Insulating between and under the rafters for a loft conversion
HTML-код
- Опубликовано: 16 фев 2023
- How to insulate correctly for a "cold roof" loft conversion using between the rafter insulation and below the rafter insulation to UK regulations.
Also check out the other Robin @ukconstruction who has done an amazing video showing how he installs cold roof insulation. I highly recommend it! • How to fit insulation ...
Don't miss any loft conversion videos by subscribing to the channel now: ruclips.net/user/RobindeJongh...
Get my free timber reference tables:
www.subscribepage.com/timber-...
Get my loft conversion assessment for your home:
geni.us/loftsurvey 
Наука
I am loving these videos, it's like you've been to my house and perfectly modelled my attic and then told me step by step how to do what I am thinking for the attic conversion
Thanks Robin. These videos are super clear and helpful. I'm planning a potential loft conversion and while I'll probably be getting someone in to do it this really helps me understand the potential approaches and pitfalls better. Much appreciated!
Hi robin
We are a loft conversion company based in cork ireland
We do exact same as you outlined but put 50by 44 mm timber onto existing truss next to new 150mm by 44mm new rafter c24 that fills infill then we use intello plus vapour membrane wrapping all joists then a 62.5 mm phenolic slab underneath with venting and new airtight boxes for recess lights and all cables and intrusions sealed and taped with vario tape
Love your videos
Willie
Thanks Willie - appreciate your comment and thanks for watching! 👍
Hi William, do the 50mm battons get attached directly onto the rafter or are they counter battoned?
Thanks Robin, great video. I'm about to do this myself. I'm planning to use the removed truss timbers to increase the depth of the rafters and avoid having a step in the rafters for max insulation efficiency
thanks Robin. Always trustworthy and knowledgable 1st rate information.
This is very interesting and I will hopefully be putting this great information to help in our next house purchase. Thanks for sharing.
As always, very detailed and thoroughly explained. Thank you.
Thanks Liam!
Informative thanks. In my experience it’s more economical to use one thicker sheet of PIR between the rafters than two thinner and either notch out the back around the original rafter of fill the void with a strip of PIR and foil/aluminium tape the joint! It’s prob worth, or may be mandated, to fit a vapour barrier sheet before over boarding with plasterboard (insulated or not depending if additional insulation is required) but if it’s a low occupancy area it shouldn’t be needed.
I have found this very informative. Thank you
The initial comment about the airflow is slightly 'wrong' in that the airflow should be exiting at the apex / ridge line through a suitable breather. All the moisture will aggregate at the apex.
There are a number of technical seminars by Dr Joe Lstiburek that cover the multiple issue we all encounter with modern building efficiency needs. well worth a watch.
Wow thank you, extremely helpful
Hi Robin, are you able to do a video for vaulting a bungalow ceiling. I believe our roof structure is a purlin roof, but planning to do as much of the work myself. I’m a carpenter by trade but roofing isn’t my forte so just trying to get as much info before the structural calculations come back from our structural engineer
Hi robin, you added the stud wall on either side, how far apart can these vertical members be without affecting the structure? Also I am part way through a build, the builders have put steels in instead of a flitch beam, how does one attach the bottom plate of the stud wall to the steel?
Wanting to maximize the space under the eaves for both storage and clothing cupboards
Great video, clear audio and drawings. How would the brick gable end wall be included in the insulation? Im aware of a parge coat to help AT, but could this be internally insulated with the PIR also? What if there was EWI in the picture? Worth insulating both sides?
Nice one Robin, I do wonder about using 2x 50mm PIR, so the lower board undercovers the existing rafters, may be?
will still need access outside to fit vented soffits & possibly vented ridge tiles, what about rebating the PIR to get over the step in the timbers?,
my roof has already been compromised back in the 50's when they changed from slate to redland 49's
Great Video as usual
My advice is to counter batten the roof, the allows for full depth of Joist to be filled with Insulation
Air gap above Joist
Its a bullet proof system and makes felting really easy during windy weather
You buy a special vent strip which is rated to support the first row of tiles or slates, also means no vents in the soffit
Some House Designs are now without a Soffit
Don’t suppose you have channel to show what you mean 😏 🤷🏻♂️
Sorry mate
Do a Google search
What's the vent strip called? Presumably, it vents at the top via a dry ridge system?
Great vid again. Done one loft with 100mm insulation between the rafters and then superquilt over to stop cold bridging, nightmare to put up. Usually my norm is 100mm between then 25mm over rafters, foil taped then PB. Been advised by my SAP guy to use the insulated PB on my next build.
Thanks! Good to have your take on it. What reason did your sap guy give for the insulated pb?
@@RobindeJongh I’ll be insulating a listing building next, the general convenience of it being one unit oppose to fixing insulation and then PB i suppose.
As an Architectural Consultant, I was always taught by my peers to avoid insulated plasterboard because as soon as you penetrate it for services i.e. lights, sockets - you are cutting into the VCL and creating a cold bridge at that point making it more prone to IC. But I'm based on Scotland, so maybe it's not really an issue down south.
As someone in the process of insulating exactly this right now, having had a building company do the structural work. As per a conversation with the guy from building control; I'm using two separate sheets of PIR to make up the 100mm rather notching out a 100mm sheet, using Gapotape to eliminate the gaps, then aluminium taping to bridge over the rafter, then will foil quilt over it all, before battening and plasterboarding.
Knowing what I know now, and if it's a structurally sound idea, I'd have asked the building company to alternate the new rafters, so that every other sheet could have been one 100mm PIR sheet, with nothing fancy to do to it. Would save me a lot of time!
You can't "alternate every other rafter". They're put in at 400 or 600c/c, and that is the distance your tiling battens have to span
But surely the tiling battens are still resting on the original rafters? @@Tom_Hadler
Great video, Robin. Where does the vapor barrier go ?
Hi Robin, I'm converting my loft right now and I'm in the stage of insulation. The recommendation from the building regs is 100mm +50mm PIR. then plaster board , all counter batten with 50mm Batten to the non breathable felt to allow roof ventilation. All to achieve 0.15 U-value
I'm trying to achieve the same U value for less thickness in order not to lose head hight.
I heard that I can mix PIR with superquilt, but don't know how?.
Also , I would like to have your view regarding the side wall insulation (it is a cavity wall ). Thanks for your videos , it was really inspiring
How did it go?
Interesting video, thanks. I’ve just bought an old barn conversion with 9” solid walls. Struggling to find any consistency online about how to insulate solid walls from the inside without risk of internal damp and condensation. Would love to see a video on this and/or any advice! Cheers 👍
I agree, details are hard to find. It is because condensation is going to happen, and no-one wants to be held liable!
Hemp slabs, or hemp+lime mix, or rockwool with lime plaster on lathe? That is for unusual solutions ^^ anything breathable I would thibk
Great video. The requirement to stiffen the rafters caught me off guard. I’m looking into a 60-80mm wood fibre insulation which doubles as a sarking board (Gutex) for a warm roof retrofit on a dormer bungalow. The mass works out at 15.4kg per m2. Do you think I need to budget for doubling up rafters?
Hi Gavin. I would budget for doubling up rafters or adding extra rafter depth.
Could you not just put an additional rafter on top of the original one to get a say 200mm of depth and fit 170mm celotex board. You could then overboard the rafters with more celotex and plasterboard.
Loving the content. Blows my mind at times listening to you quoting regulations.
You would be losing a lot of headroom .
What would you do on the purlin section?
I've just finished insulating upstairs in a dormer bungalow. BCO asked me to put 3x2 on the underside of each rafters bringing them from ~80mm to ~150mm and then 100mm PIR between and 25mm underneath. This left an airgap of 50mm under the tiles.
I never even considered the structural side, do you think that would be a problem just adding the timber on the underside of the rafters? The BCO did not say anything either. The 2.4m length 3x2s were just enough to go from the dwarf walls to beyond the flat ceiling level
Are they still up ok? I'm intending to do the same thing, so am hoping it all worked out for you 8 months ago :)
Hi, I'm trying to work out how much insulation I would need in my rafters for my house, I'm putting a small playroom in the loft in our extension and I've put 100mm between the rafters and wanted to put 25mm plus plasterboard over the top to stop the cold bridging, hoping that is OK as that is the insulation I've already got! Also how does the ventilation work when you have the wood top and bottom of the velux window? Wondering how the air moves above the velux as its been sealed by the noggin?
Hi James. Fair point. You would need to ask a joiner.
Couple of thoughts. 1. Extend the rafter depth to keep things aligned. 2. Superfoil quilt. I'm going down the superfoil quilt route, it's easier to work, more airtight, thinner and cheaper for the same performance.
Thanks for the tips Darren! I'll take a look at Superfoil.
Just an FYI, but I've experienced Building Control not being keen on superfoil as an alternative. It is easier and better for DIY work, but the performance figures aren't the same as PIR. I do welcome any info you have 👍
@@bikerchrisukk Thanks for the tip. My approach was going to be 1 layer, see how warm it feels, then more than likely do a 2nd layer. I'm converting the attic bit by bit and the initial stage is to make it into a warm storage space with intentions one day I might go all in and make it a habitable space
@@sygad1 You are welcome, you might want to get a thermometer/hydrometer that can record the temp/humidity difference after you've done a bit of it. Govee models are good but price has hiked lately, I got 2 for £35 once. Good luck 👍
We put Actis hybris between rafters , then super-quilt over the top , one thing I can say it’s extremely hot up there .
Hi Robin. This series is very informative. Will there be a dormer video?
Hi Ian. I’m planning a dormer video soon, all being well 👍🏻
Is there any reason you cannot just screw a 2x2 inch rafter to the face of the existing 4x2 rafter? That would give the same gap available for insulation at considerably lower cost?
So a quick question, the insulation you have there is foiled/non breathable, wouldn't it be a better idea to use rockwool slabs for improved moisture control?
The idea is that there is an air gap above the insulation for air to travel and take the moisture away.
HI Robyn, great video. Quick question. What software are you using? Revit? or sketchup? Thanks
Well, Autodesk is the Evil Empire and Revit is the death star...
What happens with humidity in the insulation? Is some membrane material needed to control humidity and also air-tightness?
PIR/PUR board is foil backed on both sides. Self adhesive aluminium tape can be used to bridge any gaps.
For the PIR between rafters I'd probably just do as you said & put in a full thickness strip first (new rafter one side & old rafter on other) & I'd also buy some sheets of PIR at the correct thickness needed to fill in the strips over the top old rafters, which could quickly be cut to width & tapped in.
Other more faffy way would be to cut other PIR to fit the full width (new rafter to new rafter) including over the top of old rafter but then cut out material on the back of the PIR where the old rafter will be so that it slots into place over it if that makes any sense. Bit messy though & would create more waste.
I was thinking this , like multi tool out each one or template with a circular saw wouldn’t take too long once set up
@@seanmichaelo9777 I've used both & found multi-tools only good for cutting out small complicated shapes up to say a foot long as they just take to long on longer/deeper cuts, even if you get a "proper insulation cutting blade" which I think are a waste of money & don't work personally. Circular saws definitely do work & are fast but just be prepared for a lot of mess (definitely connect to a vac if pos), again I've seen special insulation blades available that claim not to make a mess but they were VERY expensive & are like hens teeth to get hold of. I think Ive seen people DIY their own circular saw insulation blades by grinding them down but I've never found the time to try it out myself 👍
Can airtight membrane be used with this insulation?
Hi Robin, can you share what CAD program (AutoCAD?), plugin and version, graphics etc you are running?
It's sketchup
Thanks, now got free Sketchup, and just have to work out how to use it @@Tom_Hadler For anyone who needs non straight stairs, Pearstairs in Wales have a fantastic free CAD you can use to create the right design staircase. I needed one winding turn, one 1/4 landing in a 6ft 6inch length space, so 3 directions of stair to the attic. Without their amazing CAD I would never have managed to design my stairs, with one width lower down and then wider after the 1/4 landing to reach the wall at the end over a doorway. When the local joiner came to quote, he said "it's the only design that would have fitted". It's now in and being used, now just need to build the room up there.
Hi Robin, is it possible to glue and screw some C24 to the underside of the rafters to increase the depth. So sister but in depth not width. Would it be permitted? Thx
Sure, that could work. Glue would need to last for the duration of the lifetime of the building though.
@@RobindeJonghThanks.
What if there are no dedicated eves vents(old house)? Is it still acceptable to insulate between rafters like this, or will it cause condensation issues?
In my old house I can see flashes of daylight between the bargeboards and the tiles, so no extra ventilation needed, are you sure yours is sealed?
@@jesshothersall There is no bargeboard, it's a terrace.
What U value do 100mm give you ? In this please
Gluing and screwing timber to the existing rafters to increase depth is also a thing rather than adding additional rafters.
Thank goodness for that, saves a fortune in wasted wood!
If its structural, do you think this would be OK to do?
Why haven’t you included a vapour barrier?
Vapour barrier ?
why not use multi foil and insulated plaster board rather than the extra rafters. So 50mm pir plus multi foil plus insulated plaster board
Robin another great video. Would you be able to comment on how to detail the insulation around exposed beams in an older property?
Thanks!
Scott
The thickness Robin is suggesting here are ideal requirements, not cast in stone law. Just put the requirement depth insulation in where you can and leave the beams as a feature. The beams have there own U value also.
@@alabinibop Thanks for the reply. That was my planned approach - just not sure how this would need to be conveyed to building control.
@@scottvirgogp suggest that you are looking to retain some of the existing character. That's a sticky wicket for them and they should accommodate it.
I've seen lads using foam filler on all the little gaps.
You could of used SF60 and strapped over before putting plasterboard on and saved yourself a fortune got a higher U value
Just put in 50 to 100 mill in between and anoter 50 to 100 mill across with a 3x1 then you have space for wires etc and no gaps foil tape the joints better job if you can lose the 20 mill
Thanks Matt. What do you mean by the "20 mill"?
(50mm) 2 inch air gap sounds excessive.
True.
Just get bigger roof joists
How did the human race ever survive before insulation? The mind boggles..
Smaller rooms!
They still do. In places like Mexico, during the Winter the internal temperature can drop to around 5C. Solid concrete/brick buildings with no insulation and lots of ventilation. They put up with it.
They still do in the UK!
House back then had plenty ventilation with it blowing through house
Sweat n shiver