When you enter the room, do you notice any unpleasant odors? Do you breathe heavily when the air is stuffy? Are you bothered by mold? All this and much more is caused by poor ventilation.

As a general rule, to properly ventilate the house means to ensure providing fresh air while removing or diluting stale air, in order to ensure healthy air in the space and eliminate the appearance of mold and moisture, while trying to minimize energy losses. This can be achieved manually, by opening windows, with natural ventilation systems or with mechanical ventilation systems.

Ventilation implies several types of air movement:

• Infiltration and exfiltration of air in a house
• Distribution of air throughout a house
• Circulation of air in a house

Infiltration and exfiltration are uncontrolled processes and infiltration can cause
comfort problems and exfiltration can lead to structural problems. Distribution allows fresh air to reach all the rooms in a house and prevents pockets of stale or moist air. Circulating fresh air within a room is necessary to reduce under-ventilation, such as in large spaces or rooms with a lot of furniture or stored items.

Why is it important to ventilate the house?

Sometimes, ventilation and clean air go unappreciated. This is due to the fact that it usually takes time for symptoms to manifest, making inadequate ventilation difficult to detect right away.

Gasses from combustion appliances, like stoves and fireplaces, can accumulate in a poorly ventilated home and threaten your health and safety. In addition to endangering your health, excessive moisture in the home can cause the growth of mold, deteriorate insulation, and even result in structural damage. Furthermore, high humidity levels might require cooling systems to work harder, which raises energy costs.

CONDENSATION: What Is It? When and where does it occur?

Condensation is the extra water vapor in the air which condenses on cold, impervious surfaces like windows and, occasionally, walls. Water vapor from cooking, washing, drying clothes, and other activities is present in the air in our houses. This warm, moist air moves to cooler areas of our homes during cold weather.

Condensation happens when humid air contacts cooler air or a surface, causing the surface to become wet. There are different amounts of water vapor in the air, and the amount of moisture that can be held depends on the temperature of the air. A portion of the moisture in moist air condenses onto a cooler surface when it comes into touch with it.

What methods are there for ventilating a house?

1. Airing the house without any system

The most frequent occurrence in the past was the absence of a ventilation system. People typically opened windows when there was a lot of steam in the bathroom and kitchen, but they also depended on architectural flaws such as lack of sealing as the main source of air flow.

Good circulation, however, requires a difference in pressure that occurs as a consequence of the difference in temperature. In the winter time, the temperature difference is sufficient, but then the heat losses are large, and in the summer, the temperature difference is insufficient, so there is not enough circulation.

Furthermore, if the old house is renovated, and especially if thermal insulation is installed, the amount of moisture that remains trapped inside the house will lead, as many owners who have been in this situation can testify, to the appearance of moisture and mold.

It is highly advised to think about installing one of the systems described below because the cost of doing so will be justified by saving money on remediation costs and protecting your health.

2. Natural ventilation sistem

In this unusual approach, particular architectural elements are used to let in fresh air and exhaust stale air. One strategy is to build a ”solar chimney”, where air is heated by the sun, becomes more buoyant, and rises upward and out through vents towards the top of the structure. This decreases the pressure inside the home, which allows fresh air to enter through properly arranged input ports.

3. Mechanical ventilation systems

This is, in modern construction, by far the most common and efficient method of ventilation. However, due to the high price, many owners decide on the option of installing it only in certain rooms, where it is most necessary (most often it is the bathroom and kitchen), and not in the whole house. In any case, there are several different types of mechanical ventilation.

a. Supply-only ventilation

As the name suggests, a fan circulates fresh air as stale air escapes the home through holes and other air leaks. The air supply can be brought to a single place, distributed by ducts, or provided to a forced-air heating system.

A supply-only ventilation system pressurizes the home, which can help prevent the entry of contaminants like radon, but it also runs the danger of driving wet air into spaces like the wall and ceiling cavities, which can lead to condensation and moisture issues.

b. Exhaust-only mechanical ventilation

This is a very typical technique whereby small exhaust fans, typically in bathrooms, run continuously or periodically to remove stale air and moisture produced in those spaces. This tactic generates a small amount of negative pressure inside the home, which draws in fresh air either through cracks and other air-leakage sites or through intentionally placed air inlets that are placed in strategic locations. This tactic has the benefits of being straightforward and inexpensive.

The negative pressure has the potential to draw in soil gasses like radon and others that we don’t want in our homes.

c. Balanced ventilation

Through a balanced system in which separate fans drive both the input and exhaust airflow, much greater ventilation is achieved. This gives us the ability to choose where fresh air is provided, where it flows from, and where exhaust air is drawn. Systems for balanced ventilation might be ducted or point-source systems.

d. Balanced ventilation with heat recovery

If fresh air intake and exhaust are handled by different fans, it is logical to group the fans together and add an air-to-air heat exchanger. In colder climates, an air-to-air heat exchanger—nowadays more frequently known as a heat-recovery ventilator, or HRV—is the best option.

An energy-recovery ventilator (ERV), a slightly different design, doesn’t transport moisture (often an advantage when a house would get too dry in the winter or too humid in the summer).

If budgets allow, this is the option to go for!

How much ventilation does the house need?

Timers and electronic programmable controllers are available, simple to sophisticated, to assist in regulating the appropriate level of ventilation and to prevent over ventilation, which consumes energy and has the tendency to dry up a property. If your budget does not allow you to purchase such devices, then you rely on your own sense of how much is enough without being too much.

There are situations in which high ventilation rates are required, including:

• for a new or significantly remodeled home, the first fall and winter to eliminate construction-related moisture
• residences with a large number of tenants, either temporary or long-term
• residences that have just had renovations (drywalling, painting, floor refinishing, etc.) or received new furniture wich are generating heavy pollution levels
• residences with tenants who have breathing difficulties. People with outdoor pollution allergies need source of filtered outdoor air

Even though some homes need constant mechanical ventilation to manage moisture and its potential to harm the house (for example, to minimize condensation collecting on windows in the winter, which can harm window frames, trim, and walls), ventilation is not as important when the property is empty.

Tips to remember

• Minimize the chance of water entering your house by keeping the roof in good condition. Check caulking and flashing around windows, doors, tubs, and showers. Clear roof gutters of debris and drain moisture away from the house.
• Kitchen and bathroom vents should lead directly outside and should never be vented into the attic, where moisture can cause serious problems and pose potential health problems.
• Seal all air-leakage paths between living spaces and other unconditioned parts of the house, such as attics, basements, and crawl spaces. Insulation alone cannot prevent moisture problems.