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    • CommentAuthorKenny_M
    • CommentTimeDec 11th 2017
     
    Hi all,
    Just joined the forum today. Moved into an 1800’s detached sandstone house with flat roof rear extension built in 1989 about a year ago. The last year has mostly involved dealing with things like internal damp issues, repairing cast gutters, blocked downpipes, sealing up gaps at windows, reopening blocked under floor vents and a host of other diy jobs, and my main shelling out of cash has been for a mason to repair some of the ashlar stonework cornice and some stone at the front and to rebuild a chimney which was taking in water (one part of the dampness issue, the other part seems to have been mainly internal condensation (sash windows were all painted shut and no vents in bathroom and kitchen).

    My next step is to attempt to improve the energy efficiency and trying to decide what to do first. The GCH boiler is a quite old Ideal Mexico Super RS 125, which was allegedly 73% efficient when new, but presumably not now. This boiler is a bit of a workhorse and has lasted around 30 years, but the amount of heat coming out of the flue is criminal!

    The other side of things is insulating the fabric of the building. Despite the fact that the old part of the house still has single glazing and no insulation, it seems that it’s the ‘modern’ part that is the weak point. When I got up this morning before turning heating on it was 7 degrees C in the south facing 1980’s extension, but 12 degrees in a North facing room in the original house which has single glazing but had the wooden shutters closed all night. I wandered around the house this afternoon with an IR gun and was getting varying readings from -2 to zero degrees C on the outside walls, but on the double glazing pane around +5 degrees C, and parts of the frame were reading around +8 degrees C. I know that replacing double glazing is not usually the most cost effective thing to do, but this seems to be where most of the heat is leaving the house so I am wondering if I should go there before attempting to insulate walls. I think the issue in the extension is the amount of glass. It’s an L-shape and the sitting area is the bit that juts out, which means 2 out of the 3 outside walls of the sitting area are glass (patio door and windows). My gut feeling is that replacing the old DG windows will have the most impact in terms of comfort, they are old, unusually small gap, and were draughty before I silicone them up.

    One concern is that I do intend to insulate the walls eventually and I am concerned that this might be the wrong way around to do things, in terms of insulating the reveals. Is it better to do get the walls insulated first, then get window fitted taking into account any narrowing caused by insulating the reveals. Sorry I don’t know a lot about this so apologies if I am talking nonsense!

    Anyway, sorry for the long story, from my look around so far this seems like a good forum with a lot of experienced people so I would really appreciate any comments and pointers.

    Cheers
    Kenny
    • CommentAuthorgyrogear
    • CommentTimeDec 11th 2017
     
    Hiya, welcome !

    How is the extension closed off (if any...) from the main house ?

    gg
    • CommentAuthorKenny_M
    • CommentTimeDec 12th 2017
     
    Hi gg,
    It is built on to the back of the house, with what I presume must have been the original back door connecting the two. Its modern brick construction which has been harled/rendered, with the harling continuing on to the sides of the original house.

    I have tried to attach a pic but the site won't let me upload a jpg so will need to figure out how to upload photos.

    Kenny
  1.  
    Hello, and welcome.

    You need to work out relative areas of different elements. Let's say that on one elevation you have 10m2 of poor-DG windows (estimated U value 3.0W/m2K). That's 30W/K (where K is a degree temp diff).

    What the U value of a sandstone wall is will depend on thickness and whose figures you believe. Historic Scotland, IIRC, has done quite a bit of in-situ U value testing which shows better 'base case' U values than a simple calculation would suggest. If the walls were around 450mm thick, U value could be around 1.3-1.8W/m2K.

    If we take the worst case, and a wall area of 48m2, less the 10m2 of windows, that gives us 38(m2) x 1.8 = 68.4W/K
    •  
      CommentAuthordjh
    • CommentTimeDec 12th 2017 edited
     
    Hello and welcome.

    Your image file is probably too big. There's no problem with jpegs. Cut it down to 800x600 or similar.

    In terms of what to do first, I'd say the first thing to do is nothing! Take your time. Most people learn an awful lot once they start thinking about a building or renovation project and consequently their idea of what they want to do can change quite a bit. So it's generally best to wait a bit and get an overall plan for everything you intend to do before you start work.

    On parts of your house that are rendered, you will quite likely finish up wanting to add external insulation (EWI). If you have parts that have exposed stone or brick that you want to keep then you will have to use internal insulation, which is more tricky, or else use EWI and then put stone or brick slips over it.

    Once you've decided what you're going to do with the walls, you could perhaps replace the windows first. By then you'll know what size they need to be and where in the wall you want to mount them (inside vs outside, that is).

    Good luck.
    • CommentAuthorKenny_M
    • CommentTimeDec 12th 2017
     
    Thanks Nick, I think I saw that Historic Scotland document, and I think the point they were making was that the walls of a lot of traditional houses were much thicker than the software allows for, and that depending what the rubble gap was filled with, and whether there was a gap between the lath and plaster and the wall, all added up to a better U value than that specified in software.

    I had been originally thinking about trying to get planning approval for appropriate external insulation or insulated render on the side walls and the part of the rear that is above the extension, but between that historic Scotland read, and the values I am measuring I am starting to see this as a lower priority. Between the measurements I have taken on the outside of the house and experience of living in it, (with the exception of the single glazed windows on the old part) the modern extension seems to be where most of the heat is being lost.

    I am interested in trying to work out the U values for the house based on actual measurements. In the attachment at this link from the states that I found on the web there is a table for this, does anyone know of an equivalent for the UK in C and with U values rather than R, or can point me towards the calculation to work this out.

    https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwi_wP7RvITYAhWB5xoKHXf8C0gQFggpMAA&url=https%3A%2F%2Fwww.ag.ndsu.edu%2Fpubs%2Fageng%2Fstructu%2Fae1373.pdf&usg=AOvVaw2fIxmoSSVgQM6_MXqlfwsQ

    I presume there must be an equation where the external temp and the heat loss across the wall can be plugged into to work out the actual U values?

    There are some oddities even in regard to the modern extension that make estimating the U values tricky, for example the main side wall is of unknown thickness, or whether there is a cavity, and is butted up against a historic stone garden wall on one side which must also affect the overall U value.

    Kenny
    • CommentAuthorKenny_M
    • CommentTimeDec 12th 2017
     
    Thanks djh. The error said that jpg was not accepted but I have reduced the size and attached.

    I believe that I will want external wall insulation, but its complicated by a few factors. Firstly the fact that I won't get planning to do that on the front as I am in a conservation area. I might get planning to do this on the sides as they are already rendered, but this would mean the rendered insulation jutting out 100mm or so and would look fairly odd from the front, so again even if I decided to do this it might fail planning. Finally, one side of the house is right up against the next doors garden, so although the neighbours are very nice and would be fine about getting access, I would be extending my wall by 100mm or so into their property which could be complicated legally as well as potentially being a bit of an imposition on them. Also the side of the extension is butted up against a garden wall so there isnt an even surface for fixing insulation boards.

    EWI on the rear wall of the extension shouldn't be a problem though, and there seems to be a decent overhang from the roof as you can see from the picture. My thoughts at the moment are to think about the extension as a separate project from the old part of the house and:

    External insulation boards to the rear south facing wall of the extension
    The east wall of the extension doesn't matter too much as it is an unheated utility room
    An insulated render on the west wall of the extension (effectively actually rendering the old garden wall), combined with some internal insulation on the inside wall.

    Regarding the latter part, is there any issue with insulating both the outside and the inside of a wall if you can't get the thickness required from one or other?

    I also need to think about the floor at some point but its covered with tiles and I have no idea of the construction below.
      rsz_2017-11-17_112811.jpg
    • CommentAuthorgyrogear
    • CommentTimeDec 12th 2017
     
    Maybe for now, you could do with just sticking 40 or 50 mm boards of XPS tight-fitted in those windows, overnight. Sounds like a bit of a pain, but relatively cheap, and might work !

    gg
    •  
      CommentAuthordjh
    • CommentTimeDec 12th 2017
     
    Posted By: Kenny_MI am interested in trying to work out the U values for the house based on actual measurements. In the attachment at this link from the states that I found on the web there is a table for this, does anyone know of an equivalent for the UK in C and with U values rather than R, or can point me towards the calculation to work this out.

    That's an interesting article, thanks for finding it. I haven't seen a metric equivalent I'm afraid.

    Most IR thermometers will read in °F or °C or its an easy conversion if not. The R-value is the reciprocal of the U-value, but its complicated by the different units. There's a lookup table at http://www.myonlinediary.com/index.php/Insulation/US-EuropeanRValueConvertionTables

    There are some oddities even in regard to the modern extension that make estimating the U values tricky, for example the main side wall is of unknown thickness, or whether there is a cavity, and is butted up against a historic stone garden wall on one side which must also affect the overall U value.

    At some point, you'll probably want to answer questions like this by drilling a small hole to see what's there. Easy enough to fill again afterwards if you don't want a hole.
    • CommentAuthorgravelld
    • CommentTimeDec 12th 2017
     
    Great advice from @djh about waiting, experiencing the house, and taking your time. My own journey has been exactly that.

    I arrived in my house knowing nothing other than I wanted to get some security from energy costs. This initially led me to researching alternative methods of heating, like heat pumps, and also different technologies like zoned thermostats, solar PV etc etc as the solution

    Then I learnt it was actually possible to radically reduce the heat demand. This not only meant lower energy costs, it just made everything easier; lower maintenance and so on.

    Then I began to learn about the health implications of all this, which pointed further to the fabric first approach. All the time learning bits and pieces about how to design and implement a building in this way.

    It's been three years along this journey and I'm still learning, but I'm really glad I didn't splurge a lot of cash early. I feel I'm much more informed now and our building will end up better for it.

    Posted By: Kenny_MI know that replacing double glazing is not usually the most cost effective thing to do, but this seems to be where most of the heat is leaving the house


    This depends totally on the 2G concerned. If we're talking 6/8mm alu spacer and uninsulated frames you can get a huge improvement.
    • CommentAuthorKenny_M
    • CommentTimeDec 12th 2017
     
    Gyrogear,
    That's not a bad idea, even just to get an idea of the impact of DG or TG. I did something like this last year with the skylights in the same room, although I just taped some bubble wrap in place and after feeling the difference I ordered a couple of DG sealed units and fitted them as a semi permanent improvement the old metal framed/polycarbonate skylights. These made a huge difference which shows that as bad as it is this year its massively improved since putting DG into the base of these two skylights

    djh,
    I did this a while back using he F deg scale on the IR gun, but I knew that there was something about different units. From what I remember the walls were in on the lower end of the table but I figured at the time that it would only be an estimate anyway, and was just reinforcing the fact that there was no insulation in the wall. I could probably do what you suggest by just opening up where the satellite cable comes in, rather than drilling another hole.
    •  
      CommentAuthordjh
    • CommentTimeDec 12th 2017
     
    Posted By: Kenny_MI did this a while back using he F deg scale on the IR gun, but I knew that there was something about different units. From what I remember the walls were in on the lower end of the table but I figured at the time that it would only be an estimate anyway, and was just reinforcing the fact that there was no insulation in the wall.

    Does that mean you have some estimates of the U-values?

    I could probably do what you suggest by just opening up where the satellite cable comes in, rather than drilling another hole.

    Yes, indeed, that will save some drilling. It might make it a bit harder to determine whether there is a cavity and what the centre of the wall is filled with.
    • CommentAuthorRick_M
    • CommentTimeDec 12th 2017
     
    I've had success investigating this sort of thing using a cheap USB endoscope camera connected to a phone.
    • CommentAuthorKenny_M
    • CommentTimeDec 13th 2017
     
    Hi djh,
    What I had was some very approximate American R values and in the table the attachment what I was getting was on the lowest end, at the R5 end of the scale. Your comment above reminded me that the American values would be imperial and yesterday I did a bit of digging and found an old thread from this forum which gave 5.678 as the number to divide the American R value by to get the metric equivalent.

    If this is correct then the calculation to give the Metric U value should (I think) be 1/(5/5.678) = 1.1356. To be honest I think this is probably better than any of my walls are currently. Something else that I picked up from an old thread discussing in situ measurements, is that in the USA there is a tendency to have a constant temperature in the house. When I lived in Oregon I remember that there was no on-off or timer for the heating, just a temperature dial, and you just set the temp to what you liked and left it there forever. This presumably means that the temperature of the walls will have reached an equilibrium, while here where we tend to time the heating on and off so perhaps I would need to leave the heating on constant for at least 24 hours to get a more realistic value.

    Rick,
    Got one of those, will try that.

    Thanks,
    Kenny.
    •  
      CommentAuthordjh
    • CommentTimeDec 13th 2017
     
    Posted By: Kenny_MThis presumably means that the temperature of the walls will have reached an equilibrium, while here where we tend to time the heating on and off so perhaps I would need to leave the heating on constant for at least 24 hours to get a more realistic value.

    Possibly, although the outside temperature varies throughout the day and night of course. You probably should repeat the measurements on the hour every hour for twenty four hours or something. Easy with an automatic logger, not so much fun with a hand-held thermometer :cry:

    PS Yes, the 5.678 sounds right.
    • CommentAuthorKenny_M
    • CommentTimeDec 14th 2017
     
    Sorry gravelld, I didn't see your post before. I totally agree, and I have been in the house a year now doing exactly that.

    I've already done a huge amount of work myself and just drying the house out has made a huge difference as a damp house obviously takes more energy to heat. Little things like opening out the old Victorian shutters which were nailed and sealed shut, secondary glazing, weatherstripping etc have made a huge difference but I think I am at the point that I need to start to think about glazing and insulation.

    I like the idea of heat pumps, solar etc, but I think I need to be realistic about heating a large old house like this I think that probably means sticking with GCH but going for a modern condensing boiler.

    Another thing I need to be realistic about is my time. I have a tendency to want to do everything myself but with a full time job, a 3 year old, part time study, and even just the maintenance required on an old house I am going to need to get the experts in for the glazing and insulation.

    However, one of the biggest problems I have found is finding contractors who are actually 'experts'!!! I had a guy out from a local company the other week and he showed me the insulation they would use externally, but when I asked him what it was made of he couldn't tell me, other than say "it meets all the regs". He was talking about putting the same stuff on the sandstone walls but couldn't tell me if it was breathable. I'm far from an expert in this area, but its worrying me that I seem to know more about the issues involved that some of the people who are doing it for a living!!
    •  
      CommentAuthordjh
    • CommentTimeDec 14th 2017
     
    Posted By: Kenny_MI think I am at the point that I need to start to think about glazing and insulation.

    As long as you think about it first and don't just leap into action immediately.

    I like the idea of heat pumps, solar etc, but I think I need to be realistic about heating a large old house like this I think that probably means sticking with GCH but going for a modern condensing boiler.

    An efficient gas boiler is still a pretty good solution to a lot of problems, so I would certainly keep it as a possibility at this stage.

    one of the biggest problems I have found is finding contractors who are actually 'experts'!

    its worrying me that I seem to know more about the issues involved that some of the people who are doing it for a living!!

    You'll be very lucky to find a tradesman who is more expert than you will become, or even one that agrees with you 100%. That's why it is important to learn enough to be confident of what you want, and to be able to persuade the tradesmen to do what you want.

    At the end of the day, it's you that will be paying for whatever is done, and you that will pay to sort out any mistakes. As long as the final result is acceptable to you, that's a good result.
    • CommentAuthorgravelld
    • CommentTimeDec 15th 2017 edited
     
    Posted By: Kenny_M
    However, one of the biggest problems I have found is finding contractors who are actually 'experts'!!! I had a guy out from a local company the other week and he showed me the insulation they would use externally, but when I asked him what it was made of he couldn't tell me, other than say "it meets all the regs". He was talking about putting the same stuff on the sandstone walls but couldn't tell me if it was breathable. I'm far from an expert in this area, but its worrying me that I seem to know more about the issues involved that some of the people who are doing it for a living!!
      This is one of the most common memes in high performance building.

      The reality is that, on the contrary, very few people do it for a living (building to high performance that is).

      It depends where you live (some areas have higher concentrations of high performance builds than others) but most likely you will have to find trades that are willing to learn and work with you, or are genuinely interested in the subject.
      • CommentAuthorKenny_M
      • CommentTimeDec 15th 2017
       
      djh/gravelld,
      This is actually quite insightful. I've worked most of my life in engineering related jobs and although its not my field I probably understand the principles behind heat transfer better than most double glazing or insulation fitters. I've probably got a tendency to feel that I need to respect the tradesman's expertise but I suppose the expertise a joiner applies in fitting a non standard window is their practical skills, making the window fit well and look good, and its probably unfair to expect them all to also understand the physics behind heat transfer! I think you are right, I probably need to take a Project Management approach to this, decide what I want, research it thoroughly then pay someone to meet my specifications.

      There is one question I asked above that I think got buried in amongst all of my waffling. My problem wall in the extension is the west wall as the other side is in the neighbours garden and its unsuitable for EWI because of its irregular surface and the fact that I would be extending into someone elses property. However, on the inside of that particular wall I am short of space for internal insulation. I have been thinking about this for a long time and my current thinking is that if I applied a thinner than normal layer of insulated render on the outside and a thinner than usual insulation layer on the inside wall, I could sum to a reasonable U value for the wall as a whole.

      I of course would have to calculate all of this out, but in principle is there any issue with having insulation on the inside and outside of a building wall?

      I can't think of any reason there would because all materials in the wall are insulators to varying degrees, but is there something I am not considering here?

      Thanks,
      Kenny.
      •  
        CommentAuthordjh
      • CommentTimeDec 15th 2017
       
      Two things to be a bit careful about when running a building project rather than an engineering one are: (1) Forget any hope or idea of being able to control the timetable; too many events are out of your hands. (2) Tradesmen by and large don't read specs much, you're lucky if they look at the drawings. So somebody who does read specs needs to supervise them.

      Thermally, there's no problem about splitting insulation layers as you suggest, assuming that what's in between is solid and doesn't permit air movement. Where you do have to be more thoughtful is ensuring that the design is also moisture and condensation safe. Don't put a thin layer of impermeable insulation on the outside, for example, if the rest of the structure is permeable.

      The layout of insulation throughout the wall will also affect the propagation of heat and rates of change of surface temperatures. Concepts like 'decrement delay' and 'thermal admittance' are relevant.
      • CommentAuthorKenny_M
      • CommentTimeDec 20th 2017
       
      Thanks DJH.

      Doesn't sound all that different from an engineering project, technicians don't always do what they are asked either, although in some cases the technician knows more than the engineer fresh out of Uni!

      Will have to research 'decrement delay' and 'thermal admittance', new ones on me. I suspect this is related to thermal mass or ability to resist rapid changes in temp but will look it up. The wall in question is only about 1/4 or less of the total wall area of the extension so such effects will be limited.

      Regards,
      Kenny.
      • CommentAuthorKenny_M
      • CommentTimeJan 3rd 2018
       
      Happy new year all.

      During the break I got a chance to open up a couple of power sockets in the extension and I do indeed have a cavity wall there. It seems to be around 80mm gap in there and the amount of wind blowing in with the power socket off would suggest that the cavity couldn't be far off the outside temperature - not sure where this is coming in as there are no vents so presumably it is open to a well flat roof attic (which I can't get access to at the moment which is another story/job to do). I understand that depending on who you talk to there may be a lot of potential dampness related problems with retro fitted CWI, but the other problem is that one wall as I mentioned before is butted against a stone garden wall so probably couldn't be cavity wall filled from outside. As this means that it would probably have to be cavity filled from inside, which would presumably mean pulling off the internal plasterboard, I am starting to wonder whether it would be better just to insulate internally. It also appears that the cavity is also being used for cable runs, which I presume would have to be pulled before installing CWI.

      P.S. I looked up the terms mentioned by djh, which do appear to be related to thermal mass. As the extension is built on to a former outside sandstone wall I would imagine that there is a significant enough mass there regardless of what I do with the outside walls. The floor is also tiled.
      •  
        CommentAuthordjh
      • CommentTimeJan 3rd 2018
       
      Posted By: Kenny_MAs this means that it would probably have to be cavity filled from inside, which would presumably mean pulling off the internal plasterboard

      I would expect it to mean that you have to drill a few holes in the plasterboard that can be patched up afterwards, just like injecting from outside, though I'm no expert.

      You'd have to calculate the derating of the cables for running inside insulation and decide whether it could cope with the demands of the circuits. Otherwise it would need replacing with a larger cable, or rerouting somewhere else.
      • CommentAuthorKenny_M
      • CommentTimeJan 3rd 2018
       
      Thanks djh.

      From memory the cables were standard flex and my gut tells me they would need to be rerouted, or rerun through conduit back down the cavity before filling with insulation.

      The problem is that to do either I would need access to the roof space and earlier tonight I found it that it's not accessible. Its a flat roof and I had presumed there would be a crawl space above the ceiling, but from pulling away a section in the back porch area its just a series of joists with about 150mm fibreglass insulation pushed between them. It looks like access to the roof space to do anything, including to add more insulation to the roof would require pulling down all the plasterboard from the ceiling.

      I had hoped to do this bit by bit without too much internal disruption but it looks like this project might need to be postponed till I am in a position to do a complete renovation.
    •  
      If the flat roof felt needs replacing, you can add insulation boards on top of the existing roof deck, before covering them with new 'felt'. Interior ceiling stays untouched. Cut some hatches down through the deck to access the cavity wall while you're at it.

      Which direction do the rafters run? If you remove say a 1 foot strip of ceiling and wool alongside the cavity wall, can you reach over to access the cavity? With care this needn't be massively messy.

      Think about abandoning the existing cables and blocking their holes through the wall to the cavity. Run new cables chased into the inside face of the wall, or glue on internal insulation boards and run the cable in conduit within that.

      We used all the above tricks
      • CommentAuthorKenny_M
      • CommentTimeJan 4th 2018
       
      Thanks Will, some good suggestions there.

      The rafter runs to towards the front of the extension, so yes it might be possible to access the cavity on the front wall, but for the sockets on the side wall it would probably depend on how close the rafters run to the wall. One socket is on plaster and I would have to open up the plaster to get it past the horizontal studs. The socket on the side wall is directly on to brick (left bare as a feature by the looks of things) so the only way for it to be run at the moment is through the cavity or visible conduit.

      The thing is that the flat roof is ok at the moment, and the interior is fairly freshly decorated so anything I do will require making a lot of mess in order to get the insulation in so I need to think this through as something for the future when I can do it as one big project rather than piecemeal as I had been hoping.

      The other thing that concerns me is where the draughts are getting into the cavity and I need to figure that out. If its from the roof space then any tied to the roof deck might be a bit redundant. I can't see any vents on the wall so barring the roof I can't see how else it is getting in in such volume.
    •  
      Posted By: Kenny_MThe other thing that concerns me is where the draughts are getting into the cavity and I need to figure that out. If its from the roof space then any tied to the roof deck might be a bit redundant. I can't see any vents on the wall so barring the roof I can't see how else it is getting in in such volume.


      If there are groundfloor underfloor vents it's possible that they may be allowing air into the cavity somehow.
      •  
        CommentAuthordjh
      • CommentTimeJan 4th 2018
       
      Posted By: Kenny_MThe other thing that concerns me is where the draughts are getting into the cavity and I need to figure that out.

      Fill the room with smoke (dance hall smoke generator?) and positively pressurise it, then see where the smoke comes out. Alternatively, just positively pressurise it and go round the outside on a cold day and spot the warm spots with a thermal camera.
      • CommentAuthorKenny_M
      • CommentTimeJan 7th 2018
       
      Thanks Peter, but no vents that are visible.

      Thanks djh, this is a good idea, maybe even one of those smoke tablets you use to test chimney flues - although they might need to be lit so not a great idea to through that into the cavity! :)

      I'll find something to create smoke and give that a try.
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