Why Ventilate?

– Create a comfortable environment in terms of CO₂ & humidity.

– Purge pollutants such as VOC and NOX.

– Combat condensation.

Moisture Production:

Our home is an important part of our everyday life, and good air quality contributes to a healthy living environment.

Good air quality is achieved through effective ventilation . An effective ventilation strategy incorporates extract ventilation from “wet rooms” (such as a kitchen or utility) to remove stale air, supply ventilation to habitable spaces (living rooms or bedrooms) to provide fresh air, as well as purge ventilation (achieved by opening a window e.g.) to rapidly remove stale air and odours.

Until recently, the structure of the house itself would allow enough air to infiltrate through gaps in windows and wall, in addition to passive wall vents. However, as building methods and materials improved,  and energy efficiency standards became tighter, this infiltration was reduced to a minimum.

Excessive ventilation greatly reduces the energy efficiency of a building by increasing the load on the heating system.

Fresh air drawn in from the outside must be heated to a comfortable temperature by the building’s heating system. Stale air, exhausted to the outside, carries heat energy away from the building. Excess ventilation therefore, can reduce the energy efficiency of a building.

New methods of air supply are required. These methods of ventilation must balance competing for the demands of comfort and hygiene, with the requirement to reduce energy consumption.

System 1:

Intermittent Extract Fans & Background Ventilation.

How does it work?

This system comprises of background ventilators such as trickle ventilators fitted to windows, or standard hole-in-the-wall ventilators, with extract fans fitted in wet rooms. The background ventilators act to supply air to habitable spaces, while intermittently operated extract fans provide the extract ventilation removing odors and excessive humidity from wet rooms.

System 2: 

Passive Stack Ventilation and background ventilators.

How does it work?

A passive stack is a non-mechanical approach to ventilation, where air vents are located in various locations around the dwelling. Using the principle of convection, currents allow the movement of air through the ducts.

With passive stack system, airflow rates are very much weather dependant. Strong gusts can cause over ventilation and surges in ventilation rates; little or no wind may result in inadequate ventilation.

The system is completely uncontrolled. Large amounts of cold air can be drawn into the building, increasing the heat load.

System 3:

Demand Control Ventilation.

Demand-controlled ventilation (DCV)  automatically regulates ventilation based on actual demand using a suitable sensor. DCV can be triggered by occupancy sensors, moisture sensors or air-quality sensors detecting carbon dioxide or other pollutants, or a combination of these.

The difference between DCV and basic intermittent ventilation is that DCV operates automatically, without requiring any manual user intervention.

How does it work?

A central fan provides a continuous background extraction rate. A controller in the fan maintains a constant air pressure in the system, increasing or decreasing the fan speed as required. Humidity sensitive extracts located in wet rooms open and close depending on room humidity. If a particular room has high humidity, the extract opens.

When the extract opens, this causes a pressure drop in the system. The fan automatically increases speed to return to the target pressure.  The more extracts open, the higher the extract rate is.

Other models of extractor can be triggered by occupancy, carbon dioxide or other air contaminants.

Coupled with the boosted fan speed, this combination means that stale air is extracted only from areas where air quality is below the required standard.

The system ventilation rate is always matched to the actual demand, reducing energy consumption by fans and reducing overventilation and heat energy consumption.

System 4: 

Continuous Mechanical Supply & Extract with Heat Recovery.

Mechanical Ventilation with Heat Recovery (MVHR) continually removes stale moist air from wet rooms, while supplying a balanced amount of outside air directly to habitable rooms.

The difference between MVHR and other ventilation systems is that with MVHR, the heat energy carried by the stale air is used to partially heat the fresh intake air through a heat exchanger.

This reduces the demand on the building’s heating system and minimises the loss of heat to the outside atmosphere while maintaining fresh clean air.

How does it work?

Stale, humid air is extracted from wet rooms at a continuous rate. This air is carried through ductwork to a central ventilation machine where it is passed through a heat exchanger element before being exhausted through the

Fresh cold air is drawn in from the outside through an intake grille. It is then passed through the heat exchanger where it is heated by the stale exhaust air. The fresh, warmed air is then supplied through sealed ductwork to the habited rooms of the house.

The supply rate and extract rate are balanced to maintain comfortable air pressure and reduce draughts.

It is important to note that the intake and exhaust air streams never mix.

A picture is worth a thousand words…

This is mold.

Nothing illustrates the importance of good ventilation more than this photograph. It was taken in a bedroom that had no natural ventilation whatsoever. Worsening conditions was the fact that this bedroom is located right beside an unventilated bathroom, regularly used for showers, and tends to capture humid air.

Once all that moisture reaches the cold surface of the window at night, it condenses into water, soaking the surrounding plaster. As this is a South-facing window, it heats up during the day, warming the moisture trapped in the plaster, creating ideal conditions for rapid mold growth.

The resident who sleeps in this room complains of regular coughs and head colds.

It has – according to the homeowners – resisted any and all attempts at eradication. Thorough cleaning with bleach and even applying fungicidal paint have failed to eliminate the growth. Plaster has already flaked away in places, damaging the weather seals on the windows in the process. This is a sure sign that the mold has penetrated deep into the plaster itself. The only way to remove it at this point would be to completely remove the plaster and replace – something that will cost both time and money to put right.

Even then, this will only treat the symptom, and not the cause.

Keep Mold from Taking Hold

Maintaining good ventilation not only ensures your comfort, it minimises the chance of mold taking hold in your home. Heat Recovery Ventilation from Greentherm extracts humid air from your bathrooms, utility room and kitchen, exhausting it to the open atmosphere while simulataneously drawing in fresh, clean air to the inhabited parts of your home, ensuring your comfort.

Greentherm Ventilation Systems are designed to capture the heat still in stale air, using it to preheat the incoming fresh air to ensure valuable heat isn’t lost from inside your home, while maintaining a clean air supply. Bad smells and odours are pulled from your home, carried away along with the stale air.

Greentherm Heat Recovery Ventilation is an active solution, ensuring optimal ventilation rates regardless of weather conditions. A single electronically controlled silent-running fan unit provides extraction and ventilation, helping to maintain air quality in your home, ensuring that you always have fresh clean air in your home and that mold can never take hold.

Part F of the Building Regulations.

Recent revisions to the building regulations have – since March 2014 – effectively made some form of active heat recovery ventilation mandatory for new constructions, in order to achieve the required performance while still maintaining adequate ventilation levels. While it is possible to achieve compliance with passive systems, it can be difficult and the performance can be variable and weather dependant. For an optimal solution, Active Ventilation is the only convenient option.

Greentherm are experts in the new regulations, and can advise you on installations for your new-build home in order to ensure that you both remain in compliance with the regulations and have a system that is comfortable and reliable for years to come.

Contact us for technical inquiries on Heat Recovery Ventilation.