The Mechanical Ventilation and Heat Recovery unit is a vital part of a passivhaus. With an airtight house you need a way for fresh air to get in, whilst at the same time not loosing the heat in the house. Ours is a Paul Novus 300 which sits in the coat cupboard by the front door. Warm moist air will be extracted from the bathroom, shower room and the kitchen. This enters the unit via one of the silver pipes, warms up the incoming air and the goes to the outside world via one of the black pipes. Meanwhile fresh air is brought in through the other black pipe and after being warmed goes out through the other silver pipe around the house.
So there is a lot of ducting as each room has either an extraction or supply vent.
Upstairs the ducts come up through the airing cupboard and then into the two bedrooms. If you look closely to the left of the window where there is an upright post you can see the extraction vent for the bathroom. Looks rather like a periscope at the present
Whereas the outside of the house has gone blue, the inside is going a fetching green colour. The ceilings and walls are being covered in SmartPly VarPairTight: an OSB board which comes with an airtight layer already attached. The blue tape seals the cracks between the boards to make it completely airtight.Once everything has been boarded the Warmcell people can start filling the gaps between the Ibeam joists with insulation.
Last week saw the rest of the roof joists added along with a rainproof blue membrane. Nearly all the upstairs windows also went in. So now we are pretty much weather-tight with the exception of the tall two-storey window and the front door and window. Here is a picture of the main roof.
Now we can really begin to get an idea of the views from the windows – this is looking out of the landing window across the roof of Mike’s study.
Saturday brought 24 hours of continuous rain, which meant that the ground which had been drying out is back to being a quagmire again. On Friday the ground floor of the house had been swept dry, but by Sunday there were again puddles up to an inch deep across the whole area as the continuous rain had seeped through the temporary plastic sheeting and the joins in the floor sheets above.
And then on Monday storm Imogen arrived. Not so much rain this time, but sudden very strong gusts of wind. I visited the site, to find the scaffolders had returned and were tightening up all their joints. The plastic membrane around the pod was also being battened down to stop it flapping in the gusts. It was rather alarming to stand upstairs looking through the landing window at the swaying silver birch a few yards away. However house and trees are still standing and the main roof is now nearly water tight so we are ready for the next storm.
This week the first floor upright I-beams were completed and the walls were clad with the fibre board, so you really begin to get a feel for the shape of the building.
Then came another layer of I-beams, but this time they range in height to give a sloping roof ( from East to West ). The first roof joists have also been hung, which start to give us a feel for the height of the sloping ceiling in the upstairs rooms.
Visually the house seemed to move very quickly this week, though it does look like it has been covered in cardboard. First the downstairs windows were added, with a few hiccups as explained in the previous post. Then Steico tongue and grooved woodfibre insulating boards were added.
And then on Friday afternoon they started on the first floor I-beams and amazingly two-thirds of them were up in one afternoon
We thought we were doing so well with the windows – they arrived in time for the build and they seem to be the correct number and size, but in true “Grand Designs” fashion we have encountered a little problem. All bar two of the opening windows and the patio door have their hinges on the wrong side.
As far as I can work out, it is a bit like the Mars Orbiter which missed Mars because one team worked in pound-seconds(Lb/s) and the other team worked in newton-seconds. This is what a window looks like at the plan stage – it is viewed from the outside and the point of the dotted V shows where the hinge is. Unfortunately the window manufacturer does it different. The windows are viewed from the inside and the V point is where the handle is. Some-where along the supply line the drawings were incorrectly converted, though not consistently as not all the windows are wrong.
Fortunately we can work round it – two opening windows are fortunately the same size and can be switched. Other ones it did not really matter which way they opened. The biggest change has been to the patio door where the drawings shown the door on the left (as viewed from the inside). And as you can see from the photo it is now on the right.
We had a session making sure it would not impact on where furniture could be put and on the whole it seems it might be the better place for it any-way.