Heat Pump: Part 2 - ground loop installed!

Amongst the generous mix of mud, scaffolding and construction materials we're relieved to have the 300m of 40mm diameter heat pump 'collector' pipe safely buried 1.4m underground. This photo from the upper scaffolding shows the end result in the middle distance which should re-vegitate over next spring.

We are very fortunate in having an ideal location for this collector system, being on gently sloping ground with a high water table. This will ensure that that low grade 'heat' taken out of the ground will be quickly replenished by this water movement under the ground at pipe level, with heat transfer aided by the sand used to protect the pipe aganst sharp rocks when backfilled.

Roof progress & problems

Since last week when I mentioned that it hadn't rained much it has of course chucked it down most days this week! Ironically we had no water for most of yesterday as there was a burst water main somewhere on the west side of Loch Lomond which is a good distance from here.
Even the joiners finished early yesterday as they were soaked to the skin but this was also around the time that Steve and I realised/believed that some of the roof windows were not in the positions we had expected/designed. We arranged for the architect to visit site this morning....

The main problem was with the vertical position of the two main bedroom windows and the ensuite window, in that when standing up and viewed out from the inside, they are below level of vision! This is made even worse by the fact that the soffits from the top of the window frame are set square to the window (as shown in the photo above), which appeared to be an error that had crept into the final tender drawings. We were keen to resolve this asap as the sarking board is to be fitted next week with slaters booked the week after, and thus the opportunity will soon be lost (forever) to make adjustments.

Discussion on site with joiner and architect largely sorted the problem with an agreed plan to set the three offending windows higher in the roof, and an amended detail on the upper soffits to bring them closer to the horizontal as intended. As an aside, our joiner rightly cautioned this latter detail to ensure that sufficient insulation space is allowed for between soffit and sarking to avoid cold bridging and even condensation.

The view right is from the top of the scaffolding looking back to our 'trailer park' and some of the farm buildings. The office roof is just visibile to the right of the caravans.

Rather wierdly in the last week we've found 2 dead hares and a dead rabbit in different places around the steading area but none of them appear to have any injuries.....

Up on the Roof

Since last week's blog progress has been slow but steady. The roof is quite involved and various references have been made back to the timber frame manufacturer and the strucural engineer during the course of the week. To an extent it appears to be over-engineered (but I'm only a surveyor!) We employed a structural engineer to undertake much of the design as this was meant to save time with the timber frame manufacturer; I'm not sure this has been achieved and certainly the cost seems to be a good chunk higher. If we did this again we would handle this aspect differently but 'it is what it is'. The gloom of some dreich November days don't help and I'm beginning to hate the small cold caravan bathroom!!

On the plus side - the house is looking fabulous, we love the creation of the structure and its a pleasure to show people around. Our ever professional builder has put 3 additional joiners on site today to help get the roof structure finished. The first delivery of windows arrived last Friday and we bought the majority of the contents of the 3 bathrooms last week. The pavatherm external insulation is late but hopefully on its way, we've been chasing that delivery today. There's always something to do, as well as the day job which pays the bills. Last week we received the first interim certificate and invoice.

The photos were taken on Friday 23rd, illustrating the late Autumn sunshine at 8.30am; good light levels falling on the east elevation of the house (top photo). It was still below freezing as we'd had -4degC that night; but the views are glorious. The piccie above right is of the dining area, with its 3.5m ceiling height and lovely big window and door openings. The photo below is the view from this room to the north/northwest.

Heat Pump: Part 1 - ground loop

As previously mentioned we have opted to use a ground source heat pump to provide both space and hot water heating. With no mains gas, an adjacent field and the opportunity to design a well insulated house from scratch with underfloor heating, the heat pump was the lowest carbon and lowest running cost option for East Cambusmoon.

For anyone considering a heat pump for their own house there aren't that many situations where it is the most cost effective and efficient choice, and certainly if you have the luxury of a mains gas supply a high efficiency gas boiler, coupled with say solar thermal panels will likely be a lower capital cost and running cost option than a heat pump doing both. If not on mains gas, then the costs need to be compared to LPG or oil and the decision will largely depend on the type of heating distribution system you already have, ie. radiators or underfloor heating. For the same heat input to a room, radiators need to be run at a higher temperature than underfloor heating simply because the heat emitter is concentrated into a relatively small wall hung panel, rather than the entire surface area of the floor. The problem with heat pumps is that their efficiency rapidly decreases in proportion to the heating medium temperature, such that running small radiaors from a heat pump is a bad idea. This can be alleviated to a certain extend by increasing the size of radiators so they can be run at a lower temperature.

Then there's the heat collection system, in our case this being a 300m length of 40mm diameter pipe buried 1.4m underground. This particular aspect of our build was a separate 'client item' from the main build contract so Debs, me, Stewart the digger driver and £60k's worth of band new JCB set to for four days of hard graft to get this pipe buried in the ground to in such a way as to absolutely maximise every joule of energy that could be sucked out of it .....which of course would be continuously be replenished by the sun. In effect, a huge solar panel!

In designing the collector system, we followed the heat pump manufacturer's (http://www.nibe.com/) advice on pipe depth, separaton and layout. Our supplier (http://www.ecoliving.info/) also offered advice on site and once certain of our plan, we got cracking! We ended up digging three 40m trenches, each 2m wide and 1.5m deep at 4m centres. We also imported 35 tonnes of sand to cover the pipe below and above to avoid the possiblity of damage from sharp rocks when backfilling and to ensure good contact with the ground. Bfore covering and backfilling, the pipe was pressure tsted and to finish off, fed into the house via the 'slow bend' duct pipes already built in to the floor slab.

Turning Chillier part two

A continuation of the previous blog - the technology sometimes prevents such things.

The step shown left was finished on Friday. The stone for the whole wall and the step has been recovered from the demolished farmhouse save for the coping stones which have been bought from a nearby farm where the wall had fallen down.

The weather forecast for later in the week is distinctly cooler with daytime temps nearer zero and we have had our first conversations around the subject of 'how long can we/will we stay in the caravan'. No decisions to move out yet as most of the time its really not difficult. Naturally we would prefer more space and a lovely big bathroom but that is, quite literally, a work in progress. The office is in an old toolhouse adjacent to the barn which adjoins the house and with its high level of insulation it is a very pleasant place. Steve has been insulating the water pipes within the caravan and we need to tackle the ones outside where they are not underground.

Turning Chillier

As Steve's previous blog mentions the first floor is in place and in response to Jane's query on keeping the water out you can see the blue sheeting which is keeping the worst of the rain out. Even so I don't think we're getting as much rain as usual for this time of year .....famous last words?!

The builder has lined up the slaters to do the roof in early December which is terrific news if all goes to plan. The 'hooded man' in the photo is Davie the joiner. Today he and his 2 lads attached all the rafter shoes to the ridge beam. I spent 15 mins at the top of the scaffolding before deciding it was too chilly and retired to the office which is lovely and toasty. It is terrific seeing the room formations and the height of the ground floor rooms.



Our friend Alan finished the wall late last week with the final stretch of coping stones and a rather fab step up to the chicken's enclosure. He found a curved piece of red sandstone from the demolished house and has utilised it in the step.

By close of play last Friday - 2hrs after this photo was taken - the ridge beam and both gable walls were complete. During the couple of days prior to this, by quirk of structural engineering design the first floor boarding was glued and nailed in place, the idea being to provide a strong joint between the 1st floor I-beam joists and the binder plate (a deep beam which runs along the top of the ground floor wall panels against which the ends of the joists are butted).

In my (and our joiner's!) view this was quite an unusual detail, but a call to our stuctural engineer - "just to make sure..." - clarified the thinking behind it. The downside was that the T&G chipboard flooring had to be protected from the weather until the building is made watertight, as being merely 'moisture resistant' isn't exactly a qualification for survivablity for up to a month's battering by the west of Scotland's climate in November!

This coming week should see the completon of the 1st floor wall panels and start of work on the roof. On the 'goods inwards' front, the windows are due to be delivered this week and possibly the Pavatherm wood fibre insulating cladding board.

Ridge beams...

With the three portal frames now in place (which, by the way, fitted perfectly!) the end of last week saw the the central ridge beams lifted in place to tie the portals together at their apex and of course form the centreline of the roof against which will be fixed the rafters.

The ridge beams is made from mltiple bonded laminations of wood ('glu-lam') and is as strong as it looks! It's nice to see the height of the house now and easier to imagine how the 1st floor rooms will look.

This coming week work will start on installing the first floor joists, 1st floor walls and gables, so things should really start to take shape soon. Last but not least, a letter came though from the Enery Savings Trust at the weekend with the grant offer for the heat pump, which in Scotland is 30% of capaital cost up to a maximum of £4k; every little helps!

Dry stone dyke

With work continuing on the house portal frame, the finishing touches to the dry stone retaining wall are well underway. With the wall having been substantially completed a couple of weeks or so ago using stone from the old (demolished) farmhouse, our friend and expert wall builder came across a source of coping stones from a derelict wall at a nearby farm. No sooner as a price was agreed these hand-cut half-round stones were picked out of the ground and brought the couple of miles to ECF to top off our new wall.

Complete with moss and lichen the 'copes' are well weathered and match perfectly with the old stone from the house. Behind the stone wall is a 150mm dense concrete block wall which will do most of the work, such that the coping stones are laid across the two on a bed of mortar to tie the whole lot together. At the back of this the soil will be cultivated to form a raised bed that will completely hide the concrete blocks as shown in the photo.

Portal frame arrives

Late afternoon yesterday saw the arrival of the prefabricated portal frames along with the brackets and bits to put them together. These are more than a week overdue and their late arrival has meant a temporary stop on site for a few days as nothing further could be done without them beyond the ground floor panels which are now in place .

However, things moved along again today as our main builder/project manager and two joiners started to the erect this steel framework into the gound floor panels. By the end of the day two of the three frames were in place and secured.

So why a portal frame? Well, this 1.5 storey house is very open plan internally with generous internal room heights (2.7m ground floor, 3.5m kitchen/diner, 2.9m first floor) such that the upper floor ceilings follow the roof line almost to the ridge, with a small loft space around 1.5m high. With this internal design it was tricky to use a (more conventional) truss system, so the portal frame is used to provide torsional stiffness to the building and carry a roof ridge beam, against which rafters will be supported for the roof. In effect, this is a contemporary take on a traditional method of roof construction.

In designing the roof we have also avoided the use of roof purlins (horizontal rafter supports) by using timber 'I-beams', each of which will span around 5m from eaves to ridge at a 45 deg. pitch and carry the weight of the slate roof supported only at either end. This not only keeps the internal structure clean and uncluttered, but their 352mm depth will be fully filled with insulation and their thin shear web minimises thermal bridging. The end result is a stiff, clean, super-insulated roof structure.

The down side to this constrcution has been additional labour/time and ultimately cost, but the end result should be worthwhile.

Daily Changes

The two joiners erected much of the ground floor on Monday and Tuesday which has been really exciting. Its terrific to see the rooms take shape and we are really pleased with the size of the window openings, particularly as we spent a long time last winter working through that element of the design. The joiners can't progress further until the steel arrives, this is delayed but due next Wednesday. In the meantime the scaffolders have been taking delivery of their kit and today have erected scaffolding on the west and south elevations. This photo is taken through the caravan window.

By and large we've had good weather since the start of the build, it is very mild at present which makes life comfortable for early mornings in the caravan.....however the past 2 days weather have included a large amount of rain and the area at the back of the house is somewhat muddy. Thankfully the caravans are on a concreted area.

Final photos today - 2 days collection of eggs and a piccie of Dora; generally the hens are laying 4 eggs per day which is quite good I think for ex battery hens and for the time of year. We've no idea if some hens are not laying at all but those that are have been using the nesting boxes. At this time of year with the daily reduction in light levels we can expect them to lay fewer eggs but at the moment our hens seem quite consistent.