We finished off the two air ducts we started last week. We put on the extra layer of MDF boards underneath to complete the downwards chute before it runs into the PU foam boards. We coated the MDF with several layers of acrylic varnish to seal the wood material against moisture and also sealed the joints with two-part resin wood filler, to smooth off the sharp boundaries and bends to reduce the air turbulences.
The rafter had layers of PU foam boards inserted to a depth of 250mm, with a smooth surface exposed outwards. This forms one of the four sides of the ducting travelling inside the rafter, with the two narrow edge strips glued and positioned in place with long CLS pieces of timber while the glue dried.
Finally, a lid was put on, a 25mm thick layer with its smooth surface facing inwards this time, creating the fourth side for the air to be transported downwards and into the main house ducts.
The next job was to drill a large circular hole through the Skylight to provide a 100mm diameter ducting, ready for servicing the upstairs toilet and shower room.
We then had a big tidy up of all the rubbish we generated and moved things around to make them neat and tidy. We decided that we won’t continue with putting any more insulation boards up into more rafters because it is not really making any major difference to retaining the heat, the Skylight is still completely uninsulated and all the heat will escape that way. We will continue working on the Ground floor and continue in building the next room.