PRINCIPLE DESIGN FEATURES
The inclusion of a steel frame and factory made structural insulated panels for the roof, was intended to shorten the build time. However, this became of particular relevance as the spring of 2012 was one of the wettest on record, so the completed the roof acted as a giant “umbrella” providing shelter for such as the masonry works which would otherwise have been “rained off” on numerous days.
Similarly, by having a concrete first floor supported by the steel frame before the walls were built, allowed the trades to be duplicated making it practical to work on two floors simultaneously.
Whilst the “rain-shield” panelling for the external elevations was intended as an ECO feature – see below – it too, reduced the construction period. For example, had the exterior been traditional brickwork it would have taken several weeks longer to complete, before the windows could have been installed, and without the windows such as internal plastering could not have commenced.
We were fortunate in that the previous owners of the “Hill End” bungalow had been avid gardeners, and we preserved as much of the original as was practical, so that on completion the new “Hill End” house was situated within a garden with mature trees, shrubs and roses.
Whilst the external appearance of the house might be considered “controversial” by some, the traditional timber frame carport and workshop with their cedar shingle roofs, were designed to “soften” its impact in the rural hamlet.
In demolishing the original bungalow, part of an external wall in which the electricity meter was installed was carefully retained, thus saving the cost of disconnecting and subsequently reconnecting, the mains electricity supply.
The retained section of wall became a screen behind the air source heat pump to shield its sound and act as a heat sink in the summer to improve its efficiency.
As a further benefit of this, and of completing the roof at such an early stage, the PV panels could be installed, connected to the mains and start generating electricity whilst the house was still being built.
ECO CREDENTIALS
Insulation
Starting with a “clean sheet of paper” allowed us to design insulation into the building from the outset, rather than simply cladding whatever one could, retrospectively. However, we had to strike a balance between increasing the thickness, by say just another 25mm and the possible resultant energy saving, against the additional cost.
With any self-build project, it is important to resist “just adding a little but more”, if budgets are to be adhered to.
Structural Insulated Roof Panels
SIPS are widely used in new roofs but are generally installed perpendicular to the slope. However, when used in conjunction with a steel frame that would have needed purlins to support them. That in turn would have added some 200mm to the height of the ridge which would not have complied with the planning permission requirement not to exceed the height of the original bungalow roof.
Hence, for Hill End, the SIPs were purpose made to the length of the roof and with laminated (“engineered”) timber purlins rebated within their thickness. These were craned into place, then bolted directly to the portal rafters of the steel frame.
Standing Seam Steel Roof
Whilst various roof finishes were considered, colour coated steel was selected as it could readily include the fascia, gutters and soffits of the substantial eaves overhang, so creating a totally integrated appearance.
Whilst the 40-year warranty on the roof was a further attraction – a major consideration was to achieve a clean run off of rainwater for the rain water harvesting system.
PV Solar Panels
With the benefit of a south facing 26° pitch roof and open aspect, the output from the PV panels has been maximised and monthly meter readings suggest that even after 8-years there had been no significant degradation.
Air Source Heat Pump
The intention was to install a ground source heat pump, but to disturb as little of the original garden as practical that would have necessitated sinking two vertical bore holes each 30-40m deep, the cost of which could not be justified.
At the time, latest developments had improved the performance of air-source heat pumps, as well as reducing noise level and hence a Mitsubishi Ecodan was chosen, and in its location, has the benefit of a solid free standing brick wall some 300mm behind it, to shield any noise from the neighbouring property as well as to act as a heat sink in sunny weather.
Rain Water Harvesting
A 3000-litre rectangular underground tank was installed at the rear of the house into which all the rain water from both the house and car-port roofs discharge.
Within the tank is a submersible “on demand” electric pump that pressurises a separate cold-water plumbing system within the house which feeds the 4 WC’s and washing machine.
In the event of a drought, there is provision for the underground tank to be automatically topped up with just enough mains water to keep the system functioning, until the next rains come.
Mechanical Heat Recovery Ventilation System (MHRV)
Although the overall height of the house is low, there is still sufficient room in the “loft” space to install a MHRV system.
At its simplest, this extracts warm stale air from the bathrooms by way of ceiling vents and insulated ducts, then discharges it through a heat exchanger before being blown out through a vent in one gable end.
At the same time, fresh air is drawn in from the opposite gable end, filtered to remove dust and pollen, then passed though the heat exchanger to recover the outgoing heat before it is discharged as warmed fresh air via ceiling vents on the first floor.
Integral Vacuum Cleaning System (IVC)
There was just sufficient space between the underside of the concrete first floor and the ground floor ceiling to include the UPVC ductwork for an IVC system with the actual vacuum unit included within the utility room, where the heat from its motor is recovered.
Around the house there are six vacuum sockets into which the vacuum hose is plugged in order to clean house.
Rain-Shield Panel Cladding
This is one aspect of the design that the planning officers really objected to, for whilst they could appreciate the intended architectural contrast, they considered it could be achieved with coloured render.
However, render, along with traditional brickwork absorbs moisture in the winter months which in turn needs energy to evaporate, thus reducing the building efficiency.
In practice, the rain-shield panel system used is a self-coloured fibre cement manufactured under high pressure so making it totally impervious. With a 50mm vented cavity behind it, the system has proved to be exceedingly effective, and has attracted favourable comment, even from passers-by who have knocked on the door to enquire about it.
Carbon Footprint
All construction projects have a comparatively high carbon “footprint” although we were certain that over a period of time, the enhanced sustainability of the new Hill End, would off-set the construction demands.
However, even from the “drawing board” stage we sought to design out as much embedded carbon demand as practical, by:
“A” - Recycled from the Bungalow:
Marley Garage
The original pre-cast concrete single garage was removed soon after we moved into the bungalow, so as to provide access for the new timber frame car-port to be constructed in the rear garden. Its cement/asbestos roof sheets were removed, double wrapped and disposed of to a licensed site strictly in accordance with regulations.
However, the exposed aggregate concrete wall panels, were carefully dismantled and reused on-edge to provide a decorative face to a shallow retaining wall at another property.
Insulation
The roof space in the bungalow was well insulated with encapsulated rockwool. This was removed and re-used to insulate the walls in the new timber framed workshop, before its internal plasterboard lining was installed.
Fenestration
The aluminium window frames and sealed double glazed units, were carefully removed and donated for re-use to a group who were self-building an extension to a village hall.
However, one double glazed unit was retained, and became a feature of the new front door.
Gutters and Downpipes
AS the UPVC gutters on the bungalow were in excellent condition, they were carefully removed and donated to replace failing gutters on a bungalow in Gloucester.
Kitchen Units
The kitchen units were removed and stored in the car-port. At the fitting out stage the carcasses were refurbished in the workshop, and along with new doors and fittings, re-used in the utility room of the new house.
Structural Steel
3 No. rolled steel joists that acted as lintels in the bungalow, were cleaned, cut to length and re-painted, before being reused in the new house, to support the galleried landing above the entrance hall.
Electricity Supply
As previously referred to, an outside wall of the original kitchen which housed the electricity meter was retained, and the electrical layout of the new house designed so that the Consumer Units could be installed within 3.0m of the meter to comply with regulations. This saved not only the disconnection and reconnection, but the new underground cabling, that would have otherwise have been required.
Drainage
Being in a rural location there is no mains drainage available where Hill End is situated. The original bungalow had a septic tank in the front garden, and although it had been registered with the Environment Agency, its condition was unknown and hence was scheduled to be replaced with a new GRP installation.
Subsequent inspection revealed that even though some 80 years old, the septic tank had clearly been constructed by a master craftsman. Other than the need to replace the rusted inspection cover, the installation was large enough and in such excellent condition that the Building Inspector suggested that it should be retained as part of the foul drainage of the new house.
Timber
The bungalow contained a considerable amount of timber, whereas the new house has virtually none in its construction.
Therefore, arrangements were made to strip and de-nail the timbers, retaining some for use in concrete formwork and donate the rest to a group of volunteers who were reconstructing a former railway station.
Sadly, that was not to be. When stripping started, the roof timbers and ceiling joists were found to be so riddled with wood worm, that sooner or later, structural failure would have been inevitable.
Almost as bad the ground floor joists were found to be rotten no doubt as a result of the air bricks having been blocked off by a previous owner.
A limited amount of timber was suitable for re-use in the concrete formwork, but the rest was cut to lengths, loaded into skips and sent for specialist timber re-cycling. Nothing was burned on site!!
All was not lost though; there was a veranda across the front elevation of the bungalow, supported by 3 No. oak columns. One was rotten beyond reuse, but the other two were salvaged and re-used as “faux” columns to support for the balcony on the new house.
Masonry
Perhaps, fortuitously, the bungalow was old enough to pre-date the introduction of concrete building blocks, therefore as all the external walls were brick, it was easy to crush them beneath the tracks of the excavator used for the demolition so that the resultant rubble could be reused as the base to the forecourt in front of the house that was needed to provide off-road parking for up to 8 cars.
The surplus masonry was collected by the neighbouring farmer, transported some 800m and used to form the base on a new barn.
Excavated Spoil
The footprint of the new house followed closely that of the bungalow, the foundations of which were constructed entirely of brickwork, some 900mm deep. So, although the existing foundations could not be re-used, the bricks from them were used as described above.
Hence, being wider and deeper, the foundations for the house generated some excavated material to be removed from site. Whilst resigned that this would ultimately have to go to land fill and create a substantial “negative” in our ECO principles, it was tipped temporarily in the former veg’ garden.
Surprisingly, within a few weeks, the owners of the neighbouring farm asked if they could have the surplus, as they could use it filling a hollow in the ground which was water logged for much of the year.
“B” – Materials Sourced Within 15-mile radius of site:
Ready-Mix Concrete
Steel Frame
Facing Bricks
All new timber - including decking and round timbers for garden retaining walls
Upvc Window Frames, Doors and Glazing
Rain-shield wall panels
Kitchen Installation
“C” – Sub-Contract Services Sourced Within 15-mile radius of site:
Architectural services - viz. planning application
Planning Consultant – viz. planning application
Ground/Concrete works
Brick Laying
Plumbing installation
Electrical installation
Painting and Decoration
“D”- UK manufactured products in preference to imported:
Facing bricks - made in Blockley - Gloucestershire
Air Source Heat Pump and associated equipment. – made in Glasgow
Heat Recovery Ventilation System Equipment – made in West Sussex
Internal Doors – Frames and Architraves – made in South Yorkshire
Kitchen units made in West Yorkshire.
Kitchen worktops made in York
Bespoke Toughened Glass – made in Glasgow
Oak Strips for Stair Balustrade – sawmill Abingdon ex a road side tree in Oxford
The inclusion of a steel frame and factory made structural insulated panels for the roof, was intended to shorten the build time. However, this became of particular relevance as the spring of 2012 was one of the wettest on record, so the completed the roof acted as a giant “umbrella” providing shelter for such as the masonry works which would otherwise have been “rained off” on numerous days.
Similarly, by having a concrete first floor supported by the steel frame before the walls were built, allowed the trades to be duplicated making it practical to work on two floors simultaneously.
Whilst the “rain-shield” panelling for the external elevations was intended as an ECO feature – see below – it too, reduced the construction period. For example, had the exterior been traditional brickwork it would have taken several weeks longer to complete, before the windows could have been installed, and without the windows such as internal plastering could not have commenced.
We were fortunate in that the previous owners of the “Hill End” bungalow had been avid gardeners, and we preserved as much of the original as was practical, so that on completion the new “Hill End” house was situated within a garden with mature trees, shrubs and roses.
Whilst the external appearance of the house might be considered “controversial” by some, the traditional timber frame carport and workshop with their cedar shingle roofs, were designed to “soften” its impact in the rural hamlet.
In demolishing the original bungalow, part of an external wall in which the electricity meter was installed was carefully retained, thus saving the cost of disconnecting and subsequently reconnecting, the mains electricity supply.
The retained section of wall became a screen behind the air source heat pump to shield its sound and act as a heat sink in the summer to improve its efficiency.
As a further benefit of this, and of completing the roof at such an early stage, the PV panels could be installed, connected to the mains and start generating electricity whilst the house was still being built.
ECO CREDENTIALS
Insulation
Starting with a “clean sheet of paper” allowed us to design insulation into the building from the outset, rather than simply cladding whatever one could, retrospectively. However, we had to strike a balance between increasing the thickness, by say just another 25mm and the possible resultant energy saving, against the additional cost.
With any self-build project, it is important to resist “just adding a little but more”, if budgets are to be adhered to.
Structural Insulated Roof Panels
SIPS are widely used in new roofs but are generally installed perpendicular to the slope. However, when used in conjunction with a steel frame that would have needed purlins to support them. That in turn would have added some 200mm to the height of the ridge which would not have complied with the planning permission requirement not to exceed the height of the original bungalow roof.
Hence, for Hill End, the SIPs were purpose made to the length of the roof and with laminated (“engineered”) timber purlins rebated within their thickness. These were craned into place, then bolted directly to the portal rafters of the steel frame.
Standing Seam Steel Roof
Whilst various roof finishes were considered, colour coated steel was selected as it could readily include the fascia, gutters and soffits of the substantial eaves overhang, so creating a totally integrated appearance.
Whilst the 40-year warranty on the roof was a further attraction – a major consideration was to achieve a clean run off of rainwater for the rain water harvesting system.
PV Solar Panels
With the benefit of a south facing 26° pitch roof and open aspect, the output from the PV panels has been maximised and monthly meter readings suggest that even after 8-years there had been no significant degradation.
Air Source Heat Pump
The intention was to install a ground source heat pump, but to disturb as little of the original garden as practical that would have necessitated sinking two vertical bore holes each 30-40m deep, the cost of which could not be justified.
At the time, latest developments had improved the performance of air-source heat pumps, as well as reducing noise level and hence a Mitsubishi Ecodan was chosen, and in its location, has the benefit of a solid free standing brick wall some 300mm behind it, to shield any noise from the neighbouring property as well as to act as a heat sink in sunny weather.
Rain Water Harvesting
A 3000-litre rectangular underground tank was installed at the rear of the house into which all the rain water from both the house and car-port roofs discharge.
Within the tank is a submersible “on demand” electric pump that pressurises a separate cold-water plumbing system within the house which feeds the 4 WC’s and washing machine.
In the event of a drought, there is provision for the underground tank to be automatically topped up with just enough mains water to keep the system functioning, until the next rains come.
Mechanical Heat Recovery Ventilation System (MHRV)
Although the overall height of the house is low, there is still sufficient room in the “loft” space to install a MHRV system.
At its simplest, this extracts warm stale air from the bathrooms by way of ceiling vents and insulated ducts, then discharges it through a heat exchanger before being blown out through a vent in one gable end.
At the same time, fresh air is drawn in from the opposite gable end, filtered to remove dust and pollen, then passed though the heat exchanger to recover the outgoing heat before it is discharged as warmed fresh air via ceiling vents on the first floor.
Integral Vacuum Cleaning System (IVC)
There was just sufficient space between the underside of the concrete first floor and the ground floor ceiling to include the UPVC ductwork for an IVC system with the actual vacuum unit included within the utility room, where the heat from its motor is recovered.
Around the house there are six vacuum sockets into which the vacuum hose is plugged in order to clean house.
Rain-Shield Panel Cladding
This is one aspect of the design that the planning officers really objected to, for whilst they could appreciate the intended architectural contrast, they considered it could be achieved with coloured render.
However, render, along with traditional brickwork absorbs moisture in the winter months which in turn needs energy to evaporate, thus reducing the building efficiency.
In practice, the rain-shield panel system used is a self-coloured fibre cement manufactured under high pressure so making it totally impervious. With a 50mm vented cavity behind it, the system has proved to be exceedingly effective, and has attracted favourable comment, even from passers-by who have knocked on the door to enquire about it.
Carbon Footprint
All construction projects have a comparatively high carbon “footprint” although we were certain that over a period of time, the enhanced sustainability of the new Hill End, would off-set the construction demands.
However, even from the “drawing board” stage we sought to design out as much embedded carbon demand as practical, by:
- Recycling as much of the old bungalow as possible.
- Sourcing all materials as close to the site as practical, and if at all possible, within an arbitrary radius of 15 miles.
- Sourcing all sub-contract services as close to the site as practical, and if at all possible, within an arbitrary radius of 15 miles.
- Using products made in UK, in preference to imported ones.
“A” - Recycled from the Bungalow:
Marley Garage
The original pre-cast concrete single garage was removed soon after we moved into the bungalow, so as to provide access for the new timber frame car-port to be constructed in the rear garden. Its cement/asbestos roof sheets were removed, double wrapped and disposed of to a licensed site strictly in accordance with regulations.
However, the exposed aggregate concrete wall panels, were carefully dismantled and reused on-edge to provide a decorative face to a shallow retaining wall at another property.
Insulation
The roof space in the bungalow was well insulated with encapsulated rockwool. This was removed and re-used to insulate the walls in the new timber framed workshop, before its internal plasterboard lining was installed.
Fenestration
The aluminium window frames and sealed double glazed units, were carefully removed and donated for re-use to a group who were self-building an extension to a village hall.
However, one double glazed unit was retained, and became a feature of the new front door.
Gutters and Downpipes
AS the UPVC gutters on the bungalow were in excellent condition, they were carefully removed and donated to replace failing gutters on a bungalow in Gloucester.
Kitchen Units
The kitchen units were removed and stored in the car-port. At the fitting out stage the carcasses were refurbished in the workshop, and along with new doors and fittings, re-used in the utility room of the new house.
Structural Steel
3 No. rolled steel joists that acted as lintels in the bungalow, were cleaned, cut to length and re-painted, before being reused in the new house, to support the galleried landing above the entrance hall.
Electricity Supply
As previously referred to, an outside wall of the original kitchen which housed the electricity meter was retained, and the electrical layout of the new house designed so that the Consumer Units could be installed within 3.0m of the meter to comply with regulations. This saved not only the disconnection and reconnection, but the new underground cabling, that would have otherwise have been required.
Drainage
Being in a rural location there is no mains drainage available where Hill End is situated. The original bungalow had a septic tank in the front garden, and although it had been registered with the Environment Agency, its condition was unknown and hence was scheduled to be replaced with a new GRP installation.
Subsequent inspection revealed that even though some 80 years old, the septic tank had clearly been constructed by a master craftsman. Other than the need to replace the rusted inspection cover, the installation was large enough and in such excellent condition that the Building Inspector suggested that it should be retained as part of the foul drainage of the new house.
Timber
The bungalow contained a considerable amount of timber, whereas the new house has virtually none in its construction.
Therefore, arrangements were made to strip and de-nail the timbers, retaining some for use in concrete formwork and donate the rest to a group of volunteers who were reconstructing a former railway station.
Sadly, that was not to be. When stripping started, the roof timbers and ceiling joists were found to be so riddled with wood worm, that sooner or later, structural failure would have been inevitable.
Almost as bad the ground floor joists were found to be rotten no doubt as a result of the air bricks having been blocked off by a previous owner.
A limited amount of timber was suitable for re-use in the concrete formwork, but the rest was cut to lengths, loaded into skips and sent for specialist timber re-cycling. Nothing was burned on site!!
All was not lost though; there was a veranda across the front elevation of the bungalow, supported by 3 No. oak columns. One was rotten beyond reuse, but the other two were salvaged and re-used as “faux” columns to support for the balcony on the new house.
Masonry
Perhaps, fortuitously, the bungalow was old enough to pre-date the introduction of concrete building blocks, therefore as all the external walls were brick, it was easy to crush them beneath the tracks of the excavator used for the demolition so that the resultant rubble could be reused as the base to the forecourt in front of the house that was needed to provide off-road parking for up to 8 cars.
The surplus masonry was collected by the neighbouring farmer, transported some 800m and used to form the base on a new barn.
Excavated Spoil
The footprint of the new house followed closely that of the bungalow, the foundations of which were constructed entirely of brickwork, some 900mm deep. So, although the existing foundations could not be re-used, the bricks from them were used as described above.
Hence, being wider and deeper, the foundations for the house generated some excavated material to be removed from site. Whilst resigned that this would ultimately have to go to land fill and create a substantial “negative” in our ECO principles, it was tipped temporarily in the former veg’ garden.
Surprisingly, within a few weeks, the owners of the neighbouring farm asked if they could have the surplus, as they could use it filling a hollow in the ground which was water logged for much of the year.
“B” – Materials Sourced Within 15-mile radius of site:
Ready-Mix Concrete
Steel Frame
Facing Bricks
All new timber - including decking and round timbers for garden retaining walls
Upvc Window Frames, Doors and Glazing
Rain-shield wall panels
Kitchen Installation
“C” – Sub-Contract Services Sourced Within 15-mile radius of site:
Architectural services - viz. planning application
Planning Consultant – viz. planning application
Ground/Concrete works
Brick Laying
Plumbing installation
Electrical installation
Painting and Decoration
“D”- UK manufactured products in preference to imported:
Facing bricks - made in Blockley - Gloucestershire
Air Source Heat Pump and associated equipment. – made in Glasgow
Heat Recovery Ventilation System Equipment – made in West Sussex
Internal Doors – Frames and Architraves – made in South Yorkshire
Kitchen units made in West Yorkshire.
Kitchen worktops made in York
Bespoke Toughened Glass – made in Glasgow
Oak Strips for Stair Balustrade – sawmill Abingdon ex a road side tree in Oxford