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 mass of regulations that cover safety, health, welfare, convenience, energy efficiency etc. in the way buildings are constructed. Not to be confused with Planning consent (which is more to do with whether you can put up the building in the first place) provide a “better than nothing” standard
The building regulations
cover the ways that houses should be ventilated –
Northern Ireland Technical Booklet K
Scotland Domestic handbook
Taking the example of the English and Welsh 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 ventilation in 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 Passivhaus 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 E 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
is ventilation incorporating a heat exchanger. When it is installed as a whole house system 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
In the case of highly insulated houses such as Passivhauses there is often a case for a summer bypass mode so that overheating does not occur in summer.
It is worth considering incorporating a service duct where all the services such as MVHRMechanical Ventilation with Heat Recovery. This is usually a double fan arrangement which extracts stale air from the house and sucks in fresh air at the same time. As the warm stale air is blown out, heat is extracted from it and passed over to the cool incoming air by means of a heat exchanger. With the latest technology, over 90% of the heat can be recovered. (see Passivhaus standard) , boiler, pipes, cables etc. can be housed. See Service Ducts
A recent study by the Zero Carbonbit of a slippery fish. It tends to mean that a building uses no carbon (oil, coal, etc) to heat it (meaning in a 'net' way). It usually ignores the carbon which goes into building it (the embodied energy). See the page on Zero Carbon? Hub"The Zero Carbon Hub is a non-profit company limited by guarantee. We are a public/private partnership established to take day-to-day operational responsibility for co-ordinating delivery of low and zero carbon new homes" highlights the importance of the competence of companies supplying and installing MVHR
A lack of good practice across industry in dealing with ventilation systems serves to highlight competence as a key issue. Regrettably existing training schemes have made limited progress and Task Group members are calling on DCLG to consider mandatory competency requirements for MVHR installations so that standards can be driven up.
Fairly new on the market is the fresh-r by the Dutch company VAVENTIS. This is a balanced heat exchanger fitted to an outside wall and works by transferring heat through huge lengths of very fine copper wires rather than through the interleaved plates of the more traditional type of heat exchanger. It needs no filters. Typically two units would serve a medium sized house. Viking House, who are very committed to 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. construction are very enthusiastic about their future. See also the Breathing Window.
Other through-the-wall systems are coming on the market: A German one, Lunos, is claiming up to 90% efficiency for heat recovery with very low running costs.
What needs remembering about all MVHR systems is that their efficiency is dependent on how clean they are kept. If they are venting a kitchen, for instance, particles of cooking oil can coat the internal heat exchanger surfaces, which then clog up with dust. This reduces not only the exchanger efficiency but also the flow of air. So the way in which the heat exchanger surfaces can be cleaned becomes important along with what type of filter is incorporated.
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 even over 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
Ventilation for heating appliances
The Building Regulations have a good deal to say about permanent ventillation required by heating appliances such as open fires and wood burning stoves. These appliances require a certain amount of air to keep them burning properly and to avoid carbon monoxide (which is poisonous) escaping into the house. The requirements are laid out in the Approved Documents, part J.