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]

Climate change. Site context, topography, orientation.

Currently, climate change is a major issue in society. By using non-renewable energy and burning fossil fuel, Carbon dioxide (CO2) is emitted into the atmosphere. This effects the environment and causes natural disasters such as floods, heat waves and extremely cold winter to occur. About 30-40% of CO2 emission comes from the housing. Therefore, targets have been set by the Government for UK housing. This would help reduce the harm done to the climate. The main goals are to reduce the CO2 emission to at least 80% by 2050 and also, design all new dwellings to be zero carbon by 2016.

The well-chosen building location, orientation and well-researched topography leads to the successful zero carbon house development.

Site context

Site context consists of all elements that might influence the building. It is important to consider site location, surrounding objects, weather conditions, local culture and politics and accessibility before starting the design. It might affect building shape, choice of materials, building technology, energy efficiency strategies, etc. 

Location

It is essential to know the purpose of the construction, for example, residential construction, student apartments, hotel, offices, warehouse, factor, etc. This will let us to choose the most suitable area for the development. Our decision leads to the choice of the different environments: rural or urban. However, those two sectors can be divided into more different areas, which depend on various factors. This includes:

•         Security
•      Locality
•         Population
•         Ethnics
•        Pollution
•        Habitats

For example, student accommodation possibly be built not far from university and city centre, with easy access to public transport close to the pubs and cafes. When family house more likely be outside the city centre, with less noise pollution, close to the local shops and schools, but with the easy access to the public transport as well. 

Weather conditions

All the elements that might affect the construction are closely related. Thus, weather conditions depend on the location. Site could be on coastal area, green fields vice versa shaded by trees or other buildings (especially in the cities)Also, in the North, where the weather is cooler or the south, where it is warmer. By knowing these parameters it is much easier to make a proper design. For example, the better insulation is required for houses on the coastal areas as the humidity is higher, as well as, the risk of flood. Houses without any shading such as trees, hills or other buildings are exposed by environmental loads. It means that more attention should be given to structure of the building, insulation and ventilation as it will have to resist stronger winds, bigger amount of precipitations and direct sun light. On the other hand, if the house design would be well-consider, all these natural resources could be used as renewable energy to provide electricity, heating and water supplies by installing solar panels, rainwater harvesting system and wind turbine.  Weather conditions in cities are a bit different and more difficult to understand. Artificial structures affect wind flows, the direction of sun light and the amount of precipitation. However, with the good design it is still possible to make the wind, sun and rain ‘work’ for us.  

Local culture and politics

Design is highly dependent on local culture and politics. Designer has to be introduced with local culture and environment, because every culture has its own values and styles of housing. Different cultures prefer various materials, building technologies, designs, etc. For instant, if East Asian style houses (timber frame, light materials, bright colours, with lots of patterns on the walls, slide doors inside) be built in Birmingham City Centre, UK, where most of the dwellings are made of strong material (mostly masonry/timber frame construction with brick cladding) there won’t be potential buyers as the construction won’t look heavy and secure.

Nevertheless, the politic influence is more important than cultural. When building the house, designer has to full-fill all the requirements the Government had approved. This includes: Building Regulations, Code for Sustainable Houses, etc. Without achieving all the standards, there is no possibility to begin the project.

Topography

If site is flat, it won’t have any influence on the layout of the building. However, if it is sloping it will have a significant impact on the design. A slop of the site or of the adjacent site might block the sun light and the view. All this could cause and additional construction cost as the earthworks will be needed and it might damage the environment. Also if the development site is near the sea or river, it is on a high risk of flood, which again requires some changes for the foundations and insulation.

Orientation

Site orientation refers to sun path - the sun position changes according to the seasonal periods and time. Sun path determinates the position of house front, windows, and shading. The knowledge of the sun path is essential when taking a decision about solar panels, natural lighting, shading and green roofs which are the features of sustainable housing.

Case study

Greenwatt Way development of zero carbon homes – a total of 10 new dwellings has been constructed since autumn of 2010 in Chalvey, Slough, United
Kingdom.

Location. Site is located in urban area surrounded by other residential housing. However entire development seems a bit separated from the neighbourhood as it is fenced with metal rail (which helps to improve the security).

Weather conditions. Site is in the south of the UK. According to the weather observation records it is the one of the sunniest inland city in the UK. This only confirms that the solar tile roof was well deliberated. The rainfall rates are not very high compared with other cities, however it is enough for the usage of the rainwater harvesting system.

Topography. The site was flat, which means it did not required any changes.

Orientation. Only 2 of 10 houses have south facing façade. Other 8 houses are facing east/west side. All houses has south facing roof covered with solar tiles and north facing roof light which also works as a natural ventilation in summer.

To sum up, the accurate information about the site details could help to improve the design of development and make it sustainable. That is why all the sustainable house developments are unique.

References:

'Greenwatt way' [Online] Availabe at: http://www.thisisconcrete.co.uk/home_page/case_studies/greenwatt_way.aspx [Accessed at 13th of November, 2013]

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

Historic Scotland Alba Aosmhor. ‘Fabric improvements for energy efficiency in traditional buildings’ [Online] Availabe at: http://www.historic-scotland.gov.uk/fabric_improvements.pdf [Accessed at 13th of November, 2013]

‘Greenwatt way’ [Online] Available at: http://www.house-builder.co.uk/documents/WILFORD-Chris.pdf [Accessed at 13th of November, 2013]

Suncalc [Online] Available at: http://www.suncalc.net/#/51.508,-0.125,2/2013.11.12/17:29 [Accessed at 13th of November, 2013]

Weather statistics [Online] Available at: http://www.yr.no/place/United_Kingdom/Northern_Ireland/Slough-na-more/statistics.html [Accessed at 13th of November, 2013]