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  • HPH017 : Can a Ground Source Heat Pump Make an Old House Energy Efficient? – with Justin Broadbent from isoenergy

    HPH017 : Can a Ground Source Heat Pump Make an Old House Energy Efficient? – with Justin Broadbent from isoenergy

    Justin Broadbent from isoenergy explains what a ground source heat pump is and how it could be used as a solution to make a period property energy efficient.

    Justin Broadbent

     

    Interview with Justin Broadbent

    Justin founded isoenergy 14 years ago after he sold his software company. An engineer by trade, Justin was keen to reduce the running costs of his period home and also get rid of his dependency on oil. As his father-in-law was a part owner in a Swedish manufacturer of heating systems, he began to discover more about Sweden’s approach to low energy buildings with very high levels of insulation and soon realised that the UK had a lot to learn about energy efficiency.

     

    Before Plugging in Something Mechanical, Reduce Your Heat Losses

    Justin started out as a consultant and as things grew he begun to import the machinery, too. This soon led to doing the installations as well. Even though isoenergy designs and installs renewable energy systems, a fabric first approach is always the starting point. The most expensive heat that you put into your house is the heat you’re putting in the second, third or fourth time, and so on, because you’ve lost it the first time.

     

    A Heat Pump Compresses Energy

    Justin explains how a heat pump works, using a bicycle pump as an example. As you inflate the tyre you may notice the end of the pump starts to get warm. This is because, as you compress the gas from the ambient air pressure (1 bar) through to the pressure you’re putting into the tyre (say 5 bar), the molecules get excited and so they get warm. Thus while the bicycle pump is running, it is a heat pump.

     

    Fridges are Heat Pumps

    A fridge takes the ambient air pressure out of the kitchen, which is perhaps at 18 or 20 degrees, compresses that heat and radiates it out at the back of the fridge. That is why the back of a fridge feels warm, normally at about 40 degrees. In engineering there’s always an equal and opposite to everything, so as heat is generated, so is cold. With a fridge freezer, the cold is kept but the heat is thrown away. In this case that doesn’t matter because you probably want to heat the kitchen anyway. A ground source heat pump works in the same way, using the heat for heating the house and putting the cold back into the ground.

    Refrigerator

     

    A Heat Pump Can Reduce Running Costs by up to Two Thirds

    In Justin’s experience most people become interested in reducing their energy usage because of the cost. He has had clients with heating bills of up to £80,000 a year and typically they can reduce running costs by two thirds.

     

    Even in a Period Property You Can Improve The Fabric of a Building

    Insulating the loft is often a very good starting point and sometimes insulating the cellar is an option, too. Most Grade I listed buildings nowadays have shutters built in, which are extremely good insulators when used. Stopping draughts can make a big difference.

     

    Use Old Buildings as They Were Originally Designed

    If you’re in a big house, there may be part of the house that can be sealed off when not in use. Use the fireplaces. Some chimneys draw very well and don’t create any draughts in the house.

    18th-century-house

     

    Secondary Glazing is Effective and Barely Noticed

    Justin has leaded light windows with wooden frames, but in front of the old oak frames there is a single pane of glass with a very thin oak frame going round it. In this case it is the size of the whole window area, but most people don’t even realise it is there, because you think you’re looking at the original windows. This not only drastically reduces heat loss but also acts as a sound buffer.

     

    The Cavity Wall is Left Uninsulated

    Even though Justin’s property has a cavity wall, he refuses to insulate it. This is because he has an oak-framed house with beams that have stood for hundreds of years. If any damp bridging occurs the wood could rot within in a decade. So Justin chooses to use an extra 20% on heating his house so that he knows that the walls remain secure.

     

    The House Stays at a Constant Temperature with Weather Compensation

    The difference between this and traditional heating systems is that a stable temperature, in this case 20 degrees, is maintained all year round. That means that the walls are also at 20 degrees. Even if the outside temperature is -6, the inside walls stay at 20 degrees and actually act as a radiator. This therefore takes advantage of the thermal mass, which is a good quality. Around the time when the house was built, it would have been run in the same way. A fire would have been kept going throughout the day and temperatures would be fairly constant, even if significantly colder than how we live today (perhaps 15 or 16 degrees).

     

    The Radiators Never Get Above 50 Degrees

    Many people say that you need to oversize the radiators when using a ground source heat pump, but Justin is using the same radiators that were heating his house when it ran on oil. The difference is that with oil, you tend to switch the heating on and off, especially if you think you’re saving money. What Justin does is put in a lower grade of temperature but for a 24-hour period. So it’s all about maintaining the temperature. Rather than the radiators getting up to 70 or 80 degrees, his radiators probably never go above 45 or 50 degrees.

     

    Heat Pumps Are Reliable

    Justin explains that more could go wrong with a boiler than it can with a heat pump. When it’s done properly it should be just as reliable as a fridge and most people replace their fridges when the door handle falls off or the seal breaks rather than when the compressor malfunctions.

    Plant-room-equipment

     

    Problems Arise if You Don’t Understand Where The Energy Comes From

    Some people perceive ground source heat pumps as magic, but there is an engineering reason why it works. You are taking a small amount of heat from a large area. For example if you tried to take half a million kilowatt hours out of a piece of land the size of a tennis court, it will turn into a block of ice. So you would need to take that half a million kilowatt hours out of a 5, 10, 15 or 20-acre field. The larger the better. The more the load is spread, the more efficient the system will be.

     

    The Ground Must be Taken Into Account

    There are many factors that must be understood before a system can be designed. For example, it matters how much water is in the ground, how much of a slope there is, what substance the ground is (e.g. clay, sand, shale, etc.). Different substances have different heating properties and different heat transfer ratios. So, it’s important to understand what they are and do the calculations properly. Equally it’s vital to make sure that the turbulence in the pipe is right so that you can extract the heat properly and that the flow pressures are right. Justin says it’s all about understanding pressure losses, heat curves and algorithms.

    Ground-Loops-12 Ground loops being laid

    Hydro Systems Can Payback Quickly

    Justin suggests that you need to consider the renewable technology that will work for your particular situation, whatever that might be. For example, if there’s a stream with a good flow and a good drop in it, then a hydro system could have potential. The payback can be very quick.

    Archimedes-Screw-going-in

     

    Be Aware of Government Grants

    In the UK, the government is bringing out the Renewable Heat Incentive. This will pay people to replace their oil fired boilers with heat pumps and biomass boilers to heat their houses. Those grants are looking like they’re going to be particularly generous. There is, of course, an upfront cost of installing the equipment.

     

    Find Out More About isoenergy

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    Follow isoenergy on Twitter

    Download a PDF of case studies

     

    Transcript

    Download a transcript of the interview with Justin Broadbent.

     

    Ask Your Questions or Share Your Feedback

     

    Home Style Green Podcast

    If you enjoy listening to the House Planning Help Podcast, then Ben recommends that you check out Home Style Green. Matthew Cutler-Welsh is based in New Zealand and is involved in green building there. He shares some invaluable information.

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  • HPH010 : Can You Damage an Old House When Making it Energy Efficient? – with Roger Hunt

    HPH010 : Can You Damage an Old House When Making it Energy Efficient? – with Roger Hunt

    Roger Hunt explains how to make a period property energy efficient without damaging the building or creating problems for yourself in the future. Also House Planning Help gets its first guest blogger, Paul Mallion from Conker Conservation.

     

    Interview with Roger Hunt

    Co-author of the Old House Handbook Roger Hunt has just finished work on a companion volume called the Old House Eco Handbook (which will be available in March 2013). Although the first book was written in 2008, Roger says environmental issues and energy efficiency have now become much more pressing and so the time is right to focus on how this can be achieved for old houses.

     

    An Old Building is a Solid Wall Building

    The Old House Eco Handbook is in association with The Society for the Protection of Ancient Buildings. If you own a period property that was constructed anywhere from the Medieval era to the Edwardian period, then this book aims to help you. Roger points out that after the Edwardian period building technology started to change and move away from solid walls to cavity walls. Lime-based products became less popular while the use of cement-based materials increased.

     

    Lime-Based Materials Work in a Very Different Way to Cement-Based Materials

    In an old building it’s not about keeping the water out, as the walls absorb moisture. Both the inside and outside walls are constantly absorbing moisture or allowing it to evaporate out. Modern cement-based materials try to keep water out of the building by using impermeable layers. Mixing the two methods causes problems.

     

    Old Buildings are an Essential Part of Our Landscape

    Roger believes that old buildings are not only part of the landscape but part of our communities. Getting rid of them will break up communities and destroy landscapes. Towns and villages have grown very organically through the years with little accretions, creating much-loved wibbly-wobbly streetscapes. In his opinion removing the old to make way for the new would be a bad move, not to mention all the embodied carbon and historic detailing that would be lost.

     

    Take a Holistic Approach to Energy Efficiency

    View your house as a whole and don’t just do one thing in isolation (like putting solar panels on the roof). Take time to consider all the things you could do. For example, loft insulation can make a big difference and it’s a relatively simple project. Draughts can make a building feel colder than it is, so deal with those sorts of things.

     

    Keep Original Timber Windows

    Roger illustrates the point by suggesting you wouldn’t throw out an Edwardian chair because it had a damaged leg – you would get it repaired. In the same way if you have original windows you should not be looking to replace them with double glazing. Instead get them repaired and also draught-proofed at the same time so that they perform better, too.

     

    Simple Measures Can Often Make a Big Difference

    • Draw curtains and blinds to make a room warmer.
    • Put a wooden flap over the letterbox to stop the draughts coming in.
    • Use a fabric sausage to stop draughts coming under doors.

     

    Passivhaus is an Excellent Standard for New Builds

    Roger is a great believer in Passivhaus and he thinks that it can really produce high performing houses.

     

    Bringing an Old Building up to Passivhaus Standard is Quite an Invasive Process

    Roger has seen retrofit projects himself and he agrees that they have reached a high level of energy efficiency. However, the problem is the loss of character and historic detail of the building. These are the very features that make these buildings desirable in the first place. A Passivhaus retrofit means losing a lot of the original fabric of the building and balanced with the carbon, Roger is not sure whether it adds up. Some of those materials are irreplaceable once pulled out.

     

    No Single Solution Works For Every Building

    The holistic approach is about insulation and finding the right energy generation methods to suit the building. If you’re in a very old leaky building in the countryside a biomass boiler might be the answer. If you’re in a town, an air source heat pump might be the answer. Every building is different.

     

    A Passivhaus Retrofit Would be More Appropriate if a House Had Already Lost its Original Features

    When Ben explains that he didn’t notice any loss of character in a recent Victorian Passivhaus project he saw, Roger stresses that he is not against a Passivhaus renovation in the right circumstances. However, where original features exist such as dado rails, skirting boards, cornices and windows, he believes this is a lot to lose.

     

    Retrofitting Old Houses is Something We’re Still Learning About

    This is not something that is set in stone and different people have different ideas on how it should be done. Putting together the Old House Eco Handbook has involved a lot of research to understand the current thinking. Roger believes this thinking will evolve as better ways of doing things are discovered. There is a fear that what is being done to many buildings will have to be ripped out in 10 or 15 years because of damp problems, etc. This would clearly not have a positive impact on the environment either.

     

    Don’t Slap on Wall Insulation Without Understanding the Science

    Although this book is offering solutions, it’s also saying in many cases don’t do anything. This does not just apply to you but to the wider community. So tackle all the other simple measures first to make the house warm and air tight, and perhaps leave wall insulation for a later project.  Balance the cost versus the gains, bearing in mind the potential risks of trapping moisture in the wall.

     

    Insulating Will Lead to Loss of Features

    Whether you insulate on the outside or inside of an old building you will lose features. While it’s easier to insulate the outside of a building, insulating on the inside of the building is generally considered to have less aesthetic impact. There is also a risk of interstitial condensation occurring where the warm air meets the cold surface and dampness occurs. The science of this is not fully understood. This can cause timber in the wall, for example, to become rotten.

     

    Moisture Levels Are Being Monitored

    A lot of test projects involving wall insulation are underway at the moment. Wireless moisture sensors are being embedded in the building materials to see whether there are really any problems. This is something we will only find out over time.

     

    Think Beyond The House to The Neighbourhood

    Good design looks beyond the house to the neighbourhood. Roger uses an example of why a cluster of 12 houses might be a good idea, because it would be possible to for you to know all of your neighbours. He also says simple things like a bench out on the street or low garden fences to encourage interaction allow for good sustainable development.

     

    Good Modern Design Needs to Meet Regional Variation

    As an advocate of modern architecture, Roger likes simple white rendered buildings. However, he is aware that it would be a bit boring if they were everywhere. The character of a place is down to the variety of materials used there. In the past houses would be constructed with materials that were available locally and Roger would like to see modern design adapted to reflect this regional identity.

     

    Grade 1 and Grade 2* Listed Buildings are Difficult to Make Energy Efficient

    Roger is adamant that we need to improve the energy efficiency of our buildings. He does, however, think that buildings of historical significance are difficult to deal with and suggests that perhaps these buildings should remain as they are. It is the bulk of the housing stock that needs to be addressed.

     

    Classic Cars Still Exist as Classic Cars

    Roger talks about a picture in the Old House Eco Handbook (affiliate link), where a Morris Minor is parked in front of an Edwardian House. While cars have changed hugely in terms of energy efficiency, it does not mean that the classic cars have been updated with today’s technology.

     

    Everything is a Balance

    While future generations may love us for making old houses more energy efficient they may hate us if we destroy what was good about them.

     

    Check out Roger Hunt’s Blog

     

    Transcript

    Download a transcript of the interview with Roger Hunt.

     

    First Guest Blogger on House Planning Help

    We’re always trying to create more great content and one way of doing that is with the help of a few carefully chosen experts. Paul Mallion from Conker Conservation has become the first person to write a blog for us and we are very grateful to him. Read his article about why white paint is potentially a colour you don’t want to use.

     

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