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    • CommentAuthorlineweight
    • CommentTimeMar 10th 2017
     
    Around three years ago, I completed a renovation within a Victorian end-of-terrace which involved retrofit of fairly substantial internal wall insulation to the original 9" brick walls.

    At the time my researches brought up some concerns about what happens to brickwork (especially absorbant, crumbly Victorian brickwork) when it's heavily insulated on the inside and therefore no longer sees any significant heat coming from inside the building that might help to dry out moisture.

    This is mainly simply about moisture that gets into the brickwork from rainfall. Obviously there's interstitial condensation to think about too but I am pretty confident I have a very robust airtight layer on the inside of the insulation.

    Some may be aware of simulations carried out by Joseph Little around 2010 that suggested that moisture buildup over time could be a worry.

    http://www.josephlittlearchitects.com/content/breaking-mould-5

    There was disagreement about whether these simulations accorded with what happens in real life. So I decided to take the opportunity to find out what happened in my walls over time.

    Part of the concern is about moisture in the brickwork reaching levels that could cause any embedded timber (joist ends etc) to rot. Therefore I placed sensors into sections of timber built into the inner side of the brickwork. One is in an existing floor joist. A couple in other bits of existing embedded (but redundant) timber. And a couple in strategically located bits of timber which I embedded myself (in these cases, I used pieces of timber taken out from walls elsewhere though).

    I've now just about got results for 3 yearly cycles. Graph below shows the WME (wood moisture equivalent) levels over time.

    (The high levels at the beginning reflect moisture that was introduced during installation - wet mortar etc.)

    Some thoughts at this point (based on my very non-expert analysis):
    - Too soon to say whether the trend for the midwinter peak is to decline or increase
    - Some of the sensors are indicating WME levels that could be a concern rot-wise
    - The sensor embedded in an actual joist end shows the least concern. But it's also not in the most weather-exposed location.

    I've also been recording temperature, RH, and AH. Happy to post more data if people are interested. I'd also be interested in any comments as to interpreting the significance of my results. I'm an architectural designer but not a building physicist.
      Screen Shot 2017-03-10 at 15.57.16.jpg
    • CommentAuthortony
    • CommentTimeMar 10th 2017
     
    Thanks for this, I am interested

    You say Victorian brickwork, has it been repointed with cement mortar?

    Are the gable walls in rooms on the inside or in the loft on the inside?

    is the scale on the chart % moisture content?

    Very happy to hear that the sensor in the joist ends is not showing a problem.

    Are those ground floor joists or first floor joists and do you have any under floor insulation or insulation on the walls in the floor void?
    • CommentAuthorlineweight
    • CommentTimeMar 10th 2017 edited
     
    Posted By: tonyThanks for this, I am interested

    You say Victorian brickwork, has it been repointed with cement mortar?

    Are the gable walls in rooms on the inside or in the loft on the inside?

    is the scale on the chart % moisture content?

    Very happy to hear that the sensor in the joist ends is not showing a problem.

    Are those ground floor joists or first floor joists and do you have any under floor insulation or insulation on the walls in the floor void?


    The brickwork has been (badly, before I moved in) repointed externally with cement mortar. Not very deeply so bits are already falling out.

    Internally I took the plaster off back to the brickwork. Where i did repairs I did it with a part lime part cement mix. Where I embedded timber I did it with fully lime mortar to try and keep as close to original as possible.

    There's a small partially vented cavity between brickwork and insulation.

    Gable walls at 1st storey and also in the storey above which is in the roof space. Sensors are installed at various heights in 1st storey. Floors below are in separate ownership. The cavity behind insulation is isolated from the flat below at their ceiling level. The insulation layer is continuous from that ceiling upwards. On the warm side of insulation I have mineral wool between joists in the floor separating me from below. The joist end is in the first floor so just above their ceiling. So not best one to use as representative but it was what was possible/easy to do at the time.

    Yes scale is %WME. As I understand it, >18% is potentially worry zone.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 10th 2017
     
    Excellent to check these things for yourself.

    The annual peak doesn't look to be increasing anything like the year on year manner that Joseph showed.
    In fact looks like even tho it didn't completely get rid of the construction xs over 1st summer it nevertheless settled to a regular cycle.

    Got any links, names or clues to 'disagreement about whether these simulations accorded with what happens in real life'? Crucial question.

    Try to get yourself one of the free copies of http://www.buildingconservation.com/books/retrofit_subform.htm just out - really good, touches on this amongst other things.
    • CommentAuthorEd Davies
    • CommentTimeMar 10th 2017
     
    Nice to see some real data.

    Is 18% a problem if it's only for a few months and then it dries out again?

    The other possible issue with cold wet bricks is spalling when the wet freezes. Any signs of that? I don't know where you are but I'd guess none of these winters has been hard enough to really test that.
    • CommentAuthorlineweight
    • CommentTimeMar 10th 2017 edited
     
    Posted By: fostertomGot any links, names or clues to 'disagreement about whether these simulations accorded with what happens in real life'? Crucial question.


    It's what I recall from my general explorations at the time, but really it boils down to a lack of real world data in general. Especially when there are so many possible combinations of specific building fabric and climate all of which could give different results.

    In my case it looks like there's a kind of equilibrium year to year but I'm in south london where summers are warm and rainfall low compared to other parts of the country. I wonder how many extra mm of rain per year could break that equilibrium?

    Maybe it would be interesting to do a WUFI simulation of my example and see how well it matches my real world measurements. Not something I'm able to do at the moment though.
    • CommentAuthorlineweight
    • CommentTimeMar 10th 2017
     
    Posted By: Ed DaviesNice to see some real data.

    Is 18% a problem if it's only for a few months and then it dries out again?

    The other possible issue with cold wet bricks is spalling when the wet freezes. Any signs of that? I don't know where you are but I'd guess none of these winters has been hard enough to really test that.


    I don't know if the 18% is a problem if only intermittent.

    Where I am, it doesn't drop below zero very often. There is evidence of spalling but this was going on before I insulated and I think a result of the cement pointing.
    •  
      CommentAuthorSteamyTea
    • CommentTimeMar 12th 2017
     
    Data is always good. Can you post up the raw data (there used to be a way to post up zip files).
    Have you correlated it to a local weather station?
    • CommentAuthorlineweight
    • CommentTimeMar 13th 2017
     
    Posted By: SteamyTeaData is always good. Can you post up the raw data (there used to be a way to post up zip files).
    Have you correlated it to a local weather station?


    Sure, I'll try and post up the data when i get a chance.

    No, I've not correlated with a local weather station but I expect this could be done.
    • CommentAuthorgoodevans
    • CommentTimeMar 15th 2017
     
    What was actually measured at each point - RH or RH+Temp - or some other data.

    Looking at the graph it looks like if one sensor has a peak event over a period of a day/week or so they all do.

    Therefore I would say that the data is dominated by the water content of the outside air and the temperature of the sensor - with each of the sensors being relatively warmer/colder to each other depending on how they are affected by the internal/external temperature (notice that in summer the lines converge due to the internal and external temperatures converging). I think any calculations/analysis involving vapour resistance will not match this data.

    I don't suppose you also took a measure of the outside air at the same time?
    • CommentAuthorlineweight
    • CommentTimeMar 15th 2017
     
    Measured at each point: Temp, RH, AH and WME.

    The graph posted above shows WME, not temperature.

    As I said above I'm not mainly interested in vapour coming from the inside of the building - I'm fairly confident that the way I've insulated means there will be negligible transfer of air or vapour from inside. My interest is mainly in the level of moisture in the brickwork, which is largely determined by rainfall and the speed at which it can dry out.

    There may of course also be more complicated things going on in the air void between the back of the insulation and the brickwork because this is partially connected to outside air and I'm assuming that moisture in the brickwork may be dispersing into this void.

    Unfortunately, no, I don't have a record of outside air temp, although I could obviously try and correlate with local weather data.
    • CommentAuthorgoodevans
    • CommentTimeMar 15th 2017
     
    Yes I understand your concern.

    I suspect AH and WME are derived from the direct measurements of temp and RH that the sensor made.

    What I am saying is that the bricks look like they are drying out as fast as the climate around your house allows with virtually no delay. Or, to put it another way, the moisture content of your bricks will be the same as any other house with similar temperature bricks. Other than the first few mm of brick subject to rain I think your data shows that the rest of the brick work (at sensor level) is mainly influenced by the AH of the outside air and the temperature of the brick (warmer bricks are dryer than colder bricks for a given AH (because the RH is lower)). Your data can confirm that hypothesis when matched to the climate data your house experienced.

    Another way to test this hypothesis is to graph the AH of all the sensors - I think they will correlate closely with each other (and as it happens with the AH of the outside air).

    BTW its great to see some real world data for vapour/humidity/condensation - there is so little of it about. If you can post the raw data I would love to play with it also. I would also like to perform similar measurements in my house - can you give details of your setup.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 15th 2017
     
    Some great 'how to' info in excellent new Heritage Retrofit annual mag http://www.buildingconservation.com/books/retrofit_subform.htm - you may still be able to get a free copy.
    • CommentAuthorlineweight
    • CommentTimeMar 15th 2017
     
    Posted By: fostertomSome great 'how to' info in excellent new Heritage Retrofit annual maghttp://www.buildingconservation.com/books/retrofit_subform.htm" rel="nofollow" >http://www.buildingconservation.com/books/retrofit_subform.htm- you may still be able to get a free copy.


    Thanks - have requested one.
    • CommentAuthorlineweight
    • CommentTimeMar 15th 2017
     
    Posted By: goodevansIf you can post the raw data I would love to play with it also.


    I've now got the raw data downloaded in a csv file. As it's probably got my address and things in there I'd rather not put it up completely publicly but if you'd like to whisper me an email address, I'd be more than happy to send you a dropbox link and then you are very welcome to see what you can do with it, especially if you could report back with any comments you can draw from it.

    Anyone else interested (steamytea?) just drop me a message and I'll do the same.


    Posted By: goodevans I would also like to perform similar measurements in my house - can you give details of your setup.


    I have an account with this company:

    https://shop.omnisense.com/

    You buy the gateway and the sensors, which then report back to their servers, for a monthly fee. You can download the data at any point. So far it's worked well (except for some problems with the gateway unit interfering with other wireless systems in the house...whose system is to blame there - that's a long story).

    I could find very few other options for what I wanted to do. This seemed the best - or pretty much the only - bet. See my previous thread from when I was looking around:

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11966&page=1#Item_13
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