• Direct natural ventilation, via windows, should be provided to all rooms that require direct natural light. (section 1.5.1.) This applies to kitchens, kitchen/dining rooms and all closed (closable) spaces in the home apart from kitchens in one- or two-occupant homes.
• Indirect natural ventilation should be provided to corridor spaces, dining rooms, storage rooms, storage areas for non-perishable materials (e.g., wardrobes, built-in cupboards and general storage), and sleeping areas (galleries or cubicles) that feature a large unobstructed opening onto adjoining living areas that are continually supplied with direct natural ventilation.
Direct ventilation – via windows, air ducts or mechanical systems – must be provided to all sanitary spaces (e.g., bathroom, shower and toilet), housekeeping rooms and pantries.
Mechanical ventilation (extractor fans) should be used, with caution, over cookers, in food preparation areas that are not separated from other rooms, and in windowless kitchenettes in one- or two-occupant homes.
Note
Extractor fans (cooker hoods) should not be used in the same spaces as fireplaces or heating stoves. The hood creates a drop in pressure that could cause a back draft from the chimney. The same applies to chimneys of incorrect height as well. In the past, this has also occurred where gas appliances were used. More recently, though, gas appliances have a closed combustion chamber where oxygen is drawn directly from outdoors. This back draft problem might also occur with other ventilation systems, central vacuum cleanings and bathroom extractor fans. Therefore, if such mechanical systems are built into a home, simultaneous use should be avoided. (AN)
Previously not mentioned, and not generally required, is ventilation in residential spaces depending on the nature of its intended use. Direct ventilation (i.e., windows) is necessary to exhaust odors, steam or the residue of pollution-producing activities.
1.5.3. Thermal comfort and heating
Thermal comfort does not refer solely to the air temperature within the home; other factors also apply.
We can feel cold near a large window due to a chill wind (cold radiates from the surface of glass), so more heating is required. Or we may feel warm when near heat-radiating surfaces (heated floors and walls) even though the air is cooler. Thermal comfort can also be affected by the movement of air and ambient humidity levels.
Note
Well insulated walls and floors are associated with thermal comfort. A better insulated outer wall leads to better inner surface temperatures, so inside air temperatures can be lower than usual for thermal comfort. For general good health and physical well-being, the inner wall surface temperature should be not less than 16ºC, even in corners of rooms.
To maintain a surface temperature of 16ºC, the air temperature should be about 23-24ºC for an activity in the sitting position. If the wall surface can be kept at about 20ºC, then so can the air temperature. This means that with better insulation, less energy is required.
Further savings can be achieved by providing a lower interior air temperature inlet level and high comfort levels. The heating of homes and buildings can be solved in many ways, and technology is providing even more, ever newer methods of doing so. One thing is certain, design should strive to reduce winter heat loss (good insulation, good surface/
volume ratio and avoidance of thermal bridging) and increase heat gains (orientation, juxtaposing spaces and zoning). (AN)
The heating of a building is usually designed by a mechanical engineer. However, energy demand is a function of architectural and structural design. The following paragraphs refer to all different energy-efficiency aspects of residential buildings.
Solid fuel heating systems are rarely used, gas-fired central heating being widespread. Individual homes or multi-unit homes employ an independent central heating system or shared heating network, respectively. The most commonly used system is a wall mounted boiler and exhaust flue (or chimney).
Dimensions are given in figure 1.49.
Figure 1.41. Gas fired boiler
Not only low temperatures are uncomfortable, high temperatures also are not so pleasant, especially on a hot summer day. Over a 24-hour period, the temperature varies form cooler overnight and in the morning to warmer at noon. A building with a higher physical mass loses the ability to gain or shed heat over time, creating a stable average daily temperature; while external materials with a high thermal inertia remain cooler (traditional thick-walled brick and stone buildings). Summer overheating tends to occur in light building structures. An important factor is the ventilation of dwellings. Multi-unit housing is better when windows are provided on opposite sides of the building, allowing for a cross-draft overnight when the walls shed the heat absorbed during the day. The worse type of dwelling is that which only has openings on a single high heat-load elevation.
Solar heat gain upon windows can be reduced by shielding methods. Summer sun on a south-facing wall can be shielded with a horizontal projection (figs. 1.50a, 1.50b and 1.50c), but they are not effective on the east or west sides, where the angle of the summer sun is low in the sky. This mostly applies to the western side when outside air temperature is also high in times of direct solar radiation.
Shielding against this can be achieved using mobile shielding devices. (figs. 1.50d and 1.50e)
Figure 1.42. Commonly used domestic shading devices
Demanding residential buildings often have mechanical cooling devices installed (air conditioners), but their energy consumption is very high. In light of global "sustainable development", this is a negative phenomenon; it is preferable to design homes that do not require energy consumption to provide sufficient thermal comfort in the summer.
1.5.4. Daylight, orientation and energy awareness
Daylight in the home can serve as a source of solar energy, for the sake of health and comfort as well. Direct sunlight can be germicidal, preventing the growth of harmful micro-organisms and fungi.
Rooms orientated so that they receive no sunlight can be depressing, resulting in bad moods.
A sunlit room uses external energy to generate savings. Today, homes have become more affordable when energy costs are taken into consideration – with the creation of space, the layout of glazed surfaces and orientation giving rise to "passive solar principles". Aside from technical devices (e.g., solar collectors and solar cells), this means the building’s fabric itself becomes active.
In general, the building should use appropriate structural materials and finishes (concrete, brick and ceramic tiles) to absorb solar energy.
Solar gain is a positive phenomenon during most of the year in this climate; yet, during hot summer days, it can be detrimental, causing overheating. (See previous section.)
East-facing bedrooms are beneficial, since they receive solar radiation in the morning hours when the outside air temperature is lower after a cool dawn. At noon, when temperatures become higher, eastern elevations are not sunny. Conversely, this is why west-facing bedrooms are at a disadvantage due to overheating and discomfort at night time. In kitchens, overheating is exacerbated by the oven, and a warm pantry is also detrimental. A room’s orientation should take into account two conflicting viewpoints: 1) does the room have enough daylight, and 2) does the room disturb users through overheating?