Living in a Passivhaus
Noise, energy bills, kitchen and bathrooom, drying clothes, the MVHR, entering and leaving the house, case studies (Totnes Passivhaus, Denby Dale, Grove Cottage, Passivhaus apartment buildings)
In this chapter we examine the experience of what it is like to live in a Passivhaus. The case studies include two developments in Germany, which are of particular interest because the residents did not come to the building as advocates of Passivhaus, although the architects did involve them in the design of their apartments and they learned about Passivhaus during the process. The residents’ feedback about their homes is perhaps more typical of how most people would respond to living in a Passivhaus (as opposed to the response of a Passivhaus aficionado), provided they have some basic understanding of the building’s rationale when they move in.
There are some themes that occur in much of the feedback from residents of different Passivhaus homes. These are summarised below, before we look at responses that are specific to individual case studies.
This was something that struck many Passivhaus occupants: their home is much quieter than they were expecting. There is no omnipresent sound of a boiler churning away in the background throughout the winter. External noises are also very muted when the triple-glazed windows are closed, because the airtight construction inhibits noise transmission as well as controlling airflow. This is a big benefit for those living on or near busy main roads.
Despite the very low ambient noise levels, the ventilation system does not intrude. It is completely quiet in the bedrooms and living room, and can be heard only faintly in the bathrooms and kitchen. With it being so quiet, some people say they notice residual noise more than they would do otherwise. In a home with a lot of hard surfaces, such as wooden floors, this can make open stairwells, for example, quite noisy. Wall hangings or carpet would help in this case.
It goes without saying that occupants of Passivhaus buildings enjoy very low bills, but it is worth saying what a great feeling it is! You feel highly motivated to contact your energy provider to give them a meter reading. Speaking to their customer service representatives on the phone, it is hard not to feel a little smug. Knowing that the energy bills will always be manageable is in itself very liberating.
Conventional kitchens rely on an extractor fan over the hob to remove cooking smells. In a Passivhaus, air extraction is via the MVHR system, so extractor fans must be set up in ‘recirculation mode’, with charcoal filters, rather than with a direct extraction to the outside. The main kitchen extract vent is also fitted with a filter to avoid grease collecting in the extract duct. Passivhaus occupants have observed how effective the MVHR is at quietly and steadily removing steam and cooking smells – so, depending on how much frying they do, there is often little need for the recirculating charcoal filter extractor fan at all. Aside from periodic replacing or cleaning of MVHR filters, the Passivhaus/MVHR approach demands less intervention by occupants. By contrast, conventional extractor fans, which are designed to extract air very quickly, are very noisy and are not always consistently used – not least because the noise puts people off using them.
The first benefit here is the improved thermal comfort because there are no cold walls to chill you, even if they are fully tiled. As with the kitchen, there is no noisy extractor fan of the type usually connected to the bathroom light. This is ideal when using the bathroom during the night: there is no risk of waking others in the house or of fumbling around in the dark because you don’t want to use the light to avoid causing the fan to trip on.
Some occupants note the quite common use of electric towel rails. A 50W towel rail with timer and thermostat dries towels nicely and raises the temperature in the room. The other option is to use a minimal amount of electric underfloor matting (the electrician may need some convincing that you want only the absolute minimum (say, 200W) of matting, not the 1kW or 2kW normally fitted. Underfloor heating helps if a wetroom-style bathroom is being installed.
Drying our clothes is an activity that is quite often overlooked completely or not given the attention it deserves when homes are being designed. It is of course a design consideration in any build, Passivhaus or not. However, the MVHR system in a Passivhaus offers additional possibilities to the usual ones of opening windows and/or drying on radiators.
Ideally, it makes sense to plan for the space where clothes are dried to be near or next to the washing machine. This can be problematic in homes where the washing machine is in the kitchen, as most people do not want to dry their clothes in a relatively public space, some kitchens are too small and most have periodic cooking smells – so not an ideal environment! In a Passivhaus, one option is to build in a clothes-drying cupboard – sometimes known as a ‘Swedish cupboard’ – near or next to the washing machine. The cupboard is fitted with extract ventilation and a transfer path in the door or door frame so that air can easily be pulled into it. Where a home has a separate utility room with a washing machine, this room could be used for drying clothes and could therefore have extract ventilation. In a climate with colder and drier winters, where retaining humidity in the house becomes a priority to avoid overly dry indoor air, there may be an argument for placing the clothes-drying area in a space with supply ventilation; this would distribute the humidity through the rest of the house rather than it being extracted immediately to the outside.
The other possibility in a Passivhaus is to position the hot water store (see Appendix A) and the MVHR unit (and, if heating is to be provided via the ventilation system, the supply duct radiator) together with the washing machine and clothes-drying racks in a utility room with extract ventilation. This allows the warmth from the hot water store – even well-insulated hot water stores warm a room by a couple of degrees – to be used to accelerate clothes drying. (The rationale for locating the MVHR unit here, even if there isn’t a supply duct radiator, is for practicality of installation and maintenance, as well as maximisation of treated floor area. If heating is provided via a supply duct radiator, this may be done using hot water: another reason for proximity to the hot water store.)
Many Passivhaus occupants report that, after an initial period of tweaking and adjusting the MVHR unit (involving input from the person who commissioned the system), they very soon become unaware of it. It just does its job in the background and, being so quiet, does not impinge on your everyday consciousness. The improved air quality and lack of lingering smells and steam (from cooking or bathing) are the only things you register and that remind you that there is a ventilation system running in the background.
Arriving and leaving
Intuitively, many feel that both entry into and exit from a Passivhaus have to be rather hurried affairs because if the door is left open for more than a few seconds, it will cause the building’s internal temperature to fall. Actually, this is not true. Even when people are lingering at the front door to say goodbye to guests, cold air is not drawn into the building as it would be in a leaky house. The contrast with a standard build is particularly noticeable during cold spells: one Passivhaus occupant recalled an occasion at a friend’s house, when the front door was open for what was probably only five minutes, but, even though sitting at the opposite end of the house, he felt a strong, chilling draught through the whole place until the door was closed again. That doesn’t happen in a Passivhaus: for there to be a draught, the incoming air needs a route out. In an airtight house, there isn’t one.
This retrofit project, Adam Dadeby and Erica Aslett’s home in Devon, was completed in August 2011 and certified in September 2011. It was the third retrofit project in the UK to achieve full Passivhaus Certification and one of the first 20 or so of all Certified Passivhaus buildings in the UK, retrofit and new build.
Passivhaus retrofit – before and after
Being a retrofit and involving the extension of an existing house, this project provides an interesting comparison of the house as it is now with the way it was before. In the old house, there were none of the benefits we now take for granted. The building had single-glazed windows, widespread damp problems, numerous cold spots and very poor air quality. The result was an uncomfortable and unhealthy home which, despite improvised superficial improvements such as airtightness strips around windows, was a battle to keep warm. We found ourselves limiting time spent in parts of the house that were difficult to heat. We managed to keep our fuel consumption down to just above the national average, but doing so required constant attention and monitoring.
After the building work was completed, it was a different story. Some of our observations, and those of our guests, are as follows.
• It’s a nice temperature and very comfortable around the house.
• Great that the bills are low.
• The house seems to take care of itself.
• Not having radiators is good because all the wall space can be used.
• You need to go outside or have an external thermometer to know how cold it is.
• The house is very quiet; you notice the slightest sounds because there is no ambient noise.
• We expected it to be stuffy inside but were surprised how fresh and airy it turned out to be.
• It is very liberating not having to think about keeping warm or continually having to adjust thermostats or other settings.
• The house just seems to take care of you.
The winter was quite mild, with daytime temperatures quite often reaching into double figures, and a mixture of cloudy, rainy and sunny weather: all pretty typical for wintertime in the south-west of England! During our first month in the house we had warm weather, with a couple of days in the mid- to high twenties. Unlike in some Passivhaus designs, we were forced to rely on blinds to prevent overheating in most windows that are subject to solar gain; this was because of the planners’ views about the roof orientation as well as the shading constraints of the site. We quickly noticed how sensitive the temperature in the house was to our use – or non-use – of the blinds. If we used them, the house stayed comfortable and cool; if we forgot, it gained heat quite quickly. This illustrates just how important it is to design effective shading into any ultra-low-energy house approaching Passivhaus standards.
One thing that has struck us and our visitors is how stable the internal temperature is. There are no sudden fluctuations. Changes occur slowly. The only occasion on which there were persistently uncomfortable internal temperatures was during the Transition Town Totnes Open Eco-Homes Weekend,1 when more than 150 people visited the house during a warm spell in late summer. The internal heat gains from all those bodies could not escape the building quickly enough, even with windows open. This isn’t a surprise – altering a few numbers in the PHPP model of the house very quickly tells you how big an impact all that extra internally gained heat can have.
We chose to use a supply duct radiator (pictured on page 203) to provide the very small quantity of heat needed to maintain 20°C during winter. It seems quite an elegant solution to use the ventilation system to distribute the heat as well – one system; two functions. However, we did not get the radiator connected and running until mid-January 2012. Spending a winter in a standard build without a heating system would have been very uncomfortable and inconvenient. But our temporary heating substitute, one small oil-filled electric radiator set on its lowest setting (about 400W), kept the whole three-storey house warm to about 19°C.
As autumn progressed, despite the fact that south-west England experienced an Indian summer in 2011, it was interesting to note that many homes in the neighbourhood had already started using their central heating or had started wood burning while we still felt comfortable opening our windows in November. It was good to get this confirmation of the claim that, in a Passivhaus, the ‘window-opening season’ starts earlier and ends later in the year than in a standard build.
During unseasonably cold weather in February 2012, there was a small but noticeable difference in temperature between the ground floor and the rest of the house. This is probably partly because of the way the ventilation is set up (as is quite common in a Passivhaus, air change rates are higher on the middle and top floors). It may also be partly due to the relatively poorer solar gain and insulation levels on the ground floor and the presence of a thermal bridge – unavoidable in a retrofit – around the base of the external wall perimeter. This means that a very small amount of additional heat (around 200W) may be needed in the main living area on the coldest winter days.
Living with the MVHR
The MVHR has been a great success. There are no lingering smells, and bathroom mirrors, if they get steamed up at all, clear quickly. Three months after moving in we changed the paper filters; a simple five-minute job, and the user control on the MVHR unit reminds you when to do it. It was surprising to see how much dirt the filters had collected during those three months. The reason the extract filter was so dirty was probably because of lingering dust in the building after all the construction work. The intake filter, which filters incoming fresh air, was also dirtier than expected, particularly considering our relatively rural location.
The ventilation system has a number of options that we haven’t used to date. We just leave it on the standard setting, as one of us is at home most of the time. The unit is drawing just over 40W, equivalent to about 1kWh (a cost of about 15p) a day. During the warmer weather, it took a little while to get the settings right for when the summer bypass kicks in. The user interface on the MVHR was not so friendly in this regard, and we would hope that the challenge of designing intuitive-user controls will be addressed as MVHRs are developed further. A poorly thought-out user control can make the difference between success or failure on the part of the manufacturer in achieving the intended design goals.
Denby Dale, in Yorkshire, is the UK’s first Passivhaus to be built using the cavity wall construction typical of nearly all post-Second World-War housing in the UK. Denby Dale’s occupants kept a blog2 to record their experiences during their first months in the house, from which the following text is derived. They reported similar experiences to those of others living in a Passivhaus:
• Quiet interior.
• Good indoor air quality.
• Stable indoor temperatures.
The Denby Dale house is being used as a case study by Leeds Metropolitan University and it contains a number data loggers, which record internal and external temperatures, relative humidity (RH – see Chapter 10) and CO2 levels (see Chapter 12). Interestingly, internal temperatures have been found to be very stable over time, hardly changing during the day/night cycle, and with only small variations (typically less than 2°C) between different parts of the house. The house stayed warm during 2010/11, one of the coldest English winters in many years. During that winter the occupants experienced occasional problems with overly dry air at night-time, but they resolved this temporarily by placing a wet tea towel over a chair in the bedroom. For the green-fingered, use of pot plants would provide a more aesthetically pleasing solution. As noted in Chapter 12, it is possible to specify an MVHR unit that recovers humidity as well as heat, which is worth considering in cold, dry climates. The occupants also reported a few teething problems with their heating system (although this was not via the MVHR) and a small learning curve in getting to know how the house responds to the changing seasons.
In this house, the MVHR unit is located outside the thermal envelope. During the very cold winter of 2010/11, the unit’s condensate drain was affected by frost. The condensed water from the extracted, cooled air needs to go somewhere, so this pipe has a key role in taking the water away and it is not good if it gets blocked. At Denby Dale, they remedied this by simply insulating the pipe.
Grove Cottage is a Victorian terraced house in Herefordshire, retrofitted using Passivhaus methodology, and is another pioneering ultra-low-energy project in the UK: the first to be certified as having met the EnerPHit retrofit standard. Even though this standard takes the building down to only 25kWh/m².a heat demand and 1.0ach, not the 15kWh/m².a and 0.6ach of a full Passivhaus, the occupants of Grove Cottage report many characteristics in their retrofitted home that are common to fully certified Passivhaus projects:
• Very quiet and tranquil interior because of the airtightness and triple-glazed windows.
• Very comfortable with no draughts – in huge contrast to how the house was previously.
• After some initial ‘tweaking’ of what is an early-model MVHR unit, it works well.
• Air quality seems very good.
Friends visiting Grove Cottage have been amazed at the lack of radiators or underfloor heating. Rather than using a supply duct radiator (which in an EnerPHit house would not be able to deliver enough heat to maintain 20°C on the very coldest days), the owners opted for the technically more orthodox approach of installing two or three conventional radiators, which run at a low temperature.
The owners enjoy being able to sit in comfort to work in the kitchen, an open area with good daylighting that before the retrofit was too cold for any use other than cooking. In their sitting room they installed a small, free-standing ethanol burner (ethanol gel burning in a pot) in an old living room hearth to create an occasional open-flame effect in winter. The burner gives off 500W of heat. The MVHR system takes care of water vapour and CO2 released from the burner.
More generally, the householders have noticed that their home demands much less ‘work’ to maintain the right temperature. They commented that “the house is a comfortable ‘neutral’ background to family life”.
Two Passivhaus apartment buildings
Two case studies that form part of doctoral research by Henrietta Lynch3 in 2012 shed an interesting light on what it is like living in a Passivhaus apartment building. Both are in Germany. One, the Klima-SolarHaus (pictured here), a block of 19 flats in the Berlin district of Friedrichshain, has a shared MVHR system and a communal wood-pellet boiler heating system. The building was commissioned and the residents moved in during the summer of 2009. The block is run as a housing association /tenant co-op.
The other project, which was completed at the end of 2002 and was the first Passivhaus development of this type, is also a development of 19 ‘family-friendly’ flats in a relatively central district, this time in Frankfurt, a city whose planning regulations now require that all new public housing developments are built to the Passivhaus standard. (Clearly we have a long way to go in this regard! See Chapter 14.) Each flat has its own MVHR system, but the building shares a single gas boiler.
Residents in both developments had experiences that were similar in many ways to our experience of living in the Totnes Passivhaus. In particular, they refer to:
• The comfortable indoor environment.
• Protection from external noise.
• Low energy bills.
• The lack of summertime overheating (after an initial period of learning to use the shading devices effectively).
• The affordability of the purchase price of the flats.
• The convenience of having a dedicated clothes drying space (a ‘Swedish cupboard’, which took advantage of the MVHR system).
In both developments there was a period in which residents had to make small adaptations, especially with regard to becoming more aware of overheating, and adjusting blinds or other shading devices accordingly. However, this was not seen as a burden. In general, the feeling was that the buildings didn’t trouble them; if anything the opposite.
An important factor in the success of the projects appears to have been the involvement of the future residents in the design of the building. As well as being given what they wanted, they gained an understanding of the design process. They would also have had an opportunity to get to know each other before moving in, and this social factor would almost certainly contribute much to the success of the project.
Although Passivhaus buildings do require a few small changes in how we ‘operate’ our homes, they do not demand a wholesale change in lifestyle; these are minor adjustments that, with a little prior explanation, are intuitive and very easy to accommodate into one’s daily life. Worries about noise and intrusiveness from MVHR ventilation have been found to be unwarranted, and many occupants have noted the quality of the air. The comfort benefits of their homes are appreciated by many of those living in a Passivhaus.
Indeed, there is a sense of liberation provided by Passivhaus homes – not only are occupants freed from high fuel bills, but also the building just seems to ‘take care’ of them by maintaining a comfortable and healthy environment.