Heat pump installation

Work started on installing our heat pump last week. We have specified a Nibe 1240-5kW - the smallest capacity they make - with integral 'tank-in-tank' hot water cylinder. It 's a very neat unit, being the same size as a 1.9m tall fridge freezer. The pipework next to it will be ultimately enclosed in a cupboard which will still have some storage space at the front, whilst allowing access to the pipes at the back if need be.
Specifying a heat pump uses the opposite logic to specifiying a combustion boiler, as it must be just undersized to operate at its most efficient when taking into account the building's heat loss and anticipated peak heat requirement. The reason for this is that heat pumps dislike being 'cycled' - switched on and off - and actually benefit from running for longer periods at a time than conventional boilers. In extreme circumstances where, say, there is significant heat and hot water demand (eg. Christmas with visitors!) then the heat pump employs an electrical element to supplement itself, but the trick is to set things up so this hardly needs to be used at all, electricity being a relatively high-carbon form of energy.
The unit is being installed in our utility room where all the pipes from the ground loop, hot and cold water, underfloor heating and 1st floor radiators/towel radiators terminate. The guys are making a neat job of connecting this spaghetti together and hopefully by late next week we should be in good shape to switch on and get some heat into the 40 tonnes or so of concrete which forms the floor slab.
As it happens one of the founders of the heat pump supply company - Ecoliving - popped round yesterday to look at our windows (he's building an extension to his own house!) and he told me that the heat pump even had a setting to dry the floor slab out over a four day cycle, this will be important before we fit engineered board flooring.
Anderson Floor Warming of Glasgow are doing all of the plumbing in the house using a German plastic/aluminium pipe system. Hot and cold feeds are fed to manifolds from which each tap is fed, thus reducing pipe runs. Also the hot water feed is circulated from and back to the hot water tank at peak use periods (controlled by a timer) such that when a hot tap is switched on, hot water appears almost instantly.
Apart from the plumbers, the rest of the guys on site have never built a house with a heat pump in it and we are all waiting in anticipation for switch on!

Good weather = Good Progress

Afterwhat has seemed a long spell of dreich weather, the sun finally came out today and the slaters made significant progress on the roof, now about 75% slated. Inside the joiners completed the poythen vapour membrane work on the 1st floor such that we now have a near airtight house.

As I have mentioned before airtightness is an essential element in low energy housing; it allows the insulation to work properly, prevents draughts and ensures that ventilation can be properly controlled. The old adage 'insulate tight - ventilate right' has to be the watchword for the eco-selfbuilder, and if planned and implemented properly, will go a long way to achieving significant savings in energy even before considering renewable energy systems and high efficiency boilers.

Brochure management..!

Now we're on a mission to make sure we're ahead of the game on 'client supply items', we're starting to get rid of the accumulation of brochures as we actually bite the bullet and start buying stuff!
So far we've bought the sanitaryware for the three bathrooms, external insulaton system, chosen the wood stove and heat pump, and ordered and fitted all windows and doors - all of which we separated from the main build contract to retain maximum freedom of choice. Today our fridge freezer was delivered (Liebherr A+ rated) marking the first delivery of kitchen items.
The focus now is on the overall kitchen as Debs mentioned in her last blog, with Magnet and John Lewis very much in the running and we should have costed designs from both by the end of this week.
With regard to the overall build program, the joiners we're back last Friday fitting the internal airtightness/vapour membrane and tomorrow we should have a full crew including the slaters who probably have around two weeks of work to do in order to complete the roof. That said, we have snow and gales forecast tonight which might make roofing work a little tricky in the morning!

Not quite wind and watertight after Christmas...!

On our return from Christmas with family down south it was clear that the house had taken some battering during the short festive break. The area and our exposed site had been hit by severe gales on Boxing Day, resulting in significant areas of roof and wall breather membrane being literally torn off.
This was probably no big surprise with regard to the wall, as the breather membrane is simply stapled to the Pavatherm boards which don't have much hold being a lightly compressed wood fibe board.
The roof membrane was a different matter however, this being fixed down temporarily with 3"x 2" battens nailed every couple of feet. Despite being mechanically trapped by the batten and spiked with nails, this was simply not enough to avoid being torn from beneath the battens to expose the sarking board again, by now drying out and shrinking to reveal the (intended) ventilation gaps between the butt joints. As a result, the inside of the house is soaked again!
I left a message with our joiner to let him know, who dutifully showed up a couple of hours later in the middle of his holidays to fix the damage in the dark just in time before the next downpour!