Using sheep wool to insulate my loft – a case study
Loft insulation is one of the easiest ways to save money on your energy bills- so when we moved in to our new house, it was one of the first things we checked. It was pretty obvious as soon as I ventured up into the loft that it had last been insulated quite some time ago!
How much heat is lost out of your roof?
It is estimated that approximately 25% of heat is lost out through the ceiling of your home (if uninsulated), so it is worth prioritising this area. If you can successfully insulate the loft (and it really isn’t hard) then you are going to need less heat to keep your house warm. The less time the boiler is on, the lower the bills!
In order to achieve this, it is recommended that a new loft be insulated with at least 270mm of wool insulation although if you are using something like Celotex or Kingspan you can get away with 150mm because their thermal efficiency is better. The depth of insulation in my loft was about 5cm in some places, but near enough non-existent in others – so obviously something for me to sort out one raining afternoon!
The problem with free insulation
I had thought about just getting British Gas to come in and throw lots of insulation down. They have done it for free in the past, however I have heard a few scare stories; for example pipes getting knocked, cables getting buried and the house being left in a right old mess as the installers want to be in and out as quickly as possible.
Why did I decide to use sheep wool insulation?
So with the decision made to do it myself, I then had to decide what insulation material to use. Having been involved in the energy saving industry for the best part of the decade I have come across most insulating materials. We have always tried to go for the most eco-friendly if we can and that’s why I chose sheep wool insulation. This is a premium product compared to standard insulation, but its ease of use was another reason I picked it. Since I decided to insulate the loft myself, it made sense to use this because it is easy to handle. You can carry it, tear it and put it in place without the need for any protective clothing.
The problem with mineral wool insulation
If you have ever used mineral wool you will understand what I mean; the stuff is a nightmare. Any bare skin that touches the insulation becomes itchy as hell! Couple this with how hot you get in the loft with all the protective clothing and the limited space. Sheep wool is a fantastic alternative, for the following reasons:
Sheep wool insulation can absorb water without losing insulating qualities
Loft Sheep wool Insulation can absorb water – approximately 35% of its weight. In a loft full of timber that is pretty useful, since it can regulate the humidity up there ensuring things don’t rot. Also even when the sheep wool insulation has absorbed the water, its insulating properties won’t diminish – so you can be sure it is still going to keep your house nice and warm.
Sheep wool insulation purifies the air
Sheep wool insulation also purifies the air – it is made up of natural proteins with reactive side chains that actually break down formaldehydes, Sulphur Dioxide and other nasties found in the air. This is especially good for those who suffer from allergies as it will help limit the symptoms.
Moving on to the install – the first job was to get rid of the existing insulation. This was very much a dustpan and brush job with a couple of big black bags. In all honesty you could just throw the new insulation down on top of the old stuff, but for me I wanted to start afresh (all part of moving into a new house I guess). Once I had got all the big bits out, I got a bit of help from Henry the Hoover to get rid of it all so we had completely clean surfaces on which to lay my new sheep wool insulation.
How thick to lay your loft insulation
The plan was to lay 300mm in two 150mm layers – this was despite the fact the joists were 100mm. I guess in a perfect world, I should have used two layers – one of 100mm to run between the joists and the other 200mm layer is then laid 90 degrees to this to produce a perfect insulation carpet directly above the ceiling underneath. The 100mm layer would have come to the top of the joists and then the 200mm layer of the sheep wool insulation would have run without any air pockets across the joists and the 100mm insulation.
Anyway – I used 100% pure sheep wool and this only comes in depths of 100mm and 150mm. It is easy to rip, so in theory I could have bought 2 layers of 150mm and ripped one but life is short so I just thought I would get on with it!
Sheep wool insulation is sustainable √
The reason for using the 100% sheep wool insulation so it ticked all the environmental/ sustainable boxes, but to be honest I think even the sheep wool with plastic binder would have worked well although there are claims that the plastic binder does inhibit the insulations ability to absorb water and nasties in the air.
So, as I said, the first thing to do is measure the width between the joists. The reason being is that you can buy insulation in a few different widths. Obviously you can cut it to size, but anything to make things a bit easier – basically the idea is to get the insulation of the closest width to that of your joists so that it is literally a case of rolling the insulation out.
How to tackle spotlights when insulating your loft
Now if you have lights recessed in to the ceiling it is advised to cap these – they tend to be spotlights like GU10 or MR16s and they get pretty hot if the insulation is resting on them. The caps give the fittings a bit of space so that air can flow around them helping to keep them cooler. You can buy specific cappings, or you can use a terracotta flowerpot turned upside down over them if you have any lying around.
When using sheep wool insulation there are only two bits of kit I recommend using. The first is a plank that you can spread across 3 joists which helps spread the weight and the second is a knife or pair of scissors to cut the insulation to help you manoeuvre it into place.
Starting at the furthest corner from the loft hatch, I rolled the first layer of insulation out between the joists. For me, the insulation came slightly over the top of the joists, but if you use 100mm insulation (which is the normal height of loft joists) then it should come up perfectly to the top of the joists and provide a flush surface to lay the next layer of the sheep wool insulation.
Try not to compress your insulation
There is obviously a bit of squishing required here, but try not to compress the insulation too much; the reason sheep wool in particular works is the crimp of the fibres, which trap air. If you squash the insulation you reduce the crimp of the fibres, so less air is trapped and it doesn’t insulate as well.
The key here is to use a bit of common sense. We have come across people who tell us they have used 200mm of insulation in their loft and we go up and we see chipboard nailed directly on top of the the joists which means in some cases they are squishing 200mm of insulation into a space of 100mm. This is what we are trying to avoid!
How to lay your second layer of insulation
So once the first layer of sheep wool insulation has been laid out between the joists it is time to lay the second layer. Now the joists are slightly hidden I really recommend using the plank that covers at least three joists. You can use this to work from and it means you don’t have to balance on partially hidden joists!
The second layer is pretty easy and no squishing is required – again starting at the corner I just began rolling it out at 90 degrees to the joist. Once this first one was laid out I then laid out the next piece of the insulation making sure they butted up to one another. At this point you lose sight of the joists underneath altogether.
How do you use your loft for storage and insulation?
If you want storage in the loft then read this blog, which details how to do it (you basically raise the floor of the loft using loft stilts that sit on the joists). If you don’t want the storage space (and do remember it is freezing up there once the insulation is down so don’t store anything really precious up there), I do recommend using at least one piece of chipboard somewhere around the loft hatch, so if you decide to come into the loft again you do have a stable platform on which to stand.
Underneath this piece of chipboard you will only have the first layer of insulation so bear that in mind as you are rolling out the insulation and leave a bit of space. Screw the chipboard in using a few wood screws to stop it moving. Some people like to make a complete walkway from one end of the loft to the other – I didn’t bother but it is an option. Just remember to lay the chipboard across a minimum of two joists and ideally three.
So there you have it – my loft insulation experience. It really isn’t that bad and if you use one of the natural products (e.g. sheep wool insulation or hemp for example) then you can handle it and you don’t get the dreaded insulators’ itch! I am pretty happy with my efforts!
If you have any comments or questions please let me know in the comments below and I will try to come back to you.