It’s been some time in the planning, but the end of May saw a major milestone in the ‘organic growth’ of our energy system at East Cambusmoon Farm with the addition of battery storage to store our excess solar power during the day to use at night! Thanks to our electrician, a day with a digger to lay 50m of new cable and a perfect install of the 3 x Tesla Powerwalls, we’ve brought our 22kW of PV across 3 separate system into single ‘hub’ where power is collected, stored and distributed across our all-electric farm.
We've just made it even more convenient for guests with super-efficient plug-in hybrid and pure electric vehicles to stay at East Cambusmoon with the addition of another two wall chargers!
It's been a busy week so far with four new arrivals on the lambing front to date, and both mums and the two sets of twins are doing well!
Our 'mini flock' of Lleyn ewes are almost bursting (!) at the seams, so we're on lambing standby again for the Easter holidays, albeit a week or so later than in 2016. Rearing sheep isn't our 'daytime job' by any stretch of the imagination, but is an incredibly rewarding pastime which keeps the fields in good condition and adds some diversity to our smallholding, yet can be quite a stressful rollercoaster ride at this time of year!
We've recently boosted our green energy production with a further 60 solar panels on the two 'hangars', so we now produce almost as much electricity as we use over a year at the farm!
Ok, so when we set up this blog the intention was to do 'regular'ish' new posts on developments at East Cambusmoon....the last year blog wise was rather infrequent, and it is now just over a year since our last post! Well, there's been much happening here in the last 12 months, so much so that we've had little time to report it!
It's nearly 12 months since we welcomed our first guests to Curlew Cottage and The Old Dairy. It's been great fun and we've met lots of really lovely people from all over the world.
Coming up in May we have Booked which, as you might guess, is a literature festival. Organised by West Dunbartonshire Council library service this festival is just a few years old but already has a loyal local following and has an interesting programme with a great variety of authors speaking.
It's now over two years since we dismantled our solar PV system from our previous house and nearly a year since we put the panels on the new woodshed at East Cambusmoon. So high time we made the connection to the grid again!With Jim the electrician round to do some bits and bobs around the house, we took the opportunity to dust off the inverter, check all the cables and connect it up.After a few hours work by Steve and Jim came the time of the big switch on late afternoon. Firstly the solar voltage was checked - 180V in cloudy conditions - then the final connection made. After a final check all disconnects were connected and all switches switched on, and the inverter buzzed into action. A couple of minutes later 300W of power registered on the output meter, then as the sun appeared from behind a cloud as if to clebrate our latest milestone we were up to 900W - 8 times more than we were using with our excess, renewable, organic green electrons spilling back onto the local grid!By the end of the day (we were still generating a few watts at 8:30pm) we had generated over 2kWh, half of which was exported. Next step is to register with Scottish Hydro and get paid 28p for each of those units we export!Home made power doesn't get much better than this...!
It's December, and time I blogged again. The last seven months of occupancy have been intense at ECF, not only with moving in but also just catching up with 'normal' family and work life. Despite the festive season being just round the corner, we at least feel we're getting there!
Now we're in and the snag list getting shorter, it's nice to take stock and get back to 'normal' family and work life. The good weather of late is helping (why did we build a house in winter?!)
One of our outstanding issues is connection of phone and broadband to the house (ironically the caravan is still better connected than the house!) such that once this is done and we have more time, normal blog service should resume....
Our aitightness test a week ago had me crawling around in the loft at the wekend with a big torch which revealed the achilles heel of our aitightness strategy - penetrations and unsupported joints!
For the most part the vapour/air membrane is continuous within the building with joints made with tape and silicone which were then mechanically trapped beneath battens or plasterboard.
The exception to this is the loft space where the membrane was simply stapled to the underside of the rafters, between which insulation was previously fitted. This clearly makes the membrane vulnerable to gravity (!) and any air pressure difference between outside and inside the house with the ultimate risk of the membrane pulling away from the rafters - which has started to happen in one place. I have also spotted two un-taped long joints with resulting gaping holes exposing the insulation, and an unsealed soil pipe penetration. These gaps must easily account for at least half of our dinner plate size hole given that the soil vent pipe ducts were open in the bathrooms during the airtightness testing.
The ultimate solution is probably to bring down the membrane from the rafters to the loft floor and place the insulation from between the rafters on top of it, thus creating a 'cold' loft. It goes wihout saying that the penetrations need sorting out also!
After our airtightness test was done last Friday I switched off the heating, having 'cooked' the house for a couple of days to aid the thermal imaging tests. On Friday evening it was 20.5 deg. in the ground floor and 19 deg in our unheated 1st floor bedroom.
After a chilly and breezy Friday night, both these readings had dropped by just 1 deg overnight and still no heating. During the day the readings dropped a further 1 deg (tilers in - patio door fully open!) then raised a little towards the late aftenoon/evening as the sun peeped out.
Saturday night was again cold (as snow moved into northern Britain) but temperatures only dropped a couple of degrees in the house overnight, only to rise again during today to as much as 23 deg. in the ground floor and 20 deg. in our bedroom due to solar gain, despite the continuing biting cold wind outside (and leaky patio doors!).
In essence the house was behaving passively, with perhaps the circulation pump (set to continuous within the heat pump unit) helping to spread the heat from solar heated rooms to the rest of the house, an effect which will be helped further by the MVHR unit when switched on.
Early last week we took up an offer to have the house tested for airtightness by the Leeds Met. Uni's Centre for the Built Environment. Unlike in England, such test are not (yet) a requirement of building reg's in Scotland, but given that we are aiming to achieve the AECB's Silver standard I was keen to ensure we were at the very least close to our design target!So how do we measure airtightness? Until Friday, this was a mystery - then it all fell into place; method as follows:1. Close all trickle vents, windows and doors, fill all drain/water traps.2. Open main door of house and fit blower fan sealed within frame.3. Switch on fan and measure air flow rate into house (in m.cu. per hr) when air pressure in house is a steady 50 Pascals higher than outside.4. Record this flow rate and divide by surface area of house. Hey presto, this give the air permeability figure in m3 per m2 per hr - or m/hr.The results? Pretty good for a first test appeared to be the concensus. Under the current building reg's in England, the number has to be less than 10; ours was 4.8. Put another way, if we add up all the gaps in our building we have a hole the size of a dinner plate between us and fully airtight.However, the AECB's Silver target level is 3.0 for a house using a Mechanical Extract Ventilation system, or 1.5 for MVHR (our option); in other words we need to try and reduce our dinner plate to a saucer!So where do we look? Thermal imaging and smoke tests under pressure showed airflow through the service void, all of which are connected to the 1st floor joist void and loft space. This leads me to suspect we have some leakage at the soil vent pipe penetrations and possibly the airtightness membrane joints within the loft. Another significant 'problem' is clearly the seals around the large sliding patio doors, of which we have three sets, and which were actually letting water in last week during a driving rain storm. Our tester reckoned that sorting the doors alone could bring our figure down a futher 1 to 2 m/hr, getting us much closer to our target. Other issues included leaks between plasterboard and window frames.As a postscript to this, today I noticed a 1.5 inch waste pipe in the kitchen open to the elements with a gale blowing out of it into the house which we had omitted to seal; so that's an egg cup off our dinner plate!
What we've set out to do at ECF is to build a house which will use 70% less energy than one built to current building regulations. Its timber frame construction detailing hasn't wavered too far from the 'norm' to present any major problems for a timber frame kit manufacturer, decent building contractor or building control, and the costs of going this 'extra mile' haven't been excessive to the extent that they will be paid back within a decade in terms of reduced energy costs.
As for living comfort at the levels of airtightness we are building to, it becomes necessary to use a whole house ventilation system. For this there are two main options; Mechanical Extract Ventilation (MEV) and Mechanical Ventilation with Heat Recovery (MVHR).
Having specified and designed a house to meet the AECB’s Silver Standard, airtightness plays a key role alongside high levels of insulation to achieve a low energy house. In our case we have followed the AECB’s Silver Standard construction details for timber frame buildings which advises the use of a continuous air/vapour control layer inside the building with all joints lapped, sealed and mechanically trapped.
Once again, now the joiners have finished the roughings (plasterboard etc) inside the house and are ready to move on with the larch cladding outside, we’re getting battered by gales and rain. Nevertheless, despite getting a soaking in their first ten minutes outside yesterday Craig and David did one wall of the three to be larch clad and we’re delighted with the results. Ironic really, as the larch which the kit company sent was completely the wrong profile to what we specified, but we actually quite liked it and went with it!
The profile specified was ‘bevelsiding, which is wedge shaped in cross section and simply overlaps the board underneath. But we were sent a more robust tongue and groove profile which interlocks with adjacent boards, a detail which I feel adds a more robust line of defence against the weather.
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