You probably already know that the construction sector is one of the biggest contributors to greenhouse gas emissions. Because of concerns about climate change and rising costs, energy has become a core focus in the way buildings are now designed. That’s why we, as eco house architects, can focus on creating and retrofitting houses to mitigate these issues.
The good news is most of the smart property developers in London and in the UK now recognise the necessity for sustainable design and build systems in the face of a changing climate by addressing energy conservation in buildings. There has been a movement and upward trend over the last few years to design and build eco houses all around the world.
Remember: Reducing and eventually eliminating the emission of CO2 is the global goal. Housing must play its part in ensuring that this is possible, and eco house architects are key to the two-pronged approach that is needed.
On the one hand, we must significantly invest in and improve renewable energy generation. On the other, we must simultaneously ensure that, when it comes to how we live, that energy is not simply running out the door – that is where eco houses come in.
Eco House Infographic by Urbanist Architecture
Passivhaus houses and zero carbon homes can give us a framework for the future on which to build: adding value, improving environmental credentials and creating healthy, happy homes.
Do you want to learn how to design and build design Eco Houses, Passivhaus and Zero Carbon Houses?
This entry will give you the basics for designing and building your sustainable house without the dreaded headache…
…and without spending a fortune!
Scroll down to learn more about designing and building eco houses, and us as eco house architects…
Let’s jump right in…
The resources of the planet are being used up at an increasingly fast pace. The not-too-distant future will see the human race facing a life without fossil fuels and the race is on to provide alternatives. The automotive industry has made great strides with electric cars that use a fraction of the energy (and thus produce a fraction of the carbon footprint) of petrol and diesel cars.
But here’s the interesting thing: Many other industries are starting to look at the impact their products have on the planet. There have been moves afoot within the property industry to do the same.
Building a zero carbon home used to be a pipe dream but thanks to leaps forward in the technology, it is possible now to increase the energy efficiency in new buildings and renovations without compromising on the aesthetics, safety and comfort.
Designing new build eco houses, retrofitting homes and improving existing housing stock by placing energy conservation at the heart of the process are all essential steps to achieve sustainable homes. For example, the government gives incentives to households to have their loft insulated or their cavity walls filled. In the wake of the 2008 financial crisis, there was a boiler scrappage scheme where people were given a cash incentive to remove old inefficient boilers from their home and have them replaced with energy efficient alternatives.
But more needs to be done. And it is the eco house architects that are now at the forefront of the eco house movement, designing ingand build Passivhaus houses and zero carbon houses in the UK.
Passivhaus design is a standard for design and construction. It is a code for sustainable housing that aims to create a home that stays at a comfortable temperature with minimal energy use. The aim is to create a house that is comfortable to live in and which uses passive energy sources such as sunlight and human- and appliance-generated heat to dramatically decrease the need for additional space-heating. To achieve the Passivhaus standard, the energy required for space heating must not exceed 15 kWh/m2. This is determined by calculating the maximum amount of heat that can be delivered using the fresh supply of air at the minimum required ventilation rate.
In other words, the Passivhaus standard’s focus is on energy consumption and maximum energy demand to reduce its ecological footprint by producing low energy buildings that require little energy for space heating or cooling. The goal is to provide a high level of air quality and thermal comfort for occupants while using very little energy for heating and cooling. Imagine living in a Passivhaus house!
Passivhaus House design by Urbanist Architecture
But one thing’s for sure: The main feature of a Passivhaus is that it doesn’t feel like a compromise to the occupants. It still has all the features of a high-end home such as natural light and natural ventilation. Passivhaus standards dramatically reduce the amount of energy needed to run and make it easier for a building to be self-sufficient and sustainable in its energy use, paving the way for a truly zero carbon home.
In terms of the logistics, Passivhaus design, with its focus on the fabric of a building and energy conservation, is the best point of approach for green home design and construction. Eco house architects working with Passivhaus standards focus on the size, shape and orientation of a home, and good heat retention, airtightness, natural ventilation and heat recovery systems are all employed with the aim of dramatically reducing a building’s annual carbon emissions. Do you see where we’re going with this?
Zero carbon houses are those that, in theory, produce zero or even negative CO2 emissions by maximising the use of energy efficiency and renewable energy. In a Zero Carbon houses, emissions are reduced through fabric energy efficiency standards based on space heating and cooling, energy efficient heating and cooling technologies, e.g. solar panels and “allowable offsite solutions” which is a form of carbon offsetting.
Zero Carbon House design by Urbanist Architecture
A zero carbon home will also need an efficient mechanical ventilation system. The flow of air around and out of a building will be a large factor in determining the amount of additional heating needed. Think about living in a Zero Carbon House for a moment. It is much a more cost-effective method to consume far-reaching less energy and release less CO2 by design, rather than to meet higher energy demand with building with a ‘Zero-Carbon’ renewable generation of energy due to the fact that not all building sites and locations are suitable for generating and accommodating renewable energy.
OK, I know what you’re thinking. What’s the possibility of designing and building your dream eco house in London or in the UK?
In the United Kingdom we have the type of weather extremes that challenge us as eco house architects. In the hotter parts of the world the focus is on keeping a building cool. In the colder parts of the world then the focus is purely on keeping the property warm.
Passivhaus House Section by Urbanist Architecture
Additionally, urban locations like London often come with multiple constraints imposed by their surroundings. The proximity of adjacent buildings may rule out wind turbines. The same buildings may shade the site, compromising opportunities for photovoltaic systems. Also, in cities, hydroelectric generation is often unrealistic and unfeasible.
But in the temperate parts of the globe there is a need to both heat and cool to various degrees in the different seasons of the year. This means that eco house architects can create sustainable house design in London and in the United Kingdom, but their approach has to take both heat and cold into account, along with the specific site constraints.
Achieving this standard depends largely on the climatic condition of the region on which it is built. In the UK, this typically involves ensuring very high levels of insulation, the installation of extremely high-performance windows with insulated frames, an airtight building fabric, ‘thermal bridge free’ construction, a mechanical ventilation system with highly efficient heat recovery and accurate sustainable house design.
Let me show you how…
Zero Carbon House Section by Urbanist Architecture
The insulation of the building envelope has a major impact on the heat gains during summer and heat losses in winter, and thus, the total energy consumption of the building. Insulation can be effectively used to reduce heat loss or gains and to manipulate the time when the energy is released and absorbed.
Let me explain:
The most important principle of a Passivhaus is that insulation is applied continuously around the building envelope, and thermal bridging need to be designed out to effectively and significantly reduce heat losses. Thus, Passivhauses are largely heated by the energy already present in the building (such as people and various household equipment which generate a lot of energy), and the Passivhaus conditions ensure that buildings adhering to its standards often do not require a conventional central heating system.
This level of insulation ensures that the heat losses during winter are negligible and the temperatures of the internal surfaces are almost the same as the indoor air temperature. The result is a comfortable indoor climate. In addition, external walls, slabs to the ground, and roofs are to be within 0.1 to 0.15 W/m2K
All construction methods used for Passivhaus should be tested successfully including but not limited to masonry construction, lightweight construction, prefabricated elements, concrete formwork construction and steel construction. Sounds impressive, right?
Glass is inferior to walls in terms of energy retention, hence energy consumption increases proportionately to the glazed area. There is a strong relationship between the amount of glass and optimum orientation for energy conservation, so both must be considered jointly. Excessive heat gains and losses can offset by the use of good design, orientation and technologically advanced high-performance triple glazing systems.
Let’s dig a little deeper:
In order to benefit from solar gains, Passivhaus requires glazing to be optimised on the south façade, with reduced glazing on the north façade. A benefit of triple glazing is that the surface temperature of the windows is similar to the surrounding internal surfaces, and without the three layers the heat loss is too high. Triple glazing also reduces sound transmission from the exterior of the building.
To make optimum use of the useful solar gains in winter, in addition to good orientation, the glazing must have low installed U values (≤ 0.85 W/m²K) for both the glazing and the frame, to reduce heat losses and maintain good solar transmittance (g-values ≥ 0.5).
Above all, it may be necessary to incorporate some external shading to reduce the amount of direct solar gains in the summer. Glazing suitable for use in a Passivhaus building should have been independently certified by the Passivhaus Institute to verify that a standard glazing unit (1.24 x 1.48m) has a whole window UW value of ≤ 0.80 W/m²K and can achieve U value ≤ 0.85 W/m²K once installed. Glazed components of doors must achieve a similar glazing specification. Complicated, isn’t it?
Unwanted air leakage can significantly increase a dwelling’s space heating requirement, as well as cause localised discomfort due to draughts. This can also allow moisture to build up within the building fabric which eventually will reduce the performance and lifespan of the building. Achieving Passivhaus levels of airtightness can eliminate these problems, and requires careful use of appropriate membranes such as tapes, wet plastering and/or vapour membranes to form a continuous airtight barrier.
But that’s not all. Energy consumption due to energy losses and gains through the façade can also be reduced dramatically by selecting a proper shape for the building. This can be achieved by assuming a rectangular shape and equal thermal transmittance for the walls and roof, with zero transmittance through the ground. In addition, designing a building with a ratio between the south and east façade of 1 and 2 can help; the optimum building shape in view of façade energy gains and losses is achieved.
As a rule, the height should be equal to half the length of a side. As a building’s height increases, so does its energy consumption. Ever wondered why? This is because energy is required to transport people, cooling, heating and water, and this also creates a poor façade-to-floor area ratio, ultimately resulting in increased cooling and heating loads on the system.
The bottom line is this: Airtightness is determined as the result of the absolute volume of air that will be replaced in one hour, divided by the total external envelope area (m3/m2h), also with a pressure differential of 50 Pa. The airtightness of a Passivhaus home, as measured by a blower door pressure test, must be no worse than 0.6 ach at a pressure differential of 50 Pa. It is critical that multiple continuous airtight seals are used in conjunction with a robust gearing system to ensure a lack of air leakage when tested at Q(100 Pa) ≤ 2.25 m3/hm. See the difference?
Geometric junctions and connections between elements typically provide a thermally conductive bypass route for heat loss, and must be reduced or eliminated wherever possible.
To avoid unnecessary heat loss, a Passivhaus structure should be thermal bridge free. In practice, this means that any linear (two-dimensional) thermal bridges should have a psi (Ψ) value of ≤ 0.01 W/mK. The total primary energy demand of a Passivhaus home (i.e. space heating, cooling, domestic hot water, lighting, fans, pumps, white goods and all appliances) must be no more than 120 kWh/m2yr.
This can be achieved through specifying energy efficient light fittings and appliances, a well-designed and well-insulated hot water supply, in addition to using a low-carbon energy supply.
And guess what? Careful construction detailing is also required to ensure the junctions do not create unnecessary heat loss paths. The use of external insulation provides a major advantage in reducing thermal bridges at geometric junctions. Strategic placement of insulation in and around junction details helps to reduce convection heat loss paths.
Mechanical Ventilation and Heat Recovery (MVHR) Heat has a recovery efficiency of more than 75% and a low specific fan power is required. The need for an extremely airtight building fabric means that MVHR is required to maintain indoor air quality by replacing unwanted odours, moisture and carbon dioxide generated by the occupants with fresh air.
Quite simply, occupants can still freely open and close the windows as they see fit. However, to achieve adequate ventilation rates in such an airtight building, the occupant would be required to open all the windows at least once every three hours for some 5 to 10 minutes at a time – even during the night. This would obviously be impractical and would cause unacceptable heat loss during the winter.
Since an MVHR unit runs continuously, it ensures that the correct levels of ventilation can be achieved in all rooms and provides excellent indoor air quality when specified and installed correctly. The heat exchanger does not mix the fresh incoming air with the exhaust air, but simply exchanges heat to reduce the need for actual convection heating.
In conclusion, realising the full potential of energy conserving strategies requires effective energy management during the production and operation life of the building.
The Passivhaus Institute are very protective over the use of the term. To be classified as a Passivhaus in the UK, the heating requirements for the living space drop by 75% in comparison to the standard UK home.
Let me say this straight: This is a huge reduction and you can see why the design needs to be both innovative and comprehensive to gain this type of saving. But the design is only one part of the build. Believe it or not, studies show that the energy efficiency forecast on a UK new build property is often overshot – to the tune of up to 100% – when the building is actually constructed. To ensure that this isn’t the case in a certified Passivhaus construction, there is scrutiny at every level of the process.
The Passivhaus architects are the first stage in the process. Your eco house architects should have an excellent understanding of Passivhaus design principle to draw up plans that will give the developer the opportunity to build something that meets the requirements of Passivhaus certification. Once the design passes scrutiny then the construction becomes the focus of attention.
Once a home has been designed in the right way to achieve a zero carbon existence then the work falls to the builder. There are expert builders in the UKthat have knowledge of the material and techniques needed to have a home that is highly energy efficient. The builder must use the detailed plans drawn up by the eco house architects to produce a home that doesn’t just look like the ideas on the page, but that actually performs in the same way too.
Looking back at the standard UK new build home’s inefficiency and how it doesn’t stack up to the design principles, it’s important that the letter of the build is followed meticulously. The use of sustainable design methods and materials is of vital importance here. A word of caution: It is only when all these stages have been completed in full that a Passivhaus certification will be granted. It is only when Passivhaus certification is granted that a designer and builder can walk away from the task happy that they have not only set out to produce a zero carbon home, but have actually achieved that aim.
Designing and building eco houses is about far more than getting Passivhaus Certificate. It is about being able to look back at the work done with satisfaction. Lowering carbon usage in properties across the UK has to be a priority for the eco house architects, builders and developers.
Most importantly, the benefits are here for all to see. We get more efficiency from the remaining fossil fuels that are available to the planet. We don’t end up wasting huge amounts of this through lost heat into the atmosphere. And it will result in lower energy bills for people. The future of the plant relies on our innovation in this area in all walks of life. Make no mistake about it.
But one thing’s for sure: The carbon footprint of the average human being in the developed world is far too high to be sustainable. The way that we live needs to change in order to reduce this significantly. If we can move around the planet and heat our homes in a much more sustainable way, then the future looks brighter.
Designing and building is easier than you think. If you have any questions or would like to have a more in-depth conversation, take the next step and just let me know by sending me an e-mail now.