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Passive Housing

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Passive solar design refers to the use of the sun’s energy for the heating and cooling of living spaces. In this approach, the building itself or some element of it takes advantage of natural energy characteristics in materials and air created by exposure to the sun. Passive systems are simple, have few moving parts, and require minimal maintenance and require no mechanical systems.

(http://passivesolar.sustainablesources.com/)

What is passive design?

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Passive Housing Principles

Orientation/ layout Natural lighting Thermal mass Heating Airtightness Air quality Glazing

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In Northern hemisphere nations the sun is positioned in the south.

The sun rises in the east and goes down in the west.

In summer the sun is higher in the sky than in winter (as shown in diagram)

Sun Path

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Orientation/Layout

As sun is in south, to provide natural light the rooms that are busiest should be on the southerly façade of the home (kitchens, living area)

Rooms which are used less frequently and need little lighting should be placed on northerly façade of home (utility, bathrooms etc.)

Note: Storage rooms placed to north side of house

Note: Living room, kitchen, dining room to south of house

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Orientation/Layout

As the sun rises in the east it is best practice to have bedrooms on the south east side of the home.

This will provide light to the room in the morning when the sun rises.

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Natural lighting

To provide natural light from the sun, large glazed areas are used to let the suns rays enter the home.

To maximise the light from the sun, these large glazed areas should be on the south facing façade of the house.

This will let the sunlight into the home throughout the year.

Note: Larger overhang on roof to prevent overheating in summer months.

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Shading

During the summer months there is a high chance of overheating in a passive home.

This is due to the high levels of exposure to the sun.

In order to combat this a large roof overhang can block the rays from the sun from entering the home.

This overhang will prevent overheating during the summer and still allow all winter sun into the home.

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Thermal Mass

Thermal mass is the ability of a material to store heat produced from sunlight.

This concept is important in passive design as changes is temperature need to be controlled.

Materials with good thermal mass store the heat from the sun and let it out slowly as the day progresses.

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Thermal Mass

During the day the thermal mass materials absorb the heat from the sun.

These materials release the heat slowly throughout the day and night.

This keeps the house at comfortable temperature

Good thermal mass materials: concrete, water, clay brick, natural rock/stone

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Heating

Solar heating panels can be used to provide hot water for the home.

Panels are placed out southerly facing roof to absorb the heat from the sun throughout the year.

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How Solar Panels Work

The solar panels are made of specially designed material that absorbs the suns rays extremely efficiently and when the sun heats the solar panels, a fluid is pumped from the hot water cylinder in your hot press up and around the solar panels.

The fluid is then heated in the solar panels and returns to the hot water cylinder to heat the water in the cylinder.

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Airtightness

An important aspect in passive design to prevent heat being lost in the home.

All elements of the dwelling should have high levels of insulation to prevent heat loss.

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Wall Insulation In traditional building

systems there is a chance of cold bridges in the wall area between small gaps at joints.

As shown in the diagram warm air is being lost around the window and at the eaves.

In passive homes this needs to be eliminated in order to trap all the heat in the house.

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External Wall Insulation

Insulating walls externally is system suitable for passive homes.

This system prevents any cold air from outside entering the building.

It provides a full cover on the external surface of the building trapping in the heat inside the home.

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Viking Timber Frame Insulation

Timber frame construction is suitable for passive design.

Between the stud work of the timber frame it is packed with insulation.

The insulation is packed in tight in between the studs to prevent any cold bridging.

Insulation is usually 200-300mm depending in thickness of wall.

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Roof Insulation

This detail shows high levels of cellulose insulation which has been sprayed between the joists.

The insulation goes down to eaves level and insures no cold air can travel through to the living area of the home.

Eaves ventilator insures ventilation in roof space to prevent timber rotting.

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Roof Insulation

This detail shows the insulation between the roof rafters.

This system is used if the roof space is to be used as a living space.

The insulation is rigid board and is cut to fit between the rafters of the roof.

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Foundation insulation

Heat can be lost through the ground in a house.

In traditional foundation systems there is a high chance of cold bridges coming from the earth into the house as shown in Fig 1.

By using a modern insulated slab as shown in Fig 2 the bridge is prevented from occurring.

Fig 1

Fig 2

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Viking insulated slab

In this foundation cold bridges are prevented.

The foundation is insulated on the internal as well as external surfaces.

The foundation is made up of polystyrene insulation which when joint forms a ring beam to which the concrete foundation is poured into.

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Air quality

Indoor air quality is a important concern to take into account when designing a passive home.

Due to the high level of insulation in passive homes, stale air can be trapped in the home if it is not released.

This can lead to mould growing in the home and creating uncomfortable living conditions

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Heat Recovery Ventilation (HRV)

HRV units provide the clean air necessary to create comfortable living conditions.

These systems take the stale air within the house out and let fresh air into the house.

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Heat Recovery Ventilation (HRV)

When the hot stale air is extracted from the home, it is used to heat the cool fresh air coming in.

The air from inside and outside pass through the same system however they never come in contact with one another.

As the hot stale air leaves it heat the cool air coming in. this keeps the house at a comfortable living condition.

Hot air from inside heats cool air coming into house in heat

exchange core.

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Triple Glazing

Triple glazed systems are often used in passive homes.

Triple glazed systems have a high conservation of heat and also eliminate drafts in the house.

The main disadvantage of this system is the distortion of light between the panes of glass.

Note: Insulated window frame

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Double Glazing

Don’t have as high thermal efficiency of the triple glazing system.

However the double glazed system wont distort the light coming into the home to the same extent as the triple glazing system.

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Balance between glazing systems

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As both systems have good thermal efficiency it is suitable to use both types in the ne home.

As the north facing façade will experience the cooler/stronger conditions it would be suitable to use triple glazing system on this façade.

To the south/east/west facing façades it would be suitable to use the double glazing system as these sides of the home will take in the sunlight. This system wont distort the light as much as the triple glazing system .