Posts from November 2007

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 ( advice on pipe depth, separaton and layout. Our supplier ( 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.

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