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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.

    If you’re one of our Hub members, Chris Herring explains how to get the best value from high performance windows

    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

    Visit the website of 21 Degrees

    What makes a well designed MVHR system?

    How do you specify high performance windows?

    Two radical retrofits that use an internal wall insulation strategy

    Low energy barn conversions

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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.

    Find out more

    Follow Alan Clarke on Twitter

    Transcript

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  • HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    HPH299 : Is mechanical ventilation just something else to go wrong? – with Ben Adam-Smith

    Ben Adam-Smith shares his own experience of living with a mechanical ventilation system. While he’s clocked up a few error messages on the unit and had more problems than most, he explains why he wouldn’t want to go back to natural ventilation.

    MVHR is a key component of low energy buildings

    In case you’re wondering what MVHR is, well, it stands for mechanical ventilation with heat recovery.

    As buildings become increasingly airtight, a good ventilation strategy becomes all the more important.

    But there’s a clever twist: by controlling the ventilation you can recover the heat when you want to (transferring it to the fresh incoming air).

    Hopefully that’s clear, but if not we made a documentary about airtightness a few years ago!

    Since this documentary was made I have moved into my own Passivhaus.

    Error messages are warnings

    I am a big fan of MVHR (pun intended) but that doesn’t mean I’ve had the best relationship with my MVHR unit.

    I’ve had 3 sets of errors on the machine in the two and a half years I’ve had it.

    The first errors might have been in connection with a silencer that was retrofitted a year after we moved in. I suspect the machine was clever enough to notice something had changed. The errors resolved themselves!

    About a year later, an external pressure message cropped up a number of times.

    The fan status readings on fan speed two which should be 200m3/hour are:

    Supply fan – Speed 550rpm, Duty 15%, Flow 93% ( a noticeable drop in air flow)

    Extract fan – Speed 1900rpm, Duty 48%, Flow 0% ( air flow can be detected from the extract air valves when a piece of tissue is held up to them )

    Error messages can be reset

    Interestingly, these errors can be reset while you’re investigating the cause… but they usually return, even if that is weeks later.

    Apparently there was a known issue with the humidity sensors on my particular unit. This was changed and again it was business as usual.

    However, at the beginning of the year a new error cropped up!

    Nobody likes seeing a flashing red light on their control panel because it means something needs fixing (or at least investigating).

    At this particular point we’d been getting night-time temperatures between -2C and -5C, which is the coldest we’ve experienced since we built the house.

    When the temperature warmed up a little I was able to reset the error and everything would return to normal (or until I could get the machine looked at).

    However, that trick didn’t work the next day.

    The machine completely died and I couldn’t get it to come back on. There was also a light burning smell inside the house.

    I had a couple of concerns at this point:

    • How long will it be until I get my machine back up and running?
    • Might I get a build up of mould somewhere in my system if I can’t get it fixed soon?

    Fortunately when it comes to mould, I was quickly reassured by my friends in the know.

    So, now whilst the problem was investigated we had to survive without the machine.

    With no MVHR running, we resorted to opening windows!

    Not that I’d choose to do this experiment but it was quite interesting to see the impact of living in a Passivhaus with no MVHR running.

    Firstly, the house remained nice and warm inside (the insulation has gone nowhere). Perhaps the heat wasn’t as even; I don’t know. But it wasn’t a terrible experience.

    It was however, a right faff to have to open the windows every few hours… not to mention the heat we must have wasted… and the family complaining at having the windows open when it was freezing outside.

    Perhaps the most interesting impact of no MVHR was the instant lingering smells. My wife noticed that each room had its own smell! And it was definitely harder to shift cooking smells.

    Eliminate the simple stuff first

    On a chat with Steve Clarke at Green Building Store trying to diagnose the problem, we double-checked that power was getting to the unit.

    Embarrassingly I hadn’t even checked the trip switches. In fact, we’d managed to cover them up with a shelving unit so that I’d forgotten they were even there!

    With the machine humming to life, I had a massive sense of relief. Whatever the issue is it’s not quite so urgent when the system is at least on.

    The preheater needs to be replaced

    It didn’t take long to diagnose the problem (the burning smell was the preheater working for the last time) but British wisdom of leaving the EU meant the new preheater took several weeks to get here.

    The warranty period on MVHR units is typically 2 years

    For an essential item for Passivhaus dwellers, this does seem short.

    The clock also starts ticking when you buy it.

    Mike Coe, the self-builder behind Portree Passivhaus, bought his unit in advance and subsequent delays have meant it will already be out of warranty.

    My own unit was out of warranty, too, but the manufacturers kindly supplied the new part free of charge.

    I installed my new preheater!

    With Steve Clarke from Green Building Store on the phone, I was expertly talked through what I needed to do.

    Buying through a company with good customer service was a great move.

    We’ll have to wait for more cold weather to check it has done the job.

    ‘MVHR needs to be as reliable as a fridge’

    I was interested to see whether other people had had trouble with their units and so I posted up on social media.

    I don’t believe many Passivhaus owners have actually had problems, which is a good sign. As Fionn Stevenson says ‘good quality assurance is essential’.

    Andy Simmonds, Chief Executive of the AECB, stressed it is such an important piece of kit. The emphasis needs to be on durability, reliability and repairability.

    He likened an MVHR unit to a fridge.

    Having bought a new fridge when I built the house I have noticed that even fridges have got more complicated.

    In the past it’s normally the plastic door seal that has failed before anything else, but on the new more complex models water dispensers get jammed on and ice trays freezer up, and don’t get me started on the plastic water filters!

    I would not go back to ‘natural ventilation’

    Despite the inconvenience of investigating different error messages, my MVHR unit has never stopped! Yes, I was a bit slow to check the trip switches, but if there’s a next time I won’t make the same mistake.

    If the machine is still operating, you haven’t got a big problem

    If your machine is not working at all – i.e no ventilation whatsoever – then I would really be looking for a speedy repair.

    As with anything in life that breaks, it normally takes a little while to fix it.

    So it would be lovely to have the option of a 24-hour repair service in the years to come.

    Transcript

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  • HPH289 : Retrofitting period properties – with Roger Hunt

    HPH289 : Retrofitting period properties – with Roger Hunt

    Author Roger Hunt explains why period properties need treating differently when it comes to achieving successful retrofit projects.

    Interview with Roger Hunt

    Roger Hunt co-authored Old House Handbook back in 2008, about repairing old buildings, at a time when retrofit was barely on the agenda. Not long after, people started to recognise the importance of retrofit and sustainability which led to their companion book, Old House Eco Handbook. It has since been updated with a second edition, incorporating new thinking on how to make buildings energy efficient, and the surge of new materials available that can make it happen.

    Not enough progress is being made

    Roger recalls attending a conference not long after Old House Handbook was published where, to meet targets, it was claimed that a city the size of Coventry would need to be retrofit every week.

    “We’re nowhere near that. We haven’t scraped the surface. We are so far behind in terms of retrofitting old buildings that there is absolutely no way we’re going to meet the targets we need to meet as far as I can see. And we can’t build new homes to solve the problem because we can’t build them quick enough; there isn’t the land to build them on. And the environmental impact of knocking all the old ones down to build new ones isn’t sustainable either.”

    Typical UK housing stock – Copyright Roger Hunt
    Copyright Roger Hunt
    Copyright Roger Hunt

    Pre and post-1919 buildings need treating differently

    Roger defines old buildings as being anything from medieval through to Victorian and Edwardian terraced houses. They were houses typically made from breathable materials, such as lime mortars, renders and plasters.

    Getting the retrofit techniques wrong in a breathable type of construction can store up problems for the future in terms of damp and condensation.

    It is important to make the distinction between those breathable buildings, and ones from around 1919 onwards, when construction methods changed to concrete and cement being used with a focus on keeping water out. Those buildings need to be treated differently, as getting the retrofit techniques wrong can store up problems for the future.

    Start with a plan for the whole building

    It might be that you won’t intend to do a full retrofit straight away, just elements of it to begin with and the rest spread over several years, but it’s important to think of your long term plan of everything that will need doing.

    For example, starting by draft-proofing all the windows and floors will cut down air movement within the house and cause a build up of condensation and poor air quality, if controlled ventilation isn’t considered. That might be achieved by controlled opening of windows, or a mechanical ventilation system.

    Using controlled ventilation – Copyright Roger Hunt
    Opening windows as a form of controlled ventilation – Copyright Roger Hunt

    Roger says that some sort of mechanical ventilation is almost inevitable, particularly for kitchens and bathrooms, but heat recovery systems don’t necessarily work well in old buildings.

    Reducing drafts is as important to comfort level as insulation

    Drafts actually make you feel colder than the building really is, so introducing secondary glazing or draft proofing around windows can make a big difference to comfort levels.

    Other uncontrolled ventilation can come from gaps in floorboards. If they can be plugged and a window opened when required then you can have controlled ventilation.

    Copyright Roger Hunt

    Buildings must be properly maintained

    Roger stresses that maintenance is particularly important for old buildings. Blocked gutters for example can lead to thermally inefficient wet walls, and a slipped roof tile can lead to leaks, rotten timbers and water coming through ceilings. The repair job is going to be costly and a lot less sustainable than just maintaining the building properly.

    Copyright Roger Hunt

    Reduce energy use within the house

    Before even thinking about how to heat or light the home, you should be thinking about a fabric first approach of how to insulate, cut drafts, and increase daylight. From there you could incorporate solar arrays or air and ground source heat pumps. The heat pumps won’t work so well if it is a leaky building, so these all need to be considered as part of the bigger project.

    “You have to think of the best solution for heating combined with all the other things you’re doing. So, an air source heat pump is not necessarily going to be the solution until you have tackled some of the other issues with the building.”

    Simple things that can be achieved quickly with an instant impact include changing high energy bulbs to LEDs and putting in loft insulation.

    Copyright Roger Hunt
    Copyright Thermafleece

    EnerPHit projects can be incredibly successful

    With fairly disastrous consequences to getting it wrong, one way to have a successful outcome is to work towards the EnerPHit standard. This will probably mean employing an architect or other specialist with experience of what they’re doing. It might not be cheap or easy but will deliver on energy efficiency and comfort.

    There is a delicate balance between sustainability and retaining character

    A risk of coming in and doing a complete retrofit of an old building is that it can lose some of the character which makes us love them in the first place.

    “I’m passionate about trying to make buildings sustainable and cut our carbon but at the same time we’ve got to have places that are accessible, enjoyable and important to people.”

    Roger says it’s a complex subject as we have to embrace the value of the building in terms of beauty, aesthetics and our love for them, along with the monetary value.

    Take time to understand your building

    Roger’s tips for tackling a renovation of an old building are:

    • Don’t rush in. Live in an old building for a year, through each of the seasons, to really understand the damp and the light. That will also help with your interior decoration.
    • Don’t try and use modern materials that are incompatible with an old building. Particularly don’t use an insulating material that is going to stop your building from breathing.
    • Do your research, talk to people, go to events, look at products, don’t trust everything you read on the internet. Cross-reference everything to check that you have the right solution. What might be right for one building isn’t necessarily right for another, even in the same terrace.

    Find out more

    Visit Roger’s Huntwriter website

    Transcript

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    Follow Ben Adam-Smith on Bluesky

  • HPH202 : Designing the ventilation, heating, and hot and cold water systems for Ben’s house – with Alan Clarke

    HPH202 : Designing the ventilation, heating, and hot and cold water systems for Ben’s house – with Alan Clarke

    Building Services Engineer Alan Clarke explains how he has designed and specified the ventilation, heating, and hot and cold water systems for Ben’s new house.

    Interview with Alan Clarke

    We first spoke with Alan Clarke back in 2015 where he helped answer our question of whether a Passivhaus needs a heating system. Alan’s role is to engineer the design of the plumbing, heating and ventilation within a house, and in this podcast we focus on the designs he has created for Ben’s Passivhaus self build.

    Alan’s aim is to hand over a specification that is as short and easy to follow as possible. On one hand it will act as a shopping list for a contractor to price from, but also provide basic instructions on things to be installed in particular ways, such as pipe size, thickness of insulation, types of terminals for the ventilation unit etc. It will be a comprehensive list of all of the kit required, the instructions on how to get it commissioned, and what flow rates to commission the ventilation system to.

    Start by getting the ventilation system right

    Firstly the design must make physical space for the required services, and make them work well. Alan will develop the ventilation scheme by looking at the plans and understanding the airflow, establishing which are the supply rooms and which they will need to extract from. At this early stage he will feed the information into the PHPP energy analysis programme, along with heat loss information which will help when it comes to working out the heat load details for the heating system design.

    The ventilation systems Alan uses are all Passivhaus certified. Using a certified unit tends to be cost effective as their efficiency is tested under the methodology that fits in with the energy calculation in PHPP. Some non-certified units tend to shut down the supply air in sub-zero temperatures, but the certified units have frost protection. They also have the commissioning controls to allow you to set them up in a properly balanced way, so you’re not wasting heat through unbalanced supply and extract.

    Ventilation Ground Floor Layout
    Ventilation First Floor Layout

    Larger ducts can produce a more efficient system

    With very little ceiling space the ducts can be made flat to be squeezed in unobtrusively. The downside to these is that more fan pressure is required to push the air through the narrower ducts. More fan power requires greater energy and more noise is generated at the unit. It also tends to be a system which doesn’t come with well sealed junctions in the duct work.

    The alternative approach is to use slightly bigger, round ducts which are inherently easier to make airtight junctions. This approach tends to produce quiet and efficient systems, but does require thinking more cleverly about how to make space for them all.

    In Ben’s house the ducts are spread around easily on the lower floor because there are open web floor joists which are engineered joists with a metal zig-zag, giving plenty of space to fit services through.

    Upstairs there is a truss rafter roof. In a Passivhaus they make the air barrier the base of the trusses. Lots of insulation goes on top and Alan wouldn’t want to be putting lots of ducts through that air barrier and into the cold loft space. Keeping them inside the warm, airtight envelope means that there needs to be a dropped ceiling somewhere to run the ducts through. They will be lowering the landing ceiling to accommodate the ducts, by virtue of it connecting the rooms together and not having windows so there will be no loss of window head height. The ducts stop at the bedrooms where there is a step up in ceiling height.  Here they will use a wall mounted, side throw air terminal to push the air into the rooms.

    Ben will be using a Zehnder Passivhaus-Certified MVHR

    It has a fairly large capacity so is ideally suited for family houses. It has been designed with integral airflow measuring inside the unit, meaning that whatever the conditions it will maintain the selected ventilation rate without losing performance.

    A change to the size of the kitchen and utility areas has meant that the MVHR will now be outside of the thermal envelope and inside the garage. It will be on the house wall of the garage to make the ducting run as short as possible, and the ducts will be insulated to reduce the heat losses.

    The house will have a mainstream boiler

    Alan is seeing more projects using air source heat pumps, which although they have a high capital outlay do benefit from low running costs. Using specialist imported systems can create problems when there is a fault, with a lack of qualified tradespeople available to fix them. A mainstream boiler won’t have those problems when it comes to parts and technical support.

    The hot water will have a flow restriction

    The system is designed to get hot water to the taps as quickly as possible without circulating hot water that is losing heat to the rest of the house.  Entering information into PHPP on pipe sizes and how they will match up with the flow rates and available pressure will help calculate the heat loss.

    Ben does have a concern about how the restricted flow will actually feel in the shower pressure, so it will be important to select a shower head that has been designed to work in conjunction with flow regulation.

    Hot and Cold Water Ground Floor Layout
    Hot and Cold Water First Floor Layout
    Plumbing Schematic

    Radiators have been installed to complement the flexible spaces

    Alan has considered the design of the house and how it will be used, to conclude that there will be radiators in most of the rooms. For example, one bedroom has three external walls and a balcony door so a radiator would seem sensible to accommodate people’s different comfort levels. Another spare room might have different temperature requirements depending on whether it is being used as a guest bedroom or a study.

    Heating Ground Floor Layout
    Heating First Floor Layout

    Underfloor heating wouldn’t be cost effective

    Alan explains that it is inherently a high output system, with the whole floor available to heat the space. By virtue of it being a Passivhaus the heating demand will be reduced by a factor of ten, so paying full rate to cover the whole floor with underfloor heating doesn’t seem logical.

    Find out more

    Follow Alan Clarke on Twitter

    Transcript

    Download a transcript of the interview with Alan Clarke.

    Please connect with me

  • HPH181 : Improving acoustics, noise control and soundproofing – with Jack Harvie-Clark

    HPH181 : Improving acoustics, noise control and soundproofing – with Jack Harvie-Clark

    Jack Harvie-Clark from Apex Acoustics provides an overview of acoustics in the home. He also explains how we might go about controlling noises and soundproofing.

    Photograph by Martin Neeves Photography

    Interview with Jack Harvie-Clark

    Jack Harvie-Clark’s background is in engineering. His work in acoustics started when working for mechanical engineers in the power generation industry. A change to Building Regulations in 2003 meant a growth in acoustics in the construction sector and Jack set up Apex Acoustics in 2006. His work is concerned with the acoustics of buildings and how noise affects people’s health.

    Acoustics is about how sound travels

    Sound travels through structures as vibrations, and acoustics distinguishes between two concepts: sound insulation is how you stop the sound transmitting from one room to another; sound absorption is about how quickly the sound within a room gets absorbed.

    Jack explains that your ears know immediately when you’re in an enclosed space like a room, rather than outside, because you hear many reflections. Some reflection is very useful because it adds volume to your voice, but too much can be uncomfortable. Jack says that someone building a home should consider the room acoustics and how good they want it to be.

    There are restrictions for sound levels between attached dwellings

    Jack provides assistance for projects that need to comply with Building Regulations. People rarely call him just to make the acoustics better on their build; rather they want a competent specialist to help them meet the required standards.

    Building Regulations are mostly concerned with sound insulation between attached dwellings; so much of Jack’s work is on the airborne sounds through walls and floors and impact sounds through floors between flats.

    Reducing noise from neighbours may require sacrificing space

    If a client has a noisy neighbour, Jack will firstly find out whether there’s a problem with the wall that can be rectified. Then he has to interpret the client’s needs, to balance noise reduction with space lost and money spent. Jack explains, “You might think maybe they want it to be 10 dB quieter or 20 dB quieter. And then we’ll suggest the sorts of things they would need to build to achieve that.”

    Noise levels shouldn’t interfere with sleep or cause any annoyance

    Jack often advises homebuilders on how to keep out external environmental noise in order to comply with planning conditions. By considering the building plans and measuring the noise level outside they can recommend the required type of glass for the given window sizes and any appropriate treatment for the ventilation system.

    Whether or not there are planning conditions, noise levels outside might make you reluctant to open your windows. So Jack says good design should account for this.

    Rules on sound insulation between rooms aren’t very demanding

    Noise between internal walls is covered in a small way by Building Regulations. However, they don’t ensure any particular level of sound insulation to rooms that might be sensitive from other rooms within your house. Jack’s advice is to be sure to consider the issue of noise through floors and walls between rooms.

    There are ways to reduce noise between and within rooms

    In the design of a room the door will be the weak spot for sound transmission, including the gap at the bottom. Acoustic doors and an acoustic seal on the bottom will improve performance.

    In a house with ventilation, noise can sometimes travel from one room to another through ducts. You can improve sound insulation by including crosstalk attenuators in the vents, which let the air through but not the sound.

    Rooms designed for recording sound need to have minimal reverberation. Sound absorption can be achieved by putting carpet on the walls and similar use of soft furnishings.

    Large and high spaces need more sound absorption

    Rooms with higher ceilings or larger volumes are naturally more reverberant and can feel noisy and echoey. The noise level will increase dramatically when more people are in there, says Jack, especially if you have children! The more sound absorption you put in, the more comfortable it will be.

    The earlier the better where acoustic advice is concerned

    Jack says that acoustic consultants always get brought in too late, or only asked to look at very small bits of very big projects. He understands this, as you don’t want to build your whole house around the acoustics, but says if it were his house, he would want someone like him to look in more detail.

    Some audiophile clients might require advice about how rooms respond to sound. Jack can advise on the shape of the room, and recommends that wires for the sound system are planned as part of the electrical works, to avoid more holes in the walls later.

    Ventilation systems are designed to deliver and extract air, not to limit noise

    As most people will have some kind of ventilation system, Jack says that attention should be paid to getting the acoustics right. This could start with a specification for noise that the builder or the designer has to achieve, so that it will get taken care of in the design. In a Passivhaus, noise levels must not exceed 25 dB(A) in living spaces and 35 dB(A) in bathrooms; noise levels that are very unlikely to annoy.

    For other houses, the Building Regulations are less stringent and their legal requirement is even debatable, so they’re not being enforced. Many new houses have some form of mechanical extract, but Jack says that nobody is checking or designing the noise levels for these systems. This presents a big problem: people turn the fan down to reduce the noise, but that then means that they’re not getting enough air.

    Racecourse Passivhaus project – measuring the noise levels from the MVHR

    Mechanical ventilation systems need to be designed and maintained properly

    Absence of design, poor procurement and bad installation can be typical of ventilation systems in current mainstream housing. According to Jack, problems include:

    • houses handed over with dirty filters
    • residents not knowing they’re supposed to change the filters
    • residents not even knowing they have a ventilation system running

    Inadequate ventilation in airtight houses can lead to health problems

    Mechanical ventilation systems have become more common in new houses as a more efficient way to meet energy performance requirements. However, recent research has suggested that people prefer to control their internal environment by opening windows. Jack warns that if ventilation systems get turned off in very airtight modern houses, you can get health-related issues such as poor air quality and mould growth.

    Furthermore, opening windows to provide additional ventilation is the default method to mitigate overheating. However, there is no current assessment for resultant noise so if you’re building in a noisy place, Jack advises bearing in mind both how you provide the ventilation and how you control overheating.

    Award-winning double height open plan house – gaps between the timber laths provide the sound absorption with acoustic absorbent material behind

    Find out more

    Visit the website of Apex Acoustics

    Follow Apex Acoustics on Twitter

    Transcript

    Download a transcript of the interview with Jack Harvie-Clark

    Please connect with me

  • HPH059 : What Qualities Should an MVHR System Bring to a Low Energy Building? – with Andrew Farr from Green Building Store

    Andrew Farr from Green Building Store explains what qualities mechanical ventilation with heat recovery (MVHR) should bring to a house. He also shares how to make sure you get a system that is properly designed, installed and commissioned.

    Andrew Farr

     

    Interview with Andrew Farr

    Andrew Farr’s background is a mixture of mechanical engineering and building work, having done multi-material fabrication for a number of years. When Chris Herring, the founder of the Green Building Store, was developing their Mechanical Ventilation Heat Recovery Department he invited Andrew to join them as they had previously worked together on various building projects and as Andrew is a fluent German speaker.

     

    HRV and MVHR are the Same Thing

    HRV (Heat Recovery Ventilation) and MVHR (Mechanical Ventilation with Heat Recovery) refer to one and the same thing. Andrew clarifies that there are various other acronyms out there, but the broad idea is that you are ventilating and recovering the heat energy out of the ventilation air.

     

    In a Balanced Ventilation System the Same Quantity of Air is Supplied as is Extracted

    An MVHR system can be a pragmatic way of delivering very good air quality into a building. The Air Handling Unit (AHU) or the Mechanical Heat Recovery device of the MVHR system draws air into the building from the outside, filters it, takes it through a heat exchanger and supplies the clean air into the habitable spaces of the house, usually bedrooms, living rooms, studies etc. A completely separate ducting system extracts air out of the foul air rooms (toilets, bathrooms, kitchens etc.) through the other side of the same heat exchanger and exhausts it out of the building. This enables a balanced ventilation system where you are supplying exactly the same quantity of air into the building as you are extracting out of it.

    MVHR systems may not be essential for every project, however, they are recommended for very airtight buildings with an airtightness of 3ach @50pascals or lower. For an MVHR system to be energy and cost effective, the airtightness of the house should be below 1ach.

     

    Getting the Design of the MVHR System Right – Sound Thresholds and Air Flow Rates

    The criteria set out for MVHR design by Building Regulations and Code for Sustainable Homes in the UK are primarily intended to create an energy efficient system. This has led to a common occurrence of noisy MVHR systems in the mainstream building industry owing to their poor design.

    Andrew argues that in the case of a house, the primary criteria should be comfort and good air quality. A well designed MVHR System does not impact on the consciousness of the people who are living in that building. It should not be the first thing you notice when you walk in, nor the last thing that you notice when you’re going to sleep.

    To achieve this, the main criteria of the design should be to deliver an inaudible – in everyday activity – ventilation system which generates less than 24 dBA of sound at a distance of more than one meter away from the air valve (The human threshold of hearing is somewhere around 24 to 27 dBA). With the amount of noise that the ventilation unit is going to create, the location of the MVHR unit itself is also crucial. Positioning the MVHR unit close to the kitchens and bathrooms, where people are used to hearing noise, is more suitable than locating it close to a bedroom.

    Another important criteria is to deliver exactly the right amount of air into the building. Over ventilating will tend to dehumidify the air in winter and also use excess energy. While under ventilating will result in unpleasant odours and humidity remaining in the building.

     

    The Traits of a Good MVHR Unit

    Green Building Store has the franchise for selling PAUL Ventilation units (PAUL is a German company) which they believe are some of the very best on the market as they are very well manufactured. The ventilation unit itself emits a relatively low frequency which doesn’t travel as well through walls, as compared with other units. The fan has a constant volume function to continually deliver exactly the same amount of air through both sides of the heat exchanger – as set up at the time of commissioning. This is extremely important, as during the yearly cycle of a ventilation unit there are various things that happen which change the resistance to the air moving through both the intake and the exhaust ducting systems.

    One of the major influences on the performance of the MVHR system are the filters on the ventilation unit. A filter on the intake prior to the heat exchanger protects the heat exchanger from the very fine debris that can be drawn into the air stream. There is also a filter on the extract prior to the heat exchanger. These filters will get dirty and provide resistance to the air-flow at different rates depending on what the pollution load is. In the case of a house being situated close to a main road, carbon particulates will block up the very fine filters resulting in the intake filter becoming dirtier sooner than the extract filter. To maintain a balance between both air-flows, the fans will increase their effort against the filter resistance in order to maintain the same volumes of air. Thus having a fan with a constant volume function is very crucial to maintaining the heat recovery efficiency of the ventilation unit.

    PAUL-Clima-F-200

     

    Maintaining the Efficiency of the MVHR System

    Modern ventilation units are very similar in their tested performance (the one against which they will be certified). However, there is a very real difference between the unit’s individual tested performance and that of its performance embedded in the building. The efficiency of the MVHR system depends on two important factors:

    1. maintaining the balance between the two air flows, and
    2. the design of the ducting associated with the MVHR system

    If the resistance to the air moving through the ducting system is high, then the fans will have to exert a lot of effort in order to move the air. Consequently they will make more noise and use more energy, which in turn will cost more. The energy efficiency of the MVHR system is the efficiency of the whole system, including the ducting and everything associated with it, and not just on the efficiency of the MVHR unit alone.

     

    Round and Rigid Ducting Works Best

    The most important criteria when considering what type of ducting to use is which type of ducting will allow the air to move through most easily and offer the least resistance. Round ducting is the most efficient in this case, as it offers the best surface area to volume ratio – the surface area is smaller than the volume of air. Rigid ducting is sealed by design, not by the addition of mastics and tapes as in the case of flexible ducting and is less likely to fail.

     

    Invest in a Well-designed MVHR System from the Get Go

    The design of the ducting system should be of paramount importance in order to deliver a ducting system that you will want to live with. Ducting systems should be designed to reduce pressure loss and to attenuate the associated sound. If it is not designed properly and especially in larger houses, some air valves could end up being very noisy because they’ve got too much pressure on them, and in other rooms the air valves are not getting sufficient air out of them. A well designed system with rigid ducting and appropriate sound attenuation however will come at a premium cost. Rather than going for a cheaper poorly designed system, Andrew’s advice is to invest in a well-designed system from the outset that won’t have to be replaced after a year.

     

    Quality of MVHR Design Currently in the UK

    Up until now the industry has seen experienced commercial mechanical and electrical installers bringing their knowledge from commercial spaces into domestic MVHR installations, where the requirements for sound are not the same.

    In an office, you probably won’t notice a bit of fan noise in the room because you’re busy, there are computers on or you are talking to people. But when you’re at home and you’re working on your desktop PC, the running fans and hard drive generate such a constant background noise, that when you turn it off, you realise the blissful peace that follows.

    According to Andrew, an MVHR system should be giving you this blissful peace all the time despite the fact that it’s running, and if it’s not, then it’s not designed to quality. Andrew believes that in the next few years the quality of delivery of MVHR systems in the UK will improve and that more people are now beginning to understand what the appropriate criteria for MVHR design in domestic buildings is.

     

    Find Out More

    Green Building Store

    Follow Andrew Farr on Twitter

     

    Transcript

    Download a transcript of the interview with Andrew Farr.

     

    Passivhaus in Plain English

    We are very excited about the fact that Elrond Burrell has launched his own blog! And we expect big things from it. Titled ‘Passivhaus in Plain English & More‘ it has already been noticed by Lloyd Alter from Treehugger.

     

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  • HPH025 : The Myths of Passivhaus (Passive House) – with Elrond Burrell from Architype

    Elrond Burrell from Architype helps bust some of the common myths that surround the Passivhaus standard.

    Elrond 1

     

    Interview with Elrond Burrell

    Elrond is originally from New Zealand, which is also where he trained as an architect, but in 1998 he moved to the UK. After working on various sustainable projects he then joined Architype in 2006 and became more aware of the Passivhaus standard.

     

    The Passivhaus Standard was Developed to Close the Performance Gap

    Passivhaus is a performance standard for a building that is not specific to the type of building. It was developed over 20 years ago by professors Bo Adamson and Wolfgang Feist, who were looking into why buildings didn’t perform as well as they were predicted to do. By carrying out lots of careful analysis they established that in order for a building to be comfortable and energy efficient, it needs to be airtight, well insulated and have good ventilation.

     

    Understanding Passivhaus with Coffee!

    Elrond gives an example of two ways that you could keep your coffee warm. In the first situation there is a hotplate, where energy is continually put in so that it keeps bubbling and at temperature. In the second scenario the hot coffee is poured into a thermos flask and kept warm by screwing the lid on. Passivhaus works in the same way. Some warmth must be provided initially, be it through solar energy from the sun, occupancy heating (movement) or cooking, etc. But, by having the building built correctly and well insulated that heat is kept in so that you are not losing it.

    thermos-vs-hotplate

     

    Mechanical Ventilation with Heat Recovery Provides Fresh Air Without Losing the Warmth

    Instead of throwing out all the warm air and bringing in fresh cold air which then has to be heated, mechanical ventilation with heat recovery allows fresh air to be brought into the house and the old air to be expelled but importantly the heat is retained.

     

    The Myths of Passivhaus

    This episode is slightly different from any that we’ve done in the past. We put out a message on Twitter asking Passivhaus builders and designers to tell us what common misconceptions they hear. Now we discuss the items that cropped up the most.

     

    A Passivhaus Heats Itself – MYTH

    This is not factually correct, because nothing heats itself. A Passivhaus needs to get the heat from somewhere, but a Passivhaus building retains the heat (as discussed above).

     

    You Can’t Open the Windows in a Passivhaus – MYTH

    This may be easy to buy into but in a Passivhaus there is nothing to stop you from opening the windows. Elrond says that it really depends on the time of the year and what you want as to whether you open the windows. In summer (UK) it is likely that the mechanical ventilation would not be running anyway, so natural ventilation would be important and that means opening the windows. In winter there’s probably no need to open the windows because there’s enough fresh air and it doesn’t feel stale or stuffy. In a traditional buildings that’s why people tend to open the windows in winter because it’s stuffy, which is essentially the CO2 levels getting a bit high, whereas in a Passivhaus there’s constant ventilation in the background and there just would not be the need.

     

    The Aesthetics of a Passivhaus are Not Good – MYTH

    Elrond suggests that many of the first buildings to meet the Passivhaus standard were located in Germany and Austria, and so had a continental aesthetic. As these buildings attracted a lot of publicity it is no great surprise that there is the perception that a Passivhaus will look a particular way. Also, many of the initial attempts at doing Passivhaus may have mimicked these buildings as designers were grappling with a new challenge. However, as time goes on, Elrond believes we are seeing more buildings in the local vernacular styles.

    Having worked on three certified Passivhaus schools, Elrond is proud that Architype achieved a similar aesthetic to their non-Passivhaus schools.

    Architype-school

     

    A Passivhaus Must be Built with Sustainable Materials – MYTH

    Elrond finds this one interesting because he hears the other argument, that Passivhaus doesn’t put enough emphasis on encouraging use of natural materials. At Architype they have always had an interest in using healthy materials that don’t emit noxious fumes, so that there is no knock-on impact with occupants suffering from conditions such as asthma.

    The choice of which materials to use in a Passivhaus will normally be determined by the designer or client’s preference. When it comes to insulation there are also complexities in balancing how much carbon might be involved in the materials, for example using polystyrene, and how much carbon is being saved due to the energy saving attributed to a good insulating material.

     

    Building a Passivhaus is Too Expensive – IT DEPENDS

    Elrond says there’s quite a lot of published data which shows that Passivhaus buildings can cost more than non Passivhaus buildings. However, when designing a Passivhaus building it’s a quality assurance standard, so what gets built has to match what gets designed and it has to meet the appropriate standard of workmanship on site with the finishes, etc. Thus, comparing that with a building that only reaches standard building regulations (in the UK), there’s very little quality assurance that a finished building matches what was designed at the outset. This means there is an issue of comparing like for like, because if that building was constructed exactly as it was designed it would probably cost slightly more than it did.

    Another factor that increases cost is when existing plans are adapted to go down the Passivhaus route, which of course will add extra cost. The best way to approach Passivhaus is to have it as an objective from the very beginning. Take the budget and prioritise how the money will be spent. For example, in order to meet the standard there will need to be triple glazed windows, etc. This way, once the essentials have been priced up, there will be an amount of money with which to work. The building may need to take on a simple but elegant form but it will allow the overall budget to be balanced.

     

    The Air is Too Dry in a Passivhaus – IT DEPENDS

    Elrond says that this issue is more complex than it might seem on the surface. For an in-depth answer he suggests reading a paper on Passivhaus ventilation that Mark Siddall wrote for the AECB. However, most occupants are used to living in buildings that don’t perform very well and perhaps have more moisture than would be ideal (which may lead to environments that encourage mould growth and in turn can cause occupant respiratory difficulties such as asthma). In buildings which are built right – high levels of insulation, airtight, well ventilated, etc. – the humidity will definitely be lower in certain circumstances than traditionally constructed buildings. That’s not necessarily a bad thing because a drier building will tend to be a healthier building. If things are not balanced properly or something is not quite right, then it may feel slightly drier than is comfortable.

     

    MVHR is Too Noisy – IT DEPENDS

    Careful design and installation should mean that noise from MVHR is not an issue. In a Passivhaus building the MVHR should be in a separate area (like plant room or cupboard) but it can even be outside the building (providing good acoustic separation).

    The Passivhaus standard also requires that background noise from MVHR should not be greater than the World Health Organisation‘s recommended noise levels for people to sleep comfortably. It’s also worth noting that the fans are running at an incredibly low speed so there should be very little noise coming from them.

    Where there might be the possibility of sound travelling through the ducts from one room to another, there needs to be acoustic attenuation built in, which will eliminate the problem.

     

    MVHR Costs More to Run Than the Energy it Saves – MYTH

    Clearly when you move from a house without MVHR to one that does have MVHR, there is a new cost to pay. However, as discussed earlier, it is often difficult to compare like for like between a Passivhaus and a non Passivhaus.

    But, so long as the airtightness of the building reaches a certain level (approximately 1.5 air changes per hour), it’s been proven that the amount of energy saved and the cost of that energy saving is much greater than the cost of running the MVHR.

     

    Mechanical Ventilation Has to be Running All the Time in a Passivhaus – MYTH

    Elrond quickly shoots this one down by saying that at Architype they design their buildings to use natural ventilation in the summer and MVHR just for the winter months.

    It should be easy to tell when to switch off the MVHR. When opening the window, if it feels dramatically colder outside than indoors then a lot of heat energy is being lost and there’s also a cold draught coming in. This would be when you would want the MVHR to be on. Alternatively, when opening the window if the fresh air coming in feels comfortable and there’s no cold draught, then probably you don’t need to have the MVHR running.

     

    Mechanical Ventilation is Too Complicated to Use – MYTH

    Elrond argues that this is a myth because the controls are simple to understand with a small amount of training. Most people can operate a boiler, switching off the heating for the summer, for example. Mechanical ventilation is no more taxing.

     

    You Can’t Have a Woodburner in a Passivhaus – MYTH

    This is more a case of there’s no need to have a woodburner in a Passivhaus. People often desire them for emotive reasons because it’s nice to sit around a fire or to feel heat emanating from something.

    Having a woodburner in a Passivhaus is generally discouraged for a couple of reasons:

    • It would only be used for a very short time of the year
    • A lot of heat will be generated and that heat will be retained

     

    Passivhaus Will Only Work on a Sunny Site – IT DEPENDS

    Passivhaus does optimise the solar gain so as to make the most useful benefit of the heat from the sun. With a small building on a site that gets little sunlight it would be more of a challenge and would really have to be addressed on a specific case by case basis as to whether it was viable or not. As a building gets bigger the parameters change slightly. Elrond uses Architype’s schools as an example. Having more people in a building means there’s more heat energy being generated and so there’s less of a need for using heat from the sun.

    school-interior-arch

     

    Passivhaus is Best Suited to a Domestic Market – MYTH

    Elrond wonders whether there might be some confusion in the word Passivhaus (or passive house). One of the reasons the German word is the preferred form is that the literal translation of ‘haus’ means building. In other words a Passivhaus can be any type of building.

     

    Elrond is All Over Twitter!

    Follow Elrond Burrell on Twitter

     

    Transcript

    Download a transcript of the interview with Elrond Burrell.

     

    UK Passivhaus Awards

    Ben shares the exciting news that his production company, Regen Media, is producing video inserts for the UK Passivhaus Awards. This means that very soon you’ll be able to find out why the following projects have made it to the shortlist:

    Private Housing (sponsored by Ecology Building Society)
    • Crossway, Hawkes Architecture Ltd.
    • Plummerswood, Gaia Architects
    • Totnes Passivhaus, Passivhaus Homes Ltd.

    Social Housing (sponsored by Kingspan Insulation Ltd)
    • Ditchingham Passivhaus, Parsons & Whittley
    • Lancaster Cohousing Project, Eco Arc Architects
    • Racecourse Passivhaus Bungalows, Gentoo

    Non-domestic (sponsored by Munster Joinery)

    • Green Base, Simmonds Mills Architects
    • Canolfan Hyddgen, JPW Construction
    • Interserve Office, Interserve

     

    ArchiHaus Granted Planning Approval to Build 150 Passivhaus Homes

    Ben also has more good news. In episode 24 he interviewed Jonathan Hines about ArchiHaus and Architype‘s proposal to build 150 houses in Kingstone. Well, not long after the episode was published they received the go-ahead!

     

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  • HPH020 : An Introduction to Ventilation in The Home – with Andy Simmonds from Simmonds Mills Architects

    HPH020 : An Introduction to Ventilation in The Home – with Andy Simmonds from Simmonds Mills Architects

    Andy Simmonds from Simmonds Mills Architects explains ventilation in the home, why it’s important and what the options are if you’re looking to retrofit a property for energy efficiency.

    Andy-Simmonds

     

    Interview with Andy Simmonds

    Aged 12, Andy got his first taste of sustainable construction taking a few courses at the Centre for Alternative Technology. After attending architecture college, Andy worked with engineer Chris Wallis, son of Barnes Wallis, on numerous interesting projects including stonework, timber frame construction, repairing windmills, etc. With a love of nature and the countryside, he developed an awareness of the importance of ecology when designing and building. As well as running Simmonds Mills Architects he is part time Chief Executive of the AECB (the sustainable building association).

     

    The AECB is a Network of People with a Common Aim of Promoting Sustainable Building

    Andy gives some background about the AECB. It was set up by a builder and his wife in 1989, focussing on construction but with an awareness of ecology and the environment. It’s got a very broad mix of members and there are many resources, such as the low energy buildings database, the technical discussion forums, the annual conference, local groups and so on. With about 1500 members, this vibrant group of people share their practical experience and expertise with each other. Andy says it’s a very fast way of learning, getting to grips with things and improving your business as well.

     

    Ventilation is Necessary to Get The Air to Breathe, But Also to Remove The Pollutants

    Andy uses an example of the International Space Station to illustrate the fundamentals of ventilation. They are in a sealed unit (although not completely airtight) and need air to breathe, but also a way to flush away pollutants. These could be carbon dioxide or other gases created by equipment, etc.

     

    Early Buildings Just Let The Wind Blow Through

    Although early buildings had a lot of natural ventilation, some stone and brick buildings with solid floors were actually pretty airtight. As people found new ways of building, some constructions (from 60s, 70s and 80s, for example) were potentially leakier and more open to the elements than some of the older buildings. Draught proofing without thinking of ventilation can create quite unhealthy environments.

     

    Over Ventilating and Under Ventilating Are The Two Extremes

    A house with all its windows open could be an example of over ventilating. This might be useful to clear a fug but if it’s cold outside, a lot of heat energy from the house will be wasted during ventilation. The reverse situation could be keeping all the windows shut and draught proofing well, so any pollutants from off-gassing carpets (for example) or from cooking with gas hob, etc., cannot escape. In the heating season neither of these extremes is an effective way of ventilating a house and getting good air quality.

    andy-simmonds-(by-window)

     

    In a Retrofit, Mechanical Ventilation Lets You Control The Situation

    Mechanical ventilation is an approach that’s becoming used much more often. Two systems worth considering at are extract-only or mechanical ventilation with heat recovery (MVHR).

     

    Extract-only Mechanical Ventilation

    This approach extracts air from wet rooms, kitchens, bathrooms and so on, and then the fresh air is drawn in through trickle vents in the windows. These are slots in the windows, which will provide a background level of fresh air coming into the house. However, with the extract ventilation system, which is basically a box with a fan in it, the air is continually pulled through at a very low level. Even with a peak load during cooking, for example, this background ventilation can cope without turning up the fan.

     

    Incoming Air From Trickle Vents Will be at The Outdoor Temperature

    Andy explains that on a cold winter’s day, you might feel that incoming air as a cold draught if you’re sitting near the window. This is why radiators have often been positioned underneath the windows, so as the cold air comes in it falls down and to some extent warms up. Andy outlines a good approach used in Scandinavia, where they put an air inlet through the wall, maybe behind the radiator, so as you pull in air from outside it comes and warms itself on the radiator and doesn’t feel like chilled air.

     

    Mechanical Ventilation with Heat Recovery Provides Fresh Air and Keeps The Heat

    Mechanical ventilation with heat recovery both extracts the air from the wet rooms (kitchens, bathrooms and so on) but also puts it back in via ducts and air terminals throughout the house. This is therefore a balanced system. Although the heat is taken out of the outgoing air and put back into the incoming air, the air itself doesn’t mix. The heat is transferred as the air crosses through a matrix, a plastic honeycomb for example. So just the heat is transferred. The warmed incoming air is fresh.

     

    In a Low Energy Retrofit, Ventilation Air and Air Leakage are Considered Separate Issues

    Andy points out that until recently ‘ventilation air’ and ‘air leakage’ (the air that finds its way in through cracks, gaps and holes in the building) were much the same thing. However, in a low energy retrofit where the objective is to make the building as airtight as possible, the issues are considered separately. Creating and designing a system specifically for ventilation is vital.

     

    Think About Ventilation From The Outset

    Your ventilation strategy will depend a lot on the building you’re hoping to retrofit. Once you have a professional assessment of how airtight you can make the building, then you can make an appropriate strategy. British houses from the 1970s and 1980s can be difficult to make airtight, whereas solid-walled properties with solid floors are often much easier. This year the AECB aims to release a retrofit guidance programme to help in this process.

    grove-cottage-front

    Grove Cottage meets the EnerPHit standard

    Larger MVHR Units Are More Efficient

    Andy talks through the MVHR unit he has at Grove Cottage, which has two low voltage, low wattage fans, one for extracting air from the house and one for pulling air into the house. The largest part of the box is the heat exchanger. Andy’s unit is situated behind cupboard doors in a utility room. While it does take up a fair amount of space, Andy points out that the larger the unit, the more efficient. This is because the more space the air has to move through, the less work the fans have to do, so very small units tend to be much less efficient than Passivhaus certified units.

     

    Mechanical Ventilation Only Makes Sense With Certain Levels of Airtightness

    Andy generally only recommends mechanical ventilation with heat recovery when the air change rate for the house is less than 1.5 air changes per hour. This is because the savings must warrant the investment in electrical energy. However, for the extract-only system an air change rate of 3 would be acceptable. Part of the difficulty is in planning for the air change rate when you’re deciding what sort of ventilation system to have, because after construction you may not have achieved the level of airtightness you had hoped for!

    grove-cottage-(snow)

     

    Externally Insulating Grove Cottage Was an Easy Route

    Andy explains his approach to retrofitting Grove Cottage, which is a solid brick house. As the brickwork was of no particular architectural quality – it was painted white – externally insulating was the easier option (compared to internally insulating). The starting point was to mark on the plans in a red pen where the continuous air tightness plane goes, forming a strategy of how to deal with weak points. Andy describes how he sealed the brickwork to the roof membrane (which is basically a plastic sheet) with bitumen tape, which proved to be very successful. He emphasises the importance of a clear strategy and not leaving it to the last minute.

    grove-cottage-(back)

     

    The Right Advice Can Save You Money

    It is essential to spend time early on thinking through the detail of the retrofit. This could stop all sorts of problems arising on site and prevent a poor result at the end of the job. Andy reflects on how people can be reluctant to spend money on these services, preferring to invest in the measures instead. However, this upfront thinking could actually save a lot of money.

     

    Maintaining a Ventilation System is Not Onerous

    Andy’s MVHR unit runs throughout the year and supplies fresh air which is slightly warmed by the outgoing air (although it’s not a heating system) to about 21 degrees. The system has been set so that the fans go up to a higher speed around mealtimes, etc. While you can adjust it manually on the control panel as required, most of the time no intervention is necessary. The one exception to this is when the cardboard and fleece filters need changing. A light on the unit may even indicate when to do this.

     

    Make Sure You Have Easy Access to Your Ventilation Unit

    Think carefully about where the ventilation system is located. If it’s positioned in the loft or screwed down behind a panel, this will make the simple maintenance jobs more of a pain. Equally, in a retrofitted house like Grove Cottage (that has been well-insulated and has triple glazing, etc.) and is therefore peaceful, you want to locate the ventilation units away from quiet spaces. There will be a slight hum, so keep it away from sleeping areas, for example.

     

    Ventilation Systems Must be Properly Commissioned and Balanced

    When these systems are put in, it’s very important that they are commissioned and balanced properly. There’s a number of reasons for that, but in terms of comfort, over ventilation could mean that you start to notice draughts!

     

    Not Considering Ventilation Could be a Health Risk

    Andy outlines his concerns about the choices some people are making with their homes. He gives an example of putting in a wood stove. Leaving aside the combustion products and air pollution, Andy suggests that without an external air supply vent for the wood stove, you will be pulling in cold air up through your basement, through the floorboards and cracks and gaps. This will create cold draughts, which will add to discomfort, but the whole reason the stove was installed was to be more comfortable!

     

    MVHR Systems For Retrofit Likely to be a Small Niche

    Andy believes that we need to be much more conscious of ventilation because air quality is very important. He sees mechanical ventilation with heat recovery as being a relatively small niche for retrofit, but that extract-only ventilation could have a bigger role to play.

    grove-cottage-(grass-roof)

     

    Useful Links

    Download a PDF About Retrofitting Grove Cottage 

    Simmonds Mills Architects

    Follow Andy Simmonds on Twitter

     

    Transcript

    Download a transcript of the interview with Andy Simmonds.

     

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