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  • HPH308 : Testing the thermal performance of a house – with Tom Fenton from Veritherm

    HPH308 : Testing the thermal performance of a house – with Tom Fenton from Veritherm

    Tom Fenton from Veritherm explains how to test the thermal performance of a home, what this data can reveal and how it can then be used.

    Interview with Tom Fenton

    Tom Fenton began his career working in the family’s design consultancy that focused on the envelopes and facades of commercial and industrial buildings. From this unique vantage point they were able to see the pitfalls in the design and construction process that impact on the performance of the building fabric, which led them to develop Veritherm’s test of thermal performance.

    Thermal performance measurement should be affordable and scalable

    In general, the construction industry’s understanding of thermal performance has been based on theoretical design assumptions and desktop modelling. Academic approaches to measuring thermal performance are lengthy, costly and complex, and only really used at a research level. Veritherm’s aim was to develop a solution that would be simple to use while being affordable and quick enough that it could be implemented at scale into a range of projects.

    Heat will find the weakest point

    Even in properties with high-performing materials and quality specifications like a Passivhaus, if the build quality or detailing isn’t quite right, then it will be sub-standard compared to its design predictions. Heat is like water and will always find the weakest point, which is where the energy will be lost.

    A phased testing approach can be beneficial

    The assumption is generally that testing would be carried out on completion of a new build home, but Tom says that actually, the retrofit market is accounting for around half of their business. Using a phased approach, an initial test will give a baseline measurement of the existing home and how it is performing. That information can be fed back to the design team to consider the most suitable fabric upgrades for the property, rather than relying on design assumptions. Further testing can then be used at other stages as new elements are introduced, to quantify the difference that eg, replacement windows or external wall insulation have made. A final test can determine whether the project goals have been achieved.

    A phased approach can also be useful on a new build, with measurements being taken before linings are installed. Together with further diagnostics, this can help to identify the possibility of any errors in the external envelope and allow them to be rectified before being sealed up.

    There are three phases to a Veritherm test

    The Veritherm test is carried out overnight and is broken down into three stages.

    The first step is to retrieve relevant design information for the property, such as its thermal specification and basic dimensional information, which is entered onto the Veritherm dashboard.

    Also in this preparation stage, the equipment is deployed in the property which includes temperature sensors in each of the habitable rooms, along with fans and heaters.

    During the measurement stage, the Veritherm platform activates the equipment remotely and a controlled and measured heat load is applied to the property, using the fans to ensure temperatures are rising uniformly throughout. It is heated for the first half of the night before then being left to cool passively for the remainder of the time. All of the heat load and temperature data is sent throughout the night to the cloud-based software platform, which uses its integrated algorithms to generate the results.

    On completion of the test the following morning the results are instantly available in a full report. This quantifies the rate of energy loss from a building per degree of temperature difference, expressed in units of watts per kelvin. The report also breaks down the data from the individual temperature loggers to give a better understanding of what is happening, and where, in the building.

    A Veritherm test is quite often carried out alongside other diagnostic tools, such as an airtightness test, so that you can understand what losses are attributable to air infiltration through gaps, and what losses are attributable to the fabric.

    Thermal imaging can pinpoint problems

    Veritherm’s test quantifies the rate of heat transfer, giving the average U-value for the building as a whole. However, if the test flags up any areas of concern, further diagnostics such as thermal imaging could be carried out to pinpoint anomalies.

    The performance gap can be quantified

    The Veritherm report compares the ‘measured’ data from the test, with the ‘designed’ data that was entered into the system in the preparation stage. This gives you a quantification of what that difference is between the designed and as-built performance, ie the performance gap. That information can for example be fed back to the architect to help them improve their design processes. If there’s a 400% gap in performance it might mean that the self-builder needs to look at considerably improving their envelope, but if it’s only 5% then that’s not going to make a significant difference on their fuel bills post-completion.

    The data that is produced can also be fed back into energy modelling software to communicate to clients what the longer-term impact will be on emissions and heating demand. This is particularly useful when it comes to designing heating systems to be correctly sized for the property. A new build property that doesn’t perform to its designed intent, means that the heating system may not be suitable or efficient. And conversely, many existing buildings have heating systems that are oversized in order to compensate for the unknown, which means there are many capital and operational savings to be had by getting it right and installing the correct system based on the particular property’s requirements.

    Also in the Veritherm report is a thermal efficiency rating, which is where the rate of energy loss is divided by the usable floor area. Using this traffic light style rating means you can compare for example a 5 bedroom house with a 1 bedroom bungalow, and identify where your property sits on that scale.

    The ‘designed’ and ‘measured’ data almost never tally!

    With the experience of carrying out these tests comes the knowledge that there is nearly always a difference between the designed and measured values. In general, new builds will tend to underperform against their designs. Existing buildings that use EPCs or reduced data standard assessment procedure (rdSAP) will pluck thermal values from standardised tables based on the building’s construction type and year of construction, to come up with basic thermal specifications for that property. Once measured, these properties will often outperform what was expected of them and the client can actually have a cost-saving on their planned improvement works. With upgrades being rolled out to millions of homes across the UK, Tom says that there is serious value and savings to be had by using a measured approach to retrofit.

    The goal is to have thermal performance testing in legislation

    Even testing identical properties on a development can throw up variable results and identify pitfalls in the construction process, in much the same way as when air tests were first introduced, showing why it’s so important for testing to be carried out.

    Tom is keen therefore for thermal performance testing to be included in Part L of the Building Regulations, and with the introduction of the Future Homes Standard which has a requirement for photographic evidence of insulation, he suggests that using a measured approach is actually of far greater value and a better way forward.

    Find out more

    Visit the website of Veritherm UK

    Follow Veritherm on Twitter

    Follow Veritherm on Instagram

    Find out more about Veritherm’s thermal performance test

    Transcript

    Download a transcript of the interview with Tom Fenton.

    Building Performance Interactive

    Ben Adam-Smith is taking part in a new series for Passive House Accelerator which aims to share lessons and best practice from low energy projects across the UK and Ireland. Hugh Whiriskey of Partel has devised the hour long format and is hosting alongside Ben and Mike Jacob of KISS House. The Building Performance Interactive is held monthly and everyone is welcome.

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  • HPH062 : Does a Passivhaus Need a Heating System? – with Alan Clarke

    HPH062 : Does a Passivhaus Need a Heating System? – with Alan Clarke

    Building services engineer Alan Clarke explains what factors should be considered when choosing a heating system for a low energy home.

    Alan Clarke

     

    Interview with Alan Clarke

    Alan Clarke has been involved in energy and buildings his whole career. He’s worked on a variety of projects, from schools to housing developments and individual self-builds.

     

    N.B. In this episode we are talking about heating systems relevant to the central European climate. In hotter climates you will be focused on cooling rather than heating!

     

    A Passivhaus is Likely to Have Fewer Radiators than a Traditionally-Built House

    When it comes to looking at heating systems for a Passivhaus there are a couple of key differences to consider.

    Compared to a traditionally-built house it is not necessary to heat every little corner (as the heat loss from each room is a lot less).

    There are also no cold surfaces. So, in a Passivhaus (where thermal bridges have been eliminated, etc.) it will not be necessary to put radiators under the windows.

     

    The Amount of Heat a Building Needs Comes Down to the Heat Loss!

    In simple terms, the heating requirement of a house will be determined by the heat loss of all the elements of the fabric and the ventilation.

    The total heat load will clearly be affected by the size of the building, but then it comes down to the insulation value of the wall, the windows, the ventilation system and so on.

     

    Even in a Passivhaus You Can’t Dispense Completely with Heating

    Working with Passivhaus specifications and including heat recovery ventilation very low levels of heat might be needed but there’s no expectation that we can do without heat completely.

     

    The Snag with Solar Gains and Internal Gains is How Variable They Are

    Alan gives an example of why it’s a good idea not to do away with a heating system.

    He says: “You could have a sunny day when it’s -5ºC and with the right house no heating is needed. It’s great. Then a week later it could be raining, it could be 3ºC, completely overcast and actually it would get a bit cold.”

     

    Good Temperature Control is Essential

    In a Passivhaus it’s no longer simply a case of it’s winter we need heat: some days you need a lot and some days you might not need any.

    So good temperature control based on the temperature inside the house is important.

    Generally, if you’re using gas heating you’re trying to throttle down a boiler which is really too big for the job. So controls that are able to lower the temperature that it runs at are a good option. They effectively reduce the power of the radiators by reducing the temperature at which they run, as well as increasing the boiler efficiency.

     

    Reducing Energy Demand is Always the First Step

    Alan does not advocate moving away from gas as a fuel in situations where there is already a connection to the gas main.

    The reason for this is that the emphasis of a Passivhaus building is always to think about energy first and reducing the energy demand. So to some extent it is less important where that energy comes from afterwards because one source of energy is often convertible to another. The key point is to use less.

     

    Find Out More

    Follow Alan Clarke on Twitter

     

    Transcript

    Download a transcript of the interview with Alan Clarke.

     

    Join the AECB

    For building professionals in the UK, the AECB is a fantastic organisation that shares knowledge and aims to promote sustainable construction.

    Their yearly conference is also an opportunity to be invigorated by like-minded individuals.

    They have just hosted their 2014 conference in Bristol but this video from 2013 sums up what people get out of it.


      Video produced by Regen Media

     

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  • HPH012 : Should You Invest in Renewable Energy? – with Dr Derek Taylor from Altechnica

    HPH012 : Should You Invest in Renewable Energy? – with Dr Derek Taylor from Altechnica

    Dr Derek Taylor from Altechnica weighs up the pros and cons of various renewable energy sources and shares his thoughts on whether you should be generating at home. He also talks about his role in creating one of the UK’s most energy-efficient homes.

     

    Interview with Dr Derek Taylor

    Dr Taylor trained at the Architectural Association but got interested in renewable energy and low energy building design in 1972. From then he started to pursue more of a renewables orientated career and did a masters in designing wind turbines and renewables, and came to the Open University. He is particularly interested in bringing together renewable energy and architecture to try and make it much more effective.

     

    There are still Fossil Fuels Available But CO2 Emissions are the Problem

    A lot of people believe we have reached peak oil and that we are now at the point of depletion. There’s still a lot of coal in the ground and a fair amount of gas available but their CO2 emissions are a big concern for climate change. It’s clear we need to make a step change. The scientists say we need to cut CO2 emissions by 80% in the next few decades.

    Cooling tower

     

    UK’s Best Renewable Energy Source is Wind

    In terms of renewable energy Dr Taylor believes wind energy and offshore wind energy offers the most promise to the UK. He explains that 40% of the potential wind energy resource in Europe is actually in the UK. That figure is looking at land based resources, with even more potential offshore.

     

    Phenomenal Increase in Wind Power

    Dr Taylor has recently been updating the wind energy section of the Open University renewable energy course. He noted that in the year 2000 there was about 30,000 MW of wind energy globally whereas in 2010, there was 38,000 MW installed in just one year. Now globally there is over 200 GW. Dr Taylor is impressed with the progress. The UK currently has the largest offshore wind farm in the world, which is off the coast of Thanet (installed by Swedish company Vattenfall), and they’re currently building a third offshore wind farm in the Thames Estuary, called the London Array, which will produce a fair proportion of London’s electricity needs.

    Wind-farm-on-hill

     

    Floating Wind Energy Technology Has a Huge Potential

    Tapping into floating wind energy technology, the wind energy resources in UK waters would be equivalent to the Gulf Oil reserves but every year.

     

    Renewable Energy Solutions Fit into Different Scales

    Generally there are three types of solution: building scale, an intermediate scale – which Dr Taylor calls neighbourhood or community scale – and large scale.

     

    Solar Makes The Most Sense For Buildings

    In terms of buildings, solar energy often makes the most sense for electricity generation, hot water and also for reducing space heating loads. In the summertime it can be used for cooling.

     

    Heat Pumps

    The temperature of the ground below a certain depth is constant throughout the year, so this provides another ambient source of energy.

     

    Wind Energy Isn’t Normally a Good Solution for Urban Areas

    The usability of renewables depends on the location as to whether they will perform effectively. Wind energy can make sense but in most cases it doesn’t in urban areas. Wind energy technology usually starts to make sense at community scale upwards, for example, a medium scale turbine might be appropriate for a village or a town. Costs can then be spread amongst householders.

     

    Former Watermill Sites Could Have Potential for Hydro Power

    The best sites for hydro tend to be in mountainous areas, but Dr Taylor suggests that former watermill sites could be good places to generate. It’s important to note that when watermills were in use there was less water extraction so there was more water running through the system. Dr Taylor did a renewable energy study for Merton Council which found that a short stretch (19km) of the River Wandle once had about 90 watermills in operation.

    Old Water Mill

     

    Biofuels Make Most Sense When it’s a Waste Product

    Growing energy fuels is very difficult to justify when you haven’t got much land. A forested area can obviously provide wood as a fuel. Dr Taylor believes the situation with biofuels probably makes sense if you can use it as waste, such as food waste and oil waste. You can then process that with biology to produce gases and fuels. In Denmark there are community digesters where manure, food waste and sewage combine to produce methane – the process mimics a cow’s stomach and produces gas that can run small power stations.

     

    Tidal Barrages Expensive to Build and Maintain

    The main problem with tidal energy is that it’s been exploited using tidal barrages, like a big dam across an estuary. These are very expensive to build and can impact on the rich eco systems. In France, there is an example of a successful barrage called La Rance.

     

    Tidal Stream Technology Shows Promise

    Essentially they are underwater wind turbines which capture the currents as they flow around the coasts. One of the big advantages is that because water is 800 times denser than air for a given size of rotor diameter you get a lot more power out compared to wind turbines because air is very low density. This means much smaller devices can give more power output. The downside is that these devices are situated in difficult locations and have to be able to cope with the water reliably. They’re still in the early stages of development.

     

    Devices Built to Harness Wave Energy Have to Survive The Stormiest Seas

    Dr Taylor reckons that wave energy is an even more difficult one to achieve. The energy resources from the waves are substantial but you have to build devices which can survive 24/7 in the most stormy seas.

     

    Failures Important to Progressing the Technologies

    Very few of the wave energy projects actually go through the iterative stages that are needed to develop a technology. Lots of funding goes into building one device and that fails and there’s no money to carry on. Those failures are vital to progressing the technology.

     

    We Can Use Fossil Fuel Reserves Much More Effectively

    While fossil fuels might still be available, Dr Taylor believes that the price will be the main constraint to using them. He stresses how in other countries they’re actually much further on with many aspects of design, performance of houses and also the use of wind energy.

     

    Combined Heat and Power Makes Use of Waste Heat

    One approach for district heating is to use the waste heat from power stations to heat houses. Dr Taylor calculated that if you add up all the energy being lost from the cooling towers around Britain, it amounts to more energy than is used to heat all the houses in Britain. Currently this energy is just allowed to go into the atmosphere or into the sea at coastal locations. In Denmark 65% of houses are heated this way or from large scale boilers. To achieve this heat mains are laid under roads or gardens and each house is then connected up. Part of the difficulty is that electricity networks are privatised and they would rather do what they’ve always done.

     

    Heat Stores Play an Important Part

    Dr Taylor explains that Battersea Power Station was a combined heat and power station when it was operating. There was a pipe under the Thames which provided heat for 4000 houses in Pimlico. They’ve subsequently re-installed a small combined heat and power station at Pimlico which delivers the same thing. Part of that scale of development enables very large heat stores to be built in, so that heat can be stored when you’re generating electricity for use later. Heat from other sources such as solar or wind energy can also be used to charge up the heat stores.

    London Battersea powerstation

     

    Nuclear Energy is Expensive and Funding Must Be Offset to Look After The Waste

    In France about 80% of their electricity comes from nuclear, but this doesn’t mean its future is clear. Not only is it expensive but disposing of nuclear waste is still a big problem. How much money will be needed in the future to look after nuclear waste from the past? There are also discussions about what’s going to be the most useful type of fuel after uranium.

     

    Low Energy Buildings Fall into Two Strands

    Historically there are two strands of developing low energy buildings. One is known as the super insulated approach that tends to be a lightweight construction with lots of insulation. The other approach is known as passive solar, which is reliant on lots of solar orientation, lots of glazing and high thermal mass. The solar gains are trapped in the thermal mass so that it acts like a storage heater.

     

    Super Passive Solar

    In the UK passive solar hasn’t worked well in the spring or autumn times when there tends to be quite high cloud cover. There is also not much benefit in the winter time whereas super insulation then works well. So a super passive solar approach combines the two so you have a high level of thermal mass but it’s inside a super insulated envelope. Dr Taylor worked on a house in Herefordshire which might be one of the UK’s most energy efficient homes.

     

    Super Passive Solar Goes a Step Further Than Passivhaus

    Dr Taylor really likes the Passivhaus standard although he finds it unfortunate that they chose the name Passivhaus as it’s easily confused with passive solar. It is really an ultra super insulation approach. The Passivhaus design system doesn’t really take into account the thermal gains from thermal mass, so you can’t get that extra point further of actually optimising the design to get to zero space heating, although a lot of Passivhaus buildings are getting pretty close to that.

     

    With New Builds, Push the Envelope as far as You Can

    For new buildings Dr Taylor thinks you have to push the building’s envelope as far as you can because it’s much more difficult to upgrade. If you can design as much insulation as possible and get to Passivhaus standards then it will be well worth doing and shouldn’t cost you a great deal more on top of the building.

     

    If You Have The Money, a Passivhaus Retrofit Can be a Good Investment

    Upgrading an existing building to Passivhaus is not a cheap option. However it’s probably better using that money to go into the building’s fabric rather than getting an expensive new kitchen!

     

    Internal Insulation Must be Done Correctly or You Risk Damaging the Building

    External insulation is a much easier solution but risks affecting the aesthetics. The problem with internally insulating walls is that there will be a reduction of floor area. Also, with solid walls, for instance, prior to that wall being internally insulated, it’s been kept warm by the space heating of the house but once the insulation is between it and the heating then it’s obviously a cold object and it’s a cold surface. So, unless the internal insulation is done correctly, if any vapour gets into that structure it will hit the cold wall and condense. This can cause rotting problems.

    craftsman insulating a wall

     

    Combined Heat and Power Could Buy us Some Time to Retrofit

    Dr Taylor refers back to how we might reduce the CO2 emissions from buildings. Investing in combined heat and power, and district heating would enable the existing buildings to start to use heating which is actually low carbon. It would also buy some time to upgrade the performance of the existing housing stock.

     

    We Only Have One Chance to Make our Homes Energy Efficient

    In order to reach 80% reductions in CO2 Dr Taylor believes that we must go beyond a little cavity wall insulation. He thinks we only get one shot at this and it should be done properly. The challenge will be funding it. If there were a scheme where everyone was connected to a heat network then there’s a potential revenue stream for the sale of that heat to people which could be used to fund insulation of buildings down the road.

     

    Incremental Improvements Should Have a Long Term Plan

    Try and have a plan or a strategy so you’re not going to foreclose on the options. Do the thinking upfront so that improvements compliment each other. If you have a loft that can be insulated then certainly the more upgrades you can do to that the better.

     

    Dr Derek Taylor’s company

     

    Transcript

    Download a transcript of the interview with Dr Derek Taylor.

     

    Goals for House Planning Help in 2013

    Ben Adam-Smith outlines his objectives for making House Planning Help an even better resource. This includes:

    • Getting more detail into each podcast episode
    • Creating more videos for the House Planning Help YouTube channel
    • Hand-picking more industry experts as guest bloggers
    • Hosting Google+ Hangouts to debate key issues

     

    Regen Media Wants to Help Your Business

    Regen Media produces the House Planning Help Podcast. Ben Adam-Smith explains how if you are in the UK and you need video or audio for your business, then Regen Media wants to help you. It is very important to have a presence on multiple platforms in the age of the Internet so that your company can be heard above the noise! Regen Media can create media that will do this and market your business in a much more dynamic way than advertising. Contact us today to find out more.

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