Category Archives: insulation
I have started installing the insulation in the extension. There is 130mm of insulation being installed in the roof (100mm between the rafters and 30mm on the back of the plasterboard). There is 75mm of insulation going underneath the floor. The underfloor heating is clipped to this and then 75mm of screed goes on top. This insulation is in addition to the 100mm of insulation that has gone into the wall cavities. Current building regulations require 50mm, so we are well above the current specification.
The insulation comes in large sheets (1.2m 2.4m) of foil backed high density polystrene. Kingspan is the most well known make, but there are others that are just as good and half the price. The sheets are cut to length with a hand saw. It isn’t a difficult job, but it is messy and the bits of polystrene get everywhere.
The complication with the extension is that the rooms have high ceilings and you have to use tower scaffold to reach the ceiling. You can’t do this off a set of ladders.
By my reckoning, it will take about 41 sheets to do the floors and 48 for the ceilings. We have order 30 sheets of each (75mm for the floor and 100mm for the ceiling). Once these are installed, we will order a top up. It only takes a couple of days to arrive. The sheets are around £30 each, so this part order is £1,800. Insulation isn’t cheap.
Or rather the materials for insulating a property are expensive. And we have lots of it!
There is 50mm insulation between the roof rafters which is then insulated with plasterboard that has a further 50mm of insulation on the back. The walls are dry lined with insulated plasterboard and then is insulation underneath the underfloor heating.
I have spent a couple of days this week putting insulation in the ground floor ceiling. This is more for sound proofing, however, it does help ensure that the heat from the underfloor heating goes up (heating upstairs) rather than down (heating downstairs). This consists of putting 100mm of rockwool between the ceiling joists. This is pushed above the wires and pipes already in the floor. This helps ensure that the insulation does not fall out before the ceiling is plasterboarded.
It is a pretty horrible job – arms constantly above your head with itchy fibres dropping on your face. Strangely enough, everyone seemed keen for me to do it. Strange that.
One thing I have learnt is to shop around for insulation. Everyone knows the big names – kingspan, rockwool etc. But with the big brands come a big price tag. Have a look at some of the lesser known players and you will find products that are just as good, but a fraction of the price. Our insulation has been purchased from Tyne Insulation Supplies (www.tyneinsulation.co.uk).
A studwall was erected this week to cover the damp proof membrane that has been installed on the end gable. This will ensure that the plasterboard can be easily fixed to the stud (rather than trying to attach it to the waterproof membrane).
Fortunately, we seem to have over ordered the 50mm insulation boards so it is a simple case of cutting the boards to fit tightly into the panels in the stud wall.
It only took 1/2 day to complete this. I seem to have got the hang of this! You can see the time lapse here.
We have decided that it would be a good idea to put up a studwork partition and then attached the insulated plasterboard to it. The original plan was to attached the plasterboard to the damp proof membrane (that brown stuff), but we have decided that this is a better approach.
However, it does mean that insulated boards have to be put in the studwork. Just as well since we have some boards left over!
The roof insulation consists of a 50mm board of high density foam fitted between the rafters. This is then covered with plasterboard before being finally plastered and painted.
The boards are cut to size with an ordinary hand saw and jammed into position between the rafters. As you can imagine, none of the rafters are straight or parallel, so this is a time-consuming business. It has taken me 5.5 days to nearly complete the job. There is a section of roof still to be done, but I need to set up some tower scaffold in the stairwell to be able to reach the roof. All in all, I reckon I have cut somewhere in the region of 300-400 boards so far.
The good news is that by me doing the work, it has reduced the cost by £860. The plasterers (who would normally do this work) were very keen for me to do it. Having spent the best part of a week doing it, I can now understand why!
We need to install 50mm of insulation between the roof rafters. This will then be covered with insulated plasterboard (67mm) that is finally plastered. This will achieve a U value of around 0.2 which is pretty good for a property of this type.
The insulation arrives as 8ft x 4ft boards that need to be cut into strips. These strips are then jammed in between the rafters. The board is cut with an ordinary wood saw, but getting it to the right size can be a bit of a challenge as not all the rafters are parallel. It is a fairly messy job and the bits of polysytrene seem to get everywhere (particularly my eyes). However, I hope that we will have finished this job by the end of the weekend.
The insulation in the roof consists of 50mm slabs of insulation between the rafters and the insulated plasterboard on top. The plasterers weren’t very keen on fitting the insulated boards. It has to be cut into strips and jammed in between the rafters. It is a messy and time-consuming job.
So guess who gets to do it?