How Much Insulation Do I Need - UPDATED Building Regulations
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- čas přidán 1. 12. 2022
- How much insulation do you need in your floor, walls and roof? Since June 2022 the building regulations changed in the UK, now requiring higher U-values, meaning thicker insulation. I get straight to the point and go through each element, telling you exactly what you need. Let me share with you what I've learnt over my 17yrs in construction. The failure to plan is planning to fail, so why not let me help you. If you have any questions I’ll be happy to answer them.
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Thanks for providing such a clear guide. It was bad enough for me as a BCO in 1983 to get builders to put 25mm jablite in the cavity but 150mm cavities is a whole new ball game!
Really helpful, thank you. Fully explains the spec on my architects plans for a loft conversion starting soon. Everything you list matches his specifications eg 300 mm of mineral wool in the roof void; two layers laid at 90° to each other. Spot on; great help.
Thanks Peter. All the best with your loft conversion.
Very informative - thank you.
you smashed it ... Brilliant thank you spot on video
Thanks Stuart! Glad you liked the video
Cheers for this, what a pain
Thank you
Great video. Really helpful. Im prepaing for a self build. I'll get an architect and some labour for carrying etc but the rest I'll do myself over 18months.
A self-build sounds like an awesome project, I wish you all the best!
ProjectWise specialises in supporting self-builders throughout their build with everything from technical building regulation advice and logistics through to air testing and interior design to name a few. If you come across an issue we’re here to help you find a solution! Visit beprojectwise.co.uk to learn how we can support you.
@@BerkleyBuilds perfect! I just submitted a query on the site.
@@davidflavin I’ve replied, check your inbox.
Over hang your roof joists and notch them out to create a shallower soffit area for smaller facias.
I can understand your thinking and that would reduce the depth but only by a small amount still leaving you with a large fascia. If your notch is too large, you compromise the strength of the roof joist potentially rendering that joist incapable of spanning the distance desired.
@@BerkleyBuilds just cut the soffit area, all the timber bearing is unaffected, and i run noggins flush with the exterior face, above the plate.
Thanks for your excellent info. Meanwhile though, those super insulated sealed houses very easily go mouldy, and need some form of fresh air input/air circulation system. What is specified in modern builds to alleviate mould and stagnant air?
Thanks, glad you found the video helpful.
In new houses that want to achieve a high level of air tightness, an air handling system must be installed to remove moisture from the air and also bring in fresh air else it would go stale.
In older houses this is done with trickle vents, allowing air to be exchanged constantly along with purge ventilation by opening doors and windows.
Hi Ben, thanks for the useful video! I'd like to insulate a small pitched roof to create a high ceiling in a room in my house, but the sarking felt is likely original (from the 50s) and I gather this means it is not breathable. At 2:27 you specifically mention pitched roofs with breathable felt, but what can/should I use in my case? Can I still achieve my goal? The rafters are 100mm deep. Thanks in advance!
Hi Lily,
Everything is possible when It comes to building, the only limiting factors are money and time.
If your sarking is undamaged and the roof already has ventilation through the soffit then you’d be ok to insulate. If the sarking is damaged or you haven’t got ventilation then I’d suggest fitting a breathable membrane before insulating. Ventilation is crucial as it prevents condensation building up.
Hope this was helpful!
Nice video! do you have similar one for new loft dormer conversion?
Thanks!
I’ve filmed a loft conversion video but it’s not edited yet. Essentially the same rules will apply because it’s a habitable space. I suggest using the vaulted ceiling detail with the PIR between and below the rafters.
Hi there, might be a silly question but we're planning on doing a traditional suspended timber ground floor. Is there any regulation on insulating between joists? All I know is I need to leave 150mm gap between ground and bottom of the joists.
ThIs isn’t a silly question it’s a valid one. The work you describe falls under building control and will need to comply with current regulations.
You’ll need to insulate between the floor joists with a rigid insulation such a Celotex. I’d suggest you’d need 150mm.
If the work is part of a larger project then you can speak with your architect to specify the thickness and type of insulation.
You are correct, 150mm is the minimum amount of clear void required below the joists. You’ll also need to vent the void with air bricks.
A solid floor could potentially be less hassle and be better for under floor heating, something to thing about.
I hope my answer was helpful.
All the best with your project. Ben
Hi, on the solid floor detail at 1:16, shouldn't the cavity wall insulation continue further down into the cavity, as it looks like there will be a cold bridge due to the lack of overlap between the wall and floor insulation?
Hi Jon, excellent question!
For a solid floor there are two acceptable ways to mitigate the cold bridge through the ground bearing slab.
1. As you mentioned, you can take the cavity insulation below DPC by 150mm
Or
2. Shown at 1:16 you can fit a 25mm PIR upstand to separate the internal masonry leaf from the concrete slab. I chose to draw this detail as that’s the most common detail I see guys do when I’m inspecting sites.
I hope that answered your question.
Thanks, Ben
Hi, really useful video but can superquilt be used with celotex for pitched roof? I would save at least 50mm and works out cheaper?
Thanks I’m glad you found it helpful. Yes, superquilt can be used in combination with Celotex.
Hi mate, in a retrofit cold roof, we currently have 300mm rolls over the ceiling joists. Whats the equivalent of that in PIR? Currently treading the insulation down to top up the boiler pressure and not enough headroom to stilt and board. Pir would allow max headroom.
300mm loft insulation in equal to approximately 150mm - 175mm PIR depending on the spec and quality of the PIR
You mention a thermalite inner leaf. Does a dense inner leaf achieve 0.18 if pb on dabs is provided internally?
That’s an interesting question. My initial thought is it wouldn’t however, Im away on holiday and I don’t have my technical notes to hand. I’ll follow this up when I get back at the end of July.
Thank you.
This seems much clearer to most videos I’ve been researching, we have a small lean to vaulted ceiling kitchen floor space 4mts x 2.4mts, I’ve stripped the old lath and plaster From the ceiling revealing 4x2 rafters (no insulation) with a 7x3 beam running perpendicular in the centre supporting the rafters. So as you can imagine very cold in the winter! Do I just follow the guide in your video regarding the pitch roof section? I’m guessing I would need to bulk up the existing 4x2 rafters to fit in thicker insulation?
Any advice would be greatly appreciated.
Hi John. That does sound cold.
There are are multiple ways to go about it, mine being one of the more common methods. Yes you could follow that detail and ensure you maintain the 50mm air gap above the insulation. The 7x3 is your purlin, it provides the strength for the rafters else they would bow. However you decide to do it you’ll most likely need to increase the depth of your rafters to accommodate the insulation, roofing lathe is good for this.
As you are upgrading a thermal element you’ll need to involve building control.
A suggestion. At this stage you have the option to install velux windows. You would need to remove the purlin and install new rafters but it would flood the kitchen with light. Just a thought.
@@BerkleyBuilds
Thank you for your quick reply!
So basically just add the roofing lathe battens on top of each other along the rafters till the desired thickness?
Yes we did think of the velux route but decided against it due to budget and extra work and time involved.
@@johnmurphy1466 yes if you leave the purlin in position you can build out the rafters to the desired depth with lathe.
If budget allows I would suggest removing the tiles and adding a breathable membrane then reinstalling tiles.
If you need ongoing advice and support visit my website beprojectwise.co.uk to find out how I can help you more.
All the best with your project!
@@BerkleyBuilds
Brilliant! 👍
Thank you Ben.
There is a breathable membrane in all ready when the roof had been leaking in the past I suspect as a couple of the rafters and also the end of the wall plate is partially rotted which will be rectified.
There is the issue with 3 of the walls being external, the larger with a front door and the two ends with windows, again cold in the winter but insulating the walls which consist of solid stone outer and brick inner will encroach an all ready tighter space, solid floor also! Fridge box!
Thanks again Ben 👍
You’ve been most helpful 🙏
Also, is it still recommended to use a osb on top of the insulation of a warm roof? I thought that was frowned on now?
Yes, you should install a sheet of OSB on the top of the insulation. This is so the insulation can be fixed securely to the roof and so that a uniform surface is achieved for your roof covering, else water may pool.
Does the cold flat roof need these requirements when replacing ceilings or replacing the roof covering? It’s impractical for me to add 50mm underneath the joists as this will reduce the ceiling height by 50mm and they are already very low. This seems somewhat draconian requirements given the restrictions of the roof that is already in place. For example if you had 150mm joists in the roof then 125mm of pir between the joists would leave you with insufficient air gap and adding the extra 25mm plus 50mm would put the ceiling height too low. It can’t be acceptable to force major structural change just to comply with insulation requirements that are going to give a marginal gain.
So am I right in thinking that if its a cold roof timber frame dormer then the side cheek walls will need min of 100mm? Architect has put in for 60mm in between timbers and 25mm inside?
I would expect to see more than 85mm total but thicknesses of PIR can change depending on the grade / quality of the insulation.
I have not had it confirmed if OK, but I have done warm roofs where the osb/pir/osb sandwich just overhangs the wallplate, makes for a less tall fascia of just the 20+20+150
Hi Chris, you’re right for the warm deck to carry across the cavity, up to or slightly beyond the wall plate as this ensures full coverage. Warm roofs will always have a large fascia purely due to they’re design.
Cheers, Ben
@@BerkleyBuilds Hi Ben, yeah they do - I saw one other day 450mm fascia on a little res extension. Cheers, Chris
@@BerkleyBuilds Not always. I've been using a detail for a while now where if I use a 56mm Plywood deck, I can cantilever the the overhang and set back the insulation above to cover only the interior part. The overhang hides the insulation upstand from below and it looks like entire roof is only 50mm thick.
@@craigstephens93 Thanks for your insight, I’d be interested in seeing a detail of that. I’m aware and have seen other ways to achieve it but this video was made to make it easy for the average person to understand, without getting too technical else people wouldn’t watch it.
The people that make celotex defo in cahoots with those who enforce the regulations that insists on thicker insulation 😂🤣
Good evening,
Is there a certain calculation for insulating a garden room?
My frame is 50mm so I need to factor in an air gap.
I’ve seen people placing the insulation tight up to the outside wall with an air gap on the inside and also the other way around too.
Is there any benefits or negatives to either way.
Kind regards
Mark
Hi Mark! Depending on the size of a garden roof and if it’s detached from the house, it might be an exempt structure meaning you don’t have to follow the building regulation requirements for insulation and can do as you please.
Again depending on the product and construction method the air gap can change location but generally it’s on the outside so condensation doesn’t build up.
With a 50mm stud work I work suggest looking at a multi foil.
All the best with your project. Ben
Hi Ben, I have 197mm rafters don't know why can I put two 90 mm boards together to get 180 mm insulation and leave a 17mm roof void for ventilation
Hi, I’m short no. You need a 50mm air gap to allow air to circulate correctly. It is possible to put two PIR boards together, but you need the right air gap. For your project I’d suggest 150mm between with 25mm under.
That 3D construction detail of the roof looked really good where did u find it ?
I found it on Google images
@@BerkleyBuilds amazing thanks
3:06 flat warm roof you sandwiched the PIR betw een OSB boards with no Vapour barriers? I'm expecially worried about the edges of the PIR where it seems a lot more permeable than the silvered sides. I'm doing this soon... The sticky film Altruix 600 which Steve Roofer recommends is so expensive so I'm thinking of wrapping the PIR in some kind of plastic, and taping it, all 6 sides like a birthday present?
A vapour barrier is required under the insulation for the warm roof. My detail didn’t show it as I was only highlighting the insulation build up and didn’t want to overwhelm viewers with to much information.
Altruix 600 is a high performance vapour barrier however, a 1200gauge plastic membrane would also suffice. It sounds like Steve takes pride in his work wanting to use quality materials ultimately giving you a high standard. My recommendation is be lead by your roofer, and see it as an investment that a job is done once and not redone at a later stage because you tried to save a few hundred on a project that’s probably already costing thousands.
All the best with the project.
Steve Roofer is a youtube star channel on insulation, roofs etc @@BerkleyBuilds
@@DICEGEORGE ah I see. Sorry I thought you were referring to your roofer called Steve, that’s funny.
If you don’t want to spend the extra on the high performing vapour barrier, as mentioned before I recommend using a 1200gauge plastic (same stuff you’d use for DPM in the floor), it’ll do the same job.
Hi Ben this video is very informative. But my question is i was planning to change the conservatory roof to lightweight tiledroof my concearn is that 120mm sufficient? For conservatory?anyhelp would be very much appreciated.
A great question! Not a straightforward answer though because conservatories are classed as exempt structures and do not fall under building control. However, there is a counter argument that because building control look at roof structures and insulation, if these were upgraded then they should be signed off. Most tiled roof companies do get them signed off as it gives peace of mind to the clients.
Regarding insulation, many conservatories that I’ve inspected that have sort building regs often use a combination of rigid PIR insulation such as Celotex between the rafters or aluminium roof structure and a multi foil, opposed to the full depth of just PIR.
Insulating a conservatory roof is sufficient to make it more useable all year round. Beware if you remove the door between the conservatory and the house, a heat loss calculation will need to be done to justify the thermal efficiency of the house has not been made worse by increasing the glazed area where heat could escape. This is the 25% rule, where the area of glazing can not exceed 25% of the floor area.
In short insulating a conservatory roof does make it more comfortable and a mixture of insulation is used so the build up doesn’t go past the frames.
I hope this was helpful.
@@BerkleyBuilds thanks ben and wishing more subscribers to come for you.
Really interesting stuff, I’m adding a dormer extension to my cat slide roof, 90mm rigid with 30mm insulated plasterboard over - the croudace homes development over the road that’s just now being completed has only 75mm with no air gap between the brick and block - how do they get away with this?
It’s best just to make sure your project is right and not to worry about how poorly others do it, it’ll get picked up at some point. The new regs came in June 2022 so if they registered their project before then they are allowed to use the old regs. Equally if a SAP calculation has been done then the thermal values have been worked out using a number of factors potentially allowing them to use less insulation in some areas but increasing in others.
They likely applied for building regs before the change. 75mm batts in a cavity wall is fairly adequate especially as they’ll almost certainly have used thermalites. Walls don’t need as much insulating as the floor/roof. Heat tends to rise. In a roof, you need everything you can throw at it really, but watch that dew point!
Thank you this was very helpful
The embedded energy and sheer volume of chemicals in these products must be enormous and the future disposal of these items at the end of the buildings life is going to be a problem in the future
I agree Chris, it’s scary what goes into these products and there’s been no thought in how to dispose of them. It’ll be a real problem
@@BerkleyBuilds I have been a contractor for a long time now ,where do green products such as sheep’s wool sit in the new legislation ?
@@chriswild2458 that’s a very good question!
From my experience I’ve found it’s very tricky to get green products that aren’t considered ‘normal’ through the approval of building control. More justification is required to prove those products meet the standard they claim. This isn’t helped with legislation because the Approved Documents don’t give specific guidance on green products. This isn’t to say it’s impossible for someone to use something like sheep’s wool but it’s certainly harder, will need more paperwork and more involvement from an architect.
I hope this changes in the future.
Along with an infestation of moth, unless the sheep were dipped in dangerous chemicals before sheering?@@chriswild2458
Hello, please give me advice. I have just done new roofing. The roofer took all the felt and insulation out and put a membrane and did not put any insulation in roof and he sweara to me that we don't need insulation in roof. If there is insulation in loft. We dont use loft for anything.
Hi. From your description I understand you’ve had a pitch roof re-done with a new breathable membrane?
You need insulation in the loft, 400mm of loft roll will do the trick. This is something you can do yourself by rolling one layer out then rolling the second layer at 90 degrees to the first.
If you need further support for your project or you need building regulation advice, visit beprojectwise.co.uk and learn how we can support you.
Could 40mm air gap be ok for the rafters? Got 110mm insulation cheaper .
A valid question but you’re not gaining anything by reducing the air gap. Look at it this way, it’s 50mm for a reason so condensation doesn’t build up and so you don’t increase the risk of water damage. You’ll also need more insulation underneath the rafters anyway. Building control won’t pass it so it’s not worth it. My opinion is always If you’re going to do a job, do it properly and don’t compromise.
Wish you all the best with your build
More building control surveying videos 👍🏾
Thanks for the video request. Any topic in particular?
Why the 50mm air gap with breathable membrane? Surely it is breathable for the very reason to eliminate the air gap?
That’s a great question Ryan!
A pitched roof are what we call a ‘cold roof’, a roof with insulation between the rafters. These types of roofs need venting, which is why the 50mm air gap is there. It aids in how that type of roof functions and the air flow prevents condensation building up.
I hope this answers your question.
Thanks for you video very helpful! Is it possible to use a 100mm insulation to achieve the 0.18 U value for a warm roof? Is there a insulation out there that will achieve this? Thanks!
I’m glad the video was helpful. I’m not aware of any insulation with a thickness of 100mm that would achieve a U-value of 0.18
@@BerkleyBuilds thanks. Just found at Kingspan TR24 will achieve this U value at 120mm
@@saharasultana4172 thanks for letting me know I’ll remember that one! I bet it’s not cheap but it’ll give you the lower profile you’re after.
I wish you all the best with your project but if it get too overwhelming check out ProjectWise at beprojectwise.co.uk
We help make life easier and less stressful for homeowners undertaking building projects.
@@BerkleyBuilds Try eg SuperFOIL SF40BB or Kingspan Optim R.
Hi Ben, I was looking to see it you had any videos on windows upvc etc I have a scenario where the glass in my windows has blow and needs replacing, I’m seeing conflicting information if this job is notifiable or not. I understand that new doors windows need building control approval or a FENSA registered company to self certify. But for a simple double glazed glass replacement would it still need to be signed off by building control ? Any information would be great Ben 👍 as I will ring my local authority, but wanted to ask yourself first 👍👍
An interesting question, one I wasn’t expecting 😆 If you are just replacing the double glazed unit like for like and not the window frame along with it, then this work does not need building control, it’s simply a repair. Make sure to get toughened glass in a window where needed. You can check the zones of influence by googling ‘Approved Document K Diagram 5.1’ that’ll show you a drawing of shaded areas that require toughened glass.
Thanks for the question Trowel King 👍🏻
For my next video, I’ll do it on when you need building control and when you don’t. Thanks for the video idea 👍🏻
@@BerkleyBuilds excellent stuff just what I needed 🙌🏻🙌🏻 Thanks again Ben really do appreciate it mate 👍👍 yes I do believe it is a toughened glass as it has the stamped kite mark so will replace with exactly same. Cheers Ben 🙌🏻🙌🏻
@@BerkleyBuilds yes that would be brilliant mate 👌👌 honestly I’m learning more off your videos than I did at college for bricklaying 🤣🤣.Its the smaller jobs that confuse me as to weather or not they will need building regs or not, or even if they don’t can you still pay the fee to have work inspected etc sorry I could go on forever asking questions mate 🤣🤣 really looking forward to the video nice one Ben 🙌🏻🙌🏻
@@kingofthetrowel1725 I’m pleased you find my content helpful, it’s a real encouragement. I enjoy your questions so keep them coming 👍🏻 if you have specific ones drop me an email the address is on my about page.
It maybe possible to have building control inspect even though they’re not needed but it would depend on the provider and how helpful they feel. Technically because the work wouldn’t fall under their control they wouldn’t have much to say.
I’m currently in the process of setting up a company which can actually do what you need! It’s designed to help homeowners and builders a like with advice, site inspections among other services. You’ll no doubt see a video when it’s launched.
Hi there, is this for new builds or refurbishments? Thanks
Hi Ryan, the June 2022 update to the building regulations applies to all new builds, extensions and refurbishments.
These look like the existing building extension number to me. YBS Insulation say from 15/Jun/2022:
New Build: Roof=0.11; Wall=0.18; Floor: 0.13
Extension: Roof=0.15; Wall=0.18; Floor: 0.18
Refurb: Roof=0.16; Wall=0.3(ext/int)/0.55(cav); Floor: 0.25
@@bobdobalina276I can assure you they’re not. Insulation thicknesses have increased by approximately 50mm
Hi, i live in a 60's chalet style detached with cladding onf the top half at the front and coombe ceilings, so attic space behind some of the rooms. Just put a hatch in one of the rooms that had no access to the attic space to find (as expected) no insulation of this area. joists are 175mm, studs for the walls are 75mm. I was planning on 170 glass wool between the joists, then another layerbof 170at 90 degrees on top of this. In one of the other rooms fir the walls i used 100mm glass wool with netting to hold it in place. This time i was thinking 100mm glass wool with netting then maybe 170mm at 90 degrees to this again with netting ( this was cheaper option) or would i be best using 75 or 100mm celotex/kingspan, and if so will that be enough? Obviously better than the 0 that is there now!!
Celotex will be too expensive, loft roll will be the cheaper option and achieve the same result. You’ll want two layers with the second layer at 90 degrees to the first as you described. 170mm per layer will be a good improvement.
@@BerkleyBuilds thanks, what about the insulation in the wall. 2 layers of Loft insulation with netting to keep in place a good option, and I take it I need to keep this clear of the wall sockets?
@@graemestruthers4991take the loft roll all the way up to the eaves leaving a 50mm air gap to the felt and you won’t have to insulate the stud wall in the loft.
My room is like that shown in the image at 2.04in the video, so I need to insulate between the joists behind the wall, but also need it insulated the wall - there is no insulation there either.... I am also considering removing the plasterboard from the main wall behind where the cladding is to insulate there and reboard it, as there is no insulation between the boarding behind the cladding, and the plasterboard of the room... It's no wonder that room gets so cold!!
I understand the requirements for renovations are lower, and that there are some exceptions where meeting them would be impractical? How is that decided? For example insulating the interior of an older pitched roof with only 70mm rafters, so very little room for an air gap. All below the rafters would reduce height substantially. In such a case, would thinner insulation boards be acceptable?
Hi Scott, new build homes are held to higher standards as their insulation thicknesses are worked out with SAP calculations but renovations and extensions have the same requirements.
There are some exceptions and in some cases yes its impractical to request such requirements. Its decided through criteria and what is reasonably possible.
In your example, is this roof part of the works I.e is it being altered or are you converting the loft space, else it’s existing and isn’t controllable. If it is part of the works there are options you could discuss with your architect and building control inspector, 1) use multiple layers of multi foil 2) the architect could justify uprating other elements to mitigate the lack of insulation in the roof.
Consult with your architect and building inspector as it doesn’t sounds like you have a typical case.
Hope this helped. Ben
@@BerkleyBuilds Yeah its part of a bathroom renovation, so existing. There's no insulation and it's the coldest room in the house (mid-terrace). Was thinking of DIY-ing some insulation, some form of below rafters or between and below (foil and/or phenolic). Are you saying if as it's already an existing ceiling it's exempt, or?
And thanks for your advice!
@@scottwilson1039 certain work is exempt from building control meaning you don’t have to meet the requirements.
Renovating a bathroom and changing like for like is exempt work and doesn’t need the involvement of building control. From what you’ve mentioned it sounds like your project or at least that portion is exempt.
If it’s a ceiling with a roof void you might consider adding 300mm of loft roll. If it’s a vaulted ceiling and to maximise head height I’d suggest multi foil, then 25mm batten along the length of the rafter, a second layer of multi foil, then plasterboard.
If the budget doesn’t stretch that far one layer of foil will make a noticeable difference.
I hope that all makes sense.
Ben
@@BerkleyBuilds Great! I'd assumed I'd need to comply as it was altering a 'thermal element' but how that's determined is a bit unclear, so that's super helpful to know. Thanks!
What if its a timber frame building with a timber weatherboard/cladding on the outside
So no brick or blockwork.
I’m not quite sure what you’re asking.
If you’re needing a construction detail to follow then the NHBC website has all the technical details you can need. In terms of U-value you’ll need to achieve a minimum of 0.18 as per Approved Document L1(a) table 4.2. There are numerous ways you might achieve this figure, but there are many variables that play a part. I’d suggest you consult your architect for specific insulation and thicknesses.
I hope this helps. Ben
If you need more advice my company ‘ProjectWise’ can help you. Check out beprojectwise.co.uk
Does any one know the u value of a 100mm celotex + 50mm celotex?
A great question however, that’s not a straight forward answer. It all depends which grade of Celotex you have because they’re not all made equal. I suggest asking Celotex directly for a definitive answer.
anything on multi foil insulation. doing a loft conversion with 50mm celotex between rafters on 100mm rafters leaving a 50mm air gap. 25mm batten on top following joists then using superquilt over then counter battened at right angles leaving a 25mm gap. what would this equate to. sticking 175mm insulation wont leave any headroom at all. Loft dwarf walls built on top of steels so only have 100mm pir between studs. what happens to the steell area as won leave an insulation over??
What’s your architect suggested? What’s on the drawing? If 175mm isn’t achievable you could consider keeping the 50mm PIR as described and having two layers of multi foil separated by battens.
ProjectWise specialises in supporting homeowners and self-builders during their builds, to make their lives easier and less stressful. We can help with everything from technical advice, project management through to snagging. Visit beprojectwise.co.uk to learn how we can help you!
@@BerkleyBuilds there wasn't an archiect involved or drawing but going through building control. this is my second self-build loft conversion
@@JayG2K fair play! Send me an email through the ProjectWise website if you ever need any advice or support. I wish you all the best with the rest of the build.
Hello I want installing kingspan insulation in my ceiling inside of rockwool because 300mm of this I lose lot head room how much kingspan do I need use please this not going on roof
300mm rockwool is only used for an open roof void.
If you want to insulate the roof with Kingspan or equivalent then you will need a total of 175mm. I suggest 125mm between the rafters ensuring there is a 50mm air gap and then a further 50mm Kingspan under the rafters. You can then plasterboard and skim
If you are converting your loft to create a habitable room you with need building regs.
@@BerkleyBuilds thank you for getting back to me and for answering too
I live in an 1895 stone built terrace with no cavity, this year I plan to internally insulate the bedroom wall it's the full width of the front of the house it was originally lime plasterered but it seems over the years it has been skimmed with gypsum plaster so no longer breathable and the plaster has blown in quite a significant area, I was thinking of removing all the plaster back to brick across the whole wall, and fitting 50mm foil backed rigid insulation with 12.5mm plasterboard on top of that and skimming what do I need to be aware of to be compliant with part l of the building regulations and is it notifiable many thanks and sorry for the essay
Thanks for the question, the essay was helpful for context as it allows me to give you a more detailed answered.
Depending on the scope of work, you may need building control as significantly altering the thermal performance of a building is notifyable. I’d suggest one room would be ok.
You’ll lose some floor area by adding insulation internally but install a stud wall that is 50mm away from the external wall and insulate the stud.
All the best with it. Ben
@@BerkleyBuilds Thanks for the reply, is there a reason you suggest a) building a timber stud wall, and b) building it 50mm away from the original wall. Is there a reason that 50mm rigid foam cellotex or similar with foil backing as a vapour barrier can't be affixed straight to the wall, also is it removing the original plaster that would interest bco if the original plaster was repaired and then insulation installed would that fall outside the scope of part L1B again sorry for the essay
@@carlhirst2480 building a stud wall allows the wall to breath without interfere with the existing structure, the same is done when converting a garage.
Substantially improving thermal elements triggers the requirement for building control so it depends on the size and scope of the project and its undertaking. This can be a little bit of a grey area and is open to interpretation.
Can I chuck one in? Remove the gypsum plaster and have it wholly re-done with proper lime plaster. You will benefit from (a) the original room footprint area, (b) the plaster will be a relatively 'warm to touch' material, and (c) original design breathability will be restored.
If someone was converting an existing space to create a habitable space for example conversion of a timber framed barn. Would these same insulation levels apply?
Thanks
Yes they would apply. On a project like a barn conversion your architect will be able to spec everything for you.
If you want additional advice or support I set up a company called ProjectWise that specialises in supporting builders, self-builders and homeowners during their build with everything from technical advice, project management through to snagging. Visit beprojectwise.co.uk to learn more.
@@BerkleyBuilds
That’s a shame I have a building that one day I’d like to convert and live in. the roof space is modest in size already, I think 50mm under the rafter timbers would be the difference between it being an ok space and not really worth doing. I think they are only 6” timbers so the ventilation space between the celotex and tyvek also won’t be sufficient. Looks like I should have tried before 2022 ☹️ I was hoping to go 100mm between and 25mm under.
@@limekilnfarm9657 I’d suggest it’s still possible! 100mm PIR between and a multifoil under the rafter. The regs will only increase over time, I reckon you can still achieve it.
If you need any support in the future email me at headoffice@beprojectwise.co.uk I’d be happy to assist.
Thanks, Ben
@@BerkleyBuilds
Thanks Ben. Very helpful
Hi great video. Slightly confused as you mentioned 150mm celotex in the floor then 100mm after. Is new regs for 150mm or 100mm ?
Hi Kavan , sorry to have confused you. The old requirement for floors was 100mm Celotex however, the new requirement is 150mm in the floor.
@@BerkleyBuilds thank you for your swift reply. I am planning on doing a rear extension. And my architect has suggested for 150mm slab , 100mm celotex and 75mm screed. Is this correct !
would 100mm celotex with 150mm concrete work ?
All help or guidance will be appreciated.
@@Karan-Singh999 your architect isn’t necessarily wrong to request 100mm because they may have specified a higher spec celotex however, If I walked onto site for an inspection I would be asking questions because I would expect to see 150mm celotex. The concrete covering the insulation doesn’t increase its energy rating. Ask the question of your architect and I’m sure they’ll be able to explain why they requested 100mm
@@BerkleyBuilds thank you for your help I will raise the question. Will deffo subscribe and like the video 👍🏾👍🏾
Hi again, just seen a email from my architect which I must have missed this afternoon. I did ask the same question and his response was new dwelling need to have a thickness of 150mm PIR and extensions can get away with 100mm Celotex GA400.
Does this sound right ?
To start with, you mention 150mm celotex, then a few seconds later, it was 100mm celotex??
100mm was the old standard, it’s been increased to 150mm as the new standard for floors and flat roofs. Pitch roofs need 175mm.
Wow! short, sharp and clear, but painful! As I look at my 3 bed end of terrace Victorian house with wooden floors, 9" solid brick walls, a cellar and Welsh slate roof.......demolition????
I like to keep my videos short and deliver the information people are actually seeking without wasting their time.
Haha demolition is a bit extreme, I’m sure the property has character! If you wanted to improve its thermal efficiency you could consider insulating walls internally but you would lose some floor area.
I'm looking to insulate and board my large loft space which is about 150m2. I would like to use it for storage purposes and increasing the efficiency of the home. There is just enough space to stand in the loft without any insulation. The depth in the joist is about 100mm which I understand is not enough. So I was wondering to do 100mm insulation between the joists and board on top, then insulate the roof between the rafters with something like foil. I dont know what UV value this will make. Are you able to suggest if this would suffice to meet the required UV value?
Hi, great question!
You’ve got a generous sized loft space which will be excellent for storage.
If you are simply updating your insulation and using the loft for storage purposes then this doesn’t need building control and you can achieve whatever U-Value you desire. However, on the other hand if you were to convert the loft space into a habitable room such as a bedroom or office then you’d need building control and would have to comply with current regulation standards.
Your suggestion of adding 100mm loft insulation between the ceiling joists with board on top and a multi foil quilt over the rafters would certainly be acceptable and give you a better energy rating than you currently have.
If you’re budget allows, I would suggest adding 50mm celotex or more between the rafters (allowing a 50mm air gap above) with multi foil quilt over the face, this will allow you to get the most out of your multi foil further increasing your energy rating.
All the best. Ben
@@BerkleyBuilds Thanks for your suggestion.
@@MrAppukuttan93 you’re welcome. It’s a pleasure answering genuine questions.
@@BerkleyBuilds I've just measured my rafters, they are only 3inch (76mm) in depth. What thickness of cleotex do you recommend and how much gap should I leave?
@@MrAppukuttan93 you should have a minimum of 50mm air gap above the Celotex else you risk creating condensation. This leaves you with 25mm available for Celotex between the rafters, you could leave it like that however this wouldn’t offer much performance.
If budget allows you could increase the performance by adding Celotex under the rafters (I’d suggest 50mm or 75mm and foil tape. Or even one layer of multi foil). Fix the Celotex over the rafters with screws and penny washers or staple the multi foil.
You are only upgrading the insulation so you don’t have to achieve the same standard as the regs, do as your budget allows.
All the best, Ben
I have an existing loft converted bungalow that I’m moving into. No insulation above plasterboard in upper rooms. Does anyone have advice on the minimum thickness of Celotex (foam taped edges). I haven’t much room to play with, so don’t want to intrude into the rooms too much.
How much headroom do you have to play with? 175mm celotex is the minimum you need however, some of that could potentially go between the rafters.
I would probably suggest doing two applications of multi foil and counter batten, this should give you the lowest profile.
Thanks for the quick response. I was intending to avoid film due to its ability to block radio waves. I am going to insulate between rafters (leaving 50mm gap) but didn’t want to go further as this is an existing build. I’ll know more in a couple of weeks when I have the keys, so I’m sure I’ll be back in touch. Thanks again
@@mickelmcc I’m intrigued, why do you care that it blocks radio waves, are you a radio amateur?
Look forward to hearing from you when you have the keys.
If you need more specific advice or support during your project, i run a company called ProjectWise which specialises in supporting self-builders and homeowners throughout their build. Check out how we can support you at beprojectwise.co.uk
Can you use 90mm celotex with a 10mm residual gap
You must leave a minimum air gap of 25mm above the Celotex. I suggest attaching any additional Celotex that is required to the underside of the rafter, counter batten, then plasterboard.
Sorry I meant in the cavity
@@dominictinsley2565 I assume your cavity is only 100mm? The latest regs call for 150mm cavity, it’s possible to do a 100mm but you’d lose space internally due to needing additional insulated backed plasterboard.
You can have a fully filled cavity, double check manufacturers spec/detail for best installation practices to prevent any moisture build up.
Hi can I use 100mmm pir boards instead of rockwall to insulation the loft? Floor
Hi Philip. It’s not cost effective enough to use PIR than loft roll. Is the loft space a cold void or is it a habitable room?
@@BerkleyBuilds thanks for the reply. After doing the maths I would agree with you. What's the best system for boarding out the loft with squash loft rool please? 😊
Using pir was around £700 more. 😂
@@philipsawyers719 if you want to board your loft and have loft insulation already down, your boards must not squash the insulation else it loses its thermal efficiency. Ensure your boards are raised about the insulation by either having the boards rest on stilts or fit larger joists along side the existing.
Does a back door need to be specific...ie only x amount of glass for neighbours privacy etc....?
Thanks for the question Wormwood.
Although that question is one for your local planning department as that requirement isn’t covered under the building regulations. Sorry, my knowledge is in building regs and not local planning policy.
In terms of buildings regs an external door does have to meet certain requirements. A new door must reach a specific U-value depending on how much glazing is installed, have a robust locking system and have toughened glass should it be glazed.
@@BerkleyBuilds thanks for feedback. So if all was well with u value and toughen glass,etc, it would be ok generally to have a full glass door.. as my kitchen is very dark and I would love some extra light to come in?
@@wormwood6424I can understand what you’re trying to achieve and it would bring in a lot of light into your kitchen however, as planning policy isn’t my specialty I couldn’t say for certain it was ok. I recommend you ring your local planning department and enquire, I don’t see them having too much of an issue. They may ask you to use obscure glass.
All the best. Ben
Next edition regs will call for the whole roof void and the second floor to both be packed full with insulation material, habitable occupation to be on the ground floor only!
You’re probably not far off with that prediction.
@@BerkleyBuilds Hahaha, yes indeed.
What installion do you need now when you have bedroom over a garage.
If you’ve fitted your installation and foil tapped it, then you can install your plasterboard
I was thinking installing rock wool or similar for the installation, taking the old plaster board down, what installion needs to be put in 150 or 200, has the timbers are 8x2.
@@garypritchard865 to put rock wool in a roof void you need 300-400mm if it’s a cold roof space but you shouldn’t use rock wool for a vaulted ceiling, that should be a rigid PIR board (125mm between the rafters with 50mm under).
It's a room over a garage that's needed installation underneath.
Hi,
My building control advised that 150mm floor insulation could be
either polystyrene or celotex . I understand that celotex is better though more expensive ,but how much of a difference will that really make in terms of heat transfer?
That’s correct, floor insulation can be Celotex or Polystyrene (jablite). Celotex is better due to its density, with that said you typically need more polystyrene to equal the performance of Celotex.
For example if Celotex was 150mm you’d need 200mm polystyrene to achieve the same thermal performance.
@@BerkleyBuilds thank you for your reply .
I asked because the way BC said was whatever I decided , as long it was 150mm. Surely Jablight may not achieve the required R value. Perhaps they aren't strict in my area. After all , till recently, the requirements were 100mm of Jablight . Or 100mm PIR.
Thanks again .
@@July-A7 because Celotex is a higher performing product they don’t achieve the same R value when compared at the same thickness, polystyrene always needs to be thicker to achieve the same performance.
Before the regs changed in June 2022 you could use 100mm celotex or 150mm polystyrene however, since that change the values have increased meaning 150mm celotex or 200mm polystyrene is now required as a minimum standard.
I would suggest using a celotex type product as it’s a better product
@@BerkleyBuilds thanks again. I already used Celotex , just that BC wasn't quite right and your useful video prompted me to raise this question with you.
@@July-A7 pleased I was able to help. I wish you the best with your project.
I'm confused, how come these numbers don't match the notional dwelling in table 1.1?
Are you using "Limiting U-values for new fabric elements in existing dwellings"?
The majority of my audience isn’t technical and I can’t expect them to understand or interpret the building regulations. I’ve broken it down into a format they can understand.
The depths of insulation noted are what is typical for compliance under the June 2022 changes however, this video does not guarantee compliance. I created the video to help people have a better understanding. It’s the responsibility of the homeowner to prove compliance with there chosen building control provider.
Why is rigid insulation board so expensive?
A very good question! I would say greed
What is the building requirements for loft insulation
For loft insulation the minimum requirement is 300mm.
surely the minimum requirement is the U value? not necessarily the thickness, which depends on the type of insulation you use to achieve U value.
@@webcore2 yes, you’re right the minimum requirement is the U.value. However, an easier why for people to understand and quantify the U.value is to talk in insulation thicknesses. A U-value number means nothing to most people so I was trying to present it in a way people would understand.
I'm not a builder but wanting to understand more about what's possible. I moved into a 1960/70s Dormer bungalow (with a pitched roof and flat roof dormer addition) back in October 22 and couldn't get the place warm. I recently found out that there is rockwall insulation in the roof cavity and the walls are insulated. I am considering topping up the insulation by having insulation put between the rafters in the areas that the rockwall isn't ie over the stairs by having the roof tiles removed. Is this a good idea and what should I be aware of before I agree to the work?
Excellent question… how much time do you have. I always say everything in construction is possible with enough money and time so it depends how far you want to take your upgrade.
Increasing your loft insulation with rockwool is a wise move, as it’s a cheap upgrade and by doing this you don’t need building control.
Consider a few things:
1. if you plan on doing any additional work in the near future for example, an extension or first floor addition. Then adding insulation now might not be worth it if it’s going to get ripped out later.
2. Don’t get over excited and pack the roof to the brim with insulation. The roof void in your attic will be vented, most likely through the eaves or soffit, ensure your tradesman leave an air gap (50mm-75mm) around the edges so air can flow. Else condensation will build up
3. if you have a loft hatch to enter the loft, that’ll be easier than taking tiles off the roof to create an opening.
4. Consider upgrading your windows and doors as a lot of heat loss occurs here.
5. Going a bit further you could investigate how much insulation your dormer walls and roof have, upgrading if required but this is a larger job and would need building control.
I hope that was helpful. If you need more support check out beprojectwise.co.uk to learn how I can support you further.
Thanks, Ben
@@BerkleyBuilds Thanks Ben - The Dormer is a bungalow conversion done some time ago, which is why, as far as I'm aware I don't have insulation above the stairs but only in the roof void where the access hobbit doors are fitted. I have already replaced windows and the door will be the last job after all the trades have finished. I may have to have the flat roof on the dormer replaced soon so will look into making sure there is enough insulation fitted in that space at the same time.
I wonder if in China and India they demand this.
I doubt it! but that’s a different issue and I don’t make policy. I’m purely here to help you understand the current regs
@@BerkleyBuilds,No problem, thank you for your help.
I live in China and it's the wild west, they still build with bamboo and rope as scaffolding and you can pretty much build with what ever you want inside.
good video but volume is low
Thanks I appreciate the feedback. I’ll keep an eye on that during editing in the future.
Jesus... This applies for an annex as well I assume? That's crazy.
Correct, this would include an annex as it’s a dwelling and a habitable space.
@@BerkleyBuilds god damn, I don't think I've seen a garden room or annex company on the market that are even close to that. Most use 100 rockwool.
@@RollCorruption i assume those companies would aim to be within the requirements of an exempt structure which doesn’t need building control.
@@BerkleyBuilds true but the moment you put a soil pipe in the bc would be needed right? and all of them advertise wc's and ensuites etc.
@@RollCorruption yes, installing new drainage falls under building control.
1:07 mins, why the heck would anyone need a dpm on a suspended cross ventilated floor?
A good question!
Approved Documents C calls for it, to prevent the passage of moisture going up into the building. AD C 4.17
The beams also sit on a 4’” DPM to prevent them from coming in contact with moisture. In addition to the DPM you refer to there is a second layer on top of the insulation however, this is there to separate the concrete/screed from the insulation so they don’t react causing deterioration.
I hope that answers your question.
@@BerkleyBuilds I reckon it will be to 'cover' the current trend of building new dwelling developments on topographically obvious former flood plains........ and on former brown field sites too, which were themselves often former reclaimed boggy land or salt Marsh. Ah, the healthy selubrious airs of a former chemical plant and abbatoir.
There is a point where the shear extent of dpc coverage on the 'undersides' converts a structure from being defined as a "dwelling" into being classed as a "boat or vessel" instead, hahaha, which will then dictate the fitting of navigation lights and an anchor handling system, hahaha.
@@onanysundrymule3144 I love your imagination. I’m not sure it’ll get that bad, in my opinion regulations are brought in for one of three reasons.#1 health and safety of occupants #2 to limits insurance claims #3 meet government goals for energy efficiency and lower carbon footprint
Return on investment for a larger property is diminishing returns. In business you look at a return or something like 5 years at the most as being a worth while investment., Some of these are 15 - 20,
Sadly I don’t set the regulations
@@BerkleyBuilds I appreciate that. Its just that the 15 year mark would never be considered viable for anything other than major government projects. These decisions are inflicting costs on many who cant really afford it (in terms of small extensions etc.) Im researching to update my property so slightly different and because its old and the design is prohibitive Ill have to use what I can make fit anyway; may be more mix and match depending on where its needed. Otherwise very informative and succinct vid.
@@BerkleyBuilds my new place is 3 bricks thick solid wall with no cavity and no loft insulation and solid floors. The previous owner had a massive Oil boiler. Definately kept it warm but not hard to make meaningful improvements without breaking the bank.
@@richzxc99 I agree, the government hasn’t considered how this actually affects people. In your situation I’d suggest consulting with an architect as they’ll be best placed to assist in recommending products specific to your needs. Thank you for the feedback, all the best with your research and project.
@@BerkleyBuilds no architect needed. Its a function of how much room Im able (configuration dependant) or willing to loose.
Not a single mention of the need for controlling passive convective losses which account for 5x more heat loss than conduction.
Anyone retro-fitting their home should:
1. Remove all old insulation from attic.
2. Install Mechanical Ventilation w/Heat Recovery (MVHR)
3. Seal all air-gaps in ceilings (cold-attic floor) including capping & air-sealing all downlighters. Install ventilation-maintaining cards at attic edge to wall plate, then sprayfoam at 25mm across attic floor, useful tool to achieve an airseal in a renovation (as opposed to new-build).
4. Where cabling and plumbing prevent clean installation of insulation bat, use blown cellulose to 400mm to re-insulate attic. The barriers installed earlier with sprayfoam prevent the blown material entering soffit.
5. Target windows /doors next: Ensure they get properly pinned-in, foamed with an ‘air-sealing’ (as opposed to gap-filling) foam, then use airtight tape around internal reveals to seal between window frame & reveals. Tape should only be applied to a smooth substrate so skim rough brick /blockwork first.
Insulate reveals with drylining.
6. Treat wall cavities with BASF CV100 -provides massive U value improvement while eliminating air flow in the cavity which, typically, enters ceiling spaces. (Have a block tested for Mica /Pyrite first as filling the cavity could activate dormant block issues)
…Finally, have a door blower test to check airtightness after all measures are complete to see whether you’re Air to Water compatible.
In any event, above measures will transform your home.
Hi Greg, you mentioned some useful information however, that’s not what this video was for. My video was aimed at builders and homeowners who are building extensions and needed to know how much insulation was needed for their new construction elements, in respect of the change in the building regulation in June 2022 as per Approved Document L volume 1.