03 - Building ventilation

We saw that the accumulation of hot air and humidity inside a dwelling not only make it less comfortable but also give rise to the development of mold and other unhealthy organisms.

There is another problem caused by poor ventilation. Smoke from the stove or from the fireplace used for cooking and heating also accumulates inside our dwellings.    

 

This smoke is very unhealthy and causes respiratory problems in all human beings, but especially in women because they are the ones who spend the most time cooking. This smoke also causes respiratory problems in children because they are more sensitive and their bodies are less resistant.
  

 

Openings that naturally exist in buildings, be it windows, door or holes in the wall, like in the picture above, may not provide enough ventilation and enough air circulation to clean up the air from all the smoke.

If there is not enough ventilation in a building a lot of smoke and humidity will be retained inside the dwelling during the night causing long term respiratory problems in all the building occupants, men, women, children, young and old.

It is very important to find a way to continuously and effectively ventilate and circulate the air inside a building to make sure that all the smoke, the excess humidity and the stale air are cleared every day.
  

02 - Humidity in buildings

We are going to deal with residential buildings only, dwellings that serve as living spaces for human beings.

We know very well that the sun heats up the walls and roofs of buildings and that this heat is transmitted to the interior of the dwelling often making them unbearably hot.

But when the sun sets the walls, the roofs and the interior of the dwelling begin to cool off until the sun raises again the following day.

 

This cycle repeats itself every day of the year.

 

In addition to the heat it is very important to know that the air humidity level also builds up. There are various sources of humidity inside a building:

• in the kitchen where the water boils and the stew cooks, water vapor drifts off from pots and pans and joins the natural humidity in the surrounding air, increasing the level of air humidity in the building, 
• all human bodies generate water vapor, during the day or night, even though we often do not even notice that there is humidity coming out of our bodies, even when we are not perspiring,
• in the bathroom or toilet hot water evaporates, fogs our mirrors and the glass in the windows, and this water vapor drifts into the building turning the air even more humid inside the dwelling.

This humidity keeps building up in the air, in our clothes, in the walls and makes the air inside the building more and more humid. Humid air is less comfortable, be it during hot or cold weather. The higher the humidity in the air the less bearable will be the cold or the hot weather.

Humidity contributes to the discomfort in a dwelling but the humidity will also give rise to the development of mold, fungus, other microscopic organisms and even insects that are not good for our health. 
And so, to improve the level of comfort in our dwellings we have to ventilate the air inside the buildings to expel this excess humidity. The more the air circulates inside a building, the more natural ventilation, the more comfortable our building will be.

01 - Heat and humidity

The two main contributors to an unhealthy and uncomfortable dwelling are:

• Heat (and lack of heat, cold)
• Excessive humidity in the air

We have to try and control both factors in the simplest and most economical manner to obtain a more comfortable environment for the building occupants.

A human being can tolerate heat and humidity within some limits. What these limits are depends on each person's physical built, the amount of clothing one is wearing at any given moment, the wind conditions, and the humidity of the surrounding air.

If we ignore the effect of the wind and of the direct sunshine we can say that a person wearing a thin cotton blouse or a T-shirt will start feeling cold when the temperature drops below 20ºC (68ºF) and will start feeling hot when the temperature climbs above 25ºC (77ºF).

So, generally speaking, we feel cold when:

• The air temperature drops
• The humidity is high
• The wind blows harder
• We are wearing less clothing

And so, when it is cold, we want to:

• Raise the temperature around us
• Make the air dryer
• Reduce our exposure to the wind
• Wear more clothing

Similarly, we feel hot when:

• The air temperature goes up
• The humidity is high
• The wind is not blowing
• We are wearing more clothing

And so, when it is hot, we want to:

• Lower the temperature around us
• Make the air dryer
• Increase our exposure to the wind
• Wear less clothing

Some of these factors can be controlled in order to make us feel more comfortable, but not all of them can be controlled without the use of equipment that can be expensive.
 
Air temperature and humidity can be controlled with air conditioning equipment. Air circulation (the equivalent of wind) can be controlled with fans. And, in most cases, we can chose the amount of clothing we are wearing.
 

But all solutions based on equipment can be expensive and need electricity to operate, something not always available. And so we have to take advantage of simpler and often more efficient solutions.
 

Even though we cannot control the temperature and the humidity of the air outside, inside our dwellings we can:

• control the inside air temperature - by taking advantage of the shade of surrounding trees, building shading surfaces, and using insulation on walls and roofs,
• reduce the inside air humidity - by circulating the air inside the building to exhaust the humidity from the kitchen, from the bathroom and toilet, and the humidity released by the human body to avoid a buildup of the level of humidity in the air,
• reduce the effect of the existing humidity - providing or increasing exposure to the prevailing wind and/or creating a natural air circulation of the inside air. The effect of this air circulation can be very pleasant and greatly improves the level of comfort inside the building.