With the crisis of global climate change worsening every day, it is imperative that we find solutions and strategies for building & living sustainably.
Building an average, four-bedroom, house-builder home emits around 80 metric tons of carbon dioxide (for reference the average household in the UK emits around 8 tons per year) in the manufacture of materials such as cement, which emits 1.25 kg of CO2 for every kilo of the material, the firing of bricks, which releases ~23 kg of CO2 per m² or (0.38 kg per brick) as well as the making of cast concrete floors, clay and concrete roof tiles as well as the transportation emissions to site and the process emissions on-site, not to mention to the prevalence of unsustainable plastic windows.
There are many ways to drastically lower the environmental cost of building homes as well as minimising their emissions in use (lowering the 8 tons of CO2 the average household emits annually). At Samuel Kendall Associates we have been integrating a host of approaches to the design of low carbon, sustainable homes for over 2 decades & in the last 12 months have developed many new, innovative eco-homes (with several schemes currently on site) which have pushed the boundaries of how sustainable a modern family home can be. These are not homes of the super rich with budgets typical of the average UK household, ranging from £60,000 to £300,000, well within financial comparison to the ill-considered, generic house-builder estates we see up and down the country.
Dusk-Dawn House is a low carbon home we recently received planning permission for in Cottingham, East Yorkshire. The project extends a 1920’s detached home with a passive solar extension made with low carbon materials of SIPS panels and timber cladding.
1. Maintain, Enhance & Extend
A great way to minimise the pollution of a house build is to start with an existing home. By retaining and adapting an existing dwelling you prolong the building's lifespan, locking in the emissions of the original build for generations to come.
The issue is that old houses typically take a lot of energy to heat due to their lack of insulation, low quality glazing and general lack of airtightness. By enhancing an existing house with new insulation, high performance glazing and airtightness work throughout as well as the integration of renewable energy systems and passive solar design principles you can achieve a century old home with state of the art performance.
Our recent project at Dusk-Dawn House in Cottingham, East Yorkshire, which we recently received planning permission for, is a prime example of this approach.
Beginning with a 1920's detached house which had a very poor thermal performance of 1.6 W/m²K we added a substantial 200mm layer of new insulation and render, dropping the home's heat loss by 90% to 0.16 W/m²K. We then extended the upgraded home with a new wing constructed from SIPS panels, a prefabricated system of insulated timber-framed panels which achieve an extreme level of thermal efficiency at 0.11 W/m²K, beyond the (0.15 W/m²K) requirements of the Passivhaus Standard. These panels form the walls and roof of the extension & being predominantly made from timber achieve a negative embodied carbon due to the fact that wood grows by extracting CO2 from the air, a process known as carbon sequestration.
Dusk-Dawn House integrates a solar courtyard at its heart permitting natural light, heat and air to the core of the home.
Dusk-Dawn House locks away 37.1 metric tons of carbon emissions in the existing home's fabric & extends the home emitting just 14.2 metric tons of carbon, which achieves a embodied carbon per square metre of 225 kgCO2e/m² (for comparison the typical brick and block developer house emits more than twice as much carbon at 513 kgCO2e/m²). If we assume a thermal performance for a partially insulated cavity wall of 0.24 W/m²K in a typical house-builder home we can infer a heat saving of 40% at an overall average U value for Dusk-Dawn House of 0.14 W/m²K. For a typical household that pays over £1000 per year for gas heating that would achieve a saving of at least £400. Energy prices have risen by between 8 & 18% per year since 2000 and will continue to do so. For the cost of 13.2 cubic metres of rigid insulation, which would be around £1400, Dusk-Dawn House lowers its heat loss by 90%, a cost recuperated in less than 3 years of heating savings.
A highly insulated timber frame, clad in materials salvaged from the original house, East Yorkshire Passivhaus achieves a radically low embodied carbon and environmental cost in use.
2. Dismantle, Harvest & Re-Use
Another great strategy to achieve a low embodied carbon home is to find a derelict house which you can harvest materials from to reuse. This approach maintains the original material character of the home whilst negating the financial and environmental costs of new building materials.
Our East Yorkshire Passivhaus dismantles a disused Post Office cottage, reusing its distinctive materials of Wolds chalk, whitewashed brick and slate to create a unique eco-home celebrating its village heritage.
The house is arranged to maximise its relationship to a verdant, expansive garden and bring natural light into the home. A central, double-height living space creates the optimal conditions for stack effect ventilation to naturally ventilate the home.
This strategy of enables far superior levels of thermal efficiency & airtightness which all drastically lower the cost of living and carbon footprint of the home in use. The home will achieve a U value of 0.11 W/m²k surpassing the Passivhaus standard of 0.15 W/m²k.
A ground floor finish of terrazzo and a central natural stone chimney create significant thermal mass in the home, stabilising internal temperatures and lowering the home’s reliance on artificial heating.
Renewable systems including an Ecodan air source heat pump, a mechanical ventilation heat recovery system and battery storage remove the home’s reliance on fossil fuel energy whilst achieving the healthiest internal environment for the family.
As the UK continues to experience record summer temperatures and move from a temperate northern European climate to a climate similar to the south of France we believe all new home’s must pay close attention to the dangers of overheating, integrating solutions into their design to minimise costs incurred in the future. This project integrates a perforated aluminium canopy across its south-facing elevation, shading the interior from the high angles of summer sun whilst permitting low winter sun to harvest solar heat in the colder months.
Our East Yorkshire Passivhaus is a four bedroom, 234 m² house which has an total embodied carbon of 61 tons. This equates to 260 kgCO2e/m², a comparison to the typical house-builder home, which has an embodied carbon per square metre of 513 kgCO2e/m² achieves a home with half the environmental impact in its construction. When we compare the two homes in use our project's extremely low levels of heat loss of 0.11 W/m²K will achieve a saving in heating costs of 55%, purely based on our project's thermal envelope.
If we consider the fact that the East Yorkshire Passivhaus will source all its heating from the ambient heat of the air through an air source heat pump the difference in the cost in use becomes remarkably stark. With the air source heat pump considered the East Yorkshire Passivhaus would save £24,865 over the next ten years in comparison to a typical new-build house-builder home.
Ignoring the fact that all heating for our project will be provided for free by an air source heat pump, if we take a typical four bedroom household's heating energy use as 18,000 kWh (£1494) per year with an 8% increase year on year, over a ten year period our project would save £13,481 on heating.
If we consider the amount of heating energy a typical new-build house uses over 50 years (18,000 kWh per year *50 years = 900,000* 0.309 (CO2 emission factor) = 278 metric tons of CO2), the electricity demand over 50 years (a typical home's lifespan) (4,600 kWh * 50 = 230,000 *0.309 kg/kWh = 71,000 kge (71 metric tons)) with the embodied carbon of the home of 80 metric tons we reach a total home carbon footprint of 429 metric tons.
Our East Yorkshire Passivhaus has an embodied carbon of 61 metric tons and if conventional heating were used a projected heating emissions value of 127 metric tons giving a total of 188 tons, however through a sophisticated renewable energy air source heating system the home’s carbon footprint in use for heating is negated. Assuming no renewables are used for electricity would give the same value as the typical 4 bed new-build house of 71 metric tons, giving a total home carbon footprint of 132 metric tons of CO2. That is a 50 year carbon footprint saving of 297 metric tons, a whole life carbon footprint 31% of the typical house-builder home.
South Cave Passivhaus, a family home made with a simple, local material palette.
3. Low Carbon Materials & Low Carbon Technologies
Building a new sustainable home requires a careful consideration of the embodied carbon in the manufacture, transportation and processing cost of the house materials, as well as the emissions on site and the speed/efficiency of construction techniques & household technologies.
The material elements of a house can be broken into 3 clear categories -
Structure
Insulation
Cladding
A typical new-build developer house has a structure of cementitious concrete blockwork, precast concrete beam and block floors and a timber-framed roof structure, a very carbon heavy way of building that also requires thicker external walls to achieve adequate thermal efficiency levels, compromising the size of internal spaces.
A comparison of a SIPS panel wall to an insulated blockwork wall outlines the difference in thickness.
These generic homes are then insulated with expanded polystyrene rigid insulation (a highly flammable and emission heavy material) and clad in carbon intensive brickwork and clay or more often concrete roof tiles.
A far better, more efficient way to build is to use an off-site manufactured, timber-framed structure, perhaps of SIPS panels. This construction method is much quicker to build with as the panels for walls and roofs come with pre-formed openings, low carbon insulation installed and achieve adequate thermal efficiency at around half the thickness of cavity wall construction due to the overlap of insulation and structural wall layers (insulation between timber studs). This structure is then best clad with locally sourced, low carbon, long lasting materials as seen in our new project in South Cave.
South Cave Passivhaus aims to reach a new standard for a low carbon, healthy and sustainable way of living, worthy of its pastoral nature rich setting. Our clients, both passionate ecologists, wanted to create a home which would have the lowest environmental impact, enhancing the character of their site.
The materials of this house have been chosen to keep carbon emissions as low as possible and this is no truer than in the choice of the home’s exterior. South Cave occupies a unique geological seam of Bajocian age, Oolitic limestone known locally as “Cave Oolite”. This stone was used for the building of Beverley Minster as well as countless local farmsteads and quarrying continues just 600 metres from this project’s site. This makes it the ideal material choice to minimise the environmental impact of heavy material transportation whilst achieving an external character faithful to the distinctive Yorkshire Wolds setting.
Engineers Webb Yates claim natural stone has between 5-40% of the carbon footprint of concrete and steel, by leaving the stone “quarry finished” you can save 95% of the environmental processing cost of the material.
As a natural unprocessed product of the earth, no issues of off-gassing and toxins present in man-made materials are present in the material. Stone is a thermally massive material, acting as passive thermal energy storage which when used within the home’s thermal line and directly exposed to sunlight will hold the heat of the sun long after the sun has set, slowly releasing that heat to stabilise the internal temperatures of the building. Stone is also fully recyclable and using reclaimed stone can further lower the carbon footprint of your home, negating the processing emissions of virgin material. Companies such as Traditional Stone provide UK sourced reclaimed stone. When using stone you must ensure it is sustainably sourced through bodies such as Fair Stone or the Ethical Stone Register.
Featured in our guide to sustainable home materials, natural stone provides a low embodied carbon, a very long lifespan and a host of passive solar effects to your home.
South Cave Passivhaus is a 220 m² home with an embodied carbon of 73 metric tons. That equates to 332 kgCO2e/m² which in comparison to the typical 4 bed developer house (513 kgCO2e/m²) is a saving on emissions density of 35%. This project is a showcase in contemporary low carbon living with a heat efficiency of 0.11 W/m²K which is less than half the heat loss of a typical house-builder home at 0.24 W/m²k. The existing pond at the site’s north end is the perfect place to install a ground source heating system which will supply all the home’s heating needs whilst also negating the often destructive and expensive groundworks of installing a conventional ground source system beneath the established and heavily planted garden. A 6.4kW solar array coupled with domestic lithium ion batteries will supply the total energy demand of the house, selling the excess back to the national grid. These systems, which will only improve in efficiency over time, effectively eliminate any carbon footprint from the building's use.
When we compare South Cave Passivhaus to the typical four bedroom household's energy demands of 18400 kWh for heating and 6400 kWh for electricity per year, against values of 0 for our project the difference in their carbon footprints becomes remarkably stark. Over a 50 year period our project will save 1,240,000 kWh of energy which equates to 383 metric tons of CO2 emissions. 383 metric tons of CO2 is the equivalent to driving the average new car (with an emission rate of 120 g/km) around the world 80 times (2 million miles) It also equates at a rate of energy cost increase of 8% year on year, starting at £1758 per annum, to a saving of £997,443 in heating and electricity over 50 years.
4. Retain, Extend & Innovate
As our working patterns shift from daily commutes to home-working routines we must consider the impact this may have on the health & sustainability of our homes and lifestyles.
Most houses are not designed to accommodate working from home, particularly for multiple people. This global routine shift is having a dramatic impact on the energy and heating demands of our homes and with energy bills rising every year (by between 8 & 18%) many households are searching for solutions to the imminent crises of fuel poverty, physical and mental health that our increased condition of sedentary domestic isolation has highlighted.
We have found that the areas of homes which are often neglected and underused such as lofts, garages and outbuildings can be successfully converted into healthy, sustainable places of work which lower stress, increase focus and productivity as well as better connecting our daily lives to the natural world around us.
Our Scarborough Photography Studio project, which we recently received planning permission and building regulations approval for, is a showcase in the potentials of sustainable, low carbon adaptation of existing outbuildings into healthy, calm and eco-friendly home-working and leisure spaces.
Beginning with an existing, rendered blockwork garage, we extended the building in length and height, increasing its area from 43 m² to 198 m². These new areas house the archive, studio and gymnasium of a prominent photographer, fulfilling our client’s aim to shift their work from a large office to a bespoke home studio, providing the flexibility and tranquillity of working from home. The project is made with the ambition to be as sustainable as possible, minimising the studio’s embodied carbon, maximising the building’s thermal efficiency & integrating a coherent suite of cutting edge renewable energy systems and passive solar design techniques.
By retaining and extending the existing garage we have locked away 12 metric tons of carbon dioxide emissions. Our approach of over-insulating the concrete masonry structure allows this space to act as a passive thermal storage zone for the heat absorbed from the sun’s rays. The new areas of the studio are constructed with a highly insulated timber frame which takes a further 9.4 metric tons of carbon dioxide out of the atmosphere and achieves an overall embodied carbon of just 25.8 metric tons, which equates to a very low embodied carbon density of just 190 kgCO2/m², a value 37% that of a conventional cavity wall construction house (513 kgCO2/m²).
A typical small business comparable in size to this Studio uses approximately 10,000 kWh of electricity a year, costing around £1225 & consuming ~10,000 kWh of heating energy, at a cost of ~£516 per year.
The aim of the studio's design is to negate all these running costs through an optimally angled 19kW solar roof array, capable of generating 16,150 kWh of electricity per year, a highly insulated building envelope with a U value of 0.13 W/m²K (beyond the Passivhaus standard of 0.15 W/m²K) & the integration of state of the art renewable energy systems. All the studio's heating will be supplied by a 13 kW Vaillant aroTHERM plus air source heat pump, a bank of 27 kW of lithium ion batteries, which will store the solar energy of the studio's photovoltaic array with a capacity sufficient to power the studio off-grid for an entire day without any energy input as well as a mechanical ventilation heat recovery (MVHR) system which conserves 90% of the heat otherwise lost through ventilation whilst maintaining fresh air to the studio.
These measures will eliminate the building's running costs to such a degree that the building will bring in its own income from excess energy sold back to the national grid and the cost of the renewable technology will be recuperated through running costs & rental savings in the first 4 years of use.
5. Shelter in Landscape, Optimise Home Envelope
When creating a sustainable home, there are a host of physical phenomena which can help conserve your home's energy, lowering its demand for heating in an automatic, passive fashion. These effects can be manipulated and exploited through passive solar design techniques which leverage thermal mass, natural ventilation currents and thermal inertia to keep a home's running costs and carbon footprint in use to a minimum at no active financial cost to the home's residents.
Our Scarborough Passivhaus, which is currently on site, leverages a range of passive environmental effects to keep its running costs to an absolute minimum. The house is built into a north facing slope, with a panoramic view across Scarborough & along the North Yorkshire coast beyond. The hillside shelters around 40% of the home's external surface area from the wind, rain and cold air meaning these sides of the building lose heat at a slower rate, lowering the need for additional heating within the home.
The three-storey Passivhaus pulls fresh air up through its core via a central atrium allowing rising hot air to escape via skylights above, this is an example of the passive ventilation process known as the stack effect, the atrium also permits high southern sunshine 12 metres down to the ground floor.
The project is built with an innovative Swedish modular construction system of insulated concrete formwork (ICF) which achieves extreme levels of thermal performance, with a U value of 0.11 W/m²K. Though the system relies on carbon intensive materials of concrete and expanded polystyrene in this instance where much of the home is subterranean and must hold back the damp and groundwater which would be problematic for a timber based construction system.
The advantage of the dense concrete floors and walls of this home is that they provide a great amount of thermal mass, allowing the building to absorb significant amounts of heat from the sun which lowers the building's demand for mains heating substantially.
The project has an embodied carbon estimated at 87.3 metric tons, at an area of 294 m² this is the largest home we have tested with an embodied carbon density of 297 kgCO2/m², ~58% of the typical cavity wall construction home (513 kgCO2/m²).
With a 7 kW solar array which will generate 5950 kWh per year of electricity and a 13kWh bank of lithium ion batteries, Scarborough Passivhaus will use little to no energy from the national grid (the average home of this size typically uses ~4600 kWh a year) & will also have no demand for mains heating thanks to a sophisticated MVHR system and the extreme thermal efficiency of the home which will need no more than the heat of the residents and the rays of the sun to maintain an optimal internal temperature.
If we compare the running costs and carbon footprint in use of Scarborough Passivhaus and a typical new-build developer house, over a 50 year time-frame the Passivhaus has an overall carbon footprint of 87,300 kgCO2. A similarly sized new-build home would have an overall carbon footprint of 429,000 kgCO2. Our project saves 341,700 kg of carbon dioxide , an amount of pollution equivalent to flying back and forth between London & New York every week for 10 years.
