15 months on

Can’t believe it’s been 9 months since I’ve updated the blog – time is flying! We’ve had bitterly cold ‘Beast from the East’ in February and the hottest summer since 1976 (or so Nick Grant says). We finished off timber cladding on the north side of the house and been focusing our efforts on the landscaping: planting new native hedging and soft fruits, building a chicken run and establishing a bit of a lawn. It’s been great to be able to spend time outside, BBQs, parties and just enjoying life. So how has the house coped with these weather extremes? Pleased to say, remarkably well. Of course this statement could be subjective, but the monitoring results (graphs below) confirmed that the house has a very good level of resilience built-in. We’ve been particularly impressed with the comfort during the heatwave, when the internal temperatures peaked at 24C, whilst the outside was 28C. PHPP indicated zero overheating (internal temperatures over 25C), but it was great to confirm this in reality.

With no gas or heating bills we were keen to see what our electricity consumption would be – the first annual statement from the energy supplier confirmed 4,500kWh or approximately 45kWh/m2 – this included all electric appliances, lighting, air source heat pump etc.

We entered the project for Passivhaus Trust Awards and we’re absolutely delighted that we’ve won the Small Projects category against a very stiff competition! Lloyd Alter predicted the winners on Treehugger back in July – amazing prophecy skills. It was fascinating to hear stories of the other shortlisted projects, all very different in character, style, budget and circumstance. More on this is on the Passivhaus Trust website.

We are going to open our home on Saturday 10th November as part of the International Passivhaus Open Days, feel free to book a visit via this website or look at other passivhaus projects in your area on PHT website.

If you’re interested in a more in-depth article covering detailed technical aspects of the house (thanks Kate & Lenny!), head to Issue 27 of Passive House Plus magazine.

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15 months on

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.

6 months on

We’re in!

In fact we moved in at the end of June, despite the house not being quite 100% finished. There are still many areas which need finishing off but the house is perfectly habitable – we absolutely love it! Surprisingly, it’s the simple things that have made the biggest difference compared to the old rented house: having the dishwasher and wash machine inside and having a simple hot water system that works. No more worries about having a shower & washing up at the same time!

Our friends Nick & Colin have made us a couple of lights which fill and complement the main living/ dining spaces beautifully. The opening petal light over the dining table is a particular hit with visitors.

We love the internal ambiance, the shimmering light on clay plaster, the freshness of air. We really look forward to making this our home.

We’re in!

Summer comfort

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With the recent heat wave in UK, it’s been interesting to experience internal comfort in our house. Although we haven’t fully moved in yet, we’ve been spending considerable time inside doing various finishing tasks. Over the last few days the external daytime temperatures have been gradually rising, peaking at a scorching 30 degrees C today. Night time external temperatures have also been going up, last night levelling at 17.5 degrees C. This pattern is likely to carry on over the next few days.

We’re really impressed with how our house has been coping with the hot weather. Internal temperatures have been fairly steady, gradually rising from 18.5 to 21.5 degrees C. We’ve been keeping the windows & doors shut and the ventilation unit on. The MVHR unit has a built-in automatic summer bypass, which kicks in at 21 degrees C. We can contribute the comfortable internal temperatures to a number of design features:

  1. exposed concrete slab with its high thermal mass acting as a giant temperature regulator (warning: this can work both ways!)
  2. 1.5m roof overhang along the south verandah means no direct sun hits the big glass = zero unwanted heat gains
  3. external roller blinds to main bedroom (south facing), and two windows to east & west gables
  4. high levels of insulation & airtightness in walls & roof (thermos flask effect in reverse)
  5. fully vented facades & roofing. It is worth noting the facades and roofing are black colour, but the vented cavities help isolate the hot surfaces from the thermal envelope, slowing the heat flux down

We don’t have the hot water system installed yet and have not been cooking/ living in the house, so internal heat gains have been minimal (bar the dehumidifier which we’ve temporarily turned off). We’ll keep an eye on the temperatures & relative humidity and will start proper monitoring once we get connected to broadband. The initial impressions are very positive though and we can’t wait to move in!

Summer comfort

Ventilation

Every passivhaus home has a controlled mechanical ventilation system with heat heat recovery (MVHR), and ours is no exception. With expert advice from Alan Clarke and Green Building Store we have designed a cascade system based around Zehnder Comfoair 160 VV Luxe ventilation unit. This is the smallest unit from Zehnder and can supply up to 160m3 of fresh air per hour – plenty enough for the two of us and a medium sized dog. Another benefits are built-in frost heater and automatic summer bypass when internal temperature gets over 21 degrees C. We have kept the ventilation ducts dust-free during the clay plastering and only installed the terminals just before commissioning.

The ventilation system works best when properly commissioned, so it was  great to have Alan and Nick coming over to help. Alan hired a nifty anemometer with self-balancing fan for accurate reading of flow rates, whilst Nick used manometer as an alternative way of measuring. We also installed a condensate drain, which wasn’t in place by default. A few hours later (including pub lunch & a game of ping pong) our system was set up. The first thing that struck me was how quiet the whole system is. The MVHR unit itself is just audible, but as it’s located in the Utility room it won’t be an issue. Supply & extract terminals throughout the house are totally quiet – a sign of good design and installation.

The next big step will be installation of hot water system and then we’re just about ready to move in – can not wait!

Ventilation

Clay plaster Pt 2

A few weeks have passed and we have finally (almost) finished the clay plastering.

After the application of base (body) coat to straw walls described in the previous blog post it was time to apply the top coats. Top coats consisted of two sub-coats, the initial 4-5mm fine clay coat and 1.5-2mm final coat, which was applied whilst the first coat was still moist. We have initially selected three different colours for the top coat (vanilla yellow, caramel brown and olive green) to differentiate various spaces in the house, but during the application we have opted for additional un-pigmented basic clay for the ‘feature wall’ in the main living space. We’ve also added finely chopped straw in the top coat for a bit of sparkle and a reference to our straw walls.

Normally it is not recommended to apply clay plaster to plasterboard because of poor bonding. However, as we’ve used fibre-based Fermacell boards for internal linings, we felt confident that this would work. We taped all the board joints with glass-fibre mesh and tile adhesive before a clay suck coat and two top coats were applied to internal walls.

Roman really showed off his skills, with beautifully crafted rounded window reveals and all surfaces expertly finished with small japanese trowels. It’s been an emotional process with ups & downs, but it has totally transformed the feel of the house, giving it a sculptural quality rarely seen in new build homes.

Clay plaster Pt 2

Internal joinery

Meant to write this blog before the previous one on clay plaster.

We have thought long & hard about the ultimate feel of the interiors, what makes the spaces: materials, textures, colours, smells. It is quite fun to go through the process of breaking down and interrogating the elements and their relationships with each other. How is a door formed in a clay plastered wall? Are architraves and skirtings essential or purposeful? What does a door handle feel like in hand and how does it fit with the rest of the interior? We have decided to complement the simple aesthetic of the house form with pared down, but beautifully crafted joinery: solid Douglas fir doors, door frames, skirtings and window boards and simple recessed stainless steel handles – all supplied by a local joiner. We discarded architraves and instead opted to use chunky timber door frames and recessed skirtings as giant stop beads to finish the clay plaster to. This decision impacted on sequencing of the works; internal joinery had to be installed before the plastering started. We can’t wait to see how all these elements will come together over the next few weeks.

Internal joinery