Garden Room Workshop: Part 15. Wall Insulation & Vapour Barrier transcript

welcome back in the last video we covered the first fixed electrics and plumbing of my garden room and it was very theory-based but in this video i'm back in diy action insulating the walls and installing the vapor barrier ready for plasterboarding the order of this series so far is probably pretty close to what you want to do but at this stage you can either turn your attention to the inside or outside of your garden room because it was winter i decided on the former there are two main options for wall insulation pir and wool bringing back this graphic from a previous video we can see that the majority of heat in a building is lost through the walls but that's only because the surface area is much greater than that of the floor or roof heat loss per square meter is lower in the walls so if you're on strict budget the walls are a good place to use cheaper wool insulation however the timbers in the wall are narrower than in the floor or roof so i decided to stick with pir as for the same thickness pir is a much better insulator than wool my wall timbers are a nominal depth of 100 millimeters but the actual size is 95 millimeters so i couldn't use the same 100 millimeter insulation as i did for the floor and roof and instead i ordered 90 millimeter pir which finishes very flush with the inside of the studs this provides for a u-value of 0.26 which is pretty close to my target of 0.25 as i've mentioned previously all pir is much of a muchness so i went with the cheapest i could find at the time which in this case was quintum i started off by cutting the insulation with a handsaw just as i'd done previously this stuff is incredibly dusty especially when you're working inside so make sure you wear a dust mask gloves if you have sensitive skin and eye protection when you're fitting air head height as the air compressed behind the pir shoots out from the sides because my electrics come down vertically from the ceiling most of the voids were empty of any cables so i started with those before inviting my friend steve over when i mentioned i was building a garden room steve revealed that he had his own plans to build one in his garden so he offered to help out to see how it was done and the one thing you need to know about steve is that he has awesome power tools including this festool sword saw that runs on a track which we thought might make light work of cutting the insulation [Music] [Applause] [Music] so [Music] having done most of the build until this point on my own it was actually really great working with a friend and we were careful not to mix too many beers with the power tools now in some cases where a void isn't being filled entirely due to the cabling or pipes the insulation wouldn't stay in place so in order to get it to do so we cut triangles and wedged them in to hold it and then we spray foamed in a couple of spots and once that was dry we could remove the triangles and the insulation would stay in place there are two ways you can cut insulation you can do what i did which is to try and get it as accurate in size to the hole you're filling but like in this case a fraction too big and you can have a hell of a time trimming it and hammering it in place the other option is to deliberately cut it 10 millimeters or so too small and that way it fits easily and you have more room to get the nozzle of your spray foam gun in the gaps around it of course with the first option there will still be small gaps so steve went around the room filling these and did a mighty fine job of it too being really diligent with getting every gap filled will make a huge difference to how warm or cool in summer your garden room will feel and this brings me to a point i've been wanting to make for quite a while you or i may not have professional building experience and may make mistakes but when it comes to things like spray foaming and many other jobs throughout the build you will do a much more thorough job because and here's the kicker nobody cares more about your garden room than you and that's not to put down professionals in any way if they took the time a diy is able to getting something as close to perfection as possible the cost would be prohibitive but it does give us an advantage now if any spray foam gets away from you i learnt from experience not to try to wipe it up but to let it dry first and then it snaps off easily so when that was all done abby and i went around the room and cut off any excess spray foam the remaining areas to fill are around the pipes and cables you could fill them with spray foam but i was mindful of what we discussed in part 14 which is not to surround cabling too tightly with insulation even if it isn't a conduit so i instead decided that i would use thermal rock wool for these bits with all insulation is actually the trapped air inside it that provides the thermal resistance and works in the same way a puffer jacket does so the trick is not to pack it in too tightly for these areas i tore off small pieces and pushed them in gently until it was filled [Music] the last job to do was around the consumer unit the position of which will be below the existing noggin so my electrician told me he needs something to secure it to first i cut a piece of osp to the right width then use some off cuts to mark up where the back side of the osb will be when it's in position i still have some red cedar battens that i use for the floor and so i use them to attach to the studs on each side lined up with those marks the osb was nicely flush with the inside walls so i marked up the position where the cables would need to come through the osb remembering that a consumer unit needs to be a minimum of 45 centimeters from floor level and i cut a hole with a drill and jigsaw next up was to cut the pir insulation to size and width and then i could thread the cables through the hole and secure the osb to the battens the bit above where the cables come out i couldn't fit pir insulation so i instead loosely filled it with rockwool so the walls are now all filled but if you've gone for a cold roof this is the time to do your roof insulation having gone for a warm roof myself i'm trying to imagine the challenges that you might face one of which is probably gravity if you're using pir you could attach battens to the underside of the joist to hold it in place while the foam spray cures wool insulation is of course a lot easier to compress and get a friction fit if you're having down lighters then you'll need to cut holes in the insulation to allow the heat from the lights to dissipate the rule of thumb here is to cut a hole in the insulation twice the diameter of the light fitting you could use slimline down lighters instead which may help reduce the amount of insulation you need to cut away remember that a cold roof needs to have a space for ventilation above the insulation of at least 50 millimeters so you shouldn't push your insulation all the way to the top however if your joists are quite deep you can push your insulation up some of the way and so minimize the amount of insulation you need to cut away for the down lighters this might not work so well with wool insulation as it's likely to sag back down over time from the last video we know that the holes for wiring need to be through the middle of the joist so your best bet is to loop the wiring under the insulation like in this photo led lights need minimal power so you don't need to worry about the wiring becoming overheated but you probably won't want the rest of your cables in the ceiling like i was able to with my warm roof now that's all the thermal insulation taken care of or is it we've discussed thermal bridging before which is the process of heat being lost through your joists or studs so what you can do is overlay 25 or 50 millimeter insulation inside of the studs or under your cold roof to create a continuous sheet of insulation you can achieve the same thing with insulated plasterboard but is the cost time and internal space lost worth it at this stage i conducted a little test comparing the outside temperature of 9 degrees celsius with the inside temperature using a fan heater and an old electric heater despite the window being slightly ajar the inside temperature got to over 20 degrees jumping ahead to the future or present i'm not sure i can tell you that my radiators have seldom on and keep the temperature at a constant 21 degrees so from my experience i would say that if you copy what i've done there is no need to overlay any extra insulation while thermal bridging through the timbers may not sound great timber is actually a very good natural thermal insulator due to having air pockets within its cellular structure it's 15 times better than masonry and 400 times better than steel which is just another reason why i like timber framing all the external walls are filled the room is warm but i also have the internal stud wool separating the main room from the shower room i will have a fan heater but i want heat to transfer through the wall into the shower room so this time i opted for sound or acoustic wool insulation as i used 63 millimeter cls for the studs i chose 50 millimeter rock wool it feels much the same as a thermal wool but must have slightly different properties which skew its performance to deadening sound rather than the transference of heat though i'm sure both products do a degree of each do you remember earlier on this series i showed a couple of options for framing corners so you have a fixing point for plasterboard on both sides of the inside corner for the shower room i tried out the california corner which did make it easier to get the insulation in behind though i don't really have any strong feelings over which style of corner is better for the rest of the wall i could cut the insulation into slabs which is really easy to do with a stanley knife and a straight edge i cut it slightly oversized and then tucked it into place around the edges and it stayed in place nicely it's a really quick and easy process so i can see why wool insulation is a popular option for garden rooms certainly if your priorities on the time and cost of your build one area i didn't fill with insulation is above the top plate here and maybe i should have as there are only two layers of plasterboard separating the two rooms but then again it's not a direct path for sound to travel i haven't been able to test the sound insulation yet as i've only just installed the shower room door but i'll be sure to do so in a future video onto the vapor barrier i'm sure i've said before that a vapor barrier should be on the inside of the insulation but to be more precise it should be on the warm side of the insulation in the uk even if you're having air con going for a couple of months in summer you'll still want an internal vapor barrier if however you are watching this from further afield and live in a hot climate you may consider having an external vapor barrier for us in the uk there are four options for a timber frame building first if you've used pir insulation you can use aluminium tape to cover the studs which is what i did for my floors vapor barrier and works well the downside to this is that the tape is quite expensive and you'll need a lot of it for the walls and of course it's not an option for wool insulation the second option is to use foil-backed plasterboard it's easy as it's a two-in-one product but it's pricey and you can't really join the foil so it won't provide a continuous vapor barrier third a polythene sheet like i use for my roof is cheap provides continuous vapor barrier but it's a little cumbersome especially for walls the fourth option is a sealant which you can paint onto the plasterboard before the emulsion i'm not sure how effective it is and it is quite expensive but unlike all the other options it won't be pierced by drywall screws weighing all of them up i decided to go for a polythene sheet mainly due to the low cost i used the same one from wix as before which is 500 gauge the higher the gauge the more impermeable it is but also harder to fold and lift as most of my walls have a vapor barrier already the fall on the insulation and pir is pretty moisture resistant 500 gauge is fine bear in mind that this stage is more important if you have wool insulation as if even a small amount of moisture vapor gets into the wall it can greatly reduce its thermal resistance so you may want to go for a higher grade [Music] it's not just water vapor that we are trying to prevent being lost but air as well because it's no good having great insulation if heat is escaping through gaps and holes i.e convection so we should strive for a high degree of air tightness so i taped up all around the sockets and when i had cut off the xf's polythene from the bottom of the walls i could use a product called acoustic sealant which stays flexible and creates a tight seal between the polythene and the bottom plate i did the same for the top as well which is why i stapled a few centimeters down you could put an acoustic sealant on every stud so that it seals around the drywall screws when you attach your plasterboard but sometimes life's too short for these things if you're wondering about the area above the top plate there's not a lot i can do to add a vapor barrier so moisture will slowly leak through the joists and that's okay the thing to remember is that as long as vapor is moving out of your walls faster than it enters then you won't get a buildup of moisture and that's exactly what the battens that go on before the cladding help with which we'll explore in a future video here is a more accurate representation of where my vapor barriers are in my build and there are some gaps if you have the combination though of a concrete floor and cold roof then you have the opportunity to create a really tight envelope with the exception of holes for down lighters you shouldn't put down a vapor barrier on top of ply or osb or chipboard but if you use polythene under the ply you can wrap it under the walls and attach it to your wall polythene in fact if i could go back that's exactly what i would do as i found out that the aluminium foil only works to radiate heat back into the building if there's an air gap of a few centimeters but hey i'm learning that's it for this one in the next video we'll cover plasterboarding plastering and readying the shower room for tiling and i might be revising some advice i gave earlier in this series on the website we have mark and brian's builds congrats to both of you for finishing i haven't done a q a with them yet and instead thought i'd leave it to you guys watching so if you have any questions pop a comment down below this video starting with q for mark or brian and i'll be sure to put it to them no doubt they'll be happy to answer see you on the next one