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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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    • CommentAuthorNanuchka
    • CommentTimeOct 31st 2019 edited
     
    Hello!
    I have really enjoyed reading the posts here, and am now seeking some guidance with a question of my own...
    My house is semidetached with the standard layout of front and back receptions (now one room), hallway running through the middle adjacent to party wall, and kitchen at the back. The reception room has a suspended floor, abutting the solid floors of the hallway and kitchen. The two outside walls of the reception room, which are at right angles to one another, have four air bricks along the side, one at the front. The air brick in the wall at the back which would have created a cross draught has become part of an internal space when the kitchen was extended to the full width of the house at some point.
    The reception room floor is beautifully finished in engineered oak, and sadly uninsulated. The tops of the air bricks are slightly higher than floor level, and plenty of air gets through above the floor in spite of my attempts at sealing. My question is: would it be feasible to block up the air bricks and install some kind of mechanical and controllable ventilation under the suspended floor to make the conditions more comfortable? I know a piecemeal approach not ideal, but I don't have the resources to do huge amounts of work. I would also like to switch away from gas central heating and I understand that air source heating doesn't work too well unless house is well-sealed so it would help with that too.
    Thanks for reading :-)
    • CommentAuthorMatBlack
    • CommentTimeOct 31st 2019
     
    Hi, do you mean the airbricks are visible from inside, being slightly above floor level ( perhaps a pic) or I have read it wrong.

    I've just ripped all my floor joists out, having no airflow (blocked airbricks) for who knows how long has rotted them, so removing the airflow may not be a good idea, although some on here suggest filling the void with something like eps beads, removing the need for venting.
    • CommentAuthorPetlyn
    • CommentTimeNov 5th 2019
     
    If you are thinking about filling the underfloor void, then using lightweight expanded recycled glass beads which are free-flowing and non-combustible, with a constant insulation value (unlike eps that reduces over time), they do not take on quantities of water (unlike vermiculite) and have a good lamda value might be an answer?
    • CommentAuthorbhommels
    • CommentTimeNov 5th 2019
     
    Posted By: PetlynIf you are thinking about filling the underfloor void, then using lightweight expanded recycled glass beads which are free-flowing and non-combustible, with a constant insulation value (unlike eps that reduces over time), they do not take on quantities of water (unlike vermiculite) and have a good lamda value might be an answer?


    I thought that one of the benefits of EPS is that it has a constant U value over time? A quick google tells me that EPS is in fact used as a long-term reference for U (or R) values, contrary to PIR or even XPS. Have I missed something?
    • CommentAuthorPetlyn
    • CommentTimeNov 5th 2019
     
    EPS has a theoretical constant U value but has higher compressibility if performing any structural function and we can testify is prone to rodent, bird and particularly insect attack as we have ants' nests in the polystyrene insulation of our caravan. We take some information from the US Department of Energy :-(https://www.energy.gov/energysaver/weatherize/insulation/insulation-materials)
    •  
      CommentAuthordjh
    • CommentTimeNov 5th 2019
     
    I have some left-over EPS sheets in the garden, which I was planning to use to make a compost bin. They've been there five years now and seem pretty much untouched apart from some scratches on the outside. They don't seem to be attractive to our birds or squirrels etc (deer, badgers, rats, voles ...). The ants here seem more attracted to life under our patio. I suppose behaviour varies in different places - I have seen horror stories of ants' nest under houses.
    • CommentAuthorbhommels
    • CommentTimeNov 6th 2019
     
    @Petlyn, your link refers to the degradation of XPS, not EPS. XPS is known to lose R value over time, EPS is not, and the same goes for structural functions, where XPS is used and not EPS.

    @djh, I am glad to hear I am not the only one with EPS sitting in my garden for years. Birds seem to like pecking at it, our chickens find it irresistible. Not good for them or the EPS so I had to block them from getting to it.
    • CommentAuthorNanuchka
    • CommentTimeNov 11th 2019
     
    MatBlack, thank you for your reply. To answer, the middles (horizontally) of the airbricks are about level with the top of the floorboards. The connecting holes twixt outside and subfloor space are roughly angled downwards, but I do mean roughly! The only thing between the holes and the living space is skirting board. Builders were as clueless as I when it was being done and time pressure meant I didn't have a chance to research. I wish now I'd put my foot down and made them work on a better solution.
    Am I understanding correctly that a bead fill means venting not required? Probably being dumb, but could you explain how?
    • CommentAuthorNanuchka
    • CommentTimeNov 11th 2019
     
    Petlyn, do you have any idea whether beads could be blown in using the air brick points (or holes made on same level) for access, thereby avoiding the disruption of lifting the floor?
    • CommentAuthortony
    • CommentTimeNov 11th 2019
     
    Building regulations require subfloor voids to be ventilated, if there is no void then they have nothing to say.

    It is a bit of a semantic question I know. Void or no void
  1.  
    Posted By: NanuchkaAm I understanding correctly that a bead fill means venting not required? Probably being dumb, but could you explain how?

    It's is quite simple really, an under floor void needs ventilation. If you fill the void then there is no void so nothing to ventilate.
    The problem with blowing in beads (usually EPS beads) is that it is difficult to ensure a full fill. If you get a partial fill then you still have voids - which need ventilation.
    From your description above regarding the air brick location and the solid floor - the reading to me sounds like you might have a dead air space in one corner (no cross flow) that may or may not cause problems in the future

    Posted By: NanuchkaTo answer, the middles (horizontally) of the airbricks are about level with the top of the floorboards. The connecting holes twixt outside and subfloor space are roughly angled downwards, but I do mean roughly! The only thing between the holes and the living space is skirting board. Builders were as clueless as I when it was being done and time pressure meant I didn't have a chance to research. I wish now I'd put my foot down and made them work on a better solution.

    When was the work done? Can you get the builders back to do the job properly? Does the ground level outside allow the airbricks to be placed in the correct place?

    Posted By: NanuchkaI would also like to switch away from gas central heating and I understand that air source heating doesn't work too well unless house is well-sealed so it would help with that too.

    Air source heat pumps should work as well as gas CH in a house that is not too well sealed - it's just that it will be expensive to install because you will need a bigger unit and expensive to run because the heat will be leaking out. But then the same will apply to gas CH. If you have got gas CH why swap to air source heat pump? - Do you mean air to water or air to air? If it is air to water then the heat emmiters (rads or UFH) will need to be sized to account for the lower temps of an air to water system. If it's air to air - how will you duct the air around the house, or do you plan individual units in each air space?
    • CommentAuthorNanuchka
    • CommentTimeNov 11th 2019
     
    Peter_in_Hungary yes, absolutely right: the internal corner won't be getting anything like the air exchange of the external one.

    I doubt if I can get builders back but could try. Being cheap, I was hoping that I could find a solution that would involve minimal disruption to the floor.

    I was imagining a (holy grail) low-energy system that could (a) regulate, and (b) direct, the air flow. On windy days the air fairly roars thru, where on quiet days it's obviously pretty stagnant, I can't believe a controllable, constant, gentle flow wouldn't work just as well if not better, and if it were possible to built it in, the ability to maintain a less extreme temperature differential would make the living space more comfortable. Given the amount of similar housing stock in the UK it seems bonkers that no-one has come up with a solution to this. But maybe I'm being ridiculous and it's impossible.

    I've basically done everything backwards and wrong, and if I knew then what I knew now I'd proceed very differently :-(
    • CommentAuthorNanuchka
    • CommentTimeNov 11th 2019
     
    Tony thanks, that's good to know.
    • CommentAuthorgyrogear
    • CommentTimeNov 11th 2019 edited
     
    Posted By: NanuchkaI was imagining a (holy grail) low-energy system that could (a) regulate, and (b) direct, the air flow.


    You could try blowing house air into the void, using a small PC fan or similar. Say 1 cfm of continuously operated mechanical exhaust ventilation per 50 square foot of underfloor area.

    (I use somewhat more -- six times in fact, but I have an ongoing excavation in progress... It is still far cheaper than the dehumidifier...).

    gg
    • CommentAuthorPetlyn
    • CommentTime6 days ago
     
    The beads can be blown up to 2m to fill a dead space because the air will exhaust back towards the airbrick over the beads and eventually the beads will form a drift up to the underside of the floor; introducing more beads will bring the filled void back towards the blower. If the distance for the blower is too great, (say 2m) then as the beads are free-flowing and could easily be poured through a 3 inch hole cut into a floorboard which can be plugged afterwards.

    The easiest course might be to cut a hole inside the house close to the wall above the airbrick, with one person pouring the beads through the floor and another directing the beads with a light from outside through the airbrick?

    What sort of area and depth are you looking to fill?
    • CommentAuthorNanuchka
    • CommentTime4 days ago
     
    Petlyn it's about 8.5m x 5m. Too damn big to heat!!!
    • CommentAuthorNanuchka
    • CommentTime4 days ago
     
    Oh, and depth approx 0.4m from memory.
    Once fill complete, can the air bricks then be completely sealed?
  2.  
    Posted By: NanuchkaOh, and depth approx 0.4m from memory.
    Once fill complete, can the air bricks then be completely sealed?


    Posted By: tonyBuilding regulations require subfloor voids to be ventilated, if there is no void then they have nothing to say.

    It is a bit of a semantic question I know. Void or no void


    Wot Tony said +1
    • CommentAuthorNanuchka
    • CommentTime4 days ago edited
     
    Tony I saw the thread where you were talking about trying EPS fill - did you? Do you or anyone else know where I can get more info both on the science and the application? I would need to find someone to do it for me, quite possibly impossible to find anyone who's done it before in Cornwall, would be good to have as much info as possible...
    • CommentAuthorNanuchka
    • CommentTime4 days ago
     
    Peter_in_Hungary / Tony, I"m sure it's a daft question, but why aren't the airspaces between the EPS beads classed as voids?
    • CommentAuthortony
    • CommentTime4 days ago
     
    The voids between the beads are too small to count as voids.

    I can help in February to fill void.

    I know of a load of floor voids filled with eps beads across the seas over 5 years ago with no problems.

    I have applied for grants to trial this in a test bed house, didn’t get the funding though should have.
    • CommentAuthorPetlyn
    • CommentTime2 days ago
     
    We weren't suggesting heating the void but using the air bricks to assist in filling the void with glass beads with a blower. To bring the floor into your 'warm space', yes, the air bricks would need to be sealed after filling the void as to leave them open would introduce air/moisture back into the filled void negating the effectiveness of any insulation.

    Your measurements of 8.5 x 5 x 0.4m would equate to approx 17 cubic metres - the recycled glass beads we have available are 4-8mm in diameter and we can send you a sample if you are interested. They are lightweight but with high compressive strength and once in the void, will not settle or degrade.
  3.  
    Hi Anna, we pumped a lot of underfloor voids with EPS and closed the vents over 10 years ago, I had no call backs so 100% sccess, I even did my own house. I don't have any commercial involvement in EPS but it is cheaper and has a better Lambda value than Glass Beads which would probably also work well. We don't do much renovations anymore as we're now building Off-Grid Developments.
    • CommentAuthortony
    • CommentTime1 day ago
     
    👍
    • CommentAuthorsam_cat
    • CommentTime1 day ago
     
    Is pumping underfloor voids diy'able? What kit would be needed?

    Not afraid of DIY, quite capable of all sorts, have access to core drills and know how to use them etc.

    8m x 7m with 0.4m depth so around 23m^2 unless my math is off
    • CommentAuthortony
    • CommentTime1 day ago
     
    I use a compressor and a bead blower gun that you may borrow if you wish, sucks beads from bulk bags dead fast and sucks them up via a "vacuum cleaner" size pipe into the gun which delivers through 22, 28, 32 or 38mm tube into your voids

    probably easiest to start by lifting a board and tipping in as much as you can.

    All very easy to DIY - happy to help if yo wish
    • CommentAuthorsam_cat
    • CommentTime1 day ago
     
    Thank you. No need yet, just gauging viability. Gotta pull some more boards up first and investigate the wiring/piping situation and if there is enough room for access... Could do with moving a couple of rads and want to add some sockets in certain spots. Guess with EPS I also need to protect the cables?

    Suspended wooden floor 1970's ish build. Cavity walls done, double glazing done, loft insulation now 18 inches.. But the floor still feels cold and on a windy day you can feel a slight floor breeze :/ Guessing its that.

    Did consider pulling carpets and putting down some vapour permeable air impermeable membrane on the floorboards then the usual underlay and carpet on top. Not sure if a good idea.

    Got a compressor and know how to use it, and lifting boards and pouring first sounds like a no brainer.. Punch nails through?
    Guess you need to fill to the brim? dont want floor - beads - void - floorboards?

    Early days of formulating a plan. :)

    Thanks again,
    Sam
  4.  
    Floor breeze -> lift the carpet grippers and squirt a lot of flexible sealant below skirting boards. Insulation will not fix the draughts, though will help make the floor warmer.
    • CommentAuthorsam_cat
    • CommentTime23 hours ago
     
    Okay, thats useful to know.
    Just on external walls or all walls (guessing all walls)?

    Sometimes its hard to know what the solution for various problems are, so much appreciated.

    Will probably start my own 'home improvement' thread once I have my thoughts straight. :)
    • CommentAuthorPetlyn
    • CommentTime19 hours ago edited
     
    Sam_Cat : Recycled glass beads are an alternative to EPS - they are more environmentally friendly in manufacture and do not get attacked/eaten by insects, ants in particular, when in place. They are lightweight and can easily be poured or blown into place and have no chemical reaction with cabling.

    Yes, you would need to ensure the void is completely full beneath the floorboards.
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