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?
Mineral wool
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.
Spray foam
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.
Benefits
- A warmer home.
- Can be done cheaply.
- Potential savings on your energy bills.
- CO2 saving of 210kg to 730kg p/a.
Limitations
- None
Installing loft insulation
Interested in installing loft installation? The Green Homes Grant is a Government run scheme, offering grants of up to £10,000.
If you are interested in this scheme, we advise you look in to this on the Government website.
What about flat roofs??
Hi Ian, Try alternative roof insulation.
Interesting article. We have a loft bedroom that was constructed by the previous tenants at least a decade ago. It’s chilly and almost certainly has little insulation. I have heard that there are two different types of roofing felt, that which breathes and that which does not. Depending on which you have – different insulation (or fitting) is advised, otherwise condensation will build up.
Is this true and if so, how do you know which type of felt you have?
Thanks!
Hi Dave,
Although many roofing felts are now marketed as being vapour permeable, until recently almost all felts were impervious. With breathable roofing felts you can use PIR board quite happily. With impervious roofing felts (which are often found on older roofs), you have to use wool – ideally sheep wool which can regulate moisture in the loft space.
I had loft insulation installed be british gas three years ago. It has made my house unbearably hot and to make matters worse our energy bill has kept going up every year. I am honestly thinking about taking the stuff out, but I went up into the loft to assess the insulation and touched it and it was very itchy. I didn’t pay for the insulation cause it was done under a government scheme but I wish i hadn’t bothered at all. loft insulation is a complete waste and hasn’t helped at all.
Hi Chris, The point of loft insulation is to slow the movement of heat in the house, so if you had this installed and didn’t turn down your heating then you would expect the house to get warmer! Do you have a thermostat or any other type of heating control? If so turning down the heating will make the house more comfortable (the thermostat will prevent the home ever getting warmer than the temperature you set) and in turn save you money on your heating bill. Honestly loft insulation is a bit of a no brainer – it is very cheap and you can make significant savings hence we really do try and push homeowners without it to get it done.
We insulated our loft with 200mm kinsman board. Made a huge difference and can store stuff on it. A useful introduction. Worth mentioning ventilation. Easiest was is to put spacers between loft felt flaps so air can easily flow. Lots of people forget and it can lead to condensation issues.
Thanks for the comment Tad, agreed – adequate ventilation in the loft space is really important to prevent condensation during the cold winter months. We have heard numerous stories of people getting their loft insulated for free under the Government’s ECO scheme only for the installers to not bother with the ventilation leading to items being stored in the loft getting damaged due to them becoming damp. Any installer should really install the ventilation as part of the loft insulation they install as the two do go hand in hand. Thanks for your comment though and glad the insulation has made a difference in your home.
useful article,,, attic insulation is always been the wise choice to keep the temperature moderate indoor and thereby reduces the utility bill.
Hi Leeshin – loft / attic insulation is definitely the way forward. It is cheap and a fantastic way to lower your energy bills.
We got our loft insulated free last September before the winter. We have been in house for 3 years now and therefore I know how cold it used to get. The loft insulation has made a huge difference, not sure on specific energy savings on bills but the house is now nice and warm and takes longer to get cold when we turn the heating off. I can see why gov. were so keen for everyone to get it done!!
How much is this loft insulation? Think we dont have any in roof.
Loft insulation is always cited as the no.1 energy saving measure and it is very easy to see why. It is very cheap and easy to do and the results are tangible energy savings that you can see on your reduced heating bills. This is a good starter piece by GreenAge again. Becoming a very useful resource for people!
This loft insulation guide is extremely useful. I need to do this before the cold weather hits and know I am pretty comfortable I can do this myself without having to pay someone to come in to do this for me. I think we are going to go with the joist level insulation just because it sounds easier, but thanks for all the insight!
1851 house loft never insulated but no one wants to do work been trying since bought house dint people do this any more l don’t fancy doing it myself but looks as if l have to with winter coming
has anyone heard of Micafil? We need new loft insulation and someone recommended it to us. I just want some ideas really –don’t mind what we go for as long as it works, but just want to make sure I’m spending the money on the right thing!
Hi Rob,
Micafil is pretty easy to use since it comes in bags and can be poured where required. The individual particles of Micafil are extremely light and are pretty good in terms of thermal performance although the rolls of wool do offer insulate more effectively when you compare the two like for like.
The downside is the cost to be honest – a bag costs roughly £20 (will do 1m2 to a depth of 100mm) where as a roll of insulation also costs £20 and will cover 8m2 (if you look at Earthwool). We actually have a specific blog on Micafil scheduled to be released in the next few weeks so stay tuned to our blogs!
We had sheep wool insulation installed in our loft and it’s made such a difference. Not that cheap but we’ve been saving money on heating ever since so it will be worth it in the long run!
We had some loft insulation installed when we moved into our house years ago but it’s really cold in the winter so I don’t think it’s doing much. Can we just add some more on the top? Or do we have to rip it all up and start again? How much will it cost?
Hi Lewis, You can easily add an additional layer of loft insulation on top of what is already there. Over time, the amount of loft insulation that the Government recommends installing has increased. It is currently recommended that 270mm is installed in the loft (which is why you can buy rolls of loft insulation that are 170mm in depth in case you had ever wondered!) so first I recommend measuring the current depth. If the insulation comes to the top of the joists you can pretty accurately estimate that 100mm of loft insulation is in place. Therefore I would recommend adding a further 200mm of insulation to take you over and above the recommended 270mm. The cost will be approximately £2-3 per m2 to achieve this kind of depth of insulation.
We moved into our house 5 years ago and I know it has some loft insulation, but I dont know what type or when it was installed. It looks a bit patchy but I’m not sure what it’s meant to look like really! how do we find out we need new insulation and what should we use?
Hi Joel, if the install was done in the last few years, there tends to be a printed page taped to a joist in the loft detailing exactly what was installed and to what depth. If in doubt, you are looking to install 270mm of insulation or more, so get a ruler / tape measure to gauge the existing depth of the insulation. If there are areas of the loft that are a bit low in terms of the loft insulation you can always top it up by buying a couple of rolls from your local DIY store – just be sure to check on the packaging the depth that the rolls comes in (as this varies between 50mm and 200mm). If the patchy areas aren’t very big (in terms of depth) then you will only want to buy the smaller thickness rolls of loft insulation.
I am looking to insulate my home with loft insulation. I wasn wondering whether to kingsman PIR board but I am worried about condensation forming and leading to damp / rotting. I want to use the kingsman though is so can easily put chipboard on the top and have a decent storage place. If you do raise the joists with timber to accomdate wool insulation is there a risk the additional weight could cause the loft to collapse?
Hi, I have been reading your website for a while because I recently bought a house and am looking for some advice on the type of insulation i should be using in the loft. I have been up there and you can very easily see the top of the joists, so I guess there are a couple of inches at best. should I remove the existing loft insulation because it looks pretty tatty and start again. or do I simply roll out new insulation on top. Also i can see that there are lots of spot lights coming up in to the loft void. If I put lots of insulation on top is there a risk of those overheating? Do you cap them or leave a space around them? Although if you do leave the space then surely you are defeating the point of the insulation in the first place as there will be lots of places without any. My final question is about which insulation to use? We have been recommend rockwall but it seems expensive compared to the earthwool insulation I can get at B&Q. Is there really any difference or are these just brands? Keen to get this done ASAP so any speedy advice would be very much appreciated.
Keep up the good work!
Carl
Hi Carl,
Thanks for getting in touch.
In terms of insulating your loft, firstly it is a great idea to do – lots of energy savings / lower energy bills! In terms of the existing loft insulation, I would leave it in place to be honest, unless it is genuinely falling apart or it is very compressed since it won’t be nearly as effective if this is the case. Do bear in mind that removing loft insulation is a bit of a pain (as is installing it) just because the wool tends to be itchy. The other reason you may want to remove it is you are starting from fresh and it is very easy to buy rolls of 100mm insulation (i.e. the roll that you put between the joists) but it is less easy to get rolls of 50mm insulation. Anyway – you are trying to achieve a total depth of 300mm of insulation in an ideal world. All the different types of wool have slightly different characteristics, i.e sheep wool is breathable, Rockwool doesn’t combust – but on the whole they all provide near enough the same level of improved thermal comfort when you use the same like for like thickness. For the downlights, you can get downlight covers that sit on top of the fitting and then you can insulate around them! Good luck with the job – hope it goes well!
Hi, I am interested in getting loft insulation, but I am aware we have an electric shower in one of the rooms directly beneath the loft. I have heard the cable that powers this shower which is currently visible in the loft cannot be covered, but it is tight to the joists. Is there anything I can do here so we don’t get a big cold spot in the loft where I can’t add the extra insulation. We are extremely keen to put the loft insulation in ahead of the colder months. We did this on a previous property and it made a big difference. Also is there a particular type of loft insulation we should be looking at it? In B&Q they sell Earthwool, which comes in lots of different thicknesses but I have also seen you can get Rockwool. Is there any difference or will all the wool insulations have a similar level of performance.
Thanks
Angie
We are interesting in getting loft insulation in our property, but unsure whether to get the wool or the rigid boards. Can you stand on the rigid boards without laying out chipboard / OSB?
Do energy companies provide loft insulation for free in September / October? Happy to install it myself, but don’t want to go out and buy the loft insulation if I can get it for free!!
Are their still grants to get loft insulation? I think we have a little bit of loft insulation but I am interested in getting it topped up as it still gets very cold in my property. Any help would be hugely appreciated.
Good Job. Great Information regarding loft insulation.
Loft Insulation Offers
Internal Solid Wall Insulation
It doesn’t allow the roof to breathe, locking in the water next to the timber – which as we have mentioned previously can lead to problems. This is incorrect if you use an open cell product like Icynene it allows the timbers to breathe and is vapour permeable it also creates an air barrier keeping out the cold air which in the winter when you have your heating on stops condensation dead in its tracks which for the most part causes most of the damp issues in the home.
I recently had my house re-roofed. Although we had 270mm – 300mm of ceiling insulation, I had an additional 50mm of board insulation put between the roof rafters to reduce solar gain to the house in our hotter summers. With Building Control agreement the roofers left a 200mm gap at the ridgeboard to allow any moisture in the loft to permeate out through the breather membrane (their is a 50mm gap between the board and the membrane and ventilation slot under the membrane at eaves level but the membrane goes over the ridgeboard so there is not a freeflow of air at the top). The roof is clay pantiles that are ventilated at the eaves and the ridge is a dry ridge so there is plenty of airflow between the breather membrane and the tiles.
I am wondering why the gap was left between the board insulation and the ridgeboard at the top (on both sides). Given I have ventilation under the tiles and a ventilated gap between the board insulation and a breather membrane do I need that gap? Do I need the gap all the way along the ridgeboard, could I not fill in some of it and get more out of my extra insulation than just solar heat rejection?
Ive just filled in the form for advise about loft insulation providers but had an error message saying there was an error processing the form; on review it all looks ok but it won’t let me send it through
Very useful information; very simple and concise. Thanks.