Warm roofs, the biggest mistake I see when doing a roof inspection.
Alway phone or email if you need help or advise
Steven Dickinson
London Flat Roofing
07802300099
info@londonflatroofing.co.uk
Nobody tucks in their warm roofs!
What do I mean?
If you bought a new quilt for your bed and you laid down under it but didn't tuck it in around the edges, you would get cold. Same for when you're doing a warm roof, you have to extend the insulation down to the next thermal element of the building. I call this "tucking in your warm roof"
The reason nobody tucks in their warm roofs is because of the cost of doing so. You not only have the labour of doing it, but you also may have to remove the fascia boards or gutter boards to get access to the area that needs tucking in. Thermally tucking in your new warm roof makes all the difference. It not only continues the thermal performance of the new water roof down to the next thermal element of the roof, but it also makes the roof airtight. I have been to many new warm roofs when carrying our roof inspections for customers and they complain about how cold it is in their house even though they have had a new warm roof. When I'm doing a roof survey, I often take out light fittings and feel a draft straight away. I know that the roof is not airtight, and normally, it's because they haven't put the insulation between the joists at the ends only. Putting insulation between the joists further into the room on a warm roof is totally another thing, and I covered this in another video; you should not have to do that if you have the core thickness on the new warm roof. I would suggest that tucking in a new warm roof on a loft conversion is the most complicated, more complicated than a rear extension flat roof. With a flat roof over a loft conversion, you have to tuck in the insulation at both ends, whereas on a rear extension, you normally only have to do the tree edges, and access is a lot easier.
Steven Dickinson
London Flat Roofing
07802300099
info@londonflatroofing.co.uk
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We had new extension done few years ago using the warm room method and they didn’t fill the gap with insulation between joists, our new extension was absolutely freezing in the winter. I showed the builder your video on thermal bridging and they took the fascia board down and corrected it and now it feels warm and cozy. Thanks for these educational videos
And he he did all that within 18 hrs of this video being posted?
@@Christopher-zt9eu Steve said in the video that he posted a video about ten years ago.
@@Christopher-zt9euposted a video 11 years ago, which viewed by 475k people so far
Your all in front of me I don't think I have posted the link to that video ill have to go and do it
warm roof have insulation on the out side, you don't need to do anything on the inside
Thanks Steve for taking the time to put these vids out. They are invaluable to all homeowners.
Glad you like them!
Thanks Steve, great vid as always. I think what you have to remember is warm air is attracted to cold air, so if you have these tight gaps the air fairly whistles out. It would be interesting to compare say 18mm ply totally sealed at the edges with insulation with gaps in that area.
Wish I'd seen your advice years back. Educating people on how to do it right no matter the cost is always worth it. But everyone wants it done cheap and fast.
Unfortunately, that's the way of the world
When we built our lofty on a 3 bed semi we spent ages and a lot of money insulating the roof and walls and getting obsesive about draught proofing. In the last three years since we have never turned on the reads up here, the loft stays very cosy all winter with just the heat leaking up from downstairs. To be fair though you do need a forward looking customer to agree the extra costs involved in getting it right, done well though a few years of reduced heating bills and you have paid for it. Good video, thank you.
We bought a house and the previous owner was really proud of the money he'd spent on insulation. We'd have bought the house regardless, but after we bought it I realised he'd wasted his money because the people who had installed it had left big gaps which allowed airflow. We're slowly working on it ourselves now, but this video was great as it showed me I was right about the issues, and my approach has been more or less correct, too. Thank you!
As a former Building Control surveyor this was such a common issue, both on new extensions, replacement flat roofs, and even on large new housing developments. On domestic work I would probably say this simple point was missed getting on for 50% of the jobs that I saw at this stage. The issue is that many builders build the walls as they always did with ventilated cold roofs, stopping the walls at plate height. This also applied to the walls parallel to the joists leaving an uninsulated void between the top of the wall, the deck and the joists either side, with only at best a 25mm gap to get the insulation into the void when the issue was pointed out. It really isnt good enough to just fill up the space with quilt as this can create condensation issues, it really needs to be PIR as Steve shows here foamed into place. Another important factor when upgrading a ventilated cold roof to a warm roof is that you need to remove all the old roof insulation from between the existing joists, leaving it in place, particularly if there is a good thickness, means that the vapour barrier under the new insulation will not be at room temperature and can cause condensation problems that the warm roof was designed to overcome.
Thanks Steve. These are really useful things to look out for as I look into home projects.
Thanks
Thanks for the info. Had a flat roof extension done last year and it saddens me that i know for a fact this tucking in was NOT done. So this summer it’s fascia’s off and do it properly … Myself 😢
If you completely seal up roofs like that the timber will rot out double quick . Sealing everything up causes all sorts of problems and we leave air gaps on purpose you will cause mould, condensation and damp .
Interesting point, I to have been wracking my brains about how to insulate effectively without trapping moisture, I have tried to strike a balance but its difficult to avoid condensation finding cold unventilated areas. Problem seems to be that we won't find out for 10 years if it's going rotten!
@@jonwilmot5331 we know that not using Vapor barriers and ventilation timbers go rotten that’s why we ventilate loft spaces , bathrooms, flat roofs and put vents on double glazed windows.
Enough roof tile vents should suffice
@@springy2670quite tricky on a flat roof 🤣
@@dragonfitter Then you should have put some vents in the lantern you've clearly installed on your flat roof 😉😘
Dear steve et Al. I have just pulled 1500 kg of lead off my annexe which after 20 years was like a burst sofa. It was laid on a warm roof done badly with no vapour barrier. I have stripped it and used Allutrix then put Res Tech flexible fibreglass over the new deck. Vapour barrier and thermal bridging control is critical when working on modern roof systems. Thanks for a very good video.
you wanna weigh that lead in you got a payday right there!
Totally agree with you Steve, I see this to often as some trades don't care? 😖😖 I do as you do as it's the only way to do it properly 👌👌 Cheers
Well said!
I thought that you had to leave a space where the ceiling insulation meets the soffit for ventilation of air to be able to get in and stop roof condensation?
warm roofs, do not have ventilation. You must be thinking of a cold
Have you got a video that shows the difference between the two?@@SteveRoofer
No worries I found one.
So did I. There is no mention of condensation or mould !
The moisture in air condenses where warm moist air contacts a cold surface. Hence if the roof structure is fully insulated without cold air ingress or cold bridging, the moisture won't condense as the insulation internal face is at or close to the ambient air temp.
Hi Steve, very informative, thanks for posting. I want to replace the polycarb roof on my 3m sq lean to conservatory. Would you recommend a warm or cold roof? Just worried about the weight of a warm roof. Also what thickness joists would you use on a small roof like mine? Cheers.
Great video! Can this be done retrospectively? i.e. remove fascia board from the outside and seal it up from there without having to re-roof? Thank you.
That is superbly explained! Thank you very much for this channel Steve. Cyril / Artisan Roofing Limited
always done this takes time but its well worth it.
Good to hear. I bet you've seen it done incorrectly a few times though?
Did I read somewhere that you been a flow of air in the foot area to prevent moisture build up and mold - which is why soffit boards have holes in them to allow for breathing?
Very good video Steve. Thanks for the info. I always thought (or think I was told when I did my Carpentry & Joinery course between '94-'97) that you had to leave a gap between floorboards for air to circulate. I guess this has now been superseded in today's world? Thanks once again and ATB
its different a roof level
@@SteveRoofer Aah, of course! Thanks for clarifying Steve. ATB
Very good Steve 👏👏👏
Thanks
When you've got a house that can't breath, do you leave the windows open to let the moisture out ? I have lot's of drafts in my old house, and it's nice and dry.
Hi Steve, loving the videos. I am learning quite a bit about vapour barriers and insulation. The only part that confuses me is where to vapour barrier the wall? I'm making a garden room with a warm roof where the osb for the roof will have a sticky vapour barrier applied on top, followed by insulation and then another later of osb on top as you explain in many of your videos. I will be tucking in the insulation in between the joists under the osb on top of the wall as you explain. My question is if i use a barrier on the inside of the wall and take this over the insulation between the joists (where it's been 'tucked'), what would i do about the joist? if i tape around the joints could there still be a dew point inside the joists themselves due to thermal bridging? will air movement pass through the joists (the wood itself) and pass laterally through the osb? is this even an issue I should be concerned about?
Hi Steve, could you give me a bit of advice. I am building a garden room and the roof joist are 120 x 45(5x2). I was thinking of using(cold roof inside to out ) 12mm plasterboard - 1000guage polythene - 25mm PIR up to joist - 100mm XPS insulation between joists and 20mm air gap under decking with continuous soffit vents back and front. will I get problems only having 20mm air gap
for a SIPS panel garden room, would you say that you need to vent the top like a codl roof, or can you just put DMP on the top of the sips?
Good info Steve but might have been worth mentioniong the cold bridge on the RSJ's, visible in the earlier (main) part of your video. 👍
This is so helpful! Thank you so much! However, I really need your advice. I am preparing to convert the cold flat roof of my dormer to a warm roof. I am having a hard time finding details on a warm roof intersection with a pitched roof. Could you please share any advice you have around what happens around this intersecting junction. For instance, should the PIR be mitred to butt up against the pitched rafters or left hollow? And how should the rubber be tucked around the side of the flat roof at this junction. I would be eternally grateful if you could shed some light on this or even point me to some resources. Thank you!
Great video Steve as always. Question's for you as a continuation to whats in the video. Would it be bad or good to fill the joists with extra insulation, and would you use an airtight membrane on underside of joist sealing back to the walls?
The golden rule is that you can put insulation between the joists on a warm roof, providing you only put one-third of the quality, the thermal quality of the insulation. No, you do not need a vapour barrier at that stage. No, you do not need to seal it against the walls at that stage, as you have sealed it against the walls higher up with the vapour barrier.
Brilliant to see this and at just the right time. We have some real challenges with how our roof has been left on our build. We had a warm flat roof joining a cold roof and one was open to the other. We have closed the junctions tightly with PIR and then painted all of the joints and gaps with passive purple. Even without the build finished we could tell a massive difference. We have a bigger challenge on the eaves of a cold vaulted celiling where the roof PIR was simply no where near joining up with the wall insulation. Would really like your opinion on how to tackle it.
Send over information, videos and photos
@@SteveRoofer Thanks so much for your amazing support. We have found your channel so so useful and your responses to our questions so quickly were such a help. Your points about trades not wanting to spend time doing the right thing are so crucial. Sadly I don't think many general builders are even aware of what they should be doing. The quality of our build in this respect was very poor.
Hello Steve, Any tips for Insulating around Roof lanterns? seems the joists and upstands they sit on are a thermal bridging issue?
I really like my builder, so I'm hoping he's done this on my new extension. I'll be checking when the wind picks up.
Hopefully he's done a good job for you
I have a timber framed house. We have put wool in the walls, between floor joists and in the loft (cold roof). I am now adding Intello Plus to the walls which will extend into the loft. To help against thermal bridging I will be adding 40mm of woodfibre insulation board to the walls on top of the VCL and extending this up into the loft to the top if the rafters to tuck it in ;) It looks on this video like you extend the insulation up into the rafters but the insulation seems thicker when viewed from the outside. Is this because you are adding insulation above the wall plate?
Hey Steve, you've been super helpful in planning my expansion, Quick Question -- Does my tuck in have to covered by vapour barrier on the external?
Good question. No, I don't think so. The vapour resistance of the PIT is probably already higher than the wall's vapour resistance so no need to
I'm having an extension built at the moment and they haven't insulated behind the fascias. The problem is there is now a very small gap between the joist and the parallel wall and very little space to get anything in - the only thing I can think of is expanding foam. Any advice?
What would be the best way to insulate under rafters if the rafters were only 70 x 50mm and head height underneath was a premium - effectively a loft used for storage but at the top it was less than 5ft between floor and floor, would superquilt or something similar be better than nothing?
Wonderful videos (all of them!). I am commenting here hoping it gets the numbers up.
Wow, thank you! The response to this video has been quite amazing. I didn't actually want to post it. I had it in my bin for quite some time thinking that I would never publish it. However, a customer asked me a question, and I sent it to him as a private video; he thought it was amazing and suggested that I put it up, so I did, and it's probably going to be one of my top performing videos. Thanks for your vote
Excellent advice! We just need to wean ourselves off of expanding foam and petrochemical based insulations now. Hard to do as they're so cheap (in comparison to natural insulation) and they have made them so easy to use too.
Could you combine the two? A foil backed insulation, with natural insulation (wrapped round it) to fill the gaps? I was surprised by the amount of foam insulation used there and thought that there must be a better solution. I know that there's gapotape, but it seems to be fairly expensive.
I think the way to go is to use multi foil insulation. There's a company called super foil out there. All of these foils are much better
It's not just that the foam is cheap to buy the material; more important than that it's so fast to install. I think it's ease and speed of installation that keeps people using it: whether professional or DIY.
@@ricos1497 I'm not a great lover of PIR style insulation either but in roof construction I wouldn't consider anything else...It is sufficiently rigid to support the roof membrane and it is relatively impermiable to vapour. If you use fibre type insulation around the perimeter vapour can pass through it and at some point within the thickness of the insulation it will likely be cool enough for condensation to occur, making the insulation wet and in turn creating even more condensation as the trapped moisture makes the insulation less effective. This is also why Steve uses so much foam...it is to prevent any water vapour from travelling through the gaps around the insulation, as well as stopping air passing through from outside.
your on the ball fair play
Thanks
How would you tackle a dormer bungalow roof? The roof line comes down to the same level as the interior ceiling.
Im a builder and youre stating the obvious( to me). I always fit 2 x 100 mm layers between the joists at that location. Blindingly obvious.
yes, but you're obviously a builder with a brain I can't believe what some people do it's just no thought in the process
I'm a builder I know better it's so obvious to me😂😂😂😂, ffs get a grip it's not a building regs course. It's helping people with little knowledge out.. billy big balls👷🏼♂️.
love the vids learning loads
Thanks
Useful videos. I have a question for a small shed/office I'm rebuilding with a cold roof. Have plenty of space between roof joists for insulation, and space above for ventilation. However, due to being on boundary line there's only a sizeable overhang on the front of the building. Obviously easy to add vents to the soffit at the front - what to do at the rear to help air circulate? Is it possible to get vertical venting that could be fitted at different points along the facia board? Have seen mushroom vents which could enable air to escape upwards, but would prefer to vent straight out the back with less possibility for leaks if possible. Any suggestions or advice welcome.
If it's only a part time she'd office it's not as important to fully vent it as there won't be much condensation build up compared to a kitchen or bathroom where there's heavy use with multiple people & cooking & steam from shower
Hi Steven. How do you ventilate a loft conversion properly when you have a warm deck flat roof box dormer on one side and on the other you have vaulted rafters which are insulated in between then insulated over them underneath? Cheers
Ridge vents or high level tile vents sufficient to provide at least the equivalent of a continuous 10mm gap....so for a 6m long ridge you would need vents with a total clear vent area of 60,000mm2. You will also need a means of making sure every rafter void is vented by whatever vents you install (so continuous ridge vents, vent tile every rafter or create a vent path at the apex of the roof by providing a flat insulated ceiling just below the ridge, and using the small void above to link the rafters)
Hi Steve, what areas do you cover? I have a full roof on the main house that needs replacing and bringing upto spec. Its a felt roof thats got a low pitch. The job is in Harlow. Ideally I'd like a manufacturer backed warranty with the new roof.
We cover that area. Send me details by email.
whats the silver stuff above the joists? I would have expected to see OSB form below in a warm roof? That looks like a vapour control layer?
Its the bottom of supper quilt as this is a warm-pitched roof
I'm concerned abiut the life of the roof tiles when the roof is highly Insulated and the tiles become frequently frozen. Any insight?
Hi. Interesting video. But perhaps you could do another to clear up some confusion. Especially for owner of older houses that require ventilation in their rooves to stop condensation. I have tried this method with my new roof and quickly discovered that the roof needed air movement yet I still would like to be able to some how seal out the cold air from out side getting into the inner space on the other side of the insulation. How do we do that?
If it requires ventilation, and is an older property, I'm assuming your roof construction is a cold roof, not warm roof. There are lots of different methods and products to help manage cold roof ventilation. I've seen people put an internal layer of insulation on the inside of a cold roof ("hybrid roof" maybe?) and then fit window trickle vents or other approach to manage what you are describing.
5:40 I think lots more water vapour will get into the PIR through the cut end than through the bigger silver sides and make it damp and useless ... Its like when you have a lot of broken windows mending one doesnt make any difference but when you mend the last one suddenly the house is warmer and less window (actually the one before last cuts the winds) I'm planning on wrapping my kingspan seconds in membrane like a xmas present and taping it up, any great reason not use any old vapour barrier and tape from Wickes or Toolsation compared with the most expensive sticky packed stuff?
Celotex & wingspan insulat6are closed cell so any moisture which will be minimal won't affect the boards,
but they get damp through the cut ends if left in the rain and take weeks to dry out .... and vapour is smuch smaller than rain molecules @@pauldavies7251
Doesn’t the air need to circulate, air vents to prevent damp?
Hi im be interested to know what your thoughts and experiences are of ecohome insulation diy garage kits? Will it work or a full plasterboard with built in insulation and vapour barrier better? Same for the roof to? Cheers
don't know, send over details and I will have a look
Moved into our bungalow with rafter level insulation that was freezing - a massively shoddy job - dropped all the insulation to ceiling level and doubled the thickness - worked this out inadvertently 😮
Did you provide ventilation?
@@ooooobpbpbpooooo the soffits were already ventilating the ceiling so now the air goes up and out through the roof vents instead - one part of the house was already done like this so it’s not clear why they chose to go warm roof on the main part without doing it properly 🤷♂️
Hi Steve. Building out a flat roof on a garden room at he moment. warm roof. Is there any point in putting timbers in now ime noggins allowing for the insulation or wait till after ?
do it as you go along
The builder who was doing our infill extension mixed warm roof with the older style ventilated system, and I had to point out to him that cold air would come directly into his roof and sit in top of the plasterboard ceiling. He didn't understand but I got him to put insulation between the old and the new. Unfortunately, as I am not a builder I didn't see he hadn't done the outer parts that you have pointed out. When I get my flat roof redone, I've a good mind to get the warm roof converted to the match the rest of the flat roof and fix the problems his roof has introduced. The other issue is the existing original flat roof slopes, and the warm roof is flat and sits proud of the old roof. It has leaked and causes the rain water to be directed to one side of the sloped part and now overwhelms the gutters. I fixed the leak as he was blaming the old roof and didn't accept responsibility for his poor work, so I wanted nothing more to do with him, but I wish I had known what you have pointed out. Oh well, lesson learned and thanks for posting.
okay, next time get in touch and we will talk things through
Great video. What do you do about ventilation?
Nothing you don't need it its a warm roof
Hi Steve, I see below that you have spoke about warm roof and cold roof but my question is, BC (sorry for swearing) have said I MUST have ventilation installed throughout the roof to allow for airflow from the outside through the roof. I have a 150mm joist and I have to use 100mm insulation. Would I be right in thinking I could install the insulation 30mm of the roof lining and this will leave a 20mm gap from the insulation to the wall which I could then fill with insulation, allowing me to "wrap the room" whilst also allowing the ventilation above the insulation for the BC approval?
Is it a warm roof or a cold roof that you are forming?
I made this mistake back in the eighties when i insulated the roof of a house i owned at the time. I didn't do this. In fairness I did get some noticeable benefit from the roof insulation. No doubt it would have been even better had i done it properly. I'm wondering now if any owner since I sold that house has noticed the problem😮
Hello, excellent video 👍 I’ve got a wooden garage that’s pretty much got open ends between the joists. If i tuck in the roof can it sweat, being a garage with no heating?
Sounds like you might have a cold roof? In which case, this video wouldn't be for you.
@@ricos1497 I didn’t want to stop airflow and then have condensation problems
@@next0845 you would only want to stop airflow in a warm roof (a warm roof is a type of roof, rather than just a roof that happens to be warm, just to clarify - in case you don't know the terminology like I didn't previously). A cold roof setup you need the airflow.
@@ricos1497 Airflow it is then. Thanks for the response 👍👍
Just to be clear . So you have a good roof then ? @@next0845
Where does the warm air escape to? If there is no air flow wouldn’t that affect the joists? Any sweating? Thanks for the video by the way 👍🏻
Why would you want your warm air to escape? You spent good money heating it up
Hi Steve . A question can you convert a sloped cold roof to a warm roof with multifoil instead of increasing the height of the existing roof by wrapping the roof joists with multi foil and another layer of multifoil before the plasterboard
Yes you can I'm actually doing two at the moment
@@SteveRoofer superb. Thanks Steve. Would be nice to see a video update
Thanks for explaining this Steve. Isn’t cold-bridging of the rafters an issue?
The rafters are all internal buried deep below the insulation. How could you ever get any cold bridging please explain?
@@SteveRoofer Hi Steve, wouldn't there be cold bridging from where the rafters overhang the wall plate to the outside? i.e. the part that the fascia board would normally be nailed onto?
Hi Steve, I'm just in the process of replacing my old cold flat roof extension, it runs to the centre with a central gutter. Im fitting a wall plate and having it slope all away from the hoise with new joists above the old. A few questions, can the existing felted but non insulated roof be left in situ or can this cause problems with damp. Im intending to put 150mm PIR between the new 200mm joists, leaving a 50mm air gap, followed by a quilted foil over the top of the joists, 50mm battons then 18mm 0SB3 followed by EPDM. Will this cause any problems, im planning to let air flow across the width of the roof via the gap in the battons above the foil layer. The existing roof had no insulation in the original 225mm cavity and is finished with polystyrene backed plasterboard. I understand i will need to expose the ends of the old roof to continue the new roof insulation to the existing brickwork. Thanks in advance Jonathan
You need to send me an email and ill send you back info
Hello. I have a 70’s house, typical brick construction with cavity walls. Where the joists meet the wall there are inch gaps into the cavity. Should these be filled? Also on one side of the house I have an attached (unheated) garage. The joists for the garage flat roof go into the outside leaf of the house cavity wall, again with a gap. Also fill? I feel it’s highly likely that cold air from the garage (and loft) goes into the (filled with fluff) cavity and would make its way into the house.
You have to be careful insulated older homes, as it can lead to rot. What happens in a lot of older homes that have insulation upgrades, is that moisture gets trapped by the insulation & condenses on the cold sheating & joists. Over time they start to rot. Because the older homes aren't insulated & have a lot of air movement, any moisture that does condense quickly evaporates. What you probably need to do is first get keep your indoor humidity low with a whole house dehumidfier, upgrade your bathroom fans (make sure they work) to pull out bathroom moisture. ideally a Timer on the fan switch is ideal because you can set it and not have to manually turn it off (reason why most people don't use them). And then test a second of your home to see if moisture accumulates. (ie test a section of your home) You need to use a removable insulation such as rockwool. I don't recommend spray foam since you cannot inspect behind it to see if there is a condensation problem.
Thanks, yes I've started with rockwool in the inch gap and then foil tape over the hole on the garage side so far. In the garage it's easily accessible, on the house side it's not because obviously it's in the ceiling space. I think the garage side is lowest risk because the other side of the house (identical except no garage) has no gaps as it's an outside wall. I have zero signs of damp as of now, but will be something I keep a close eye on. I think it is as modern/good as is possible for 1970, pretty square and overengineered. I have over fascia ventilation in my loft in preparation for doing as much insulation as possible up there. @@guytech7310
Nice neat block work! Your lucky if you find any of them filled in by any trade. Only time that would happen without getting you guys in,is on the tradesman doing his own work!
Correct DIY,s always do a better job
I prefer to use Gapo Tape than the expanding foam. Cleaner, tighter fit but downside more expensive.
steve, how about a air flow through the timber part of the roof. ps; I see a lot of cavities are not covered with Fibre cement sheets to stop moisture going up in the roof space.
They are warm deck roofs, you don't want air flow with warm deck.
It's a warm roof you don't need ventilation on a wall roof. Rob Norman below is correct.
What’s the best way to rectify this cost effectively? Do you have to remove the ceiling from the inside? Can you do it from the outside by removing the fascia board?
You can do it in many ways. Obviously, you choose the cheapest way if that means taking ceilings down inside or taking gutters and facias off outside or cutting down from up above Whatever way you need to do it.
This is perfect timing, I've just built a warm roof, tied into my houses pitched cold roof. Now the joist void under the warm roof is open into the pitched roof loft space. On the inside Should I close this off?
If the pitched roof is vented i.e. a cold roof, then you've got to stop all that cold air getting into the area between the choice of the warm roof. So yes seal it off
Yes seal it off, but don't forget your loft space needs ventilation.
Sealed = condensation central. No.1 reason for my damp surveys over the past 4 years.
In this video, I am forming a wall roof. Warm roofs do not need to be ventilated. cold roofs need ventilating. This video is only about warm roofs that do not need ventilating. In the video, I show that I go around the edges and insulate and make it completely airtight. The insulation around the edges meets the insulation on the roof. Theoretically, you could sit in the room without a ceiling and still be warm.
@@SteveRoofer It’s not just about the roof space. It’s the whole house. Houses get used by people. Damp from breath, use of water, drying clothes, etc.. That moisture has to go somewhere & usually ends up around windows & cold walls. Sealed buildings require active ventilation to remove the moisture from the air, preferably in combination with a heat exchanger. I’ve had plenty of cases where condensation is a problem for cold roof spaces too, but warm roofs have become a regular occurrence in the last 4 years with both new build & reroofed extensions. In a ventilated cold roof, there is a wicking action for some moisture to escape through the ceiling &, although when done incorrectly, adds to the condensation issues, a properly installed cold roof or a warm roof with active ventilation will significantly reduce the possibility of condensation issues for your clients.
Is it wise to insulate between rafters as well as over?
It is totally forbidden and must never be done....If you are converting an old cold roof with insulation between the joists to a warm roof then all the old insulation must be removed, if you dont then there is a significant risk of condensation because the roof timbers will no longer be at room temperature. If its 3 degrees outside and 23 degrees inside with a warm roof all your timbers will be at 23 degrees. If you have half your insulation between the joists and half above the roof deck the roof deck will likely be at say 13 degrees so colder than room temperature and potentially a surface that condensation can occur on.
What about some ventilation? Will you not get moisture and damp build up?
The risk is condensation and the theory is, if the insulation is above the decking then condensation risk is reduced. If the insulation is between the joists, then you need ventilation between the insulation and outer layer. Condensation risk is greater this way. The best way with flat roofs, is not to have flat roofs lol
Tucking in, as you put it, would that not cause an issue with warm air being trapped inside? Are you not meant to have ventilation from one side to the other? Not being arsey, genuinely not sure lol
So, just a question. Where is the moisture accumulating in the room going?
It needs to be cleared by room ventilation, opening windows etc. The important thing is that if you follow Steves guidance it wont be causing problems in your roof. The problem with moisture vapour is it condenses on colder surfaces. If your roof is at room temperature it wont condense there.
My new ECO build from Norscot ,doesnt need the rafters insulating,as its got insulation from the flat roof to the rafters.
What about the edges of the rafters, the verticals, described as "tucking in" in this video?
@pbpbpooooo Norscot say no tucking in, this is not required as in the Eco house its got insulation in the walls as usual,then there is a seperate cavity for electrics/ plumbing etc which has insulated boards ,which are aluminium taped to seal completely. Its a good idea,but more work,it means ,cables etc are not covered in any insulation,which is good,makes it cleaner,im not at that stage yet,but it seams good.
@@enoz.j3506 Sounds neat and worth the effort.
What about rotting caused by cold beanend temperatures? Is that covered?
The cold ends of the joists are fully ventilated by the outside air and will be at outside air temperature or very slightly warmer so no condensation can take place.
Hi I have just done a cold flat roof with 70m insulation between the joints and a foil vapour barrier but there is a lot of condensation on the foil where the joints are is this normal
Do you have ventilation? I would think it's good in the sense that the moisture is not penetrating the vapour barrier (condensing instead on the inside) but bad because there is no ventilation for it to escape to the outside in a managed way.
Hi Steve, can I ask how you would ventilate the roof timbers if you fully ‘tuck’ in from the eaves . Cheers 👍
No need for ventilation on a warm roof
@@pauldavies7251a warm roof?? What are you blabbering on about! A roof and attic are hot in summer cold in winter. If you seal a home up with no air flow, it causes moister to condense and cause black mold. And in worse case if you use natural gas cooking you could end up with high levels of carbon monoxide build up! You insulate the FLOOR of the attic, and allow the roof to “breath” and release moisture from the building walls.
@@martinbuss6818it’s a warm roof. The space between the joists is effectively inside the room. Moisture won’t condense inside. There is a vapour barrier above, then 120mm of celotex. You don’t need ventilation in a warm roof.
@@martinbuss6818 I love the arrogance from clueless people 🤦♂️🤐 , A warm roof means the insulation goes outside the main roof so there's absolutely no need for ventilation, You only need ventilation when you've insulated between joists or rafters, Aka "cold roof"
@@gdfggggg there's no telling some people is there
Do you have any drawings or schematics of the correct way to construct various roofs?
yes, some are generally they are supplied to us by the architects
94 year old slate roof with no felt. Holes = leaks. Thermal insulation? What's that?
What about lack of airflow and damp? Please help.
In this video, I am forming a wall roof. Warm roofs do not need to be ventilated. cold roofs need ventilating. This video is only about warm roofs that do not need ventilating. In the video, I show that I go around the edges and insulate and make it completely airtight. The insulation around the edges meets the insulation on the roof. Theoretically, you could sit in the room without a ceiling and still be warm.
For a garden room, is a warm roof or a cold roof the better choice?
Warm roof
Do you not have a sub deck on your warm roof with a vapour barrier?
You dont need it with many types of rigid insulation, then it is possible to use aluminium tape to seal the joints between the foil faced boards from the underside to create the vapour barrier. You will need a structural deck above the insulation to support the roof covering. Conversely if you do provide the structural deck below the insulation and vapour barrier as you describe you csan use a thinner ply above the insultion to support the roof covering.
Ventilation? Damp?
You need to be careful about blocking up the air gap as you can then get condensation in the roof cavity.
He was showing examples of warm roofs (not cold roofs), which don't have a ventilated cavity
Impossible to have condensation inside the insulation, there's a major problem if you have, Cold roof you need to worry about ventilation between insulation & roof deck
Where is the air gap between insulation and roof?
When roof manufacturer's produce specifications for warm roofs they don't include this and it does often get missed. At a minimum you want as much insulation as there is in the wall.
Hi Steve I'd love you to look at my loft space, condensation everywhere. Discoloured insulation. I think our soffits are being covered up with insulation. House builders have washed their hands of it, marley risk have rejected our claim. Scandalous behaviour!
Thats because moisture condenses on the cold sheathing & gets trapped by the insulation with no way to dry out. To address it, an air permeable insulation (no foil) and dehumidification is needed. The dehumidifier will reduce the amount of moisture that condenses, and a permeable insulation will allow condensate to evaporate (ie when the roof become warm when the sun hits it. The foil membrane traps moisture in. Rockwool (Roxul) is a moisture permeable insulation. Another option is to use a permeable roofing membrane that allows trapped moisture to escape from the topside of the roof, but you need a roofing configuration has an air gap so for the permeable membrane to work: ie metal, slate, tile roof with lathing set up to draw in air from the soffit up through the ridge cap. Building science {dot} com has a collection of articles about condensation issues in well insulated homes. They did a lot of experiments to test what did & did not work. You can read them for free.
Send some photos over Steveroofer@gmail.com
I thought there was supposed to be no insulation between roof beams as it traps moisture.Which is right?.
I believe depends where the dew point is. If the insulation is airtight and thick enough no moisture reaches the outer wall or condenses in the middle of the insulation.
In this video, I am forming a wall roof. Warm roofs do not need to be ventilated. cold roofs need ventilating. This video is only about warm roofs that do not need ventilating. In the video, I show that I go around the edges and insulate and make it completely airtight. The insulation around the edges meets the insulation on the roof. Theoretically, you could sit in the room without a ceiling and still be warm.
Also not to mention the amount of cellotex that ends up in the skip. If nothing else this is a good way to use up offcuts of insulation too small for anything else.
Yes, you're absolutely right, all we ever do is use the offcuts
How does any condensation in the loft escape
It’s a warm roof. Moisture won’t condense.
Through ventilation but in this video we are talking about warm flat roofs not lofts
Would this work on a pitch tiled roof
yes warm roof works on a pitched roof. However we do them slightly differently
Also I have the inside the attic spray foam insulation, but still have a draught from attic, is it possible that the felt is damaged, it’s old blizzard felt, non breathable, find your videos very helpful
Same applies when a flat warm roof on an extension goes into the pitched roof of a house.
Yes, you're correct you still have to separate the two roofs in the same way
I’m confused, I thought a warm roof meant insulation would go on TOP of the decking. This looks like insulation is immediately below the decking. Help me out, what am I missing?
A warm roof does mean that. This video is about how you should bring the insulation from the top, down the sides to meet the wall.
Correct, the insulation should sit on top of the decking which has a layer of felt tacked to it and a 3 layer of polyester membrane torched on top of insulation. A thirty year life. Just one point though, it is not possible to acquire a underwritten 20 year warranty for a F/G or rubber roof?
What about ventilation Steve?Should there be Insultion, a gap for venting?
You don't vent warm deck roofs
thanks mate! I thoughtall roofs need to be vented@@RobNorman08
Thanks again Rob, you're correct looking through some of these replies I can see lots of people are confused warm roofs do not need ventilation cold roofs need ventilation
Thanks, rob, I see you are answering a lot of people for me. This video has got quite a lot of his quite quickly. I need the help. I can't answer them all. I can't believe the amount of people that do not understand why roofs don't need ventilation
@@SteveRoofer I'm a Chippie, been in the trade for 30 years, build loads of warm deck pitched and flat roofs, on lofts/extensions. I've learned that many, many people really haven't the faintest idea how, when and why roofs need or don't need ventilation, There is a huge amount of information available on the subject if only people would take the time to research it rather than blindly harping on about ventilation!..all the best.
Where and how is the moisture from within the house, created by people living there, cooking and laundry, etc., dissipated, it's so air tight , no talk of vents or extraction fans. Moisture will find its way through the house into the attic and condense there
I'm a total newbie self builder and I knew to fill these voids... What are some professionals doing? XD
We all make mistakes however, somethings are pretty obvious so you've gotta assume they just don't understand what they're actually doing
This guy is passionate about insulation 🤣🤣
How is the warm roof ventilated
It mustn't be, that is the whole point of this video. You have to vent cold roofs above the insulation but you must never ventilate a warm roof below the insulation.
Doesn’t the air need to circulate, in other words,don’t you need some gaps, to let fresh air in?
In this video, I am forming a wall roof. Warm roofs do not need to be ventilated. cold roofs need ventilating. This video is only about warm roofs that do not need ventilating. In the video, I show that I go around the edges and insulate and make it completely airtight. The insulation around the edges meets the insulation on the roof. Theoretically, you could sit in the room without a ceiling and still be warm.
Get ready for the 'builders' and 'roofers' who say you need to keep these areas open for air flow. Those guys are absolutely clueless. Have no idea about warm and cold roof sysyems.
Neither have you pal
@@tomthumb1769 and we found one of them. I pity any poor people's homes you've been near.
@@benrichards1 I’m time served bricklayer of 34 years pal what’s your qualifications? Apart from being a know all
@tomthumb1769 Great. Stick to laying bricks, then. Let roofers roof.
@@benrichards1 in your first comment you mentioned roofers with builders so I’m not sure you have any idea what your talking about
Please understand that this is a warm roof and do your research before attempting this. If this was a standard cold roof, doing this insulation like that would be wrong.
Good point I didn't think I needed to make that clear when making the video. However, you are correct I should've done
Timber need Air don't forget that when insulating your home.