Types of Domestic Ventilation

CV - Cascade Ventilation

Form of mechanical ventilation that maximises the spread of a ventilation system with minimal or no ductwork. Often internal cascade fans (active transfer fans) are used to connect rooms to the ventilation system without ductwork.

Continuous ventilation

In contrast to intermittent ventilation. Minimum air flow rates for continuous ventilation are less than the ones for intermittent ventilation.

dMEV, dMVHR, MEV, MVHR & PIV are continuous systems.

Basic systems are operated on two levels:
A) Trickle as nominal / normal setting.
B) Boost when excess humidity, etc. need to be expelled.

Better systems offer 3 or more levels:
1) If there is one or less people in the house
2) If there are two or more people in the house
3) Increased ventilation if needed
Boost) to speed up the expelling of excess humidity, etc.
Un-occupied) As a holiday setting for trickle ventilation.

Demand Controlled Ventilation

Mechanical ventilation system that adjusts the ventilation rate automatically according to humidity, CO2 and temperature readings.
Cascade ventilation systems often use this technology.

dMEV - Decentral Mechanical Extract Ventilation

The air from wet rooms is extracted via decentral extract fans. The system runs normally on trickle extract with a demand operated boost flow, which is operated via humidity sensor, PIR sensor or manual switching.
Trickle vents in habitable rooms are needed to provide fresh air into the building if the q50 < 5m3/(hr m2).

 

Advantages:
– Relatively easy to install, – contr. ventilation-> reduced heating cost,
– low maintenance.

Disadvantages:
– Cold drafts possible,
– risk of bad air quality in habitable rms,
– can be tampered with,
– combustion gases of flue appliances &
Radon can be drawn into the building,
– no filtration& insect guard of supply air.

dMVHR - Decentral Mechanical Ventilation with Heat Recovery

Controlled balanced supply and extraction of air, based on Cascade Ventilation

The extract air from wet rooms is passing its heat energy onto the fresh air for supply into habitable rooms. The system runs continually in demand controlled (automated way). The MVHR unit is installed in an external wall and works often together with Cascade Ventilators. No background ventilators are needed.

 

Advantages:
– The only form of ventilation (apart from MVHR) that cuts out almost all ventilation heat losses,
– fresh air supply into all habitable r’ms without ducting,
– noise attenuation of outdoor noise,
– active de-humidification,
– filtration of incoming air, insect guard.

Disadvantages:
– Higher investment costs,
– more complex installation
– regular filter maintenance needed.

EAHP - Exhaust Air Heat Pump

The extract points from wet rooms are ducted to an air source heat pump, which uses the heat in the extract air for heating water. By combining a MEV system with a heat pump, the COP (efficiency) of such heat pumps is optimised. The heat pump produces hot water for DHW and space heating. Trickle vents in habitable rooms are needed to create an airflow through the dwelling.

Advantages:
– Contr. ventilation-> reduced heating cost,
– increased efficiency of the heat pump.
– combined DHW and ventilation system.

Disadvantages:
– Cold drafts possible,
– different cycles of usage (ventilation / heating)
– combustion gases of flue appliances & Radon can be drawn into the building,
– no filtration& insect guard of supply air.

Intermittent Ventilation

E.g. extractor fans in wet rooms, utility, WC and kitchen. These are usually switched off and are only activated for 15-30 min. when needed.

MEV - Mechanical Extract Ventilation

The air from wet rooms is extracted via ductwork through a central extract fan in the loft. The system runs normally on trickle extract with a demand operated boost flow, which is operated via humidity sensor, PIR sensor or manual switching.
Trickle vents in habitable rooms are needed to provide fresh air into the building if the q50 < 5m3/(hr m2).

 

Advantages:
– contr. ventilation-> reduced heating cost,
– low maintenance,
– can be demand controlled.

Disadvantages:
– Cold drafts possible,
– risk of bad air quality in habitable r’ms
– can be tampered with,
– combustion gases of flue appliances & Radon can be drawn into the building,
– no filtration& insect guard of supply air.

MVHR / HRV - Mechanical Ventilation with Heat Recovery

Controlled balanced supply and extraction of air. The only form of ventilation which cuts out almost all ventilation heat losses.

The extract air from wet rooms is passing its heat energy onto the fresh air for supply into habitable rooms. The system runs continually on different levels and can be boosted via humidity sensors or switches. Fresh, pre-warmed supply air passes through transfer areas to the extract rooms. As the system is based on a balanced supply and extract, no background ventilators are needed.

 

Advantages:
– The only form of ventilation that cuts
out almost all ventilation heat losses,
– fresh air supply into all habitable r’ms,
– noise attenuation of outdoor noise,
– active de-humidification,
– filtration of incoming air, insect guard.

Disadvantages:
– Higher investment costs,
– more complex installation
– regular filter maintenance needed.

Natural Ventilation

A mix of natural infiltration through leaks in the building envelope and background ventilators (trickle vents), mechanical extract fans in wet rooms and kitchen, as well as user operated cross ventilation through the opening of windows.

In modern dwellings, background ventilators alone are not enough to ensure good indoor air quality. The occupants need to co-operate by regular opening of windows for cross-ventilation, e.g. leave bedroom windows tilted all night.

Advantages:
– The cheapest form of ventilation

Disadvantages:
– High ventilation heat losses through uncontrolled ventilation.
– Cold drafts
– Unless correct user interaction, poor indoor air quality.
– Occupants need to open windows regularly.

NVHR - Natural Ventilation with Heat Recovery

This type of ventilation is sometimes used for schools. It is a mixture of demand controlled, natural and mechanical ventilation. In colder weather it mixes extract air with fresh cold incoming air, in order to mitigate the effect of cold infiltration.

As such it is not a heat recovery system in its true sense but should rather be called ‘Mechanically Assisted Mixed Supply Ventilation’.

PIV - Positive Input Ventilation

A fan, which is typically located in the roof space, blows air from this space into the central hallway or landing. Stale, moist air is expelled through trickle vents in the wet rooms and the kitchen. This setup is sometimes used for renovated properties, where ductwork cannot be installed.

Advantages:
– Cheap to install,
– contr. ventilation-> reduced heating cost
– utilisation of the heat gain into the loft,
– easy to use,
– minimises Radon build up through
positive pressurisation.

Disadvantages:
– Risk of interstitial condensation in ext.
walls through positive pressurisation.
– longer dry up time in wet rooms,
– filter maintenance in the roof space,
– danger of smells & fibres from the loft
transferred into the habitable spaces.

PSV - Passive Stack Ventilation

The air from wet rooms is moved by the wind and the passive stack effect, which draws warm air upwards. Trickle vents, in the habitable rooms provide fresh replacement air into the building. The exhaust outlets are usually located at the ridge of the roof or they need to be extended to at least the ridge line of the roof.

Advantages:
– Cheap to install,
– no running costs,
– silent operation,
– very low maintenance

Disadvantages:
– Cold drafts possible,
– uncontr. ventilation, weather dependant
– increased heating costs,
– difficult to accommodate vertical ducts,
– limited air quality in habitable rooms,
– no filtration& insect guard of supply air.

Whole House Ventilation System

Most commonly used form of MVHR, which ventilates all areas of a dwelling. Typically three zones are distinguished:
A) Supply zones: All habitable rooms
B) Transfer zones: Hallways, stair cases or open plan areas between supply and extract zones.
C) Extract zones: All wet rooms, kitchen, utility and WC’s.