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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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  1.  
    I'm after a few of these on a tripod or similar to dry a screed floor that was flooded

    Any recommendations?
  2.  
    Would a dehumidifier(s) be better than a heater?.... Just a thought
    •  
      CommentAuthordjh
    • CommentTimeJun 9th 2020
     
    Chicken heaters?
    • CommentAuthortony
    • CommentTimeJun 9th 2020
     
    Open the windows, fans on cold, forced convection for me
  3.  
    The dewpoint accreditation course I went on and the trainer suggested in these circumstances spot drying with infrared and natural ventilation to get the water out

    He's pretty clued up but every property is different. I get paid by the insurer to spot dry so that's my approach on this one

    The previous contractor didn't dry it for 3 months with a dehumidifier and got kicked off the job
  4.  
    Posted By: VictorianecoI get paid by the insurer to spot dry so that's my approach on this one

    then its infrared heaters

    Posted By: djhChicken heaters?

    +1
    the infrared bulbs can be got in various wattages, I have used 100W and 250W otherwise a quick dip into the internet gave
    https://www.blumfeldt.co.uk/Patio-Heaters/Infrared-heaters/Team-Mate-Radiant-Heater-1500W-IR-Comfort-Heat-IP34-Steel.html
    The bulbs or fitting as above probably depends on the area involved
  5.  
    Yep that's the type of thing I need, machine mart have one for £170 which I've ordered to collect on Thursday but something like that or on a tripod would be better I think. I'll ring them tomorrow and see if they can get 2 out to me on next day.

    Thanks
    • CommentAuthortony
    • CommentTimeJun 9th 2020
     
    The sun is a great ir heater
  6.  
    Posted By: tonyThe sun is a great ir heater

    But a bit difficult to get a bucket of it in the room !:shocked:
  7.  
  8.  
    Also found these ones but at 1.4m height is that too high to dry a floor from?
    https://www.machinemart.co.uk/p/clarke-2kw-infrared-quartz-heater-with-floor/

    I could get 2 of the above as opposed to the 1 I have on order as below:
    https://www.machinemart.co.uk/p/clarke-370spc-swivel-head-infa-red-heater-230v

    Any thoughts? Or being infrared wont make much difference how far it is from the floor?
    • CommentAuthortony
    • CommentTimeJun 10th 2020
     
    Inverse square law for distance but it is likely to have a reflector.

    I have been drying screeds for 40 years and only ever use fans Blowing on cold And open windows.

    Low cost, simple, sustainable, eco
  9.  
    I've got to follow the recommendation of the insurer on this one though.

    Out of the two clarke heaters I linked to which would be better for future use? I'm thinking two of the tripod mounted ones as opposed to the single low level one? Although the more compact one generate smore heat and could always be raised on a platform if required perhaps?
  10.  
    Posted By: tonyInverse square law for distance but it is likely to have a reflector.

    I have been drying screeds for 40 years and only ever use fans Blowing on cold And open windows.

    Low cost, simple, sustainable, eco

    The inverse square law is the gotcha factor. Its surprising how quickly heat (and light) drops off with distance

    Posted By: VictorianecoI've got to follow the recommendation of the insurer on this one though.

    You should have a window open anyway to get rid of any moisture evaporated from the floor and a fan won't be detrimental to the job either.
  11.  
    Window will be open, like I said the infrared is to simply heat up the slab to get the moisture into the air and then out the property. It's only one section. The issue with dehumidifiers etc is they are drying the whole property and unless it's tented off it's wasting energy
    •  
      CommentAuthorfostertom
    • CommentTimeJun 10th 2020 edited
     
    Posted By: Peter_in_HungaryThe inverse square law
    Wouldn't that apply to an unreflectored source, radiating equally in all directions? so the (spherical) receiving surface increases as the square of radius away from the source, hence power density decreases likewise. With (assuming lossless) reflector, it all depends on the beam's included angle or rather the beam's area on the receiving surface.
    •  
      CommentAuthordjh
    • CommentTimeJun 10th 2020
     
    Posted By: fostertom
    Posted By: Peter_in_HungaryThe inverse square law
    Wouldn't that apply to an unreflectored source, radiating equally in all directions? so the (spherical) receiving surface increases as the square of radius away from the source, hence power density decreases likewise. With (assuming lossless) reflector, it all depends on the beam's included angle or rather the beam's area on the receiving surface.

    The area still increases as the square of the distance, though.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 10th 2020
     
    Yes, but if you're intentionally relying on a reflectored source you'll prob go straight to calculating the beam's area on the receiving surface.
    • CommentAuthorEd Davies
    • CommentTimeJun 10th 2020
     
    Posted By: djhThe area still increases as the square of the distance, though.
    Approximately. It's only strictly inverse square for a point source.

    An extreme example: imagine an emitter 1 m² held 10 mm from the floor. Raise it to 20 mm and, sure, there's a small drop in intensity near the edges as the IR spreads out a bit more but nothing significant at all in the middle, not a reduction of 4 times as the inverse square law would lead you to believe.

    Holding a device like the ones Victorianeco mentions a metre or three from the floor will not be as extreme as this but the area of the emitter is still not insignificant.

    This is what has previously confused SteamyTea about the radiant temperature of the inside of a room. As you move away from a wall it is indeed the case that the radiation received from any individual point (or tiny area, say 1 mm²) on the wall decreases but the amount of wall “visible” increases too.
    • CommentAuthorbarney
    • CommentTimeJun 10th 2020
     
    As a rough measure, you couldn't reasonably accept that the IR source was a "point" until you get at least 5 times the biggest dimension of the emitter from the receiving surface (and that would be normal to the surface, if it strikes at an angle, then for constant height, the relationship is the cube of the cosine angle for a given intensity at that angle - it's why you would probably use view "factors" for convenience.

    Going back to the exam question, it's difficult to see just how much advantage that IR on the screed would have in a UK climate in summer in a well ventilated room

    Regards

    Barney
  12.  
    Posted By: barneyGoing back to the exam question, it's difficult to see just how much advantage that IR on the screed would have in a UK climate in summer in a well ventilated room

    The advantage is that if those paying the bill want an IR heater then they get an IR heater and the provider (Victorianeco) gets paid. If it doesn't work Victorianeco still gets paid and then a discussion can ensue as to how to solve the problem properly.
    •  
      CommentAuthordjh
    • CommentTimeJun 10th 2020
     
    Posted By: Peter_in_HungaryThe advantage is that if those paying the bill want an IR heater then they get an IR heater and the provider (Victorianeco) gets paid. If it doesn't work Victorianeco still gets paid and then a discussion can ensue as to how to solve the problem properly.

    Probably better to have the discussion in advance, or to change the method part way through as an experiment/demonstration.
  13.  
    The previous contractor dried for 3 months with a regular dehumidifier and air movers and it wasn't dry hence why they were kicked off

    I think they were using a basic protimeter to indicate damp when in fact my recent oven test showed it was pretty much dry other than one corner.

    The expert I use suggested infrared in that one area to spot dry and decontaminate the rest of the floor and walls with citric acid to neutralise the salts which were of course giving erroneous readings
    •  
      CommentAuthorfostertom
    • CommentTimeJun 11th 2020
     
    Posted By: Victorianecothe salts which were of course giving erroneous readings
    You mean their hygroscopicity was pulling moisture from the air, so maintaining a thin damp surface layer? I've recently encountered just a trace of spilt Epsom salts making floorboards damp to touch, causing belief that the roof was still leaking!
    • CommentAuthorLF
    • CommentTimeJun 11th 2020
     
    Elderly person nearby had insurance company drying out then bugger off. The damp in the slab had not really all gone as it takes time to come through. They were getting nice dry readings and then after a time damp equalised out and came back warping the door frames etc. We used fans and dehumidifier.

    Would IR get the deep down moisture out any quicker especially deep down ?
    Air flow preferably dry and with high capacity for moisture (warm) flowing over it sounds fastest was to dry.

    Like drying washing on a windy day - even better if it is warmer.

    I guess IR heater warms the slab so warming the local air and helping the drying.
    • CommentAuthorEd Davies
    • CommentTimeJun 11th 2020
     
    Posted By: LFI guess IR heater warms the slab so warming the local air and helping the drying.
    The temperature of the air isn't all that important, it's the temperature of the surface of the water which matters which you can only influence by warming the slab.

    The main thing you want with the air is reasonably rapid exchange with the outside to carry away the excess water vapour. The advantage of an IR heater is that it directly heats the slab without heating the air so you're not wasting heat to be carried away immediately.
    • CommentAuthorowlman
    • CommentTimeJun 11th 2020
     
    I had to build my own for drying sprayed lacquer on a big job.
    I bought two industrial IR heaters that were meant for wall mounting. I then bought a tripod mount, usuallly used for mounting on stage speakers, and with a bit of imaginative metalwork for a bracket and some timber managed to get a decent result.
    • CommentAuthorLF
    • CommentTimeJun 11th 2020
     
    Ed, I see your point, warmer the slab the faster it can vaporiser water. Warmer air has more capacity to take away water but I have no idea which rate controls. Washing dries ok on a very cold, low rh windy day though! So Tony's experience brings true.

    One case experienced was that if drying is too rapid the lower part of slab seemed to be still wet and that will equalise after the drying has stopped.So you pass the surface conductivity/ assumed moisture level but average moisture level is not good enough and the top will rewet as it equalised.
  14.  
    But if you can extract half the moisture content and then it equalises you should thoeretically halve your reading...
    • CommentAuthorEd Davies
    • CommentTimeJun 12th 2020 edited
     
    Posted By LF: “Warmer air has more capacity to take away water…”

    This notion that air has a capacity to hold water is an, at best, partly correct shorthand which can be very misleading in some circumstances. This is one of those circumstances. Previous discussions on here lead me to this rant: https://edavies.me.uk/2017/03/vapour/

    It's the temperature of the surface which governs the rate of evaporation. Of course, the rate of condensation is also significant but if the air is being changed quickly enough that matters less.
   
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