2014 Higher Level Sample Solutions
The airtightness membrane fixed to the underside of the ceiling joists/bottom chord is taped to the air- tightness membrane fixed to the inside of the timber studs in the wall, using proprietary airtightness tape.
This is shown as a blue line (10) on the drawing.
The approach to the door should be level. A ramp, with a maximum slope 1:20 should be created. A clear landing space, with a minimum area of 1500mm by 1500mm, should be provided in front of the door. This will ensure that all users, especially wheelchair users, have space to manoeuvre at the door.
The door threshold seal should be a maximum of 15mm in height to ensure that it is not an obstacle to users. The slope of the door sill should not exceed 15° to ensure that wheelchair users can easily travel across it.
The entrance should be protected from the weather by a porch/canopy that extends 1200mm min. above the door. This will shelter all users as they get out their keys or wait for the door to be opened.
An overhead light should be provided to light the entire area outside the door. This will ensure that users are able to find their keys at night. It will
also provide security by allowing the caller to be clearly seen through the side light (i.e. window) and identified before the door is opened.
Low-level lighting should be provided to ensure that the approach can be clearly seen by all users and that any obstacles (e.g. overhanging planting) can be safely avoided.
Provision for lifetime use should be considered at the design stage.
- to avoid the need to make changes to the building’s structure when adapting the building in the future. Thought should be given to the layout of the internal spaces and how they might need to be used. For example, if an internal door might be needed to allow different access to a room, the door opening could be created (i.e. lintel installed) so that installing the door at a later date is a much simpler task.
- to facilitate the installation of accessible features at a later date. For example, should grab rails be needed in the bathroom in the future, the fixing for these (e.g. timber noggings in a partition wall) can be installed during construction so that they are already in place when needed.
Three functional requirements of a study include:
- thermal comfort - the study should be at a constant temperature of 20°C. The user should be able to adjust the temperature to suit their preference.
- acoustic comfort - the user should not be disturbed by noise from the rest of the home or from outside.
- lighting - a light level of between 150 - 300lux should be provided. The user should be able to adjust the level of light to suit the task at hand. This usually requires several light sources, including natural light and artificial ceiling and desk lamps.
This design layout provides:
- thermal comfort
- a comfortable temperature is essential in a study space
- the well insulated walls (full fill cavity) could be augmented with 100mm of external insulation
- the windows and glazed door should comprise tripled glazed, argon filled low-e coated glazing units with insulated frames.
- acoustic comfort
- a study must be quiet so that the users can concentrate
- access to the study is from the hall (rather than the kitchen/ dining space) because the hall is a much quieter part of the home
- the high performance windows should exclude external noise
- an appropriate level of natural lighting through the use of glazing to the east, south and west faades.
- the long ‘slot’ window to the south will illuminate the desk area without causing overheating (thermal comfort)
- artificial lighting in the ceiling as well as several reading lamps ensure an appropriate level of artificial lighting when needed.
Revised external design to enhance its visual appearance:
- west elevation
- the facade is enhanced by the replacement of the storeroom door with a window
- the window is similar in style to the windows in the main facade
- south elevation
- the original blank wall is opened up with a long ‘slotted’ window that will bring light into the workspace
- this will provide light on the working plane
- the level of light can be controlled to suit the user using a ‘venetian’ type blind
- if this window overlooks an adjoining property, opaque lazing can be used
- east elevation
- the original small window is replaced by a glazed door
- this allows access to the private rear garden
- this provides the user a nice view of the garden area and helps to link the indoor and outdoor spaces.
Advantages of a step by step approach:
- the occupants can remain living in the home during while the work proceeds,
- the work can be paid for gradually avoiding the need for costly loans.
Disadvantages of a step by step approach:
- there is more disruption to the occupants over a longer period of time,
- it is difficult to integrate the various elements of the work to achieve a high standard of overall performance and finish.
- the walls should be insulated using materials that are compatible with the existing structure,
- these materials should be flexible and breathable to ensure that the structure can continue to respond to the change climatic conditions,
- suitable insulants include woodfibre and hemp,
- these insulants are supplied with proprietary breathable renders,
- the thickness of insulation used depends on the thermal performance required - a minimum of 150mm thickness should be used,
- it is essential that water vapour generated indoors can pass through the building fabric to the outside,
- this will avoid dampness in the structure,
- loose or damaged plaster or render should be removed and replaced using lime based materials.
- this type of house typically suffers from rotten wall plates and rafters caused by the ingress of water due to damaged or missing roof slates,
- the wall plate should be replaced with new pressure treated timber,
- the ends of the rafters that are rotten should be cut out and new pressure treated timber should be bolted onto the existing rafter to repair it,
- the ends of the existing rafters that are not rotten should be treated with a preservative as a preventative measure,
- the ceiling should be insulated using a breathable insulant and finished with a breathable lime based plaster,
- the thickness of insulation used depends on the thermal performance required - a minimum of 150mm thickness should be used .
The principles of conservation best practice should guide all work:
- do the research - analyse the building fabric and any other evidence (e.g. maps, drawings, documents, etc.),
- use expert advice - building conservation is a specialised area that should be led by experts with knowledge and experience of historic buildings,
- promote the special interest - the features of the building that convey it’s distinctiveness should be protected,
- minimum intervention - best summed up by the maxim ‘do as much as necessary and as little as possible’,
- repair rather than replace - the original building fabric should, whenever possible, be repaired rather than replaced with new materials,
- promote honesty - repairs should generally be carried out without any attempt at disguise or artificial ageing,
- use appropriate materials and methods - some modern materials can result in the accelerated decay of the building fabric - for example, replacing lime mortar with cement mortar,
- reversibility - allows for the future correction of unforeseen problems without lasting damage being caused,
- avoid incremental damage - it is important to be aware of the potential cumulative impact of minor works to the character of heritage buildings,
- avoid using salvaged materials - the re-use of architectural materials from other buildings can confuse the history of a building,
- comply with the building regulations - apart from a few exemptions, the regulations apply to all works involving new construction, extensions to buildings, material alterations to existing buildings and material change of use of such buildings.
Respecting the character of the original house:
- the use of internal insulation to the walls and roof allows the thermal performance of the house to be upgraded without impacting on the appearance of the house
- the use of lime based plasters and renders ensures that the finished appearance of the repaired and upgraded walls and ceilings is consistent with the original appearance of the building
- using natural breathable materials that are compatible with the building’s fabric ensures that water vapour can escape through the fabric preventing dampness and degradation of the structure - this will ensure that the building will continue to survive long into the future.
Prevention of thermal bridging at the wall - floor junction:
- thermal transmission is likely to occur at the wall - floor junction by conduction of heat energy down through the inner leaf of blockwork,
- traditionally this heat flow path is not thermally broken,
- to prevent this heat loss, at least three courses of aerated autoclaved concrete blocks are included in the inner leaf rising wall,
- the aerated autoclaved concrete blocks reduce the amount of thermal transmission along this path,
- also, a perimeter of edge insulation is installed around the concrete floor slab,
- in addition, the wall insulation (in the cavity) is extended downward (below finished floor level) to create an overlap with the floor insulation,
- the combination of these measures will significantly reduce thermal transmittance at the wall - floor junction.
Three features that contribute to the house having a low environmental impact:
- the primary facade of the house has a significant amount of glazing,
- this maximises solar gain,
- maximising solar gain reduces the space heating and lighting requirement of the home,
- this reduces energy consumption and carbon emissions.
- open plan layout with central heat source:
- the solid fuel (e.g. wood) stove located in a central location provides heat to the entire ground floor of the home,
- the masonry fire surround and chimney acts as a thermal store holding heat energy and releasing it as the temperature drops when the stove is no longer in use.
- timber frame construction
- timber is a sustainable construction material provided it is sourced from a Forestry Stewardship Council (FSC) certified supplier,
- a home built using a timber frame system contains less embodied energy that a traditional concrete cavity wall system.
Other design features that could be incorporated into the house:
- rainwater harvesting:
- a rainwater harvesting system could be installed,
- this would greatly reduce the environmental impact of the home by reducing the water consumed for activities that do not require potable water,
- for example, harvested rainwater can be used for flushing toilets and washing clothes,
- toilet flushing accounts for approximately 20% of a typical household’s water consumption,
- washing machine use accounts for approximately 10% of a typical household’s water consumption.
- solar water panels:
- solar water heating panels could be installed on the south slope of the roof,
- the roof form of this house is ideal as it has roof slopes facing in four different directions,
- solar water panels provide hot water for use in basins, baths and showers,
- solar panels reduce this energy consumption and carbon emissions.
Designing low environmental impact housing is important because it reduces carbon emissions and the consumption of resources:
- housing is a significant source of carbon emissions:
- the SEAI states that the residential sector is responsible for 27% of Ireland’s carbon emissions,
- houses must be designed to provide a comfortable indoor environment without the consumption of large amounts of carbon based energy,
- the construction of housing consumes a lot of resources:
- large amounts of virgin materials (e.g. stone, timber, steel, glass, plastic) are used in the construction of houses,
- large volumes of water are often consumed in the construction of houses.
The stepped damp proof course (cavity tray) (13) at the head of the window prevents the ingress of wind driven rain. The precast concrete sill is wrapped in damp proof course to prevent the ingress of moisture. Once installed, the window frame is sealed to the structure at it’s perimeter using a flexible sealant.
This bedroom is very large (35m2); it would be an ideal room for a person of limited mobility in the future. For this reason the bathroom has been designed in accordance with the guidelines from the Centre for Excellence in Universal Design.
The bathroom is located in the corner of the bedroom where it has two external walls. This gives more options for window location and efficient installation of water supply and drainage pipework.
The bed and desk have been repositioned to ensure optimal use of the space.
Above ground pipework for bathroom:
Economical use of water:
A typical family uses approximately 70% of their total household water in the bathroom. Changing water use habits and installing more efficient appliances will reduce water consumption in the bathroom.
- installing a dual flush toilet will reduce water consumption by approximately half over the course of a year
- a standard toilet flush uses 6 litres of water, a dual flush toilet uses: 2.6 litres (low flush) and 4 litres (full flush)
- installing an ‘eco’ shower will reduce water use by approximately half (compared to a mixer shower)
- reducing the time sent in the shower will also reduce the amount of water consumed.
Sound is a form of wave energy. When a sound wave is transmitted from a point source the waves travel outward in all directions. When a sound wave hits a hard surface the sound is reflected by that surface. The angle of reflection is equal to the angle of incidence. Sound and light are similar in this sense.
Reverberation is the term used to describe the continuation and enhancement of a sound caused by rapid multiple reflections between the surfaces of a room. The reverberation time is the time taken for a sound to decay by 60dB from its original level. The reverberation time depends on the floor area of the room, the sound absorption of the surfaces of the walls, floor and ceiling and the frequency of the sound.
Internal wall (stud partition)
- plasterboard is removed from one face of the existing partition
- the partition is lined with 50mm quilted insulation (e.g. mineral wool, sheep’s wool, hemp etc.)
- a second stud frame is built with a 50mm gap between the frames
- an additional layer of 12.5mm gypsum plasterboard is added to the original face and plastered with a 2mm finish coat of plaster
- two layers of 12.5mm gypsum plasterboard are fixed to the new frame (staggered joints) and plastered with a 2mm finish coat of plaster
- the existing floor is reconstructed as shown in the sketch
- the floor and ceiling below are supported by separate joists
- the floor consists of two layers of 9mm timber decking supported on a 25mm absorbent quilt of insulation on a 12.5mm layer of plasterboard
- the ceiling is made up of two two layers of 9mm gypsum plasterboard, plastered with a 2mm finish coat of plaster.
There are four principles of sound insulation:
- heavyweight structures (e.g. concrete) with high mass transmit less sound energy than lightweight structures
- the plasterboard in the wall and floor above add weight to the structure
- airtightness - airborne sound will travel through any gaps in the structure
- uniformity - sound will take the ‘path of least resistance’ - a small poorly insulated area can significantly reduce the performance of the whole structure (e.g. when a window is slightly ajar the sound insulation of the whole wall drops dramatically
- the plaster finish coat on the plasterboard provides completeness to the structure
- the perimeter of the wall and the floor could also be sealed to the adjoining structures using airtightness tape to further improve the completeness of the structure
- flexible materials (e.g. mineral fibre insulation) tend to absorb sound energy
- the quilted insulation used in the wall and floor provide flexibility
- discontinuous construction is effective in reducing sound transmission
- sound energy is lost when it travels from one medium to another (e.g. plasterboard to air)
- the staggered studs and joists provide isolation on the wall and floor.
A passive house must should have a compact form. A compact form is a simple house design that has a minimum of extensions or additions. Because heat is lost through external surfaces, the greater surface area, the greater the heat loss.
Compactness describes the relationship between the surface area of the home and its volume. In passive house design, the goal is to achieve a ratio of 0.7 or less; in other words to have a large volume enclosed by the smallest possible area.
Two houses with identical floor areas (and hence volumes, assuming equal heights) can have very different compactness ratios.
Higher density housing like terraced houses and apartments provide much better compactness ratios than individual houses because they have less surfaces exposed to the outdoors.
The glazed facade of the passive house shown in the sketch should be oriented within 30° of south. This will maximise solar gain as the sun moves across the sky.
This is especially important in the cold winter months when the sun angle is low and the daylight hours are reduced.
An insulated foundation is necessary to avoid thermal bridging down through the loadbearing walls.
Insulated foundations prevent this by ‘wrapping’ the substructure in insulation. High density loadbearing polystyrene (EPS 300) is used.
A number of proprietary systems are available in Ireland. Each of these systems ensure that there is no thermal bridging between the ground and the substructure.
Overheating is defined in the Passivhaus standard as an indoor air temperature of 25℃ or higher. The Passivhaus standard requires that overheating must be limited to less than 10% of the year.
Two reasons why a passive house may overheat:
failure of the mechanical ventilation system - a mechanical fault or loss of power to the mechanical ventilation system would mean that the air is not being renewed. This would lead to an increase in indoor air temperature
excessive occupancy - if a very large number of people were to occupy the home for an extended period of time ad the mechanical ventilation system was not switched to boost mode this would cause overheating.
Two design details to prevent overheating:
- brise soleil
- a brise soleil could be installed above the glazing,
- this would reduce the solar gain during the warm summer months when the sun angle is high,
- roof overhang
- the roof plane could be extended to create an overhang,
- this would also reduce the solar gain during the warm summer months when the sun angle is high.
In this excerpt the President of the RIAI is making the following points:
“The world is under stress and we are the cause of it”
I think this is a reference to the strain being placed on our natural resources by rapid global population growth and to anthropogenic carbon dioxide increase and climate change.
The world’s population has grown from two billion people in the late 1920’s to over 7.25 billion this year. Each of these people needs a home, energy, food and water. This rapid increase in resource consumption is depleting the planet’s natural resources.
Ninety-five percent of the world’s energy requirements are met using carbon based fuels (i.e. oil, gas, coal). This is causing significant carbon dioxide emissions. The level of carbon in the atmosphere rose above 400ppm in 2013 - the first time since records began.
This anthropogenic carbon dioxide increase is causing global warming. Ten of the hottest years on record have occurred since the year 2000.
“The most resilient and sustainable form of human habitation is the town or the neighbourhood. We must build to create neighbourhoods”
Here the President of the RIAI is stating that in Ireland in particular we must move away from the tradition of building one-off houses in rural settings. One in three homes in Ireland is a one-off house in the countryside. This is not a sustainable way to build.
Only when homes are built in proximity to each other, is it possible to provide the resources required in a sustainable way. A community requires a critical mass of people to make them work. Schools, shops, clubs, bus routes and other everyday facilities cannot be sustained without enough people to use them and make them socially and economically viable. Any model that depends on large numbers of people using their car to access everyday activities is not sustainable.
In future, the focus must be on providing homes that are in sufficient proximity for communities to develop and grow. This will require designing and building homes in higher density (units per acre) and providing these homes with a high level of local resources. When people who love near each other share resources (e.g. neighbourhood parks, schools & clubs) relationships are built and communities flourish.
“We must plan and design to avoid isolation and disconnection.”
To me, this is a reference to the principles of inclusivity and connection.
Inclusivity is an important concept that relates to the ability of all people to use the neighbourhood on equal terms. This is about more than providing wheelchair access - it’s about meeting the needs of all people regardless of ability. To achieve this the neighbourhood should have a mix of home types (e.g. houses, apartments), a layout that is easy to access and a range of public spaces that are accessible and open to everyone.
Three planning guidelines that would promote the development of resilient and sustainable neighbourhoods, include:
- variety - every neighbourhood should include a mixture of building types, including residential, retail, commercial and recreational. This will facilitate a variety of activities and lead to an active community life. Active communities are more resilient because people have positive relationships with their neighbours and are more likely to help each other out an work together on community projects. A mix of building types will also allow some people to work and live in the same area, avoiding the need for commuting long distances by car.
- public realm - neighbourhoods should have public spaces (e.g. parks) that are safe, secure and enjoyable to use. A well designed public space will be constantly used by the local people. Good quality public spaces make a neighbourhood an attractive place to live. Attracting people to an area leads to growth and ensures that schools, shops and other facilities remain open.
- adaptability - homes should be designed so that they can be adapted to meet the needs of the occupants as they get older. This is a very important feature of home design that ensures people can continue to live in their homes even if they become less mobile or if the family gets bigger. An example of this is would be ensuring that there is access to the rear of homes so that an extension can be easily bult on without the need for heavy machinery (e.g. cranes).