors with seals.
4. Planning: buffer zones and distance, trees.
5. Sealing of all openings and service penetrations.

Performance is measured by the sound reduction index (dB). Examples: 115 mm brick wall about 40 dB, 230 mm brick wall about 50 dB.

Noise is unwanted or disturbing sound. It is measured in decibels (dB); for example, a quiet room is about 30 dB, normal talk 60 dB, heavy traffic 80 to 90 dB, and a jet engine 120 dB or more.

Sources

Road, rail and air traffic; industry and construction machines; generators; loudspeakers and crowds; neighbours and domestic appliances.

Effects of noise

1. Hearing loss: Temporary or permanent damage from long exposure over about 85 dB.
2. Physiological effects: High blood pressure, rapid heart rate, tiredness and headache.
3. Psychological effects: Stress, irritation, anger, anxiety and loss of concentration.
4. Sleep disturbance: Poor sleep, less rest.
5. Reduced efficiency at work and study, and mistakes or accidents.
6. Speech interference: Poor communication.
7. Social and economic effects: Reduced property value and loss of privacy.
8. Structural effects: Intense noise and vibration may crack glass and weak parts.

Control

Site planning with distance and barriers, sound-insulated construction, absorption in rooms, silencers, and law limits on noise. The Nepal Environment Protection Rules set standards for noise levels.

Building is a structure with walls, floor and roof, built to give shelter for people, animals, goods or activities.

Types of buildings

According to the National Building Code (NBC 205/206) and the Nepal Building Act, buildings are classed by use:

1. Residential: houses, flats, hostels, dormitories, hotels.
2. Educational: schools, colleges, training centres.
3. Institutional: hospitals, clinics, sanatoriums, jails, orphanages.
4. Assembly: cinema halls, theatres, auditoriums, community halls, temples, stadiums, places where many people gather.
5. Business / office: offices, banks, post offices.
6. Mercantile (commercial): shops, markets, shopping malls, warehouses for sale of goods.
7. Industrial: factories, workshops, power stations.
8. Storage: godowns, silos, garages.
9. Hazardous: buildings storing explosives or flammable materials.
10. Mixed use: for more than one use.

Buildings are also grouped by structure: load-bearing masonry, RCC framed, steel framed, and timber; by height as low-rise, mid-rise and high-rise.

  Residential        Assembly Hall        Industrial
   /\                 ___________          _/|_/|_/|
  /  \               |  [stage]  |        |        |
 |[]  |              |___________|        |________|

In Nepal, NBC 205 covers Mandatory Rules of Thumb for low-rise masonry buildings, and NBC 105 covers seismic design.

Heat

Heat enters and leaves by conduction, convection and radiation. Control through orientation, insulation (low U-value), shading of windows, thermal mass, cavity walls, light-coloured roofs and cool roofs. The aim is thermal comfort of 21 to 27 °C.

Ventilation

Supply of fresh air and removal of stale air to supply oxygen, remove CO₂, odour and heat. Natural ventilation by cross openings (wind) and stack effect; mechanical by fans for kitchens, toilets, basements. Opening area is generally at least 10 % of floor area, as per the National Building Code.

Light

Daylight is preferred. Window area, orientation and shading give a daylight factor of 2 to 5 %. Artificial lighting is used at night and where daylight is inadequate.

Sound

Provide sound insulation (heavy walls, cavity, floating floors, double glazing) against outside noise and neighbours, and absorption to control echo and reverberation inside.

Orientation

Rooms are arranged by the sun path and wind direction: for example, kitchen in the east or north-east, living room and bedroom in the south, long side facing south.

Moisture movement

Rising damp, rain penetration, condensation and leaks cause damage. Prevent by DPC at plinth, waterproof plaster, roof slopes and flashing, cavity walls, drains and ventilation.

 sun ->  [S windows + chhajja]
 wind -> [window]---room---[window] -> cross ventilation
 ======= DPC at plinth ======= 

A good design balances all these factors together.

Heat phenomena in a building are the processes by which heat enters, leaves or is stored in a building, and which decide the thermal comfort of its occupants.

Modes of heat transfer

1. Conduction: Heat flows through a solid from the hot face to the cold face. $q = \frac{k}{t}\Delta T$ where $k$ is conductivity. It is how heat moves through walls and roofs.
2. Convection: Heat carried by moving air or fluid. It occurs on wall surfaces and in cavities and rooms. Natural (buoyancy) or forced (fans).
3. Radiation: Heat travelling as electromagnetic waves from the sun and from hot surfaces. It needs no medium. The major source of heat gain in summer through windows and roofs.
4. Evaporation: Heat taken from a surface when water evaporates; used for cooling.

Heat gains and losses in a building

• Gains: Solar radiation through glass and on roofs and walls, conduction from hot outside air, occupants, lights and appliances, hot ventilation air.
• Losses: Conduction through the envelope in cold weather, ventilation and leakage, evaporation, radiation to the night sky.

Thermal properties

• Thermal conductivity (k), resistance $R = t/k$, transmittance $U = 1/R_{total}$.
• Specific heat and thermal mass, which give time lag and decrement factor.
• Absorptivity, reflectivity and emissivity of surfaces.

Control

Orientation, shading, insulation, cavity walls, reflective finishes, thermal mass, ventilation, double glazing. Heat balance of building: $Q_s + Q_i + Q_c + Q_v + Q_e = 0$ for steady state.

Effect

Heat flow decides indoor temperature and the heating or cooling energy needed; so it should be studied at the design stage.

Requirements of lighting in a building

1. Adequate illumination: Enough light for the task (e.g. 100 to 150 lux for living rooms, 300 lux for classrooms and offices, 500 lux for drawing rooms), as per NBC.
2. Uniform distribution: No dark corners or sharp contrast between bright and dark areas.
3. Freedom from glare: Direct or reflected glare from sun or lamps must be avoided by shades, louvres and diffusers.
4. Proper direction: Light should come from a direction that avoids shadows on the working plane.
5. Colour rendering: Natural-looking colours; light of suitable colour temperature.
6. Daylight use: Windows of area not less than about 10 % of floor area (daylight factor 2 to 5 %), well placed (north light is steady) to save energy.
7. Artificial lighting: General, task and emergency lighting for night; efficient lamps (LED).
8. Control: Switches, dimmers, and shading devices; maintainable fittings.
9. Economy and safety: Low energy use, no heat and no fire hazard.

Principles of site selection and planning

1. Purpose and nearness to services such as roads, water, electricity, school and market.
2. Soil: firm and level, with good bearing capacity and a low water table; avoid black cotton soil, marsh and filled ground.
3. Natural drainage and flood-free land; away from landslides, river banks and faults.
4. Good environment: Clean air, sun and wind, away from noise, smoke and odour.
5. Orientation and shape: Regular plot, with long axis east-west and open to south and wind.
6. Legal: Ownership, land use zone, setback, ground coverage as per bye-laws.
7. Planning: Placing the building to give light, ventilation, privacy, future expansion and a landscaped open space.
8. Economy: Cost of land and development.

Sources of moisture in a building

1. Ground water rising by capillary action through foundations and walls (rising damp).
2. Rain penetrating through roof, walls, parapets, windows and joints.
3. Condensation of water vapour on cold surfaces such as walls, ceilings and windows.
4. Leakage from water supply and drainage pipes, bathrooms and roof tanks.
5. Construction moisture in new concrete, mortar and plaster.
6. Defects in design such as poor drainage, no DPC, and flat roofs without slope.
7. Hygroscopic salts in bricks and sand.

Methods of moisture control

1. Damp proof course (DPC) at plinth, 150 mm above the ground. Types: 40 mm cement concrete 1:2:4 with waterproofing compound, bituminous felt, polythene sheet, or mastic asphalt (flexible). Also DPC at sills, parapets and in cavity walls.
2. Integral treatment: Water-proofing compound is added to concrete and plaster.
3. Surface treatment: Waterproof cement plaster, water-repellent paint, pointing, and silicone coating.
4. Cavity wall: An air gap that breaks the moisture path.
5. Roof treatment: Proper slope, brick-bat coba waterproofing, membrane, flashing at junctions, gutters and rain-water pipes.
6. Drainage: Apron around the building, sub-soil drains and slope of ground away.
7. Ventilation and vapour barriers to prevent condensation.
8. Chemical injection / grouting for existing damp walls.
9. Basement tanking.

   wall
   ======== <- DPC (150 mm above GL)
   ~~~~~~~~ ground level
   apron 750 mm wide, sloping away

Moisture movement

Moisture moves through building materials in two forms.

1. Liquid movement: By capillary action (rising damp), by gravity (percolation through roofs and cracks), by wind pressure (driven rain) and by hydrostatic pressure (basements).
2. Vapour movement: By diffusion from higher to lower vapour pressure, usually from the warm, humid side to the cold side, and by air movement carrying vapour through leaks.

If vapour meets a surface below the dew point temperature, it condenses to water.

Types of condensation

1. Surface condensation: Occurs on the visible inner surface of a wall, window, or ceiling that is colder than the dew point of the room air. Common in kitchens and bathrooms in winter.
2. Interstitial (concealed) condensation: Vapour passes into the wall or roof and condenses inside the material, where the temperature falls below dew point. It is unseen and more harmful.
3. Condensation in cavities (roof voids, cavity walls).

Effects on building materials

• Damp patches and stains, peeling paint and plaster.
• Mould and fungal growth; bad smell; health problems.
• Timber rots; reinforcement and steel corrode.
• Frost damage and spalling of masonry.
• Loss of thermal insulation of wet insulation.
• Dripping water damages furniture and finishes.

Control

Ventilate humid rooms; insulate to keep surfaces warm; use vapour barrier on the warm side; use dehumidifiers and extract fans.

Damp proofing is the treatment of a building, by providing an impervious layer (DPC) or other measures, to prevent moisture from the ground, rain or other sources from entering the walls, floors and roofs.

Methods in brief: membrane DPC (bitumen felt, polythene, cement concrete 1:2:4 with waterproofing compound at plinth level), integral waterproofing compounds, surface treatments (waterproof plaster and paint), cavity walls, guard drains, and grouting or injection in old buildings.

Defects in buildings due to moisture (dampness)

1. Stains and patches on walls and ceilings; peeling or blistering of paint, plaster and wallpaper.
2. Efflorescence: White crystals of salts brought to the surface, spoiling the appearance and breaking plaster.
3. Disintegration of bricks, stone and mortar; softening of plaster.
4. Decay and rot of timber (doors, windows, floors) and termite attack.
5. Corrosion of steel and reinforcement, causing concrete to crack and spall.
6. Growth of fungus, moss and mould, giving a bad smell and unhealthy conditions.
7. Reduced strength and thermal insulation of walls.
8. Damage to floor coverings and furniture; warping of timber floors.
9. Electrical short circuits.
10. Cracks and uplift of flooring due to swelling.
11. Lower property value and uncomfortable living.

Below-grade waterproofing

Below-grade waterproofing is applied to parts of a building below ground level (basements, foundations, retaining walls, underground tanks) that face ground water and hydrostatic pressure.

• Positive side (external): A membrane (bituminous coating, self-adhesive sheet, bentonite panels) is put on the earth face of the wall and under the raft, protected by a protection board or brick wall before backfilling.
• Negative side (internal): Cementitious or crystalline coating and plaster on the inside face.
• Integral: Waterproof concrete with admixtures, and water bars in joints.
• Drainage: Sub-soil drain, gravel layer, and sump.

Above-grade waterproofing

Above-grade waterproofing is applied to parts above the ground: exposed walls, roofs, terraces, balconies, bathrooms, parapets. These face rain and sun, but not high water pressure.

• Membranes on roofs and terraces (bituminous, PVC or liquid applied) with a protective screed or tiles.
• Brick-bat coba over slab with 1:4 mortar screed in slope.
• Waterproof paint or silicone coating on exterior walls; cement-sand plaster with compound.
• Flashings at junctions, drip moulds, and sealants at joints.

Methods to stop moisture movement in a building

1. DPC at plinth and above ground floor level.
2. Cavity wall construction.
3. Waterproof plaster and paints; pointing.
4. Roof slope, coba, membranes, flashing, gutters and downpipes.
5. Surface and sub-soil drainage; apron around the building.
6. Ventilation and vapour barrier against condensation.
7. Integral waterproofing compounds in concrete and mortar.
8. Chemical injection or pressure grouting for old walls.
9. Tanking in basements.

Basement and below-ground waterproofing is classified by the side of the structure on which the membrane is applied.

Positive side waterproofing

The waterproofing is applied on the side from which the water comes, which is the outer (earth) face of the wall and under the raft. The water is stopped before it reaches the structure, so the wall itself stays dry and is protected from damage by the water. It is the preferred and more reliable system, but needs excavation space and work during construction. Materials: bituminous membrane, APP/SBS sheet, bentonite, liquid-applied membrane, covered with a protection board or a brick wall.

Negative side waterproofing

The waterproofing is applied on the inner face of the wall, away from the water. The structure itself is wet and is under water pressure, but water is stopped from entering the room. Used for existing buildings or where the outside is not reachable. Materials: crystalline coating, cementitious slurry, epoxy, waterproof plaster. The coating may peel off under pressure, and the wall can get damp and corroded inside.

 Positive:                   Negative:
 soil|memb|wall|room         soil|wall|memb|room
 water stopped outside       water stopped inside

Positive side and negative side waterproofing

Positive side (external) waterproofing: The membrane is applied on the outer face of the basement wall and below the raft, on the side from which water presses. Water is kept out of the structure itself. It is the most effective and is used in new works. A protective layer (brick wall or board) is placed over the membrane before backfilling.

Negative side (internal) waterproofing: The waterproofing is applied on the inner face, opposite to the water side. The wall remains in contact with water, but seepage into the room is stopped. It is used when the outer face cannot be reached, such as in repairs.

DPC for a basement in ordinary soil

In ordinary (non-water-bearing, well-drained) soil, a basement needs a damp-proof course on the floor and walls.

1. Floor: Ground is compacted, a layer of hardcore or stone soling is laid, then 100 mm PCC (1:3:6), then the DPC layer, a bituminous membrane or 2 to 3 layers of polythene, then a protective cement-sand screed 40 to 50 mm, and then the floor slab.
2. Wall: Wall faces are plastered with 20 mm cement-sand 1:3 mortar with waterproof compound, and two coats of hot bitumen are applied on the outer face. A horizontal DPC is placed at plinth level above ground.
3. Joint: The floor DPC and the wall DPC are joined with a lap of at least 150 mm so the barrier is continuous.
4. A brick protective wall is built outside the membrane, then backfill, with drain.

        GL ----- horizontal DPC at plinth
          |memb|wall|
          |    |    |
  floor:  screed
          membrane (DPC)  <- lap with wall membrane
          PCC 1:3:6
          hardcore