Great video - I'm a Building Surveyor and dealing with a disrepair claim like this in London at the moment (acting for the Landlord). Interestingly, the walls in this claim were pumped with insulation which caused them to perform better thermally and the cold spots moved from the walls to the ceilings (due to poor insulated ceilings). I'd say first step is to minimise the condensation below and use an extractor fan in the bathroom which has a humidistat built-in. The location of the fan is key. Make sure that it's far away from the window as possible so that when you have a shower and open the window it draws air from one side of the room to the other. As it has an as-built humidistat fan built in, it will kick in when it senses high humidity and remove any remaining moist air even when the light is turned off. No drying clothes in the house either. As for the insulation arrangement, its easier to leave the ceiling in place rather than remove or overboard it (especially if it is covered with an asbestos containing Artex textured coating). I agree 100% of your assessment to seal the sealing as best as possible and then insulate over it and pack it tightly. Install an insulated loft hatch as this is always an easy detail for air in the room below to escape though. Ventilation is then the key in the roof space to allow this to work so allow for those roof eaves vents and add tile or ridge vents if required.
Thanks for the reply yes in summary air tightness air tightness air tightness of the ceiling and then share open insulation above with plenty of ventilation above that
@@LoremIpsum1970 Artex is not moisture or mould resistant. However, the modern plastic paints you buy at your local DIY store can increase moisture resistance of the Artex when applied.
Installing vapour barriers around joists & other obstacles etc always looks fine on a CAD drawing... until you climb up into a dirty old loft to actually attempt it that is! As Steve already said: seal holes, protect vents & whack a load of new fluffy stuff down. Job done.
Absolutely... I went to do that myself over the summer and simply gave up. Getting the barrier inbetween the joists and battens and taping it all in, is virtually impossible
Thank you so much for this. I am adding insulation to an older garage with a pitched roof I use as a part time workshop. I just want storage in the loft. There is plenty of ventilation in the loft. Walls will be either PIR or rockwool between new stud walls with ventilation between the insulation and the outer breeze block wall. Yes it will be leaky from a ventilation perspective but energy efficiency due to only part time warm use isn’t my biggest concern. I kept worrying about sealing the whole inside with a vapour barrier when I have full sliced double swung doors on one end! I know obviously things would be different were this a living space.
Thank you so much for this video, great review. I was thinking of doing something along the same lines, it was so useful seeing you review the options they proposed as we have a similar loft area. I will now be fitting vent protectors and layering up with rockwool
Thanks with the cold weather lots of loft spaces are sweating and I'm geting lots of people very worried about the affects. Air open is the way to go with lots of vents
great video. Fantastic drawings from the customer, that must make your life a lot easier. Just to clarify, the solution you'd recommend is 300mm or so of rock wool or similar applied directly to the plasterboard (no foil or anything), plus plenty of ventilation above? My loft has exactly that (maybe 400mm actually), so good to hear. I'm in a timber framed house and it's very well insulated (too well, it should have ventilation in my opinion, but I'm loathe to spend the money!).
@@SteveRoofer @Rico S On the BBC a month or so ago they were discussing loft insulation and said something strange, that after the first 100-150mm depth any further thickness has diminishing returns. Based on the stupid cost increase in rockwool I'm not going for 300, I'll just go for 2 opposing layers of 100mm and a larger air gap to the loft flooring. Am I wrong (1970s house as pictured in viewer's document you reviewed).
I think this video may have just answered all of my concerns of insulating. I live in a 200yr old quarriers cottage, extremely well built with no signs of mould or condensation anywhere. Having pulled down a few ceiling now I can see there’s never been a vapour barrier, which I’ve been sweating over, but now I’m thinking that ‘vapour open’ is probably the way to go. I am replacing all of the old insulation with Rockwool. Fingers crossed this is the right thing to do.
Ok, so I’ve insulated my ceilings this way. 75mm PIR cut precisely in between the joists without Vapor barrier, is been there for over a year and I can’t see any moisture around ceiling joist. Massive difference I’ve noticed winter nice and worm summer cool. One thing would stres enough is do not leave any cold spots as moisture would eventually make way down into plasterboard 15mm sound proof. Hope that helps
One advantage of putting fluffy insulation between joists but PIR on top is that once the PIR is covered with wood you can have a use able storage space as long as it's only occasional foot fall. Just adding more fluffy insulation means for it ro become storage somehow you need to support a hard floor. One other issue that never gets mentioned is electrical cabling once covered by insulation is likely to need to be derated with smaller circuit breakers installing, cables in open air can take much more current than those covered by insulation
True, however lights now tend to be much lower wattage. A typical incandescent was 40-60 watts and now your looking at 6-8 watts. If you had 20 lamps you’d be looking at around 3 and a half amps around half the typical lighting fuse where as if you went to all 8watt led the same current would be around 1/2 an amp. Remember you can’t suddenly plug in something large in the lighting circuit like you can with a socket. So your right but in the real world it’s likely not to be a problem.
@@davideyres955 there are still stocks of halogen and incandescent bulbs out there. New lights are much lower as you say, but yo can't be certain that an older bulb will not be fitted
Love your videos Steve, could I put a request in, can you do a video showing the best practice way to join a sloping cold roof, to the warm roof section of a flat dorm roof
There is a trade off between vapor control & insulation performance. In an ideal world (such as a new build) insulation should be enclosed on both sides with an airtight layer, because this eliminates air infiltration for best thermal performance. However, as we see here in a retrofit situation, it's difficult to achieve integrity without stripping coverings such as tiles and ceilings to provide full access. It does seems to me like the viewer understands how this works, and if it's done VERY carefully it might work. However I also think your advice to go open cell is the best reliable solution. If it were me, I'd add a taped AVCL under the existing ceiling and over- board it. It's always easier to properly seal a flat surface than one with lots of timbers etc.
This is such a useful video and interesting to see a critique of those ideas in terms of making it simpler. So thank you. I am looking at installing a PIV unit but fear the unit drawing air that might hold airborne fiberglass particles/rockwool dust into the house. Is this something you've heard of or an unreasonable fear? Also wondering if a loft without felt - and just sarking boards, even needs additional vents before building up new insulation?
Hi! Great video! It was very informative and that PDF the lady made was very detailed. I was planning to the same to my loft with one slight change to her idea. So, vapour barrier on the ceiling side but rather than an air tightness layer on top, causing problems you've mentioned, I was thinking to use a breathable membrane. I believe the benefits of this system would be 2 fold. 1 to allow any creaping moisture passing the vapour control barrier to dissipate into the loft space and 2 to reduce or eliminate potential wind washing making the insulation that little bit more effective. My logic behind this is ive taken the suspended floor insulation method and reversed it. Does this sound at all plausible or am i barking up the wrong tree? p.s. Plan is to install a MVHR system and will be using rockwool in the loft and suspended timber floor, especially after watching this vid! Thanks
Steve, you're a star. Great document your viewer sent in, I've been going through the exact same (puzzled) process myself and I mentioned this graphic on here some time ago. That site promotes wool and 'natural' insulation btw. I commented on the eco-home site and the conclusion was: Eave Vents, then Tyvek Air Guard over joists/plasterboard + 200 min. Rockwool + 50mm air gap [NO air tightness layer] + OSB boarding over top. Rockwool was suggested as it's non-hygroscopic, so it doesn't hold moisture like fibreglass does, where some people blame it for rotting the timbers. Q. Are you suggesting not bothering with the Tyvek, and just sealing any 'open' penetrations? Laying and sealing the Tyvek does look like a real PITA so would it be worth it in the long run?
Hey, got the same major ussue on one side of my cold loft, one side doesn't catch sun and has a raised water tank which isn't insulated underneath it, lots of downright fitted also in 2 upstairs bathrooms, had ridge tile vents fitted, so gonna make everything airctight and replace all insulation
You recommend leaving the blanket insulation (rockwool) open & having a well vented loft,. But in doing so, could the moisture that gets through the ceiling reach it's dew point & condense somewhere inside the insulation (and not exit out the top) & so cause the insulation to be less effective & even compress & become even less effective? And if it stays in the insulation & not exit then mould could form?
That's why you have to have ventilation above so that the moisture can travel through the insulation and then get out this is a tried and trusted way of doing it has been done in lofts for many years.
@@SteveRoofer Thanks for your reply. But if moisture condenses inside of the blanket insulation & the loft space is cold (due to ventilation) won't the moisture just stay as liquid , not evaporate & so stay inside the insulation & so cause issues? I'll be insulating a loft soon so I hope you are right as this will make things simple for me but I'm still not sure.
I'm in a similar position. We bought an end of terrace house last year that was build in 2017. So quite new. I noticed, when we had colder weather this winter, that condensation was forming on the inside of the roof membrane, and we have about 80% humidity up in the loft. I didn't notice any vents in the loft, so assumed that the roof membrane that was used is breathable and so vents were not installed. But now I'm not so sure. Any ideas I could try?
@@domtomas1178 try some felt vents that go on the inside mate, I need to do mine yet but I did it on my old property and it worked 👍 anything to increase that ventilation is key
i have put a think layer of PIR (kingspan) under the joists and on top of the plasterboard, taped and foamed at its joints. So condensation wont creep up to the top of the joists. Surely this is better?
Roger Bisby staring in "The Ugly Truth about getting hits on RU-vid", I never get tired of getting tired about how many views he manages to get! I dread to think how many people he has lead up the garden path.
regarding air gap, regardless of keeping simple or not, the concept of radiant heat is that it radiates, it is not conducted by a solid material. The moment you don't have a void, there is no radiant heat and you are just conducting from one solid to another. So, from a physics perspective, the foil is useless if you have no gap, it will not work as a radiant heat barrier.
Thanks for all your videos Steve. Assuming you've got the nhbc 7.2.15 recommended amount of good back and fourth ventilation above the insulation, in a cold roof, do you think 50mm continuous air gap in the rafters is enough when there is old non breathable sarking felt, =>300mm of open air insulation, with no seperate vcl, above a shower room? Many thanks
@@HampsteadBuildersLt hi….no what im looking to do is take down a bedroom ceiling ( flat roof above) and re insulated with something fit for the job. What would you suggest?
Hi , just to ask , i am refurbishing the roof of our 1 level house extension, where before used to be shower , we have VAPOUR barrier on the plasterboard, as right now we have only toilet over there, my question is ! to keep that vap barrier or remove it ? thank you. we need that space to be nice and warm thank you
Hi I live in a downtown stairs apartment and my kitchen ceiling keeps sounding like it caving in but there is no damage in my apartment nor the upstairs apartment. This sound first happened this Sunday October 30th and today November 4th
Steve no sure of the best way to contact you and ask for some advise but l need to repair my flat roof as it wasn’t constructed properly in the first place, basically it’s a cold roof with no vapour barrier or ventilation, it’s about 12 years old and to put it politely it’s a bit spongey . It also has access to and upstairs flat so is walked on regularly, watching some of your videos lm thinking l would prefer a warm roof solution, even though it would cause me some issues with one doorway , cold roof is possible but as you are aware I would need to put a lot of effort into the ventilation design. Would love to know your thoughts on minimum fall and what material you would recommend for the top , many thanks
The problem I see with a sealed attic, is during the winter time, the chances of freezing water pipes and burst pipes, is highly possible. Its the movement of air through the rock wool and into the attic that prevents this.
Thanks - great video. A question please. I have the old felt bitumen type barrier under my tiles as you show here (around 9.30) in your summary. Can I just cut out what I can see, either all or sections maybe, and place the gas permeable material in its place (ie I'm hoping all the roof tiles dont have to come off - I'm just looking to assist with the loft ventilation due to condensation build up. Thank you for an informative video
I don't think that would work because you're growing up with bits and pieces all over the place not only that it's just not gonna give you enough ventilation. You really should get some good ventilation put into the roof top and bottom elevations. Good through ventilation is one of the keys.
Hi Steve having a flat roof fitted. But which is the better. Epdm owl lava 20 or grp. Its a 4mtr x 5mtr it's a cold roof due to hight restrictions thanks
On your way Steve - loose fibreglass insulation laid over joist (150-200mm) with air gap under eaves/tiles to allow air flow up and over- is it also ok to add kingspan to the underside of the tiles/felt (new roof) I've got 4 roof vent tiles installed to allow air flow - just thinking belt and braces or is this wastage material adding the kingspan
Maybe I worded that wrong, so rafters, vapour barrier on top of rafters, osb on top of vapour barrier , then kingspan or the like then single ply membrane
@@brutus277 no rafters firings OSB vapour barrier insulation. On a warm roof you cannot successfully lay a vapour barrier over rafters you have to put a dick down to lay the vapour barrier onto. In my book you cannot use a vapour barrier that is plastic. Plastic vapour barriers are designed for cold roofs. On a warm roof you should be using a vapour barrier that is adhered to the OSB.
Is there a reason why you can't put it below the osb deck?, I can obviously read the drawings as per the order you say bit no one can ever tell me why?
@@brutus277 it has to be as close to the insulation as possible also you cant stick it to the underside of the OSB its also called an Air Vapour Control Layer (AVCL) beouce it has to be airtight. It has to stop the air from the room below every part of the room below from getting up into the roof above its not imposable to put it below but would be far more difficult an
@SteveRoofer yeh the vents have changed the feel of the attic and its all dried out. Cost me twenty something quid and less than half hour to install. The attic door has helped (used felt draft proof tape and added wood frame) but I think it's more about saving heating costs than condensation with the door. You know the felt vents I'm on about?
Not a builder, but if @Steve Roofer is saying vapour can permeate your painted and skimmed plasterboarded ceiling, then I’d guess chipboard and OSB will also allow air vapour movement.
Hi Steve, regarding moisture passage through Gyproc ceilings, as my ceilings are still 70s with Artex would this make a difference to the passage of moisture through the Gyproc into the roof space? Hope you can help.
No difference whatsoever just make sure you haven't got any big holes for air to move through then realistically you've got quite a good vapour barrier probably over the years you've got lots of paint on that ceiling as well that also helps
She is obviously a case of a little knowledge is dangerous. The air pocket we used in Texas for radiant heat reflection on the outside of buildings, it's not brilliant for internal insulation. This lady would be far better served with Rockwool insulation to let the moisture out and forget about PIR entirely. It's fine to have around the majority of down lights where PIR isn't and it's hydrophobic. Possibly she would be better served watching some insulation videos on The Build Show Network or Matt Risinger's YT channel as her document is trying to hybrid US and UK systems for insulation and vapour management.
Yes thanks for this I I watch Matt,s videos all the time but have never seen this a gap on the outside apart from the age gap use for ventilation not in a gap used to collect radiant heat and reflect back!
@@SteveRoofer It has become quite common for foil faced peel and sticks or PIR as the last layer under the siding depending on wall/roof design. In theory it can be used internally but the loses and gains don't really support it internally and as you rightly pointed out from the design the lady has proposed it would lead to more issues with the structure.
I believe The Build Show Network and Matt Risinger's YT channel are American & the lady in question is in the UK. So wouldn't she be better to look at UK info rather than U.S?
Not directly related but in the uk for cold roofs we now need to have insulation under the joists. So where does the vapour barrier go in this situation? Does it get sandwiched between the insulation?
Do all Victorian houses (late XIX) have roof eave vents or at least gaps for ventilation purposes? Looking from outside my roof seems to end really close to the walls.
Looking at a similar situation in my 1910s terrace. Difference is there is already about 3cm insulated plasterboard that was overboarded. I’d prefer not to take everything off for a vapour barrier. So curious: 1. Is it ever okay to put a vapour barrier over the joists but under the insulation in between them in a cold roof situation? (As in the diagram in the video) This seems iffy to me as could trap vapour on the joists. 2. I’m guessing you’d recommend rock wool or similar, but given there’s two layers of plasterboard and some EPS could I assume it’s fairly vapour tight anyway, and use PIR for higher performance? Thanks.
Doesn't let air out but lets gasses out?... Air is a gas... The foil insulation is surprisingly effective with an air gap either side. It can be achieved by putting a baton on, then your foil layer, then more batons.
I was referring to the vapour resistance of the material vapour resistance is often mistaken for breathable. Some of the new air vapour control layer is on the market are what is called air open and are classed as breathable, but most of the older ones are just vapour open
Well, the roof space is going to be unusable anyhow and fluffy stuff lost an awful lot longer than 10 years, but realistically when you start looking at costs its still the best way to go
