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Author: Janice Gardiner

  • HPH363: Is it worth getting an asbestos survey for an existing home?

    HPH363: Is it worth getting an asbestos survey for an existing home?

    Greg Byrne from RB Asbestos Consultants explains what asbestos is, why it was used so widely in construction, its potential impact on health, and how you go about identifying and removing asbestos products.

    Interview with Greg Byrne

    Greg Byrne is the Managing Director of RB Asbestos Consultants, a company that provides specialist services relating to asbestos including surveys, testing and training.

    In this interview Greg gives us a potted history of asbestos, explaining how it became so widely used in the construction industry and what led to it being banned in the UK in 1999. He also stresses the importance of getting an asbestos survey when buying or planning to retrofit a house that was built between the 1960s and 1990s.

    One asbestos fibre under a microscope showing it’s actually a bundle of hundreds of thousands of smaller fibres each around a micron in width

    Asbestos is a naturally occurring mineral

    Asbestos is a natural mineral that occurs as veins in rock and is mined just like other minerals. Whereas minerals such as quartz have small angular crystals, asbestos is composed of long fibres, which when broken down become tiny fibres, invisible to the naked eye and easy to inhale.

    After mining, asbestos is broken down into its fibrous state and added to other products, called Asbestos Containing Materials (ACMs).

    “We think around 4000 different materials have asbestos in them.

    Asbestos has been used for thousands of years

    There’s evidence that asbestos was used thousands of years ago to strengthen pots and that the Greeks knew how to spin and weave with it to make mats and other products. It wasn’t until the mid-1800s that western chemists started to recognise its properties, with America then including asbestos in a range of products. For example, some Bakelite contains it. The American company Turners then came to the UK and set up a base in Manchester, so it could expand and supply products worldwide. The early 1900s saw the first use of asbestos in the construction industry, but this was interrupted by World War I and World War II. It wasn’t until the 1950s when rebuilding Britain that the use of asbestos took off in a big way. By the 1960s through to the mid 1980s asbestos was commonplace in new buildings. However, from this point its use started to decline and it was finally banned in 1999.

    “There’s almost no part of a building [from that time] that’s not been touched by asbestos, right from the floor to the top of the house.”

    Asbestos fibres on a human hair

    Asbestos is the biggest killer in construction today

    In the UK, the first recorded case of somebody dying due to asbestos exposure was in the early 1900s. It wasn’t until after World War II, with production in full swing, that the evidence starts to build as a number of people die from asbestos exposure in factories. Greg explains that even though a ‘Factories Act’ was introduced and ventilation of factories was brought in, it was not enough to turn things around.

    Asbestos doesn’t impact health immediately

    Breathing asbestos fibres won’t necessarily affect you straightaway, and some people may not be affected at all, while others will get ill 20-60 years later. One type of asbestos related illness, mesothelioma cancer has the lowest survival rate of any type of cancer. Even though asbestos was banned at the turn of the millennium this is not a problem that has gone away, with 5200 reported deaths from asbestos last year (the next biggest killer is falling from height, which is in the order of 20 deaths per year).

    Document exposure to asbestos

    Although there’s not much you can do if you’ve been exposed to asbestos, make a record of the incident. This might be useful at a later date if there is any legal action, etc.

    AIB asbestos lining to an internal garage ceiling (high risk)

    AIB asbestos lining to an internal garage ceiling

    AIB asbestos soffits (high risk)

    Before buying a property built between 1960 and 2000, get an asbestos survey

    Greg explains that RB Asbestos Consultants don’t generally survey buildings for asbestos if built before 1960 or after 2000 as asbestos is less likely to be an issue.

    An asbestos survey is similar to a standard building survey, but the surveyor will have been trained to look for signs of asbestos. They’ll go round the building, room by room, taking photos and describing the various construction materials they find. If there is anything they think could contain asbestos, they’ll take a sample and send it to a lab for testing. Your survey report will detail any asbestos found and advise you what kind of contractor you need to do any remedial or removal work. This type of report can then inform your decision on buying the property.

    Corrugated asbestos roof

    Artex textured coating

    Floor tiles and bitumen adhesive are both asbestos

    Get an asbestos management survey before refurbishment or demolition work

    There are two different types of basic management surveys, one for refurbishment and one for demolition. In both cases you would supply the surveyor with your plans for the work to be carried out and they would target those areas of the building where invasive work is going to take place. In a renovation you might be making holes in walls, lifting floorboards and taking down ceilings. The surveyor will know where to look and be aware of asbestos that might be hidden. For example asbestos packers may have been used around window or door frames.

    If you get a chance, remove the asbestos

    Asbestos is actually safe when it’s not disturbed and has a reasonably well sealed or bonded surface. It’s only when we actively damage the asbestos, through sanding or drilling or through physical destruction that it becomes dangerous. Leaving it in situ may just store up problems for the future, so Greg recommends removing it when you have an opportunity.

    Asbestos surveyor kitted up

    When dealing with high-risk materials there is a need to work within an enclosure which is airtight with specialist air movement equipment and high efficiency filters. With lower risk materials there still is a need to deal with the materials carefully with appropriate PPE masks and suits. All the waste is double bagged, sealed and taken to a specialist waste site where it is placed in a clay lined cell. The EU are looking at stopping this method of disposal as they’ve seen evidence of water leaching the asbestos elements out of the landfill back into the wider environment. This may mean super heating the asbestos to over 1200 degrees to turn it into a non-fibrous substance. Greg knows of only one place in the UK that currently treats asbestos this way.

    There needs to be better awareness around the dangers of asbestos

    Asbestos regulations 2012 are the most up to date set of regulations, which led to approved codes of practice (ACOPS) and appropriate licences to work with asbestos. Greg outlines that at the lower risk end, a one-day training course will give someone the appropriate licence, but also stresses that there is much more awareness raising needed within the construction industry. The regulations allow for a tight control of the process, but Greg points out that enforcement is under resourced.

    Greg predicts that his work will get busier with the push towards becoming carbon neutral by 2050. This will lead to more retrofit work on buildings and by default more asbestos surveys and so more asbestos will be found. And because it’s in so many different types of products, a lot of them low risk, it will keep turning up for the next 30-50 years.

    Asbestos may not be the only problem material, so wear suitable PPE

    Reseachers are already looking more closely at products like fibreglass, ceramic fibres and nano fibres. The HSE are also taking a wider approach and looking at protection from inhaling silica dusts, so it is not just asbestos, we should be protecting ourselves from all types of dust. Greg always advises wearing a mask when working in small spaces that may be old and dusty and you need to get a filter rating FFP 3 for it to offer any protection from asbestos.

    Fireplace panel – ribbed pattern at rear

    Old vinyl flooring with asbestos coating underneath

    An asbestos survey is money well spent

    Greg’s main advice is to get your building checked before you buy or sell and even more importantly, before you carry out any major work. A few hundred pounds spent on a survey could save you a lot of money and problems in the long run. And do your own research as you can’t necessarily rely on your builder to do that for you.

    Find out more

    Visit the website of RB Asbestos Consultants

    Transcript

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    Follow Ben Adam-Smith on Bluesky

  • HPH362: An easier way to build a certified Passivhaus – with Clare and Ross Booth

    HPH362: An easier way to build a certified Passivhaus – with Clare and Ross Booth

    Clare and Ross Booth from Coldwells Build share details of their prefabricated, turnkey Passivhaus designs that aim to simplify the delivery of high performance homes in Scotland.

    Interview with Clare and Ross Booth

    Ross and Clare Booth are the founders and directors of Coldwells Build in Aberdeenshire, Scotland. Ross started out as a joiner and construction worker while Clare has a background in journalism and communication. Their construction company has delivered a number of bespoke housing projects and is now launching a range of contemporary, turnkey Passivhaus designs which will be sold at a fixed price and prefabricated off site.

    This episode is set against a backdrop of potential change to the building regulations in Scotland.

    Help keep the Scottish Passivhaus equivalent on track

    Last year the Scottish Government announced plans to introduce new regulations for all new build housing to meet a ‘Scottish equivalent to the Passivhaus standard’.

    Whilst this was exciting, the devil is in the detail and this is currently being fleshed out in a consultation about the proposal. Unfortunately there are signs that it may be watered down, which means we need to have our say and get it back on track. So please take the time to respond. The Passivhaus Trust has made it easy to understand what detail is lacking, so check out their guidance to help you play your part in the consultation.

    The ‘Passivhaus equivalent’ doesn’t need to reinvent the wheel

    The Passivhaus standard works so well because it is a holistic approach which addresses building physics, and there are quality assurance processes built in so that we get the results we anticipate.

    Clare says that adopting the Scottish equivalent to the Passivhaus standard could have a profound effect on future homes across Scotland, and help the Government reach its net zero emissions target set for 2045.

    Upskilling the workforce is essential

    Clare and Ross believe that for Scotland to achieve higher building standards there is a great need to provide additional training for construction workers. Ross shares an example from his own experience as a joiner when he installed an airtightness membrane but didn’t really understand what it was doing or the attention to detail required when carrying out this work.

    Clare and Ross have both upskilled as part of their professional development

    While networking Clare discovered that some free Passivhaus tradesperson training was available and sent the whole team to Glasgow to attend. Ross admits that he was sceptical at first but was completely converted by the end of the training. This was Government funded and provided by BEST (Built Environment Smarter Transformation) who are working to decarbonise the built environment through upskilling and educating people in the construction industry.

    Clare also attended a number of satellite events at the COP26 global climate change summit in 2021. Amongst her findings was that most homes still rely on oil and gas for heating which is contributing to nearly a fifth of the UK’s carbon emissions, the UK has some of the worst insulated housing stock across Europe, and that the performance gap currently sits at a staggering 60% in some cases.

    A ‘bespoke’ home project is not a simple process

    Having worked with numerous clients on one-off bespoke projects, Clare and Ross have identified key pain-points in the self build journey. For example, it can be difficult to design projects within budget and so clients need to go back and forth between their designer and the construction team until they have refined plans. There’s also fatigue from the estimated 3000 decisions that are needed to realise a new home. Then add in the unpredictability of the build itself, which may be subject to bad weather delays and noise complaints from neighbours.

    Building off-site in a workshop is a lot more predictable

    In an attempt to address some of the challenges of self build and streamline the process for their clients Clare and Ross decided to create a collection of predesigned homes that they would sell for a fixed price. Not only would these be beautiful contemporary homes but there would be a set number of materials and colour choices, making it easier for clients to choose. Another big change would be taking advantage of modern methods of construction by prefabricating these houses off site in a workshop. This also has the potential to increase quality as everyone can be trained in specific roles.

    By increasing the insulation specification, their Passivhaus designs can work anywhere in Scotland

    Over the last two and a half years Ross and Clare have been working with John Gilbert Architects to produce six ready-to-go Passivhaus designs.

    As Passivhaus is site specific one challenge they faced was how a standard design could work on any site. The solution was to over-egg the insulation slightly so that the solar gains were not as critical.

    We’ve got quite a chunky wall and roof system. And we’ve tested the house on PHPP on a coastal exposed site in the North East of Scotland, and we’ve tried it in every orientation, and it’s passed.

    A visualisation of one of the ready-to-go Passivhaus designs

    A building plot is essential to start the process

    Although you might be tempted by the designs you need to have secured a building plot before you can engage with Coldwells Build. After selecting a house design they will check that it works for your budget, before moving on to a concept agreement.

    At this point it is possible to make a few internal layout changes, providing that they don’t lead to structural changes. The team will then prepare a site plan and get everything cost checked and prepared for planning permission.

    Once planning has been approved, Coldwells Build will create a preliminary building agreement and you can start looking at the internal finishes and kitchen designs. They will get the cost as accurate as possible at this stage and then the architect will submit for a building warrant. Once this has been approved, the client can sign a building contract, and the prefabrication will begin.

    Assembly ‘on site’ will take a matter of days

    Ross says that prefabricating the home would start within three months of having a building contract signed. Whilst the prefabrication is happening, the groundworks team can be on site, preparing the foundations, substructure and floor slab. Once the timber frame is delivered to site, it can be made wind, water and airtight within days. The cladding will be pre-installed and the wall panels and roof panels pre-insulated. The airtightness membranes will be pre-fitted, and only the joints will need to be taped on site. It is a quick turnaround from arriving on site.

    The costs will be fixed and known upfront

    Clare says that the average price for their four-bedroom turnkey design will be around £420,000. There is also a ‘You Build’ option, which gives you a completed shell that you would then have to fit out, and this is currently around £220,000. Again this is for a certified Passivhaus, which is core to their offering.

    The Passivhaus collection will be launched next month but there is already a lot of interest and they even have a waiting list! So it’s an exciting time for Coldwells Build. They are currently working with their first customer which they will use as a test run and to check all their processes, before taking on more customers. Initially they are going to be limiting themselves to producing six houses per year. Clare explains that the most important thing is not to overload themselves and therefore ensure the quality of their homes.

    Find out more

    Visit the website of Coldwells Build

    Transcript

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  • HPH361: What’s the difference between a renovation and a retrofit?

    HPH361: What’s the difference between a renovation and a retrofit?

    Paul Testa from HEM Architects explains the difference between renovation and retrofit, using his own home as an example of a deep retrofit.

    Interview with Paul Testa

    Paul Testa is a director of HEM Architects in Sheffield. He’s been on the podcast before highlighting a few hidden costs you might experience on a house build project. Today he’s explaining some common terminology when it comes to altering homes: renovation, retrofit, remodel, extension and eco renovation.

    While these words might seem self-explanatory they can get lumped together and we perhaps miss some of the nuances. So Paul is going to explain each term as well as share a few details from his own retrofit.

    Renovation is about bringing your house back up to standard

    A renovation is work that brings a house back up to a good standard. Not only will it be about making it look nice but it will deal with any disrepair, and perhaps replace the electrics and plumbing. New windows might be installed. It may also include putting in new kitchens and bathrooms, and then plastering and repainting.

    Paul gives an example of buying a Victorian terrace that needs lots of work. You are renovating the house to bring it up to date and make it suitable for modern lifestyles.

    Remodelling is rethinking how the spaces work

    Remodelling is when you consider how the spaces work together at a more fundamental level. It’s not just about what the home looks like, but how the spaces are connected, maybe bringing multiple rooms into an open plan layout. Upstairs it may be about making better use of bathroom and bedroom spaces. It will likely involve moving internal doorways and removing walls, and whilst it could include external changes to doorways and windows this is less common.

    Extensions are about creating more space

    Extensions or additions are about adding more space. Sometimes a client may think they need more space but a remodel would actually solve the problem. Often extensions are needed as families grow or needs change. Paul says that it’s quite common for people to want a larger kitchen, dining space that faces onto the garden, which is very different from how houses were laid out in the past.

    “We live very differently now, we congregate in our kitchens, and often remodelling can deal with that, but sometimes you do need to gain more space in that area to fully enjoy those benefits.”

    Retrofit deals with performance

    Retrofit is a holistic approach that improves the building fabric, making a space more comfortable, healthy and energy efficient. As part of this upgrade moisture will need to be managed and a good ventilation strategy is required.

    Clients may have different drivers for carrying out this work, such as wanting consistent energy bills, so they are not so affected by energy price jumps, or increased comfort because they can’t get the house warm enough in the winter, or they may be motivated by reducing their carbon emissions.

    With the right budget a retrofit can deal with all of these pain points but often work might have to be phased and the immediate solution will address the priority.

    Doing work on your home locks in the performance for the coming years

    While a renovation project might create a beautiful home it may not improve the performance at all and once the work is complete the homeowner is unlikely to want to make any significant changes for the foreseeable future. So this might lock in poor performance for a number of years.

    The benefits of retrofit are ‘felt’ rather than seen

    When a retrofit is complete it may look much the same as if renovation work had been carried out. The difference will be in how the building feels and performs.

    The investment is going into modelling and understanding the initial home, developing detailed designs and then installing additional insulation and introducing an airtightness layer. High performance windows and doors will be added and ventilation will have to be addressed, often using mechanical ventilation with heat recovery (MVHR).

    Paul retrofitted a 1970s semi-detached home

    In 2013 Paul and his family bought a 1970s semi-detached house, which had a two storey side extension that was poorly laid out and a small sun room to the rear. The sun room was boiling in the summer and a cold store in the winter, and the main house was also freezing. This property was ripe for an intervention.

    The harsh winter of 2013 was the driver to do something about it but it wasn’t until 2018 that work began. These processes take a long time and architects, much like builders, are always last in the queue.

    Once the plans were formulated the main structural changes saw the original extension and old garage demolished. Although there would be a new single storey rear extension and a two storey side extension, overall there would only be 15m2 of extra space (making the floor area 136m2) when compared to the existing dwelling.

    Downstairs the suspended timber floor was removed and replaced with a concrete raft. This had between 20-70cm of insulation beneath it and provided both the new floor finish and also the structure for the extension to sit on (so there was no need for separate footings).

    The extension is timber frame, with 140mm deep studs, insulated with mineral wool in between and then wood fibre on the outside of the studs and rafters.

    The original house was insulated internally with wood fibre insulation and careful consideration was given to the thickness of this so that moisture is managed well and the risks of interstitial condensation are minimised.

    If this condensation appeared inside the construction it would damage the fabric over time and potentially produce mould spores that will end up in the air.

    The roof of the original house has also been well insulated with mineral wool and wood fibre.

    When it comes to the windows, Paul used a mixture or inward and outward opening triple glazed units. The reason for this was because it depended whether the insulation was internal as in the main house or external as in the extensions.

    Mechanical ventilation with heat recovery (MVHR) provides constant fresh air and Paul describes this as a game-changer.

    “The house always feels fresh, we don’t have any condensation anywhere, and we’re not losing that heat. I think the MVHR also helps with heat distribution, as we don’t have many heat emitters in the house. In 2018/19, when we were doing this work heat pumps were not as readily available as now, so we chose a boiler with a hot water tank. It’s the smallest system boiler we could buy, so that it can modulate down low enough for our 2 kW heat demand or heat load. This provides the hot water and runs a radiator in the living room and towel radiators in the bathroom and shower rooms.”

    Paul says that in the autumn and spring they don’t have the heating on at all. The house might be at 19C initially but by the time everyone is up and moving all the incidental heat gains (from activities such as showering and cooking) warm it up to 21C or 22C.

    They also have a couple of portable panel heaters (30W each) that can be moved around the house as required.

    Unfortunately Paul’s house did not reach the EnerPHit standard as the final airtightness test came in slightly above the required levels at 1.08 air changes per hour at 50 Pascals. Interestingly during the build process they were on track, with readings of around 0.7 air changes per hour at 50 Pascals.

    This goes to show how important it is to get the team to protect the airtightness layer once it’s in place.

    The space had to work well for the family and perform brilliantly

    As this conversation has been around the nuances between renovation, retrofit, remodelling and extensions, we asked Paul what his priorities were as he considered his funds.

    Our budget was fantastic for a renovation and remodelling project, but once you included the retrofit elements it was much more constrained. I wasn’t really willing to compromise on performance… I was also aware that whatever we were doing to the house we were likely to be investing more than the house was really worth. So it wasn’t about getting a monetary return but getting a return in terms of comfort and health.

    Although the work did put the family under financial strain at the time they don’t have a huge mortgage and now they’ve got some control over their heating bills.

    They also didn’t complete everything at the time and left some DIY jobs to tick off over the years.

    If you’re one of our Hub members, Paul also has a retrofit case study of Sycamore Hall.

    Quality assurance is a big part of performance

    If you can’t afford or don’t want to do a high performance retrofit you have to realise that there will be an impact on performance.

    Paul says that if you’re adding space and extending you will need to meet building regulations which are better than they once were. The challenge is in making sure there is good workmanship on site so insulation is well installed and continuous. Moisture must also be considered and good ventilation is important.

    Damp, mould and condensation are likely if you ‘just’ renovate

    Just renovating an existing dwelling will not change the performance. So if there were problems with discomfort then they will still be there.

    Paul has been to houses with brand new bathrooms and observed black mould around window frames. This is a sign that the moisture balance, ventilation and surface temperatures haven’t been considered.

    Stripping back a building can help identify and fix problems

    Quite often damp patches can stay hidden and you might not even realise you have a problem until something fails.

    So major work is an opportunity to check that the home really is in good health.

    National Retrofit Hub is providing a central Knowledge Hub to support all retrofitters

    In terms of useful resources Paul suggests looking at the National Retrofit Hub, which aims to collaborate with those already carrying out retrofit projects, empower the next generation and facilitate retrofits in the UK.

    It’s a nonprofit organisation that brings together all those involved in the retrofit sector to share their expertise and work together to enable a National Retrofit Strategy to be delivered.

    It’s also teaming up with various organisations to reach architects and builders as well as those who might be considering a DIY approach.

    Their goal is to see retrofit carried out at scale.

    We have to start valuing health and comfort

    The dial is moving slowly but we are starting to value good air quality and comfort in our homes. A few years ago internet speed was a more important factor!

    Also, historically, energy has been cheap and it has been simpler to keep heating our leaky homes. However, we’ve already experienced sudden energy price hikes and this has forced people to become more aware of energy performance. Although this may not be translating into people investing large amounts to save money on heating bills it does mean they are paying more attention to energy performance and EPC certificates when buying houses.

    Key challenges to consider for retrofit projects

    Before you embark on a retrofit project the first thing is to make your home retrofit ready. Deal with leaky gutters, a roof in poor repair or bad pointing to make sure your home is in a good state first.

    The second challenge is who to turn to for advice. You need to be sure that the advice is independent and solution agnostic. In other words you need to be careful the advice is not part of a sales pitch.

    Paul mentions a few organisations and community interest companies around the UK:

    Finally Paul underlines the importance of working with professionals who understand the moisture risks.

    The newer the building that you’re working with, the less of a risk that is, but for example, with an old stone barn conversion you need to be aware of moisture risks. We’re now starting to see some retrofit assessors and retrofit designers who are specifically qualified in heritage buildings as well.

    Find out more

    Visit the website of HEM Architects

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  • HPH360: Why MVHR maintenance and servicing is important – with Richard Hollas

    HPH360: Why MVHR maintenance and servicing is important – with Richard Hollas

    Richard Hollas from 21 Degrees explains why regular MVHR maintenance and servicing is essential, what it entails, and we accompany him step-by-step as he services a unit.

    Interview with Richard Hollas

    Richard Hollas, a commissioning and service engineer for 21 Degrees (formerly Green Building Store), details the process of servicing an MVHR unit, using Ben’s system as a case study. 21 Degrees supply a range of products and services for Passivhaus and low energy building projects. The team can take you through the whole process for MVHR systems; including the design, supply, installation, commissioning and servicing, and emphasise the importance of each step in this process.

    There is a difference between MVHR maintenance and servicing

    Richard starts by outlining the difference between the maintenance practices we can do as homeowners and the need for servicing by an engineer. MVHR maintenance should include changing filters every 6-9 months, cleaning air vents and possibly cleaning the heat exchanger every 2 years. An MVHR system should be serviced by a qualified engineer every 3-4 years to prevent issues like increased noise levels, condensation, and reduced airflow. A service will inspect the sensors and fans, remove any contamination, check air flow rates and make any adjustments to ensure the system is working efficiently.

    Changing the extract filter in the kitchen

    It should be easy to access your MVHR unit

    Ben’s unit is in his garage and Richard explains that this is the case for about 20% of MVHR units. The best location is in a utility room or plant room with space around it. This means it’s always simple to maintain or service the machine. Putting an MVHR unit in a loft is not ideal because it will be out of the way. You also don’t want them to be in a bedroom or other main living space as there will be some low-level noise from their operation.

    A service is also an opportunity to double-check the installation

    Richard explains that during the first full MVHR service he will check that the unit has been installed correctly. A common problem that arises is that the Armaflex insulation has not been installed. This is an extra layer of insulation that goes over the ComfoPipe, which is required by regulation, and so would need to be added.

    MVHR service: step by step

    Richard uses Ben’s MVHR system as a case study to take us through the service process:

    1. The initial system checks

    Richard begins the service by looking at the status of the system in the installer menu. He checks to see if the fans are going at different speeds, which would indicate a blockage somewhere in the system. The fans on Ben’s system are working well. He then puts the system in service mode, which stops the fans, moves the bypass flaps to the right position to allow him to open the unit.

    2. Examining the inside of the unit

    With the front off, Richard uses his torch to examine the inside for contamination and notices that the sensors are dusty, but otherwise everything looks good.

    Richard points out the bypass flaps, which are activated by the external temperature. At a certain temperature, these flaps come down, so that the air from outside doesn’t hit the heat exchanger and come straight into the house. As these are modulating ones, they will partially open and so allow the air to mix together. There is also a preheater for frost protection, if the temperature goes down to zero this will come on to stop the unit frosting up inside. The main box is the heat exchanger itself.

    Alongside this is the circuit board, that is controlling the fans, bypass flaps and other elements, so it all works together. Richard needs to access the board to detach the preheater for inspection. The preheater can become clogged with insects, creating a blockage which will then affect the air flow. Even though the unit is sealed, sometimes contamination will occur. When changing your filters make sure the unit is on filter change mode, which turns the fans off to ensure that debris is not pulled off the filters into the machine.

    Contamination on the extract fan

    3. Cleaning the supply fan and extract fan

    Although the supply fan will get a clean it’s usually in a really good condition already, whereas the extract fan will almost always have contamination. It is important to remove the extract fan for cleaning so that debris doesn’t drop into the bottom of the unit. Bottle brushes are ideal for cleaning the fan as most of it is dry flaky material that can easily be removed.

    4. Testing the condensate drain

    A small amount of water is put into the condensate drain to ensure it is draining freely. Moisture is coming into the unit from our day to day living and needs to travel through it, hit one side of the unit and then drain away. Water damage on one side of the unit would indicate a blockage.

    5. Cleaning the sensors

    Richard explains that the sensors are monitoring conditions, such as temperature and moisture and that it is really important to keep them clean. If they build up with dust they may give false readings (or even trigger an error message) which will affect the efficiency of the unit. For example, if the sensor that monitors external temperature is giving the wrong information it will affect how the bypass flaps are working and impact the preheater for frost protection.

    The heat exchanger is removed and cleaned

    6. Cleaning the heat exchanger

    The heat exchanger is a box that the air flows through, so providing it is kept free of contamination it will keep working. A regular service will prevent a build up within the heat exchanger and ensure that it is easy to remove for cleaning.  Richard describes how a heat exchanger left for 5-10 years may become so contaminated that it is almost welded into place and won’t come out at all. If that happens a new unit will be needed.

    7. Resetting the system

    Once the fans and heat exchanger are clean they can be re-inserted, and everything can be plugged back into the circuit board. When the front cover is back on, the filters can be changed and the unit can then be switched back on. The first thing it will show is an error triangle as it carries out an analysis. Richard explains that it will check the bypass, the sensors and preheater to ensure it has been reconnected properly and that there are no faults. This will also happen any time the unit switched off and then on again.

    Richard and Joe check an extract valve

    8. Checking the air flow and vents

    Richard checks all the vents for contamination around them and for excessive dust in the ducts. The air flows are also checked to ensure they are meeting building regulations. Richard is able to remove the vents and valves for cleaning without changing the original valve settings, as these have been set with locking nuts and are very difficult to change by accident. They should therefore be the same as when they were commissioned.

    Bathroom extract fans often have the most contamination

    The extract valves can get a build-up of contaminants in the kitchen from cooking and the bathroom from towels and skin but any contamination generally settles around the valves and doesn’t enter the ducting system. Richard has used a camera down ducting on several occasions to check for contamination and each time it just looks like brand new, as the filters are working to remove any bits before they reach the ducting.

    Richard points out how the supply valves can have a ring of dust around them, but that it is not coming out of the vents. It is to do with the air pressure, as the air comes out of the vents and meets the air in the room the dust settles and this can easily be wiped off with a duster.

    Richard uses an anemometer to check the air flows in each room to make sure the air flow is meeting building regulations. He can feel that the air flow is good and the readings show that Ben’s unit is achieving 50 cubic metres in the kitchen on speed 2, which is what it needs to achieve at speed 3. This shows that the unit is doing well and there is good ventilation.

    Richard can also check his readings against the commissioned figures. If one valve is the same it is likely that they are all correct and with locking nuts in place there should never be a need to recommission them. If you didn’t have locking nuts in place and someone altered one valve, say from 5 mm to 10mm it would change the air flow and so affect all the other valves.

    The extract valves are the most important ones when you’re measuring air flow during a service, because things could build up and potentially cause a blockage further down. This is unlikely to happen with the supply vents, because air comes through the filters first. If Richard doesn’t have the commissioning figures, then he will be looking to hit building regulations and make sure the system balances out.

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    MVHR can automatically deal with excessive humidity

    Richard is sure that Ben will not have any problems with condensation as his Zender Q unit has a humidity protection setting, which will have been put on during commissioning. This means that if humidity reaches 75% in the house the fans will gradually speed up to remove the excess moisture automatically.

    A service is an opportunity to recap information with the homeowner

    Richard tells us how it can be hard for customers to take in all the information about their MVHR system at the start. They may just have had a heat pump fitted, under floor heating and a whole range of new products. He suggests having an MVHR service after the first 12 months, so everything can be checked and he can go through all the workings when it is less stressful. This develops a relationship and also gives homeowners the chance to ask questions.

    Without regular servicing the unit may start to develop problems

    When the service schedule is neglected it is likely that contaminants will build up. This could cause a conflict in the machine. For example, the fans might speed up to clear the air but this would then activate the noise guard, which is there to protect the house from noise. This would result in your fans slowing down again, and you may start to notice condensation. The unit is then not running at optimum efficiency and not performing well. It is much better to establish a regular maintenance and service programme to ensure your MVHR system works well for as long as possible.

    Find out more

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