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  • HPH366: Could a home energy transformation pay for itself?

    HPH366: Could a home energy transformation pay for itself?

    Howard Johns, founder of One Zero, outlines their home energy transformation service which includes topping up insulation and adding solar PV, battery storage and a heat pump.

    Interview with Howard Johns

    Howard shares his extensive knowledge of renewable energy, and how he has moved from managing a large portfolio of solar and wind farms to enabling people to generate their own energy. Over the years it has become apparent to Howard that the real sticking point with the large scale projects is the National Grid, which is currently struggling to take new connections. His new company One Zero energy, is focusing on how we retrofit homes in an efficient and light way that can enable them to become part of a new, flexible, distributed grid.

    The UK grid is no longer fit for purpose

    Electricity companies began as regional entities, with one power station supplying each local area, which worked until there was a problem with that station or too much demand. With no back up in the system, some areas of supply would have to be shut down to enable other areas to keep going. Our current grid system was a national project to join all these power stations together with transmission lines so that it had more inherent flexibility. But essentially, it was built as a one-way system, with power being generated in a small number of locations and then flowing to a large number of supply locations.

    With the advent of renewables, particularly wind and solar, distributed generation emerged. So generation is happening in all sorts of locations and Howard explains how we are rewiring the grid backwards to allow this, which has caused a lot of issues. In fact, in many areas it is just not possible to connect any more large-scale renewable generation because the infrastructure cannot take it. If we can’t do that and need energy transformation now to tackle climate change we need to look at other options.

    The current energy system is extremely inefficient

    Howard explains that for every 100 units of gas used only 40 of those turn into useful units of electricity. During transmission to our homes another 10% is lost and then we might lose more through inefficient appliances. The usable energy you’re getting in your home from that primary energy is around 30%. So if you start to generate energy where you need it you can massively reduce the wastage.

    With heat pumps we can be getting 400% more energy out of it than we put in, compared to maybe 90% efficiency with a gas boiler. It is similar with transport, a standard fossil fuel car is about 30% efficient, whereas you can double or treble the efficiency for an electric vehicle. In other words the new electric based technologies that are emerging are the future.

    A resilient energy system has more back-up options

    Howard outlines how we already have at least five interconnectors into this country to build resilience in the system. A European wide grid allows excess energy, say from Denmark, to be supplied to other European countries.

    Behind the scenes at the National Grid (NESO) people are looking at live demand, and turning on things like peaker plants and gas plants, and using batteries in some cases to meet that demand.

    A resilient system must get past intermittency

    As the amount of renewable generation increases, there’s a new challenge – intermittency. So there will be a correlation between the weather conditions and how much is generated. For example, on a sunny day we might generate 20% of our power from solar, but there will be nothing at night. At times we will get really high levels of grid energy powered by the wind, but on a still day, we may get very little. This is one of the key features of the new system and it is causing problems.

    Better storage capacity will help solve the problem

    As the cost of energy continually changes if we have the access to battery storage then we can benefit. So it makes sense to use energy at key moments, when it’s abundant and cheap, and avoid using it at six o’clock in the evening when the demand is highest and it’s expensive.

    It’s always preferable to use energy as it’s being generated

    Howard tells us that it is preferable to use energy as it’s being generated because there will always be losses associated with storage. With batteries you lose around 10% of the energy you put in, just in charging and discharging. However if you haven’t got demand for that power, it’s still a sensible thing to do.

    Part of One Zero’s strategy is to install a solar PV array in combination with battery storage. This would mean that for eight months of the year you could be virtually self-sufficient for power. With a decent control system you can effectively run your battery as a micro power station profiting from arbitrage and engaging in the flexibility markets.

    Import and export to the grid when it makes financial sense

    With many big batteries being built across the UK there may be times when power is cheap or even free! So, in addition to your own generation, in these moments it may make financial sense to import from the grid to charge your home battery or discharge power back to the grid.

    Innovative companies, like Octopus and Ovo, already have flexible tariffs that will give you different power prices at different times of day.

    Howard thinks the next step would be managed services that take into account wholesale prices, which change every half an hour. Again these have periods where energy is very cheap or even negative, and other times when it’s expensive. With an agile tariff you could see prices change from -2p to 50p a kilowatt hour over a 24-hour period. Software is needed for this management, however, and this is a service that One Zero are working on.

    “Generating and storing power at your home is probably the most cost effective way of getting power right now. Not many people realise that.”

    Heat pumps will work without a deep retrofit

    Using heat pumps is another part of the One Zero energy transformation strategy. People may be under the impression that a deep retrofit – improving the thermal performance, and the health and comfort of the building – is required to make these systems work but that is not the case. So at One Zero they suggest a light touch retrofit, topping up insulation levels and doing the easy wins.

    Howard points out that putting a heat pump on a really leaky house is going to be inefficient, but heating it with a gas boiler is also inefficient, so on one level there’s no difference. At the same time, if you use a heat pump, you may also knock four or five tons off your CO2 emissions every year.

    However, it still makes sense to do as much as you can to reduce heat loss. When One Zero assess a property, they’ll make recommendations around deeper measures, which could be done first or incrementally over the following years to improve efficiency.

    Considering payback has been a big part of this approach

    One Zero are looking at measures that could start to pay back in 5 years rather than 40 years or more for deeper retrofits. Howard believes there are millions of homes that need to be improved in the next decade or two, so it’s important that this really appeals to people and offers a clear win. By starting with solar PV and a battery people can achieve a cash flow that they then might reinvest in the next steps. One Zero are also looking at finance packages so you don’t need all the capital upfront to get started on this home energy transformation.

    One Zero plan is for people not looking to do a deep retrofit

    Howard explains that One Zero is aiming to reach people that will not undertake a deep retrofit of their property, either for financial reasons or lack of engagement with this approach. Their approach is to provide a top up for cavity wall and loft insulation and then solar PV, a battery and a heat pump all for around £21,000. You could have a home energy transformation that would drop your bills by around 50-60% and your carbon emissions by 70%, all delivered within two weeks with minimum disruption. They think this is achievable for homes built after the 1930s, which already have some cavity wall insulation, double glazing and some loft insulation.

    What is a deep retrofit? Check out the Kinver story in The Hub.

    Every technology has an impact, but this should be weighed up against the alternative

    Howard has put a great deal of research into the One Zero home energy transformation package. He believes that if we reached 100% renewable generation our rates of extraction of raw materials from the earth would drop to about a 30th of current levels. The backdrop is that we live in a highly extractive society, where 40% of global shipping relates to fossil fuels.

    Everything we do has an impact, so with solar panels, there’s polysilicon production and issues around the supply chain, particularly with indentured slavery in some provinces of China, which can be hard to get around. This is also the case with many other products we are using. A solar panel can liberate the energy that went into making it within nine months of it being in use and the panels then have a 25-year warranty and possibly up to a 40-year lifespan. Most modern solar panels don’t contain any rare earths, they are just copper, an aluminium frame, silver for the conductors and glass. Effectively, polysilicon is a form of refined sand, and so all the parts are recyclable. There isn’t a huge recycling market yet, because most of the panels that have been installed are still in use.

    People are also concerned about the huge amount of lithium being produced for home and car batteries. Howard explains that there are two ways in which lithium is produced. One is from mining, generally in Australia, whilst in the rest of the world lithium production is from liquid deposits. These exist as brines under the surface of the earth that can be extracted through a bore hole. The lithium is then taken out and the remaining liquid is pumped back down. So there is an impact but it should be smaller than for mining. Also lithium is a recyclable material, which is abundant in the UK.

    Many manufacturers are now redesigning batteries so that they don’t contain cobalt, so as we move forward there should be fewer issues around rare minerals.

    Heat pumps are generally made from copper and steel, both of which are abundant in a recycled form across the world. There’s a refrigerant involved, with two possible types, one of which has a lot less global warming potential.

    All of these technologies will have a lower impact when compared to the extraction of fossil fuels and the resultant CO2 emissions from using them.

    A repowered house – taken off the gas network

    Your home can help you reduce your carbon footprint

    For a typical dwelling One Zero’s home energy transformation could save between 3-6 tons of carbon over the course of a year, which is equivalent to 20 or 30 flights to Spain. For Howard this is incredibly impactful.

    Your electric car battery could support your home energy use

    It’s still early days but trials in vehicle to grid energy transfer could support our home energy use. An electric car could have a 30-100 kilowatt battery in it, while your home battery may only be 10 kilowatts, so if you could plug your car into your home and use your car battery to support your home that would be valuable.

    It’s also a lot of lithium sitting around that could be used more effectively. Nissan is currently the only car manufacturer that allows this but that could change. The challenge is that most car manufacturers want their batteries used solely for powering their cars and consequently you will invalidate the warranty if it is used for other purposes.

    However, these batteries have huge potential to increase storage capacity and help with the intermittency challenge in power generation. And Howard suggests that even accessing 10% of these batteries could have a meaningful impact.

    One Zero has a community focus to support people on their renewable energy journey

    People can be cautious, so One Zero is working to give people the confidence to act and then supporting them to share their experience with others. Currently they are geographically focused, working in communities where they can sign up more than one house at a time, maybe 5-10 houses across two or three streets. So they are reaching out to people who may not have thought they could be part of this journey into renewables, to help them change the way they think about it.

    One Zero is operating in Sussex at the moment and has plans to launch in more areas over the course of the coming year. The next steps could be looking at managing a micro grid behind a distribution transformer that serves a street, so there would be enough generation and storage to provide the community with power for a large part of the year.  

    “It’s turning it from, that me and my castle thing, into us and our street.”

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  • HPH331 : What is a mechanical services engineer? – with Alan Clarke

    HPH331 : What is a mechanical services engineer? – with Alan Clarke

    Alan Clarke explains the role of a mechanical services engineer on a low energy house build, in designing a heating and ventilation system that works efficiently and is affordable.

    Interview with Alan Clarke

    We’ve been fortunate enough to have Alan Clarke on the podcast before. Back in episode HPH062 we discussed with him whether a Passivhaus needs a heating system. In a later episode, he also explained the designs for the heating, ventilation, and hot and cold water systems for Ben’s own self build.

    Today, we welcome him back to conclude our mini-series, looking at different professions that we may need on our self build or retrofit project. Alan is a mechanical services engineer, with particular expertise in Passivhaus buildings.

    Most mechanical services engineers will have a background in engineering

    A mechanical services engineer will cover the design of the heating and ventilation systems of a building. Some practices would also do M&E (mechanical and electrical) or MEP (mechanical engineering and public health) work, which would cover all of the building services. As well as the heating and ventilation, that will be the electrical services, drainage and plumbing too. The majority of people practicing it professionally would come from an engineering training background.

    Relevant parts of the building regulations are Part L and Part F

    Part L of the building regulations covers the energy of the house as a whole, including the heating system. An electrical installer would be expected to be qualified and understand how to install a system that is going to be in line with the wiring regulations and building regulations compliance. This might include energy modeling of the building too.

    Part F of the building regulations is to do with ventilation. Ventilation systems in houses are relatively new, and there isn’t quite the same level of qualification and supervision.

    Pre-planning is the ideal time to involve your mechanical services engineer

    Not all architects will be familiar with integrating a mechanical ventilation system so that it works efficiently and is easy to maintain. There would be some spacial requirements at Stage 3 of the RIBA Stage of Works, but pre planning is the ideal time for an engineer to come in and think about where the main items of equipment are going to be located, and how the distribution through the building will work. Consideration also needs to be given in the design to accommodate the ductwork, although the detailed design for that would come later. If it’s for a Passivhaus, there will also need to be PHPP energy modeling at this stage, before the planning application goes in. This will have an impact on the form of the building, window sizes, etc.

    It is important to make sure the overall system is efficient

    The energy efficiency of the overall system can be broken down into separate parts:

    • The MVHR unit – this must be an efficient piece of kit with good heat recovery efficiency and quiet, efficient fans. If the fans aren’t quiet, people won’t use it.
    • Good ductwork design – fan performance can be scuppered by putting in ducts that are too small, which means the fans have to work harder. They use more energy to run, and you get more noise. A good approach to the design of the ductwork is therefore important.

    A further consideration in the Passivhaus analysis is heat loss, looking at how long the ducts are, and also how well insulated they are. Ideally, these should be as short as possible, just one or two metres length, which has implications on where to position the MVHR.

    An MVHR unit also needs to have regular filter changes. Therefore, there’s no point putting it somewhere inaccessible, where you can’t see what you’re doing!

    There are two main ducting systems

    The basic principles of a balanced mechanical ventilation system, are to bring in and supply fresh air to the rooms where we spend the most time, and take out stale air, particularly from the smelliest and wettest parts of the building. The extracted air passes through the MVHR which has a heat exchanger. This transfers practically all the warmth from that extracted air to the incoming air. Ductwork connects the ventilation unit to the rooms in the house.

    A radial system uses lots of separate ducts that run to each room. If you want more air to go to or from a particular room then you run two ducts. Also, if it’s got a long way to go, you might increase the number of ducts to a distant room to make it easier to get air from there to the MVHR.

    The other system used is a branched system. You start with the biggest duct at the MVHR and run to the first room. At this terminal, it tees off to another room before branching off again, and so on. The duct size reduces as you go along.

    Generally, the radial system ducts will have a diameter of 75 or 90mm, which is easier to thread through than the branched system, but you do need more of them. The branched system starts off at around 150-160mm, before dropping down to 100mm for individual rooms.

    Space for the ducting will need to be allowed for in the structural and architectural design of the building, so it’s good to know what system is going to be used as early as possible.

    Air should be supplied into the rooms in a way that you don’t feel a draft

    For a flat ceiling, there would normally be a disc in the ceiling that spreads the air horizontally so that you don’t feel it blowing on you.

    The other type of supply valve is designed to go in a wall. This also spreads the air horizontally. The air flows are relatively small and mix with the room air quite quickly, meaning it’s unnoticeable to occupants.

    Around 2.5 litres of moisture is generated into the house per person per day

    This is produced in a number of ways, such as:

    • Breathing and perspiration – this accounts for around a fifth of the moisture that we put in the house
    • Bathing – not just the hot water steam but also the towel and bath mat will continue drying back out into the room too
    • Water evaporation from the dishwasher drying cycle
    • Cooking – such as steam from boiling water
    • Laundry – drying washing indoors can mean there are several kilos of moisture that have to go somewhere

    Without some way of extracting all this moisture, that’s a lot of water that is just sitting in our houses. It can however be extracted through ventilation. Even on a wet day, the water vapour content of the external air is relatively low, and much less than the air indoors. Simply by bringing it in and exhausting the same volume of inside air, you can expel the water vapour.

    Part F of the building regulations has guidance for calculating the ventilation flow rate that’s needed. This is inferred from the number of bedrooms. A Passivhaus calculation is more specific and done on a per person basis.

    It is more efficient to run the ventilation constantly

    Many houses in the UK have intermittent extract fans, which just draw the vapour out when you have a bath or shower. Evidence shows however that this isn’t effective in reducing humidity levels enough, leading to condensation and mould potential.

    A house with an MVHR does focus on the wet areas, but has the ventilation running all of the time. There’s not much to be gained by turning it off, as you’re not losing any heat through it. Keeping the low power fans running continuously, rather than being off and then having to work hard for a while, is more energy efficient.

    The primary benefit is to our health

    Through living in an enclosed space, we generate a number of pollutants, some of which are a side effect of the moisture. The condensation and mould can be extremely detrimental to our health. Even at lower humidity levels dust mites can prevail, causing allergic reactions and asthma.

    By ventilating a building we can also dilute and remove the VOCs and chemicals in the air that inevitably come out of the products.

    Heat pump systems need to be designed carefully

    Traditionally, a gas boiler with radiators has been a fairly resilient system for heating. Also, it’s one which doesn’t need too much oversight from an installer or heating engineer.

    Although a Passivhaus only requires a small amount of heat, this will need to be delivered somehow. Alan commonly specifies heat pumps these days, however, he stresses that they must be designed and installed well.

    Put a hot water cylinder where you are going to be using your hot water

    It sounds obvious but is an important consideration. Positioning the cylinder centrally to where the hot water will be needed in the kitchen and bathrooms, means that you can have shorter pipe runs. Subsequently, there will be less heat lost through the pipes, and the hot water will reach the taps more quickly.

    Most of a mechanical services engineer’s work is before construction

    A typical day for a mechanical services engineer might involve:

    • A discussion with the client to understand their requirements and how they might live in their house
    • A review of architect’s designs
    • Planning the building services, distribution, emitters, ventilation terminals and key bits of plant on the layout drawings
    • Drawing up a specification. This is the shopping list for the contractors for the equipment needed. Also, it’s the particular requirements for the installation, workmanship and commissioning
    • Working on the drawings/revisions – looking at where ventilation and hot water kit will go, positioning a heat pump, and considering any constraints around where that might go

    When a client is building a house for the first time, the plans can sometimes evolve later in the process as they think more about what they really want. Ideally you should be executing the plans you have developed in the design stage during the construction stage, not altering them. This will make it harder for the whole team and more expensive for you.

    Your mechanical services engineer needs to understand your priorities

    They should listen and understand what their brief is. It’s not helpful to have someone come in with preconceived ideas of a technically complicated piece of engineering, when the client just wanted something simple. It’s a waste of their time and money.

    Ideally, you also want your engineer to have enough experience to be able to look back on other projects to see what has and hasn’t worked well.

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  • HPH323 : Can I heat my home with an air source heat pump? – with Nathan Gambling

    HPH323 : Can I heat my home with an air source heat pump? – with Nathan Gambling

    Influential podcaster and heating systems expert, Nathan Gambling, explains why choosing the right installer is even more important than selecting the heat pump.

    Interview with Nathan Gambling

    Nathan comes from a family of heating engineers and he followed suit, completing his apprenticeship with the MOD in 1991. In 2006, he started teaching, including running City and Guilds courses in a prison, before also teaching in colleges.

    With his unique background in heating systems and teaching, Nathan now runs the BetaTalk podcast; a highly respected source of content and information for engineers and those interested in the heat pump industry.

    We teach people to be qualified, not competent

    This is Nathan’s assessment of the vocational education system in the UK. Having come out of that, but still wanting to facilitate learning, he got into podcasting where he was able to use his skills and connections to disseminate and amplify the voices of quality heating engineers. He is a firm believer that the starting point of any installation should be finding a competent engineer, but this isn’t always straightforward for a homeowner or self-builder to identify.

    Using a quality engineer should be a priority

    Heating is a complicated business, yet anyone can set up a plumbing company without any qualifications at all (unless you’re also dealing with gas, which would need the necessary certification). As an engineer, you don’t need certification to install a heat pump, unless you’re doing it under the Microgeneration Certification Scheme (MCS) which is where you’re getting a government grant. Something to be mindful of, is that the MCS accreditation applies to the company, rather than an individual engineer, so it could even be possible that that person has left!

    According to Nathan, the best engineers are those that engage in peer-to-peer learning and are constantly talking to each other about different techniques and best practice. These are the people that are on social media networks looking to learn from one another. It’s not just about training but familiarisation with what’s current in this quickly changing industry.

    Nathan says that the range and quality of heat pump units on offer, whether supplied by the HVAC world, specialist heat pump manufacturers or traditional boiler companies, are actually pretty similar. It’s having a good engineer that will be the difference and make the unit work very well.

    Heat pump technology exists all around us already

    Yet, much of this is technology that most of us wouldn’t even normally associate with heat pumps, such as in vending and slushy machines. We also commonly confuse it with air-conditioning, but actual air-conditioning is quite rare. The systems in place in office buildings, cinemas, and retail centres, are much more likely to be something called comfort cooling, which heats us as well as provides cooling.

    Heat can be extracted from even the coldest air temperatures

    Essentially, a heat pump is something that moves energy from an evaporator to a condenser, and uses vapour compression to do that. It uses a refrigerant to compress it and extract more heat.

    Unless you get down to -273.15 degrees celsius, which is the temperature at which atoms stop moving, you can extract heat energy. That energy is compressed, before being released out with a condenser.

    In most domestic situations this would be an air to water system, where you’re extracting the energy from the air and emitting it to the rooms via water running through radiators or underfloor heating.

    Your power demand changes according to the outside temperature

    All homes will leak, some more than others, and if there’s a temperature difference between indoors and outdoors, then heat will move.

    Systems tend to be designed to be able to cope with the average coldest day in the UK, which is around -3 degrees. Most homes need 8000 joules of heat per second to be able to maintain 21 degrees inside when it’s -3 degrees outside. That’s 8 kilowatts.

    When it’s 5 degrees outside it will need 5.5kW.

    When it’s 10 degrees outside it will only need 3.6kW.

    Your power demand is therefore constantly changing depending on what the outside temperature is, because heat will move more quickly if there’s a greater temperature difference between inside and outside.

    Unfortunately, most gas boilers work on fixed temperatures, whereas they need to be modulating their temperature around the radiators according to what the outside temperature is.

    The trick to getting a really efficient air source heat pump installation is to match the temperature that is flowing around your radiators as closely as you can to the temperature outside. So if it’s -3 degrees outside and you can maintain 21 degrees inside with 40 degree water in your radiators, that’s going to be more efficient than a system that is running 50 degree water around your radiators when it’s -3.

    “So if you design your system to be able to reduce that flow temperature in your emitters, for the colder temperatures, that’s when you start to see these really good what they call COPs – coefficient of performance.”

    The way to do that is with the size of the emitter. A good engineer will design a system that gives you the lowest flow temperatures possible for the coldest temperatures, which could mean both underfloor heating and radiators to increase the surface area.

    There are few constraints on where to site a unit

    Planning laws in England dictate that the external unit should be installed at least a metre from the boundary. Although they do make some noise, Nathan says they’re generally no worse than standard oil boilers or gas flues. However, it’s still wise to distance units from the neighbours’ windows.

    Some people aren’t keen on the aesthetics of the heat pumps on their properties so try and cover and disguise them. However, as the pump needs to extract air from the outdoors, you don’t want to be restricting its ability to do that.

    It is critical to size a heat pump accurately

    Too big and you’re paying too much for a system that won’t run efficiently. Too small and it won’t meet the energy demands of the home.

    Traditionally, heat loss calculations were used for sizing heating systems. These take data about the fabric of your home from SAP/RdSAP reports, so are more of a prediction about how it should perform, and assume that every square metre of your home is performing the same, which doesn’t happen in the real world.

    There are now new methods that can accurately measure the speed of heat going through your fabric. This heat transfer coefficient means you know what power you then need for any external temperature. Nathan says there are two different approaches that would achieve the same result.

    Veritherm – this is an overnight test that uses heaters to increase the internal temperature of the property, while fans distribute the heat around evenly. Halfway through the test the heating is turned off. Temperature sensors inside and outside record measurements throughout the night. The algorithm knows how much power has been used to heat the property and monitors the speed at which that heat leaves through the building fabric to give you the heat transfer coefficient.

    Heat Pump Survey – this uses several data loggers placed strategically around the home where they are left for three weeks. Their algorithm takes into account metred energy consumption along with weather data to give the heat transfer coefficient.

    So tools like this are incredibly useful when designing a heat pump system.

    Swapping a boiler for a heat pump may require infrastructure changes

    That’s not always the case and is something that will be individual to each property, but is often why a heat pump installation will cost more than just swapping out an old gas boiler for a new one. Switching to a heat pump may need new radiators and pipework.

    There is currently help for homeowners wanting to purchase a heat pump, with up to £5,000 being offered under the Boiler Upgrade Scheme.

    The boiler market has traditionally been incentivised

    This has meant that installers may have been incentivised with loyalty schemes, cashback, holidays etc by the big four manufacturers to buy larger systems than many homeowners would actually need.

    Nathan explains that a marketing tactic now being used with heat pumps, is advertising new refrigerants that can heat water to 60 degrees, which sounds great to customers. However, what’s not so great is that this will actually put up their electricity bills, because the most efficient way of running a heat pump is to get the lowest temperatures as possible around your radiators.

    There are key questions we can ask to help find a quality engineer

    • What flow temperature are you going to design my system for? – you want them to be saying the lower temperatures.
    • Do you weather compensate your heat pump systems? – they should be automatically adjusting the flow temperatures going around your emitters, according to what the outside temperature is.
    • What centres do you put your underfloor heating down? – you should really be wanting your underfloor down at 100mm centres as this increases the surface area and means you can run lower flow temperatures through it.

    Nathan’s final advice is to not get too caught up in researching the actual product and things like decibel levels and SCoP. SCoP is a theoretical prediction of the performance that each manufacturer will give in their literature. It doesn’t necessarily mean that it will perform like that, because again that will come down to the installation. Instead, focus mostly on working out who is doing good things in this space and is going to provide you with a quality system that will accurately and efficiently meet your needs.

    Read more about the Verithem method of measuring heat loss, and its uses, in our interview with Tom Fenton.

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