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Data and monitoring: Moisture monitors within roof fabric?

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    • CommentAuthorShevek
    • CommentTimeJun 13th 2014 edited
     
    We're insulating our existing pitched roof with Icynene and we've added a breather membrane.

    However I'm still quite worried about the fact that the existing rafters are untreated, so I was wondering about putting moisture monitors in the roof fabric.

    Is this something any of you guys have done? Can you recommend a product?
    • CommentAuthorShevek
    • CommentTimeJun 13th 2014
     
    Is there anything like this available the in the UK?
    http://www.smtresearch.ca/products/moisture-detection-sensor-mds-wstereo-jack
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 14th 2014
     
    Just yesterday I eventually got my DHT11s set up to monitor RH and Temperature, was pretty easy in the end (just the usual stupid mistakes). £50 quid would set you up with a very basic monitor and logger, would not be hard to put an alarm on it.
    I shall post some more about it on my Raspberry Pi thread when I get time.
    • CommentAuthorShevek
    • CommentTimeJun 21st 2014
     
    Thanks Steamy. Are programming skills needed?
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 21st 2014
     
    Yes, but really not hard. I got mine up and running, stuck it in my garden and it gave similar readings to my 1-wire sensor on the temperature. Arrantly the DHT11 is a calibrated sensor, though I initially got strange readings when I used the wrong value resistor. I used the code on this site to get it running, then wrote a bit more code so that it logs to a text file.
    https://learn.adafruit.com/dht-humidity-sensing-on-raspberry-pi-with-gdocs-logging/overview
    I shall post more up on the RPi thread when I get time.
    I quite fancy setting up some in a box to see how vapour permeable the box material is.
    • CommentAuthorShevek
    • CommentTimeJun 21st 2014
     
    Can this system be wired up instead of wireless?
    •  
      CommentAuthorSteamyTea
    • CommentTimeJun 21st 2014
     
    Yes, the sensors are wired to the RPi, then a bit of CAT5 to a router, or direct to a PC, so that the data can be dragged off it.
    I use wireless as it is easy to set up and use (less wires about).
    The bit bit of Python code I wrote logs the data to a text file that can be opened in a spreadsheet. Would not be too hard to write the script to set up an alarm (flashing LED) if you wanted it to.
    • CommentAuthorslidersx200
    • CommentTimeJun 21st 2014 edited
     
    If the monitor(s) indicate humidity has reached a critical level what plan of action do you have? I think you need to reevaluate the step before this if you have doubts.

    Is the concern that any vapour barrier to the warm side of the insulation may not be continuous as this is a retrofit scenario? Presumably you are fitting one, the external roofing membrane is the breathable layer you refer to and you are certain the spray insulation between is open cell so any potential risk of moisture from the inside finding a weak spot in the vapour barrier and not being able to get out should be minimal.

    The main thing is to take your time with the vapour barrier and make every effort to get a continuous layer:-)
    • CommentAuthorShevek
    • CommentTimeJun 21st 2014 edited
     
    I'm worried about unforeseen problems rather than obvious ones like a discontinuous VCL.

    The breather membrane is laid well, all joints taped (although I wasn't around for the entire installation) but I believe there could be a problem at the bottom batten, where, despite using (12 mm) counter battens, there is no gap under the last batten and saw dust + a bit of mortar may have fallen down behind the tiles and gathered at the bottom batten.

    For a tiny expenditure we can be forewarned of any problems, lift the roof tiles and find the problem before the (untreated) rafters rot.

    (VCL not installed yet)
    • CommentAuthorargy
    • CommentTimeJun 21st 2014
     
    Have a look at the Archos Connected Home system that has just been released and comes with two temperature/humidity sensors (as well as 2 mini cameras, 2 movement tags and a tablet and all for £200) . I have one on order and was wondering what to do with both the temperature/humidity sensors - now I'm going to put one of them in the loft of our new built house to monitor the warm roof (which was complicated in insulating and making air tight due to the number of dormers and gable ends - beware if anyone else is thinking of doing in a similar construction)
    •  
      CommentAuthordjh
    • CommentTimeJun 22nd 2014
     
    Posted By: ShevekWe're insulating our existing pitched roof with Icynene and we've added a breather membrane.

    However I'm still quite worried about the fact that the existing rafters are untreated, so I was wondering about putting moisture monitors in the roof fabric.

    Is this something any of you guys have done? Can you recommend a product?

    I'm about to do it in my roof and walls, but my construction is a lot more weird than yours! I've bought a monitoring system from a chap in Canada who's done several straw bale systems before.

    One gotcha for me is that you can't put sensors everywhere and since you're looking for unforseen problems, how do you decide where to put them?

    The other problem I've got tonight is trying to remember where in the walls they should go. Top or bottom, inside or outside? I remember the risks in summer and winter are different and that the Americans and Japanese came to different conclusions about the risks, but I've forgotten where I stashed the information :cry:
    •  
      CommentAuthordjh
    • CommentTimeJun 22nd 2014
     
    Posted By: ShevekIs there anything like this available the in the UK?
    http://www.smtresearch.ca/products/moisture-detection-sensor-mds-wstereo-jack

    Dunno, but that system will only detect liquid water and then only in quantity. So it's only likley to detect rain leaks IMHO. The system I'm using has humidity sensors so I can hopefully see problems developing (or prove they are not).
    • CommentAuthorRick_M
    • CommentTimeOct 15th 2014
     
    would something like these work?

    ebay item no - 251678782452, 261478202160

    you could leave them permanently embedded in one or two rafters (assuming the 200mm will reach through the insulation, I don't know your roof build up). Or have access points drilled that you could put the probe into, and reseal when done. Alternatively you could make a small section of your insulation removable so you could take a look easily and put it back after inspection?
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 15th 2014
     
    I think they are just resistance meters. So probably won't give you much idea about what is really happening.
    • CommentAuthorRick_M
    • CommentTimeOct 15th 2014
     
    Why not Steamy? Presumably if you embed the probe a few mm into your dry rafter it will give you a reading, if there is condensation and the surface of the wood becomes damp the reading will change.
    • CommentAuthorringi
    • CommentTimeOct 15th 2014
     
    As I understand it correctly, to get rot, you need damp warm wood and it needs to be like that for some time.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 15th 2014
     
    Yes you will see a change, but you have to read it manually, then record it. Seems like hard work. Also not sure if the moisture content a few mm under the surface is relevant to rotting.
    No harm in trying though and they are half the price of my loggers (which I have 8 running at the moment so I can calibrate them, 5 DHT11s and 2 DHT22s).

    My understanding of rotting is that it needs to be damp, little air movement and warm enough for the bacteria to grow.
    Somewhere on here we looked into it, but don't ask me where now.
    • CommentAuthorTimber
    • CommentTimeOct 16th 2014
     
    You could use an electrical resistance moisture meter and embed tails into the rafters in various locations and at various depths. You can then run these tails to a single location so that you can them plug the moisture meter in each tail and get a reading (label each tail!).

    The tails can be nails driven into the wood and standard cable with a 3.5mm jack on the end. Obviously check the system is working before covering it all in. It should be possible to get it all set up for about £40 plus the cost of the moisture meter.

    Alternatively you could hook the tails up to a something like a Raspberry Pi and get it to auto log etc, but a manual check every so often should alert you to issues very quickly.

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