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Retrofitting insulation to an old house with 40 years worth of junk in the loft is not a trivial task.
It has been undertaken over a period of three years in between other activities such as photography.
Each side of the loft had to be cleared before it could be insulated, and the process of shifting stuff about was like a sliding block puzzle.

Loft Insulation:

As soon as we bought the house in 1975, I fitted 75mm of fibreglass insulation under the sarking, and 75mm under the loft floor.
This was quite effective at cutting down on draughts, but the loft was still cold.
In 2012 it was decided to cut down on heating bills and be a bit greener by upgrading this level of insulation, so we now have:
  • 150mm of fibreglass under the loft floor, between the joists.
  • 70mm of Kingspan Therma under the rafters. This is solid foam board with both sides covered in heat-reflective aluminium foil.
  • various layers of plasterboard, hardboard and carpet.
  • various items of junk insulation!
  • the hatch is insulated with fibreglass and carpet
The loft has a converted room in it surrounded in plasterboard and there's also lots of carpet covering the whole loft floor.
By the time the Kingspan is covered in boards (mainly hardboard rather than plasterboard to save space) the total insulation is probably equivalent to 270mm, and you still have a useable space.
We measured up for and bought 12 boards each 1.2 metres by 2.4 metres (8'x4') of Kingspan (which turned out not to be enough) from in Stirling.
This is a source of seconds of Kingspan, which there is really nothing wrong with (perhaps it is 5mm thinner than specified), but you get a good discount (about a third) off the price of perfect Kingspan.
A big lorry comes and there is a delivery charge of £30.
The main problem is where to store it before you can get it all fitted, which has taken months as a diy job in between other activities.

Kingspan is quite fiddly to install between the rafters, but well worth it in the end.
You need to ensure that it does not block the air from keeping the sarking and joists in the roof dry, so nail small pieces of wood (we used 3" by 2" by 1") to the roof beams under the sarking, so that there is a 2" gap between the Kingspan and the sarking.
That way, draughts will be on the outside of the insulation, where you need them to protect the roof timbers from damp and rot.

You can cut Kingspan Therma with a saw, but that produces a lot of white dust, which clings to everything, gets tramped around the whole house, and you end up vacuuming everything!
It is much better to cut it to the distance between the rafters with a very sharp kitchen knife, which if you cut it carefully, produces less mess and very little dust.
However, to fit it below the sarking between the irregularly spaced rafters, slicing the sides of each pre-cut piece with a knife gives lots of little slivers in the loft and takes quite a long time, some measuring mistakes, and some packing with slivers against the draughts where the Kingspan and the joists don't meet!
The slivers block up your vacuum and stick with static electricity to your clothing, so it is best to be hand lifted into a poly bag as you go along.
It is also useful to leave old clothes in the loft, and wipe off the little bits of Kingspan which cling to them, then change in the loft out of your old clothes before you come down again!
If you are prepared to lose loft space by fitting very large boards of Kingspan under the rafters, that would cause less mess and be much quicker.

Insulation of the solar thermal hot water tank

Although the tank is insulated in the factory, it still loses heat through the insulation, and through the connections to the pipes.
Extra insulation has therefore been fitted (£3 each for two cylinder jackets in Wickes, which come in separate bits so are quite flexible, and together cover most of the large tank).
Some leftover Sempatap (see below) has now been used to insulate the tank further.
Instead of losing 2 degrees overnight, it now loses only 1 degree.

Pipe insulation

The idea of this is to reduce losses between:

  • The solar panel and the hot tank (the solar thermal panel should be supplied with this pipe insulation).
    When the sun shines, this is the hottest water (over 100 degrees) so will have the greatest losses, and it is probably worth supplementing this insulation with spiral pipe wrap.
  • The gas boiler and the hot tank (this is also pretty hot, up to 100 degrees), and was insulated using 19mm thick grey tubular insulation, which you can buy from a plumbers merchant.
  • The outlet from the hot tank to the hot taps, bath and shower.
    At 50-60 degress, there are still heat losses, especially in a long pipe run from the loft down to the kitchen, and it is still well worth while insulating.
  • The corners of pipes still lose heat, so these have been insulated with spiral reflective pipe wrap.

Solid wall internal insulation with Sempatap

Because our house is constructed of solid sandstone at the front, and two layers of bricks with no cavity at the side and back, cavity wall insulation was not an option.
Sempatap is like 1cm thick wallpaper, and comes in a roll 1 metre wide and 12.5 metres long, which you cut to length using scissors.
Sempatap is made of a foam rubber-like material, and has a woven fibreglass surface which can be decorated.
The scissors will blunt themselves on the fibreglass, so use an old pair.
Sempatap comes with special thick glue which you paste on to the wall, then apply the pre-cut lengths, like "paste the wall" wallpaper.
We have applied this in the sitting room, which is no longer the coldest room in the house.
You don't feel the cold as you walk into it in the morning.
We have hardly used the gas fire to top up the central heating since installing the Sempatap in the sitting room, hall and kitchen, and still have a bit left over for other rooms. You can get Sempatap from the wonderfully named Mould Growth Consultants! (

Underfloor Insulation

This is the latest improvement in insulating the house (in October 2021), and is taken into account in an Energy Performance Certificate, on which it can help you to get an 'A' rating. Although it wouldn't normally be your first priority, it should prove useful in allowing the central heating thermostat to be turned down a notch, and if done by enough households should make a contribution towards mitigating against climate change.
Photos of the installation, done properly under 3 main ground floor rooms in one day by Underfloor Insulation Glasgow, can be seen at Underfloor Insulation.