How you ventilate a house depends very much on the level of energy efficiency you are aiming for. At the lower end the Building RegulationsThese are the legal regulations which govern how a house is constructed. (not to be confused with Planning Permission which is about whether you are allowed to build the house at all or what it might look like) see Building Regulations) provide a “better than nothing” standard

The building regulations

cover the ways that houses should be ventilated -

England & Wales   Approved document F

Northern Ireland   Technical Booklet K

Scotland  Domestic handbook

Taking the example of the English and Wesh regulations -

Although the performance based regulations are quite detailed and require careful reading they basically ask that a house should have 3 types of ventilation - extract , whole house and purge .

The extract and whole house combinations can be seen on page 12 diag. 1

Another way of showing the permutations is -

• Extract ventilationin places that have damp air or smells – kitchen, bathroom, toilet, utility room via -
  • passive stack ventilation – to outside or
  • extract fans which take air -
    • straight out or
    • out through ducting, either
      • to outside or
      • to heat exchanger unit and then out
• Whole house ventilation- this is background ventilation
  • trickle vents (in habitable rooms) in all cases unless you use -
  • continuous extract and supply with heat recovery
• Purge ventilation – this is basically the ability to leave the window open for a bit to clear smells, smoke etc.

There are options for controls for energy saving if mechanical ventilation is used. There are also special conditions for basement rooms and rooms off other rooms.

There are two interesting green options here for energy saving -

• passive ventilation which uses no electrical energy and is extremely reliable
• mechanical ventilation with heat recovery

Passive stack ventilation

(not to be confused with PassivHausSee more on the Passivhaus standard. The PassivHaus Institute has pioneered a standard for low energy buildings. It includes very low energy usage and ways of achieving this. The word is derived from the idea of buildings which are fundamentally low energy and passive solar heated rather than using extra gadgets to heat them. See Passivhaus for the UK branch of the organisation. ventilation) utilises the natural convection effect (stack effect) of hot air rising so that warm damp air from kichen and bathrooms simply goes up a fluepipe to conduct gas, typically ventilation air or boiler exhaust. see Flue and out through a terminal in the roof. The flue has an automatic closer in it so that it only opens when it detects moist air. This prevents warm air leaking out when not necessary. There is no power used, no noise[for the purposes of part C of the Approved Documents] - Noise is unwanted sound. and nothing to break down. The air is replaced by fresh outside air coming in through trickle ventilators. The Building Regulations part F – Ventilation have lots of references to passive ventilation and it pays to do a local search when in the pdf. See also Passivent

Heat recovery ventilation (MVHR)

is a whole house ducted system with a heat exchanger. It extracts air from all the main rooms including kitchen, bathrooms and toilets and replaces it with fresh air from outside which is then ducted back to the various rooms. There is a central fan/heat exchanger unit where the cool incoming air picks up heat from the warmer outgoing air by means of the heat exchanger. This saves a considerable amount of energy in terms of heat but does require a fan to be running most of the time. This consumes energy, will create a (very small) amount of background noise and may need repairing every 15 to 20 years. The heat exchanger and parts of the ductwork (especially close to a cooker) will need regular cleaning.

Passivhaus Ventilation

At the most advanced end of ventilation technology has been PassivHaus ventilation . This system balances several factors -

• sealing the house extremely tightly to limit any wasteful effects of draftyness
• introducing the minimum amount of fresh air needed to keep a house healthy and pleasant
• the ability to heat the house via the ventilation air (thus avoiding the need for a central heating system) This is done by an electrcal heater or sometimes a ground source heat pump.
• efficiently recovering heat from the extract air (over 75% efficiency – sometimes up to 90%)
• careful ducting of the air so that
  • the air circulation is effective but slow enough that air movement is not noticeable
  • the air is extracted from the damper areas such as kitchen and bathroom
• the ability to throw your windows open in summer