# Loft insulation questions



## Gixxer6

With the recent hot weather I thought it would be a good idea to take a look at the loft insulation as the rooms upstairs get very warm and I saw that the loft insulation is the loose fill type which looks to be made up of recycled newspaper as pictured below:










This insulation is only level with the joists and approximately 110mm high. I've read that the recommended thickness of loft insulation is 270mm or more. I've read that new insulation can be laid over old as long as the old insulation is in good condition but what about loose file insulation, can new insulation such as mineral wool/rockwool be laid over loose fill insulation?
Is the loose fill insulation a fire hazard and is the best solution to remove it before laying any new insulation down?
It looks like it will be a fun job to remove the loose insulation if I have to do it myself. Would a vacuum cleaner be useful ? Any ideas if this type of insulation is hazardous?

I was thinking of insulating the loft with Knauf Earthwool: https://www.knaufinsulation.co.uk/products/earthwool-loft-roll-44 and also looked at Rockwool which seems more expensive. Is the Knauf insulation any good or should I look at another type of brand?

Or, is it just better to just leave the current insulation alone? 

TIA


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## RedUntilDead

How old is it? Asbestos used to be used as loose fill years ago.
The recommended depth for mineral wool insulation is 270mm and other materials have different recommendations. No problem with mixing and if it’s not draughty and blowing the stuff every where, loose fill gets into nooks and crannies better.
Things to consider:
Do I need a vapour barrier
Do I have spot lights, these need covers
Cable runs, try not to bury cables, lift above insulation
Leave space at eaves to allow air circulation 

What you do not want is to leave voids or pockets of air. I have seen first hand that this leads to the spread of black mould on the ceiling.
I am not an insulation professional but the above is common knowledge for people who have already done what you are now doing:thumb:
Ps: yours looks nothing like asbestos infill.


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## beatty599

Essentially what you're suggesting with adding more insulation on top of the old is just like wearing two coats from different brands, just keeps more heat in. The loose fill insulation is bad, just because it's loose so lets air travel through easier, compared to a denser fill like rockwool or insulation board.

If you're not 100% on what you're doing I'd avoid rockwool / fibreglass based insulation, as it's not pleasant to work with especially in a tight area. I'd opt for insulation board eg Kingspan, easier to work with and performs better, just more expensive.

I would try and remove the old insulation just to get a better flatter and tidier fit, and will allow you to add flooring for more storage if you want. 

As RedUntilDead mentions the usual things to consider air flow, cables etc, you don't really need a vapour barrier up that high in a house unless you've a leak in the roof, it's more for the foundation.

If you're staying in the house along time it's a worthwhile upgrade.


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## Gixxer6

RedUntilDead said:


> How old is it? Asbestos used to be used as loose fill years ago.
> The recommended depth for mineral wool insulation is 270mm and other materials have different recommendations. No problem with mixing and if it's not draughty and blowing the stuff every where, loose fill gets into nooks and crannies better.
> Things to consider:
> Do I need a vapour barrier
> Do I have spot lights, these need covers
> Cable runs, try not to bury cables, lift above insulation
> Leave space at eaves to allow air circulation
> 
> What you do not want is to leave voids or pockets of air. I have seen first hand that this leads to the spread of black mould on the ceiling.
> I am not an insulation professional but the above is common knowledge for people who have already done what you are now doing:thumb:
> Ps: yours looks nothing like asbestos infill.


Thanks RedUntilDead. I've only recently bought the house, about a year ago and only now had a chance to take a look at the loft insulation in detail. I'm not sure when the loose fill loft insulation was done.
I do have LED flush downlights in the bathroom and see that the electrician has removed the loose fill insulation around each of the spotlights in the loft, 6 lights in total so I guess that the bathroom ceiling isn't that efficiently insulated.


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## RedUntilDead

Beatty obviously knows his stuff and has given good advice. To quantify my answer I as thinking it would be less hassle and less mess to leave the loose fill if it’s sound. Yes the rock wool is not pleasant to work with but suitable ppe is cheap enough and if rolls are cut to width in the loft it’s no problem and easy to get a snug fit. If you want to board over the lagging then use loft legs but be mindful of the extra weight being added.
Lofts are not the nicest environments to work in so make it is easy for yourself as you can.


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## Andy1972

I’m an Architectural Technician so deal with this kind of thing all the time. I would suggest rock wool quilt and wear gloves and a mask minimum ax the fibres aren’t pleasant. The depth is up to you. No idea where the 270mm comes from as it all depends on the overall heatloss from the house as whole. Without getting into SAP calcs etc I think 300 mm on top of what you have is fine

There was mention of vapour barriers. These aren’t needed and certainly not at ceiling level. If you have a ‘cold roof’ which you do ( ie the loft space isn’t heated) then you will have natural ventilation through it by default. Ie there will be gaps at the eaves to enable air to move around the loft space. When you lay the rock wool it’s really important you don’t ram it into the eaves as you will block off the airflow. Just leave it back slightly ( building regs is 50mm minimum. If you block it off Air won’t flow and your roof timbers can start to rot.

Other than that, just protect yourself from breathing in nasties and lay what you can afford. Anything will be an improvement in whatvyou have

Insulation boards are ok but for a diy loft I wouldn’t. Cutting them creates masses of dust and to benefit you really should tape all the boards tight to each other. Kingspan is the most expensive but others are available, ecotherm, celotex etc. Most builders merchants will stock and come in depths such as 50/75/100mm etc

I’d stick to Rockwool though.


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## Grin

Andy1972 said:


> I'm an Architectural Technician so deal with this kind of thing all the time. I would suggest rock wool quilt and wear gloves and a mask minimum ax the fibres aren't pleasant. The depth is up to you. No idea where the 270mm comes from as it all depends on the overall heatloss from the house as whole. Without getting into SAP calcs etc I think 300 mm on top of what you have is fine
> 
> There was mention of vapour barriers. These aren't needed and certainly not at ceiling level. If you have a 'cold roof' which you do ( ie the loft space isn't heated) then you will have natural ventilation through it by default. Ie there will be gaps at the eaves to enable air to move around the loft space. When you lay the rock wool it's really important you don't ram it into the eaves as you will block off the airflow. Just leave it back slightly ( building regs is 50mm minimum. If you block it off Air won't flow and your roof timbers can start to rot.
> 
> Other than that, just protect yourself from breathing in nasties and lay what you can afford. Anything will be an improvement in whatvyou have
> 
> Insulation boards are ok but for a diy loft I wouldn't. Cutting them creates masses of dust and to benefit you really should tape all the boards tight to each other. Kingspan is the most expensive but others are available, ecotherm, celotex etc. Most builders merchants will stock and come in depths such as 50/75/100mm etc
> 
> I'd stick to Rockwool though.


This is pretty much spot-on.

I did mine last year with 300mm Knauf mineral wool from Wickes. 100mm between joists, 200mm over the top laid at 90° to the 100mm layer.

I used proprietary covers for the downlights to maintain an air void around the lamp.

If you want to use loft-legs to board over the top, be aware that you should maintain a gap between the top of the insulation and the underside of the deck boards and most loft-legs are only suitable for 270mm insulation; so look for extra long legs.

As for the eaves, use a stick to poke it in tight unless you want to be Spiderman and shuffle across four joists to push it in with your hand.

You must maintain an air gap in the eaves, but can retrofit rafter trays before the insulation which are designed to ensure the insulation is held off the underside of the roof felt.

If you can see/feel a timber wall plate in the eaves, try to get the insulation to cover that and no further. That was the best I could hope for in a retrofit situation.


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## Gixxer6

Andy1972 said:


> No idea where the 270mm comes from as it all depends on the overall heatloss from the house as whole.
> 
> I'd stick to Rockwool though.


Thanks Andy,

I found the 270mm thickness recommendation online, Uswitch also mentions 250-270mm, https://www.thegreenage.co.uk/what-is-the-recommended-thickness-of-loft-insulation/



Andy1972 said:


> I think 300 mm on top of what you have is fine


So it's safe to lay the new insulation over the loose fill that I mentioned in my first post, no issues with it being a fire hazard or anything else?

I took a sample of the loose fill insulation from the loft and tried to ignite it and it burnt but isn't flammable, I think the loose fill insulation I have is recycled newspapers but treated with borax.


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## Gixxer6

Grin said:


> This is pretty much spot-on.
> 
> I did mine last year with 300mm Knauf mineral wool from Wickes. 100mm between joists, 200mm over the top laid at 90° to the 100mm layer.
> 
> I used proprietary covers for the downlights to maintain an air void around the lamp.
> 
> If you want to use loft-legs to board over the top, be aware that you should maintain a gap between the top of the insulation and the underside of the deck boards and most loft-legs are only suitable for 270mm insulation; so look for extra long legs.
> 
> As for the eaves, use a stick to poke it in tight unless you want to be Spiderman and shuffle across four joists to push it in with your hand.
> 
> You must maintain an air gap in the eaves, but can retrofit rafter trays before the insulation which are designed to ensure the insulation is held off the underside of the roof felt.
> 
> If you can see/feel a timber wall plate in the eaves, try to get the insulation to cover that and no further. That was the best I could hope for in a retrofit situation.


Thanks Grin,

Did you have any existing installation present before you installed the Knauf mineral wool? If you did, was it the loose fill type?


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## Andy1972

Gixxer6 said:


> Thanks Andy,
> 
> I found the 270mm thickness recommendation online, Uswitch also mentions 250-270mm, https://www.thegreenage.co.uk/what-is-the-recommended-thickness-of-loft-insulation/
> 
> So it's safe to lay the new insulation over the loose fill that I mentioned in my first post, no issues with it being a fire hazard or anything else?
> 
> I took a sample of the loose fill insulation from the loft and tried to ignite it and it burnt but isn't flammable, I think the loose fill insulation I have is recycled newspapers but treated with borax.


The 'best' thing to do would be to remove whats there and do what Grin did, as if it was a new build. Then you can be 100% on what you have. In terms of fire hazard, theres so much more things in your house that are more of a fire hazard than your loft insulation. Fires generally start in places like lounges and kitchens which is where we have to concentrate our fire protection when designing buildings.

The fire protection for a loft comes from the plasterboard ceiling. 1 layer plasterboard gives 30mins which is enough.

The depth that companies like uswitch provide is very generalised as it depends on the overall construction of the house. Eg a newer (less than 20yrs old) property will already be thermally efficient, whereas a 1930's semi wont, and would benefit from increased loft insulation. Theres no one answer fits all.


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## Grin

Gixxer6 said:


> Thanks Grin,
> 
> Did you have any existing installation present before you installed the Knauf mineral wool? If you did, was it the loose fill type?


Actually yes, a company had been paid to do it by the previous owner, but they had done a poor job, with gaps in the top layer (laziness). It was mineral wool like I did myself, but I replaced most of the old ceilings and it all came out, so I chucked it, vacuumed the roof all nice and tidy like, and then reinsulated once the new boards were up (12.5mm Wallboard with edge noggings if you're wondering).


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## Gixxer6

I had a look at the loft hatch yesterday and that has no insulation, probably due to having a loft ladder, it's a swing door type and any insulation if placed on the hatch wouldn't clear the ladder, the ladder isn't integrated into the hatch, the hatch door swings open and then the ladder is pulled down onto the landing with a metal rod. What is the best way to insulate these types of loft hatch? Would a sheet of Cellotex work, or foil insulation?


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## Grin

Gixxer6 said:


> I had a look at the loft hatch yesterday and that has no insulation, probably due to having a loft ladder, it's a swing door type and any insulation if placed on the hatch wouldn't clear the ladder, the ladder isn't integrated into the hatch, the hatch door swings open and then the ladder is pulled down onto the landing with a metal rod. What is the best way to insulate these types of loft hatch? Would a sheet of Cellotex work, or foil insulation?


It depends how much clearance you have under the ladder when it's all closed up.

There are several options to insulate the hatch. There are proprietary bags of insulation you can staple to the door; rigid insulation would work; or you could replace the hatch with a modern insulated one.  Depends on what you want to spend and how disruptive you want it to be.

Anything you do to the door, even some basic polystyrene 25mm thick to fit beneath the ladder, will be an improvement.


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## Darlofan

Are there any schemes to do it for you? British Gas did ours 3 yrs ago free. Surveyor came checked loft and arranged for it to be done. Cavity wall insulation was on offer too but house already had it. Horrible messy job so if someone else will do it go for it.

BTW. In this heatwave I curse that insulation every night while trying to sleep!! Thinking I'd rather pay extra £40 a year to heat the house and have it cooler in heatwaves😂😂


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## staffordian

Darlofan said:


> Are there any schemes to do it for you? British Gas did ours 3 yrs ago free. Surveyor came checked loft and arranged for it to be done. Cavity wall insulation was on offer too but house already had it. Horrible messy job so if someone else will do it go for it.
> 
> BTW. In this heatwave I curse that insulation every night while trying to sleep!! Thinking I'd rather pay extra £40 a year to heat the house and have it cooler in heatwaves😂😂


I think the insulation will help keep you cooler, though it probably doesn't feel that way.

Just pop your head into the loft and I'll wager it's feckin hot!

Just think how much of that heat the insulation is keeping out of your upstairs rooms


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## Darlofan

staffordian said:


> I think the insulation will help keep you cooler, though it probably doesn't feel that way.
> 
> Just pop your head into the loft and I'll wager it's feckin hot!
> 
> Just think how much of that heat the insulation is keeping out of your upstairs rooms


Funny, I was up there yesterday and said to wife it's cooler up there!


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## staffordian

Darlofan said:


> Funny, I was up there yesterday and said to wife it's cooler up there!


Ah well, scrub my theory then :lol:


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## Yellow Dave

Leave what's there. It's doing its job so replacing it will give little gain. Overlay with new rockwool. Laying it over the existing insulation and joists means it doesn't need to be cut. Just roll it out. Using a rigid PIR insulation board like kingspan or celotex isn't recommended to be used in a cold deck situation. Neither do any of the companies have BBA certification for doing so either. 

The building regs requirement for roof insulation is to meet a thermal U-Value of 0.16W/m2K. Depending on which type of mineral you use you'll get this by using 250-300mm thick. The mention of SAP calculations relates to new build or if you're offsetting excessive glazing where you need to over insulate to offset heat loss somewhere else in the building. 

Maintain suitable eaves ventilation to avoid condensation build up on the under side of the felt. Assuming your roof is a traditional felt and not a newer build with a breathable membrane not needing ventilation. 

Any downlighters. Install hoods over the top of them to maintain an airspace around them then lay the insulation over the top of that. 

The plasterboard ceiling on a newer build would typically contain a vapour barrier. Be in foil backed plasterboard or polythene sheet. Again older builds may not have anything. Draught strip the loft hatch and get a nominal amount of insulation will also help. 

A well insulated house will not just keep a house warm during winter, but also maintain a cooler temperature during summer as it reduces solar gains and the heating effect.


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## Grin

staffordian said:


> Ah well, scrub my theory then :lol:


No way. My roof was roasting; heat soak through the tiles is crazy and minimal draft traps the air.


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## staffordian

Grin said:


> No way. My roof was roasting; heat soak through the tiles is crazy and minimal draft traps the air.


Yes, every house I've had has suffered from temperature extremes in the loft. Unbearably hot in summer and freezing in the winter.

I guess Darlofan might have insulation under the tiles rather than on the loft floor, which is the only way I can think of to prevent the loft getting hot.


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## Darlofan

staffordian said:


> Yes, every house I've had has suffered from temperature extremes in the loft. Unbearably hot in summer and freezing in the winter.
> 
> I guess Darlofan might have insulation under the tiles rather than on the loft floor, which is the only way I can think of to prevent the loft getting hot.


I'm not saying it was cold up there just seemed cooler than the upstairs. Saying that I'm used to hot lofts, parents house was 2 bedroom so my dad boarded out the loft and I used it as my bedroom. No opening windows, fans etc!! You can imagine how hot it got, I even survived the summer of 76 up there😂😊 They'd be locked up these days for keeping a kid in that heat. Saying that though, I didn't complain as it was that or share with younger brother!!


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## Guest

One of the main questions should be..."What type of material is under the tiles/slates"
Modern houses use a breathable membrane..older houses use felt.With a felt covering..the soffit vents alone will not supply enough airflow to prevent condensation.
Adding layers of insulation may improve the U-value and offer a warmer house...but its not always that simple.The following are not my words but some the situation up well....
https://www.heritage-house.org/damp...wall-insulation-1/insulation-causes-damp.html


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## Gixxer6

I've finally had some time to take a look at the loft in detail as well as buy some insulation.
One thing I noticed is that there is no insulation over the bay window in the master bedroom which might explain why the room is hot in summer and cold in winter. The rest of the loft is insulated with the loose fill pictured in my initial post, I'm not sure why the bay window was not insulated. Anyone have any ideas?
The bay loft is lower by about 6 inches than the rest of the loft, I'm thinking that when the loose fill insulation was installed that the bay loft was just simply missed.

The bay window looks very similar to the one pictured below:










I take it that the same principal for laying insulation applies: don't lay insulation over the eaves, or is there a different recommendation for the bay window loft?


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