6 months on

It’s been 6 months since we’ve moved in. This period is way too short to write any definitive feedback, but nonetheless we’d like to share our findings so far.

To set the scene, we used to rent an uninsulated stone cottage over the other side of the hill for the past ten years. We loved the rural location and the quality of life, however we always dreaded the winter time. We used to spend about £1500 every winter on keeping the cottage warm(ish). The old oil boiler would break down regularly, leaving us with no hot water and struggling to keep the place comfortable. Naturally, we had big expectations for the new home.

We moved in last July. One of the early observations was the stable internal temperature of around 21°C, irrespective of what was going on outside. There was a spell of hot weather later in July with external temperatures reaching high 20s/ low 30s. In our previous cottage this would lead to overheating. We used to open the windows just to get a sense of air movement, but ultimately the internal temperatures would be uncomfortably high.

In the new house with the large roof overhang and some external blinds we managed to maintain the internal temperature below 23 degrees even during the hottest periods. The thermal mass of the concrete slab undoubtedly helped. Counterintuitively, we learned not to open windows during the highest outside temperatures, which makes sense if you really think about it. Bringing the warm air in doesn’t help to keep the house cool! At this point it is worth busting the old myth that you can’t open windows in a passivhaus – you absolutely can, and should. But think about the knock-on effects.

It’s all very well that the house is comfy in summer but what about when it gets cold out there? How are we going to cope with no radiators? Well, we needn’t have worried. As the season was turning colder, we were getting more and more ‘free’ solar gain from the lower sun, effectively balancing out slightly increased heat losses through the building fabric. It wasn’t until one evening in November when we lit the small wood stove for the first time. On average, we now light the stove for an hour or so every other evening, sometimes less often. As long as the sun is shining, the house maintains the temperature beautifully. It’s during the prolonged periods of overcast weather when we put the fire on more often. Having no radiators means the furthest parts of the house (bedrooms) do get a degree or two colder, but this works really well.

It’s worth mentioning the MVHR system does not have the capacity to even out the internal temperatures perfectly. It will constantly supply fresh air and extract used air, but there’s no active heating (or cooling) in the system to have a significant effect on internal temperatures. We have been monitoring the temperatures, humidity and CO2 and will share the data in summer 2018.

But it’s the other qualities of the house that we appreciate the most: the combination of open plan living and more intimate spaces, the sun rays shimmering on the soft clay plaster, the acoustics, the ability to accommodate big parties of friends, the luxury of being able to sit next to the large glazed window without feeling uncomfortable, the magnificent sunrises, the raindrops falling from the crinkly tin roof. We just love watching the world go by, whatever the weather.

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6 months on

11 thoughts on “6 months on

  1. Looks and sounds great Juraj, but then that’s not really a surprise. As we know, they work, it’s just a job to get everyone to understand that, and your post will help. Do you just have the woodburner for heat? I often tell people they’ll overheat the house but it seems you’ve got it worked out, although lighting it for an hour, and letting it go out must be emotionally strange?

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    1. Glad you think this helps raise the awareness Chris. Yes the wood burner is just for heat, it’s small enough (4kW) not to cause overheating. The big open plan living space and opening doors to the rest of the house helps dissipate the heat from the burner. Don’t really mind the intermittent nature of lighting – it’s a very analogue process that we’re in full control of. Cheers J

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  2. We are just beginning to consider the idea of building our own home, and are interested in the Passivhaus concept and have been excited to find your blog and design. We would be looking to also build something on a very modest scale, probably under 100m.sq. A rather blunt question, but do you have an idea yet of total cost or perhaps a notional cost per square metre? Budgetary constraints are a major concern for us!

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    1. Hi Simon. No problem, the cost of our house was approximately £1350 per m2 of Gross Internal Floor Area, this included the VAT rebate on materials as it was a self-built scheme. Good luck with your project!

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  3. Paul Hadfield says:

    My OCD brain notices on thing immediately on first readng: You say ” We can contribute the comfortable internal temperatures to a number of design features:

    exposed concrete slab with its high thermal mass acting as a giant temperature regulator (warning: this can work both ways!)
    1.5m roof overhang along the south verandah means no direct sun hits the big glass = zero unwanted heat gains
    etc…”

    I think the third word should be ‘attribute’ rather than ‘contribute’.

    Looking forward to reading the rest of your blog about a fantastic-sounding house. Many thanks. (Comment can be deleted when read!)

    Paul

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  4. nick donaldson says:

    It’s a beautiful house, thank you for sharing it.
    How are you getting on with the ariston ashp dhw cylinder? I’d love to know how you’ve connected the towel rads and whether you’d do it again. Do you think the heat pump gains are worth it Vs simple direct electric for water and towel radiator? Sorry that’s a lot of questions, but it looks like a great solution where the hot water is a big/ biggest energy requirement.

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    1. Thanks Nick. Yes happy with the Ariston unit, the heated towel rails are on a separate circuit with a Groundfoss pump, very simple setup. We haven’t explored direct electric so cannot compare, but we’d be happy to use this set-up again.

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