Why should I install loft insulation?
Insulating your loft is one of the best ways to improve the EPC rating of your home. If you have a virgin loft (i.e. 25mm or less of insulation) then insulating it will produce massive savings on your energy bill and the great thing is that for many of us, the energy companies offer this insulation free.
Without proper loft insulation, a lot of the warmth produced by your heating system escapes through the roof of your property; in fact, as much as 25% of the heat in an uninsulated house is lost in this way. Loft insulation acts as a barrier, slowing the movement of heat out of the property during the winter and into the property during the summer.
Even if you can’t get it installed for free, it is an incredibly easy DIY job. In the tabs above, you can find out exactly how to do it.
The first decision to make is whether you are looking to create a warm loft or cold loft. The majority of us just use the loft space for storage so normally a cold loft will more than suffice, but for some we use the loft space for a games room or a study. To be honest, insulating your loft as a cold loft is far easier than trying to produce a warm loft – mainly because you don’t need to fight gravity. The method of insulating your loft varies considerably whether you have decide to push forward for a warm loft or a cold loft, but since the vast majority go for a cold loft lets start there – at the joists.
Insulating your loft at the joists
The purpose of insulation is to produce a barrier that slows the movement of heat either in or out of the property. When you produce a cold loft, you need to lay insulation directly above the ceiling to produce this barrier to slow the movement of heat out of the home during the winter and visa versa in the summer to prevent the home overheating.
The latest building regulations stipulate you need to reach a U-value of 0.16 to conform – now for most of us who don’t talk ‘U-values’, this simply means you need a 300mm blanket of wool insulation (if you decide to use rigid insulation board like celotex or Kingspan then you can achieve this u-value with less thickness).
What materials can you use to insulate joists?
We describe the main types of wool insulation in detail here. Each have their own advantages and disadvantages, but all of them work in a similar way. The wool traps air, which provides an insulating barrier. They are all fairly easy to work with, in that they can be cut to measure, shaped to fit around immovable objects and also rolls of wool insulation are cheap.
The main issue with wool insulation is that it compresses if you put any weight on it, which lowers its insulating efficiency. If you lay wool insulation to a depth of 270mm, it is also difficult to locate the joists, which you should use as support if you are in the loft space. Never stand between the joists, otherwise you will more than likely come through the ceiling!
Wooden boards can then be laid over all the insulation if you need to make the loft usable for things like storage. The insulating mineral wool used normally comes in rolls of blanket, which is a consistent thickness and width.
Sheep wool insulation
If you are using sheep wool insulation you will get the added benefits of the material being able to absorb moisture as well. Warm air rises from the heated rooms below and condenses when it comes into contact with cold insulation materials. Unlike other wool products, sheep wool can absorb some of this moisture and protect the joist timbers from rotting, without affecting its own insulating properties.
Loose-fill loft insulation
Insulating your loft floor using loose-fill is great as a top-up process for a pre-insulated space. It tends to be light material such as recycled newspapers and mineral wool, which can be spread to cover any gaps between the joists. You simply open the bags of insulating material and pour into any spaces that were previously lacking an adequate level of insulation. This process is a fairly simple do-it-yourself job.
Rigid insulation boards
These boards, produced by companies like Celotex, are ideal for insulating loft spaces. They are more expensive than the wool, however they offer double the insulating capacity (therefore where you would normally use 270mm of wool, you would only require 135mm of the insulating board). In addition, since they are rigid it is easy to store items directly on top of them without laying board on top of them first. They can be cut to size using a saw to fit between the joists and also drilled to allow room for light fittings.
Blown fibre insulation
Another type of loft insulation is blown fibre insulation, which must be installed by a professional. An installer will use specialist equipment to blow insulation material into the gaps that require it.
Having a carpet of insulation in your roof will significantly reduce heat loss out of your home. The reason why we are such advocates of loft insulation and consider it the no.1 method of saving energy in the home is basically because the insulation is incredibly cheap to buy and the process of producing a cold loft is so easy.
Now a couple of important things to mention; while this is certainly the cheapest way to go, the loft space itself will be very cold in the winter. This means that anything you really value should be kept in the home itself, not in the loft. In addition you need to insulate any pipework and cold water tanks up in the loft as these may now be liable to freezing and the cost of repairing bursting pipes will far outweigh the energy savings produced!
For detailed instructions on how to insulate your loft to produce a cold loft please click the tab here.
Insulating your loft at the rafters
Gravity is a pain – it makes producing a warm loft that much harder. Unfortunately if one tries to insulate between the rafters by squishing in lots of wool insulation then 9 times out of 10 it will just fall out.
However if your heart is set on creating a warm loft space then it is definitely possible. There are four main ways to insulate your rafters; the first is to use netting and wool insulation. Using solid insulation board is again a really good way to minimise heat loss out of your home. The third way is simply to use reflective foil stapled to the rafters – this doesn’t produce significant energy savings but is by far the simplest way to go, requiring just reflective foil and a staple gun. You might want to use reflective foil anyway even if you do opt for a cold loft.
What materials can you use to insulate between rafters?
The materials you should use to insulate the rafter space will depend on the way you have chosen to insulate, however the products used will tend to be denser and more rigid than those used for joists.
- If you are looking to insulate between the rafters you can use both wool or insulation boards.
- If you are looking to insulate below the rafters then you may choose to use insulation boards or reflective foil.
Normally the process you decide on depends how deep the actual rafters are. If the depth is rather shallow the best option will be to insulate below the rafters. You can in theory increase the depth yourself by attaching planks of wood top of the rafter, but then you are giving yourself more work and adding complexity to the process.
Mineral wool for insulating between the rafters
This can be glass wool, rock or mineral wool and it comes in rolls. You will need to wear protective material, a mask and have the adequate tools to fix this to the space between the rafters. The material is then fixed to the space between the rafters, whilst ensuring there is gap to the roof membrane to avoid condensation.
The difficulty in creating a warm loft with mineral wool insulation is basically due to the thickness of wool insulation needed to hit the necessary U-value as specified by building regulations (300mm) although to be honest, if you are doing this yourself, you are not required by law to conform. The way to keep the insulation in place is to use a net that you can then staple to the rafters which acts as a hammock for the insulation.
Sheep wool for insulating between the rafters
If you are using sheep’s wool, which is not an irritant, then you can handle the material without wearing protective clothing. If you are using sheep wool insulation you will also get the added benefits of the material being able to absorb moisture. Warm air rises from the heated rooms below and condenses when it comes into contact with cold insulation materials. Sheep wool, unlike other wool products, can absorb some of this moisture and protect the rafter timbers from rot, without it affecting its own insulating properties. When insulating rafters, a more rigid form of sheep’s wool insulation can be used, which is more suited to rafter insulation.
Insulation boards for insulating between or below the rafters
Insulating board can be fitted between the rafters or below the rafters. Note: Because the material is thick, if you are going below the rafter space you will certainly lose headroom in the loft space. If your rafters are shallow then you have no choice and have to insulate below.
These boards, produced by companies like Celotex or Kingspan, are ideal for insulating loft spaces. They are more expensive than the basic mineral wool, however they offer double the insulating properties (therefore where you would normally use 200mm of wool, you would only require 100mm of the insulating board). They can be cut to size using a saw to fit between the spaces and drilled through for cabling.
Reflective foil for insulating below the rafters
A thin layer of reflective material is placed below the rafters to prevent heat escaping from the property. This is the most simple way to insulate your loft via the rafters, but obviously the insulating properties on this type of insulation are very limited compared to either mineral wool or insulating board.
As mentioned, the foil is by far the easiest way to insulate your loft; you simply staple it to the rafters. It is worth starting at the apex of the ceiling and then working down the rafters, overlapping the foil to achieve a continuous reflect surface. You can then tape over the joins.
A layer of foam is sprayed into the rafters and sets hard. This can only be installed professionally.
When professionals come in and install spray foams, they can achieve high thermal efficiency with very little depth. The two downsides of this firstly that it is very expensive compared to the other methods and also it doesn’t allow the roof to breath, locking in the water next to the timber – which as we have mentioned previously can lead to problems.
While having a warm loft space is great because you can then use the space – you are now heating an extra ‘room’ that you wouldn’t normally heat if you insulated just above the ceiling (i.e. a cold loft) – which means your heating bill will be higher.
- A warmer home.
- Can be done cheaply.
- Potential savings on your energy bills.
- CO2 saving of 210kg to 730kg p/a.
Installing loft insulation
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