Toa 2

• Visual comfort


  Characterized by a sufficient amount of natural light (and, secondly, artificial light), good glare control, and access to views of the outdoors
• Achieving visual comfort


  Correct light quantity, during both daytime and nighttime, in order not to tire the eyes
• Factors affecting visual comfort

  • The quantity of light
  • The homogeneity of light
  • The light quality in colour rendering
  • The occupants' glare risk prediction
• Visual comfort (European standard EN 12665)


  A subjective condition of visual well-being induced by the visual environment
• Factors that visual comfort depends on

  • The physiology of the human eye
  • The physical quantities describing the amount of light and its distribution in space
  • The spectral emission of the light source
• Both too little and too much light can cause visual discomfort
• Important changes in light levels or sharp contrast (which is perceived as glare) can cause stress and fatigue as the human eye is permanently adapting to light levels
• Aspects to consider when designing for visual comfort

  • Always prioritize natural light
  • Map the distribution of light, independent of the observer: Illuminance and Luminance
  • Evaluate the quantity and quality of light
  • Consider the relationship between openings and space: Window-to-Floor Ratio
  • Decide the amount of light that must pass through the glass: Visible Light Transmission
• Non-adequate lighting systems can cause problems with visual fatigue, as well as causing errors or possible accidents
• Visual discomfort markers


  • Red eyes
  • Burning eyes
  • Double vision
  • Eye fatigue
  • Blurred vision
  • Headache
• Inadequate lighting conditions can be related to the computer vision syndrome (CVS)
• Symptom categories of computer vision syndrome


  • Visual symptoms
  • Musculoskeletal symptoms
  • Asthenopia
• Symptoms of computer vision syndrome

  • Blur at near
  • Post work blur at distance
  • Slowness in focusing
  • Double vision
  • Neck and shoulder ache
  • Back ache
  • Sore wrist
  • Headaches
  • Eyestrain
  • Eye fatigue
  • Ocular dryness
  • Glare sensitivity
• Thermal comfort


  Thermal comfort can be maintained when heat produced by metabolism equals the heat lost from body
• Parameters affecting thermal comfort

  • Physical activity
  • Clothing
  • Air temperature and humidity
  • Relative air speed
  • Relative temperatures of surfaces enclosing the space (walls, ceilings, floors, windows)
  • Time spent in that environment
• Thermal comfort concepts


  • The perception of lack of thermal comfort is a warning that our body sends us to tell us that thermal equilibrium is not satisfied, and for this reason are under stress
  • When we are cold it means that we are dissipating in the environment more heat than we are producing our internal temperature tends to decrease
  • When we are hot it means that we are dissipating less heat than we are producing our internal temperature tends to increase
  • The amount of heat exchanged between a body and the surrounding environment depend on the physical activity being carrying out
• Ways the human body exchanges heat with the environment

  • Convection
  • Transpiration and respiration
  • Conduction
  • Radiative heat exchanges
• Predicted Mean Vote (PMV)

  An overall index for thermal comfort that provides the mean value of the votes, according to the thermal sensation of a large group of people exposed to the same environment
• PMV and PPD categories

  • High level of expectation and is recommended for spaces occupied with special requirements like handicapped, sick, very young children and elderly persons
  • Normal level of expectation and should be used for new buildings and renovations
  • An acceptable, moderate level of expectation and may be used for existing buildings
  • Values outside the criteria for the above categories. This category should only be accepted for a limited part of the year
• In air conditioned spaces, air velocity is less than 0.2 m/s and the relative humidity is between 30 - 70%
• For humidity values below 30% the production of dust increases and plastics can be electrostatically charged
• In the summer, high humidity (>70%) could give rise to an unpleasant indoor air quality
• The speed of cool air introduced in the conditioned space must remain lower than 0.19 m/s. An air movement of 10 m/s is the limit before papers on a desk will start to blow around
• Effect of increasing air speed on comfort in air conditioned spaces

  • Up to 0.25 m/s: not perceptible
  • 0.25 to 0.5 m/s: pleasant
  • 0.5 to 0.8 m/s: generally pleasant but the air movement is perceived
  • 0.8 to 1.5 m/s: from slightly to unpleasantly annoying
  • Above 1.5 m/s: requires corrective actions to maintain pleasantness and productivity
• Air conditioners cannot and do not purify air. The air filter located near the return air duct or air handler does filter dust, pollen and other allergens, but it's a misconception that the air filter is a part of the air conditioner itself
• MERV stands for "minimum efficiency reporting value" and the MERV rating is a measure of how effectively a filter removes particles from the air that passes through it. The higher the MERV rating the more particles the filter will catch
• Humidity


  Water vapor (in its gaseous state) is always present in the air. Relative humidity is the indoor humidity level relative to temperature, expressed as a percentage
• How humidity affects indoor air quality

  • Increases pollutant concentrations
  • Affects emission rates of VOCs
  • Affects chemical pollutants
  • Affects biological pollutants
• The healthiest home humidity level is 40-60% RH
• Outdoor noise sources


  • Car traffic
  • Industrial manufacturing activities near the building
• Indoor noise sources


  • In the environment in question
  • In other neighbouring environments
• Acoustic comfort index depends directly on noise/sound levels
• Health


  A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
• Comfort


  A pleasant feeling of being relaxed and free from pain
• 90% of time is spent inside, 2/3 of which are spent inside our homes
• Why is indoor comfort important?
• Indoor Environment Quality (IEQ)

  Encompasses the conditions inside a building - air quality, lighting, thermal conditions, ergonomics - and their effects on occupants or residents
• Basic elements that contribute to comfort

  • Thermal comfort
  • Indoor air quality
  • Acoustic comfort
  • Visual comfort
• Thermal comfort


  That condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation
• Factors affecting thermal comfort

  • Objective variables: air temperature, mean radiant temperature, operating temperature, relative humidity, and air speed
  • Subjective variables: external parameters (activity being performed influencing the metabolism and clothing insulation), organic factors (age, gender, and specific physical characteristics), and psychological and cultural factors