Ventilation

Ventilation - change of air by natural (passive) or mechanical (active) means to and from space or spaces in a building. Also, it could mean a control of thermal comfort in a building as well.



According to the Approved documents Part F, 'ventilation is required for one or more of the following purposes:
a. provision of outside air for breathing
b. dilution or removal of airborne pollutants, including odours
c. control of excess  humidity (arising from the water vapour in the indoor  air)
d. provision  of air for the fuel-burning appliances.'



Types of ventilation:

Natural ventilation - it depends on pressure between the inside and outside the building. Difference of the pressure appears because of the temperature changes, wind strength, people activity etc. Natural ventilation does not require any ductwork, fans, conditioners. The fresh air flow gets in and out through the windows, louvres, grills, air leakage paths (thermal bridges). Natural ventilation has both good and bad sides. It is energy efficiency system which lets the fresh air enter the building, however, it is not always controllable and may cause heat loss.

Mechanical ventilation - is a system which use electricity to move the fans, drawn the fresh air through the ducts inside the building and collect the existing air out of the room and exhaust it outside. Mechanical ventilation, also, has its own advantages and disadvantages. Even though it does not cause so much heat loss as natural ventilation, it consumes energy to operate the system.

Mechanical extract ventilation 

There are 2 types of mechanical ventilation:

Mechanical extract ventilation (MEV) - this system should be installed in all 'wet' rooms. It continuously extracts moist air from bathrooms and kitchens and takes it through the ducts into the outside. Then the air into the 'wet' rooms are replaced by the fresh one which comes through the background ventilators (doors, windows etc), through thermal bridging and building fabric.
Advantages: provides controllable ventilation
Disadvantages: Heat loss, requires space for ducting, might be quite noisy if the unit is installed not properly.

Mechanical ventilation with heat recovery

Mechanical ventilation with heat recovery (MVHR) - the same as the MEV, the MVHR should be installed into all 'wet' rooms. Both systems work very similarly, only before passing through the outlet the moist air goes through exchanger, where the heat is transferred  to the fresh air which is ducted to the other rooms.
Advantages: Provides controllable ventilation, reduce heat loss, provides air filtration
Disadvantages: Expensive, complex installation which requires a lot of space, filters needs to be changed regularly, requires a high lever of airtightness.




Case study

Greenwatt Way - zero carbon house with integrated natural and mechanical ventilation.

Natural ventilation - roof opening and windows with large openings helps to drawn warm air out of the house during the hot summer time, when overheating becomes an issue in highly insulated dwellings.

Mechanical ventilation - in order to preclude natural/passive ventilation and heat loss the mechanical ventilation with heat recovery system was installed.

References: 

'Greenwatt way' [Online] Availabe at: http://www.thisisconcrete.co.uk/home_page/case_studies/greenwatt_way.aspx [Accessed at 17th of November, 2013]

‘Greenwatt Way. A zero carbon homes newbuild case study’, 2011. Energy saving trust.

 ‘Greenwatt way’ [Online] Available at: http://www.house-builder.co.uk/documents/WILFORD-Chris.pdf [Accessed at 17th of November, 2013]

Richards Partington Architects, 2012. ‘Understanding overheating – where to start’ NHBC Foundation

Zero Carbon Hub, ‘Overheating in homes’ [Online] Available at: http://www.zerocarbonhub.org/resourcefiles/OverheatingInHomes8pp_2013_8March.pdf [Accessed at 17th of November, 2013]

Zero Carbon hub, 2013 ‘Mechanical ventilation with heat recovery in new homes’ NHBC Foundations

Building Regulations, Approved Documents Part F, 2010 [Online] Available at: http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partf/approved [Accessed at 17th of November, 2013]
'Different types of building ventilation'[Online] Available at: http://www.wisegeek.com/what-are-the-different-types-of-building-ventilation.htm [Accessed at 17th of November, 2013]