Insulating Between & Under Rafters | Loft Conversion Project 4.0
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- čas přidán 20. 08. 2024
- Time to get the insulation finished and get this place warm! Check out our 'How To' video at the link below.
• How to Cut and Fit Ins...
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Ok. So I am a Brit. Long time living in US. Damn I finally found a truly SENSIBLE fantastic Tutorial. I just rushedly posted this Video on my FB page as I don't want to take a chance on losing it. I didn't understand one bit about making a payment to any Content maker on FB but because of how truly wonderful this guy explains things I searched and left a much much deserved Thankyou Donation. I love that I am able to do that from a 63 year old Female Cockney Transplant to be able to see and learn from a great Brit and show my appreciation. Because honestly his video made me feel a total SIGH OF RELIEF because I feel it so makes sense and I can do this.
Yay
A handy tip to avoid the time wasted on trying to refit the insulation boards that fell out over the two year gap. If you know the insulation boards are going to be left unfinished for some time, run duct tape across the rafters and the face of the boards, then use a staple gun to affix the tape more securely, as it won't stick very well to the wood, and will dry out and fall off after a while. This will hold everything snugly in place! :)
I was thinking Liquid Nails would hold it in.
Brilliant tip. Thanks.
PtolemyauletesXII temporarily just nail a couple of tile battens over it but don’t hit the nails right in
So much quicker to drill in 40mm galvanised steel screws down both sides of all the rafters first so they project out 20mm from the rafter face, spaced at 400mm centres and 60mm in from the face of felt. Then cut your PIR board to size and simply push it into place onto the projecting screw heads resulting in a mechanical friction fit where the sides can then be filled with foam.
Gapo tape is what you need.
Top job. Fitting all of that insulation looks weirdly satisfying!
Top tip for avoiding the shoulder breaking work of sawing that stuff, and having to wear respirators... soft material jigsaw blades... ZERO dust.
Dear Ben Clarkson, some people use Rockwool. Is that fine or is that bad?
@@alikhan7903 Bad, and most probably against regulations
Ben Clarkson amazing tip thank you! I’d never heard of these but they cut the dust by 99%
Alu foil tape best
Nicely done and a great video. We’ve just moved to a 50s bungalow that needs a full refurb and your channel is packed with valuable tips, thank you
Who are these people who thump this job down ,it's a great gob done by to people who are bettering there home and family, keep up the good work
The dead man I think they are called is a one handed prop used for plasterboard or sheets really handy when working alone. This is what I used to use in my business , and at home renovating a derelict 1930s house . Great job . Nice to achieve something 👍🏻
you must seal all the joints/ screw holes in the insulation with foil tape. water vapour will condense in the colder joints, possibly giving mouldy ceilings
It’s a good video, cut and fitted same as what I’ve done a few times but just nearly 3 years later and a newer system is coming in of spraying a polyeurothene coating like expanding foam, it saves all that time cutting it in although often needs trimming up, it’s the same as these boards but just sprayed in
That's been around for years lad
Mohammed Muhammed depends what country, it may have been here🇬🇧 for years but small companies have only been more commonly using it in the last few years
Is that more pricey?
@@scorpionnetherrealm8937 not sure, I haven’t had a quote yet but know from cutting and fitting standard board into rafters that weren’t perfectly straight, it was very time consuming and dusty
I prefer Good quality Rockwool above my Head not least because Grenville fire was this same type Eurathane insulation.
I've used loads of cellotex in my house and took the offcuts outside and tried to burn them on a bonfire...they will NOT burn without a lot of effort trust me...that stuff on that tower must have been an older combustible type..not this stuff.
love the bit at 2.50 wifey trying to fit bit - hubby has to finish it lol
pro tip : you can watch series on kaldroStream. Been using them for watching loads of movies these days.
@Will Mohammed yea, have been watching on Kaldrostream for months myself :)
Enjoy all of that condensation slowly destroying the rafters.
Do you have any underroof? What about potential leaking? How do you keep the distance for air flow on the back of the insulation.
Very informative video. Thanks for sharing 👍
Why didn't you insulate down to the lower ends of the roof (leaving space for the soffits)? We have very similar houses construction wise and I am insulating between and over the rafters down to the far sides rather than just insulating the 'room'. The reason is because as we have insulation between the loft floor joists going all the way to the ends of each side (where the roof meets the floor joists (leaving air gaps), we found the temp difference was quite a bit, so much so that as the hot air went up into the cool loft (prior to roof insulation) it would condence and cause issues, so we insulated all the way down or we would still have the same issue in the roof voids. Hope that makes sense! Love to hear your thoughts.
Looks good!
I was advised to lease a 50mm air gap athe the back of the insulation to allow air flow and prevent condensation.
Did you leave a gap?
Yes that’s important. 50mm between insulation and slates. Hence why the rafters were extended. 👍
If that stuff dont give you cancer .i dont know whats in it.. but its in the top three of the worst jobs in the building trade. I hate it.
@@TheRestorationCouple - looking at following your exact process for my re-fit - but I've seen recommendations of using a vapour barrier also - did you use any barrier system (i can't see it on the vids) if not, why not?
@@markwilson2991 Yes vapour barrier in this case was the foil of the boards which was taped.
@@TheRestorationCouple many thanks!!! keep up the great work....I think a knighthood is in the offing - for Services to Renovation and Lockdown Sanity
Seems like a lot of work! You can achieve better results with sprayed closed cell foam insulation. Then if you want to achieve a thermal barrier over the studs put half inch over your inside wall like you did. Won't have to put it off for a few years.
... and when we need to re roof the house next year?
The Restoration Couple Re roof...you mean taking off the roof's wood sheathing. Well of course that would be problematic. I thought you meant the the water proof sheathing which wouldn't be a problem. Oh well different approach to fixing a roof.
Yeah, here in the UK the normal roof constructions are natural slate or tile on timber battens, no sheathing/ply type covering. Therefore all slates would be a nightmare to remove and unable to be reused plus less companies about dealing with sprayed foam than is the US. Assuming that's where you are? Anyway, the place is warm now so all ended well. :-)
The Restoration Couple very interesting about roof construction methods in the UK. Thanks for the info! Actually, I am in US Florida. Timber frame homes not many very expensive. Stick frame and truss for roof with plywood sheathing over here and in Canada too. South Florida concrete block wall with wood roof truss.
Great video!! in hot climates, would you have the foil side facing out towards the sky? My guess is yes, I live in the desert and that' s what makes sense to me. Please confirm. (I would obviously leave air gap for moisture prevention) (rafter install)
We used Incombustible Kingspan Kooltherm .........its 3 times the price but well worth the Peace of Mind.........100mm......roof And walls about £2,000 for 3 bedroom semi.
So much quicker to drill in 40mm galvanised steel screws down both sides of all the rafters first so they project out 20mm from the rafter face, spaced at 400mm centres and 60mm in from the face of felt. Then cut your PIR board to size and simply push it into place onto the projecting screw heads resulting in a mechanical friction fit where the sides can then be filled with foam, and overboarded with additional PIR insulation or plasterboard if required. You would be hours trying to shave down one piece of PIR insulation like you did to make a section of board naturally friction fit between the rafters without the aid of mechanical fixings i.e. screws!
Like the video Did you not consider using superquilt ? Good U value and finishing thickness so you can maximize space
The best way is to run an expanding foam between the edges of the insulation boards, this eliminates cold bridging. Cold bridging will still happen, even if you stagger your insulation/ plaster boards.
ha? you care giving us more insight plz ? thx
@@ioncv5295 if you use a expanding foam such as insta stik between the Kingspan boards it fills the gap, therefore cold air can't pass through, therefore stopping cold bridging as the gap is insulated as well, also good for a vapour barrier.
Quick question regarding this, I’m about to do this in my loft and insulate between rafters ect, have you got any ventilation implemented on the roof to stop it sweating behind the insulation and consequently start to cause problems with the rafters ?? I’m thinking about putting some slate vents in the roof but just wondering if you have had any issues. Does the vapour taping stop this ? Reluctant to start and then it cause issues you know. Thanks liam
I have a little opinion on this I live in a climate that had 11m of snow fall over the winter and in summer is up too the mid 30s and sometimes hotter to stop this we insulate the out side and only the habitable space by this I mean when we make a roof you see the rafter and close boarding then there is a vapour barrier insulation then a trepizoidal shape timber then a thick water barrier then a batton cross batton then a tile! It looks good as tou can see your rafter and don't lose space I guess only good if you need a new roof!
That'll work! Must have cost a small fortune for that insulation - it's the best stuff.
Fortunately we have a company here selling seconds and returns from building sites so we saved well over 50%. Won't be many years before it pays for itself considering it was just lath and plaster there before!
Good stuff, decent content
The Restoration Couple whats the brand of the two insulations you Used?
I Build It Home gghbn
The Restoration Couple is its seconds and co.? When i costed it there wasnt a huge difference between that and insulation for less for exampleo
Es
this work as insulatin and sound cover. is very nice product.
Excellent work...and quite thorough!
Condense? 2 X damp foil -> moist Inbetween?
Hi! Good comprehensive video. Thank you! Is installing double insulation (10 cm and then 5 cm necessary? When you convert your loft, would this insulation go to waste? My loft has the old wool type insulation. It retains a lot of dust. Is it worth replacing?
Would love to know the answer to this too!
more insulation is always better, as long as you have good air flow to stop condensation.
Thanks!
Are you going to install a vapour barrier, or use the foil of the insulation boards?
7:05
Would it not make sense to take advantage of the space below the perlin? Would make a good storage space, that's a large volume of space not used.
Were the eaves of the roof open to air? I ask because in my roof they are and thus I guess if I put up a small knee wall and insulate leaving air gap I should be ok?
Great video. Thanks for sharing.
That looks like it would be roastie-toastie.
Excellent job
You’re the man!
It's here!
Nice job.
George Groves got a new job?
By insulating like that -- and not trying to be a wet blanket, just pointing out something that concerns me -- if a hole in the roof develops, where does the water go? Does this exacerbate the water damage (mold, rot, etc.) that would occur?
Good question. I'm looking for a water absorbent polypropylene membrane that I can staple on the outside face of the insulation. This will absorb small amounts of water and this can evaporate later into the air gap. Haven't found anyone who will sell me 150m2 or so yet.
Great job for that time. Little concerned about air flow though
Watch the latest video. 👍
@@TheRestorationCouple - Im interested in this comment - which video do i need to watch? Thanks - Great work
very good video good information
Thank you for the helpfull video
You mentioned a warm roof system and I am looking to attempt to retrofit this as I'm getting the entire roof redone. Could you advise how this is done? Useful material?
Great video - is your loft vented or unvented? We want to do something similar but the roof in our hold house is unvented and can't find a clear answer on whether rigid foam will cause moisture issues...
The loft is ventilated via the eaves!
Hi, I haven’t been able to find the answer to this question anywhere...
Polyiso foam board with the recycled paper/fiberglass outer coating... Is it toxic?? Using it in a van build, but it makes me nervous.
Thank you.
I can’t imagine it would be a problem, especially by the time you have any vapour barrier and panelling up.
The Restoration Couple Thank you so much.
Nice vid. Really looking forward to your workshop build. If you have any sketchup plans or thoughts on materials or size, pitched/flat roof, Id be really interested to see a vid on that, even if you are a while away from starting.
Will try and get round to a video soon. Project on hold due to budget and apparently "not a priority". 😔 got plans and sketchup done though.
well, you do have quite a few projects on the go so I can see Restoration Wife's reasoning hehe but yes, you're dropped a few hints about it and got a taster from your garage to office project in your last house, so would be fab to see those plans even if it doesn't get built for another year or two! :D
It looks like you left a air gap/space between the underside of the room and the insulation. How did you vent the air from the top of the attic?
yes this i want to know. Where is the breathable roofing felt? Are there air gaps in the soffits? Can ventilation flow (prevailing wind side) through soffits and slates up to ridge board and then down other side of roof?
Hi very useful. I am looking to install 75mm kings span to my loft. Please advise what fixing shall I use.
Also I am installing the sound proof insulation to wall what fixing shall I use for this to hang insulation with the wall.
You mentioned foil tape. I am guessing you are going to use it later? Was looking forward to seeing you do it.
Foil tape to do seams before plasterboard. More detail in a video a couple weeks back in teh garage conversion.
I have been watching you channel for some time and it is amazing, really interesting, informative and inspiring. I have a 1930's house which which we have refurbished and is still a work in progress. The house does have cavity walls and is constructed from red brick and stone using black ash lime mortar. I have often thought about future proofing the house however I do have some reservations about things that were never installed in these homes at the time of construction for whatever the reason and how they would fair when we try and introduce them at a later stage. Your home seems older than my property so has this been an issue for yourself and how have you overcome any potential concerns?
I am very similar and like to keep things nearer to how they were. This is one reason why we haven't internally insulated our walls anywhere in the house. For me the risk is to much of a concern. With the loft there is far less risk as we are just replacing the old ceiling and there is always air flow above, same with the insulated ground floor. I have just filmed a video about some of the risk of insulating older houses so will be online soon. TRC
Same here we know of many people that have had their cavity walls insulated but it is not something which we feel is sympathetic to our house. I am looking to start a project in the next few months to convert the cold, badly boarded out and loose filled insulated loft space into something we can use for storage. I have watched some of the vlogs of your loft project and it has really has filled in a few gaps in my knowledge.....although I am not looking forward to getting the materials I need through a small ceiling hatch. I will keep my eyes peeled for that video you had mentioned and thank you for taking the time to reply to my question. Mandy
The Restoration Couple Hey there. Started watching your channel recently as I’m starting to renovate a house around the same age ages yours looking at the vids. I have took down all the ceilings and have took most of the old plaster off the walls as it pretty much just fell off everywhere in the house. I was planing on studding all the exterior walls and insulating them and plasterboarding them. Would you not recommend this or can you leave and air gap behind the stud and insulation so that if any damp does arise it should dry. Thanks.
We bought a cottage built @1930. The slates are straight onto batons on the outside. Inside has a lime mortar mix (feels like sand) like a layer of plaster on the inside. Covers the whole roof. The idea is to get wet and dry. Keeps the roof sealed. We are not going to re-roof as the slates are in great condition. We have to insulate the inside though. Not sure what material to use. Thin space to work with between the rafters. Any advice?
Great video thanks. Is there a video of how you fixed the plasterboard to the underside of the roof? Did you screw through the 50mm insulation back to the rafters? I have a 100mm under rafter insulation how the plasterboard can be fixed securely.
Ours was only 50mm so long screws were used. I would suggest battening over the insulation to give you a space for cables and easier to fit pb. I would try some long landscaping type screws to fit battens and then you can use standard drywall screws for the boards.
@@TheRestorationCouple Thanks for the reply. We will look into battens.
nice work
Do you need to put that 50mm layer over the top of the 100 or could you literally plasterboard over the 100mm that you first installed? czcams.com/video/DFO-asmyrP8/video.html
Seriously thinking about doing a partial conversion in mine, the only two issues I have are:
1. In the winter it’s very cold in the loft, but in the summer it’s stifling. How do you get round the heat?
2. I have solar on the roof, so if the answer to my first question is to open the windows, that won’t work as I can’t put any in. What would you suggest?
Spray foam insulation.
Insulating your roof from the outside does a pretty good job of it if it's not done yet. 200 mm thick polyisocyanurate plates wrapped in foil do the job pretty well. Saves you a lot of inside space as well. That's what I had to do for a full renovation and it's brilliant.
Probably wrong, but sure a builder mentioned you should have an air gap at top of the roof insulation.
50mm unless air permeable membrane.
Nice channel. You've been busy. Have you taken a look behind the insulation to see what if anything is happening? The foil faced rigid sheet looks pretty space age but without top notch air sealing you may still wasting energy. Any condensation?
Would it not have been much more effective to have left a small air gap between the two layers? making each layer air tight around the trapped air gap.
hi, great videos. i'm ripping down the ceilings in an 80's dormer house, i plan to renew using similar methods to what you've done in your loft.
do you have any info on how you ran electrics, sockets & light switches through the insulation/plasterboard coverings?
the same with any radiator pipework etc??
chris jones ideally put counter battens over the insulation before plasterboard which leaves cavity for cables and pipes. We ended up doing a combination of this and also bringing it through from eaves using conduit and taping airtight. Ideally try and keep all on the warm side
many thanks
At the beginning you mention insulating above the rafters but I can’t make out what you’re calling it? Warmery? This is what I’d like to do for my den/sunroom with low exposed ceilings. Thanks!
It’s called a warm roof..basically the insulation is on top of the rafters then vertical battens, then horizontal tile battens..
Hi mate have u done a video of u fitting the plasterboard I did the same in a loft room last year 75mm inbetween and 62.5 insulated plasterboard but was like 55 pound a sheet a normal sheet of 50mm was 20 quid so so much difference I’m planning on doing another room so was after some tips on fitting the plasterboard after also were did u get ur materials from
Shouldn’t the foil face the roof tiles to reflect the radiant heat back up and prevent overheating in the summer?
It’s double sided.
Foil covered foam insulation =condensation. Should have used wool because the roof and loft now won't breathe.
If the roof insulation breathed it would allow condensation to form on the underside of slates! The foil face will be at room temp so not cold enough for a dew point. Agree that natural insulation would be preferred but you also loose 2x the headroom. When it comes to roofs there is not much difference between then and modern day, you still have air space above so not risky like internal wall insulation.
TRC you are fine (as you know) - in fact you need to tape the joints to make it as airtight as possible. Not sure what the previous comment from JH was about, you wont get any condensation in the cold roof void behind your new insulation, thats the whole point of making it airtight. Granted, if any warm moisture laden air makes it into the cold void then yes condensation may occur, but if there is air movement back there then it should clear. The problem with posts like yours, is that it attracts comments from the 'I know a little and think I know the lot' internet knowledge gang! Good luck with the projects. Enjoy watching them.
I think the problem might be, much more than worrying about actual condensation, just moisture in general. Moisture needs an escape route, or some kind of air flow, or rot and mold will develop. In North America forced air heating systems generally solve this, but in the UK I come across terrible mold and mildew problems all the time. I admit that I am not an expert in house envelopes and that sort of thing, but it seems advisable that you have some kind of ventilation in your loft to avoid moisture developing into worse problems.
That’s why what ever insulation you use you need a counter batten to lift the tile lath off the felt or membrane. It will condensate what ever you do. I prefer wood fibre or wool. Mainly because I like breathability and diss like chemicals.
This is true if there is no air flow. Common building regulations in the UK state if you insulate the roof space in this way you must leave a minimum air gap of 50mm between the roofing membrane and the insulation In combination with a vented sofit or ridge system or both depending on the design of the existing roof. In short moving air doesn't have chance to condensate.
hi tim. can you recommend what expanding foam i need to fill small gaps in my vaulted ceiling insulation? its 100mm (50mm going over the top) with 50mm gap under. i need to make sure i dont block off that gap with foam if it expands too much and goes underneath. cheers
There is a product called gapotape which works better than expanding foam. it also allows the timber rafters/joists to expand and shrink. Unfortunately, it's rather expensive.
I'm just wondering whether you have any advice for keeping the insulation between rafters in place as mine have all fallen out with the expansion and contractions over the winter and into summer? They were a friction fit, but obviously not long term :(
They're in a cold storage area under the eves. Accessed through a door from the main room. So doesn't need to look pretty, just functional!
If flush with the underside then just strips of batten fixed to underside of rafters? There are clips but strips of batten just as easy if only storage area.
@@TheRestorationCouple thanks! I'll give it a go :)
The trick with stapled gaffer tape works well even longer term it also seals the air gaps
Jam them up with wedges them expanding foam.
Plastic garden mesh netting, pulled tight with just a few staples each rafter
Is the floor insulated?
Did you keep a gap between the roof membrane and the insulation? Is that the reason why you built out the rafters with supplementary ones?
Sorry no need to reply I found a comment which addresses this. Yes to all
What kind of expanding foam is best used? Never used any before
Hi I am planning to convert my single garage into a room. The roof is a metal sheet on a roof . The drafters are timber.
Can I install insulation wool pads and Gyproc underneath. Do I have to install a ventilation on the roof tops remove any heat or moister.
I mean ventilations extractor
Would it work to use unfaced batts between the rafters, and then use foil faced rigid over the top of that?
Should be fine yes.
Did you have a membrane between your rafters and battens?
I am thinking of doing my loft like this to make it a bit warmer...what is the name of those washers?
I notice no noggins to catch edge of plasterboard on inward sloping ceilings. Are you not worried about edges of plasterboard?
Just used gun grade type adhesive along the ends. Worked fine as insulation itself was secured. 👍
Pvc pvc cables should not touch the insulation as it will deteriorate them
Aren't you worried about condensation?
Tim when When fitting the 50mm over the top did you have to screw the screws into the timber or would screwing into the insulation be ok ? I’m in the middle of my extension and am about to overlay with 40mm over the 100mm between my rafters. Cheers
Into timbers. It only really needs to be enough to hold it up before the plasterboard goes over as that will secured both. Assuming you are using separate layers rather than bonded.
Yes using separate layers. Cheers buddy.
hi please can you tell me how you blagged a bulk deal on the boards?, thanks
Is this an old roof with no roof felt? I thought I could see the back of the tiles when you were installing the insulation between the rafters
Yes, however if you see the current videos that is no longer the case. 👍
Is it better to use the insulation boards with foil on or can you use just the polystyrene boards
The foil acts as a vapour barrier and reflects heat rather than absorbs it like untreated poly boards would. Also need to add a 25-50mm air gap between these boards and the upper roof tiles if no membrane installed.
1:10 not yet 😉
Hi can I just ask? Is your roof slate or tile and does it have felt? The reason I ask is I’m doing the same to my loft except it’s an old slate roof with lime mortar on the innner side. Did you have the same? Not sure wether to scrape the lime out before I place Kingspan between the ratters.
Thanks
It’s just a traditional slate roof. We intend to re roof next year but all that can be done externally. Not come across lime mortar under slates. The room was plastered with lime over large if that’s what you mean?
I understand the need for the 50mm gaps between the insulation and the roof tile, but does this only work if you've got air vents in the soffet and/or facsia?
Or an air permeable membrane as we just fitted.
@@TheRestorationCouple can you link tht video, or is it this one? You've got so many and I can't seem to get them in the right order. I'm looking to do a similar loft. It's floored already, but no vents in the soffit.
Ian Mc Namara latest three or four videos all show roof.
Nice job but I wouldn't like to sleep in that room in the summer 😬😩😩😩😰😰😰😰😰 I also thought a roof space had to breathe a bit air around???
The ventilated space is abobve insulation and below slates, this is the 50mm required for airflow. The rooms are actually very stable with regards to temperature as the solid stone walls help regulate and the insulation keeps it cool in Summer. Far better than before when it would be like an oven in Summer and single figures in Winter! :-)
Can you let me know where you got the insulation washers?
Never mind ... saw the info at the end of the video, and found them on eBay :-)
Marmox washers
eBay
Hi. Can you please tell me does the 100mm insulation you fitted between roof rafters sit against the roof felt/membrane? I'm preparing to insulate my attic roof. My roof membrane is non breathable, like shed felt and I'm not sure whether to fit insulation against membrane or leave it proud. Can you please advise. Regards.
Best to leave 25-50mm just be on the safe side just incase the membrane if any is compromised.
How much air gap did u leave between insulation and roof membrane/tiles?
Planning to do something similar however my rafters are only 75mm.
Was thinking of 50mm Rockwell with 15mm acoustic plasterboard on top. This will leave a 25mm air gap (i know 50mm is Reccomended but can I get away with the 25mm?)
50mm. Our rafters were 75mm hence why I extended them to 125mm.
Thanks for the reply buddy. Just seen your other video explaining how you extended the rafters.
I have a material under the tiles (felt type). Would I still require the 50mm gap? Ideally I don't want to extend the rafters as I will be reducing internal roof space however if it needs to be done I will do.
Would I require a vapour barrier?
I live on a busy main road so sound proofing is high on my list. Acoustic Rock Wool 50mm a good idea? With 15mm acoustic plasterboard on top? My plaster board will be fitted flush with the rafters (don't have space to install further insulation on top like you have done).
@@TheRestorationCouple Hi, I'm going to the the same insulation as you in my attic and also have 75 mm rafters. If you extended them to 125 mm and installed 100mm insulation then you ended up with only 25mm and not 50mm gap between the roof. Am I wrong? Please help!
@@michadzianach6512 at the time there was no roofing membrane so there was 50mm between slate and PIR. Having now completely replaced the roof using a fully air permeable membrane, there is not the same requirement for the 50mm gap so more like25-30mm. Always good practice to have some however many membranes will allow you to reduce that quite a bit as the whole roof becomes vented. Roofshield is what we used and rated highly.
Any reason why you didn't go for multi-foil insulation for the internal layer going under the rafters? From what I've read, in conjunction with PIR insulation between the rafters gives U values as good as any alternatives if not better (ie around 0.15).
It may be possible to achieve similar with multifoil. However I think it ideally needs an air gap either side or at least one side, that would have meant counter battens on every rafter/stud. We purchased a bulk deal of 40 sheets and I believe this worked out the best for our £££'s. Also some BCO are a little funny with multifoil products so worth confirming they are happy first.
It's true you need an airgap, but that can be provided in the rafters and I believe it should still take up less space than most PIR board - some multifoils say they can be attached directly to the rafters with 50mm thick counterbattens between the foil and the plasterboard, others say the plasterboard can go straight over with the foil pinched between the rafter and the plasterboard (which, admittedly, I find rather odd).
Some multifoils claim to have LBC approval, so I didn't think that would be an issue. Besides, if you're renovating and adding insulation to an existing roof, I didn't think it was necessary to involve Building Control?
Anyway, your solution will I'm sure give results that are at least as good if not better than the second layer being multi-foil and since you got a discount it's a no-brainer. In my case I'm researching insulation for the 250 year old limestone cottage I just bought; the roof is only from the 90s, though, and the insulation is just 150mm of rockwool inbetween the rafters. The main bedroom is in the roofspace though and so this isn't enough. I've therefore had my chippy rip all that out and I'm going to get him to put in PIR and probably multi-foil. Two layers of PIR would lose too much space inside the room.
A couple of examples of under-rafter multifoil installation instructions:
www.ybsinsulation.com/wp-content/uploads/2015/08/SuperQuilt-England-All-In-One.pdf
www.just-insulation.com/reflective-multi-foil/tlx-silver-30mm-mult-foil-bba-certified.html
I suppose if you were struggling with ceiling height then multifoil might help. However 50mm battens over M/F would be the same as the 50mm PIR, so you would have to loose the air gap. Either way like you say it will certainly do the job and multifoil quicker too. You may get away without BC if you are replacing existing but I am pretty sure the small print says any major changes to thermal elements or along those lines. Reason is probably more about vapour control and enforcing airgaps above insulation.
Well yeah as said some types - the Superquilt for eg - don't seem to need an airgap and therefore no battens, but I do find this a little odd. Seems strange that you can get effective insulation when the only insulation where the joists are is some multifoil pinched between joist and plasterboard, which is also going to squash the air out of that section. I think, though, that one advantage of the Superquilt is that it's more of a contiguous moisture control layer as instead of sections being just taped there's a 50mm overlap between already large sheets that's then taped. I'm not sure though.
This has been a useful exchange as I already have a Building Control notification in for other aspects of this project so on the back of this I'm going to give them a call tomorrow :).
So I had Building Control over about other things and spoke to them about multifoil and insulating the roof. You're right, they're not keen on multifoil and it might have been difficult to get them to sign off on it. What he did say, though, is that since I'm using 100mm Celotex or Kingspan between the 150mm joists I only need a layer of 25mm PIR under the joists to meet Part L requirements, so I said I'd do that. He also said that because the room was considered habitable before I started work, this upgrade work doesn't need to be approved by Building Control anyway. So I'm in the clear on both counts: I'm going to do it so that it meets Part L standards for my own benefit, and I don't need it to be signed off anyway. I'll most likely use PL4025, the plasterboard backed with 25mm Celotex, with the vapour control layer provided by the GA4100 and tape.
Now to look for the cheapest supplier of the stuff!
The inspector gave a couple of useful tips. Firstly, he suggested pushing wedges into the layers of felt from the inside to ensure airflow - he said they've found many roofs constructed in the 90s like mine don't allow sufficient air through. I just need to find suitable wedges now.
We also mentioned we might be using PIR board in the new stud walls we're installing throughout the house, and he said that they've found PIR board can often act as a diaphragm and can magnify sound instead of deadening it. So he suggested using rockwool instead - which at least is cheaper!
Hi there, what did you put at the very top at the ridge, more boards or wool?
Boards in the same way with counterbattens under to create cable cavity.
can the insulation boards touch the felt or should there be room for it to breath
Minimum 50mm gap for regs.
Sorry didnt quite understand how your boards are going to go on top of that,are you putting battens on top if so what thickness
Just screwed through the 50mm boards into rafters. You can use battens if you need to run services which we did elsewhere.
The Restoration Couple probably a stupid question but are the rafters easy to find under the insulation? any tips if they aren’t?
How do you know where the studs are?
Hi,
Is the insulation that you put between the rafters called cavity boards?
Thank you!
No just cut from full size pir sheets. Cavity boards are usually thinner and smaller.
@@TheRestorationCouple What depth PIR board did you use/recommend?
Why no roof felt?
why would you do the inside before the outside, seems backwards.
Well if the roof doesn’t leak and it has been up there for 120 years it’s fine for a couple more. It’s also a huge job and costly so better to wait and do it properly. 👍
Attics in summer are hell
Insulation prevents this hence the 'insulation' in the title. If done correctly it will also keep the room cooler in summer months. Good example is a conservatory, useless all year round due to zero insulation.
C
Will this prevent ice damns on roofs/gutters?? Thanks.
how are the results
Warmest room in the house. No radiators yet but barely needs them even at the moment and in our old stone house that’s impressive!
wow! are you in the uk or ireland?
I live in Ireland and the insulation you see here is plenty to keep any house warm - In Ireland the BER rating would shoot up with this insulation job
are you located in USA?