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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    I'm finally getting around to rip out the victorian mosaics in my hallway, sacrilege I know but the sub floor has sunk and restoration cost is prohibitive. Don't worry they'll be recycled/sold.

    My question is for a mid terrace floor will 50mm PIR insulation suffice and a 50mm self leveling screed on top? Just trying to work out what depth I'll need to dig out to keep the reception rooms level.

    My other question is the front door is original timber and then there's the second door. This area is unheated at present, should I run the UFH in this area or is it just wasted heat? And what's the best perimeter insulation and thickness as I will need to tile or vinyl over it I guess.

    Also what floor coverings does one suggest to create a 'grand' entrance?
    • CommentAuthortony
    • CommentTimeNov 10th 2019
    Victorian tiles!

    150 or 200 eps insulation under for me, 25 pir perimeter insulation.

    Unheated porch
    The porch area is 1m x 1m, so just leave that with no heating.

    I'll go with 150mm EPS, is 50mm self levelling screed okay or is 75mm preferable?
    • CommentAuthortony
    • CommentTimeNov 11th 2019
    Mosaiics finally uplifted, they served their 110yr old purpose and the half decent ones will soon appear on eBay

    Now need to dig up the sub-base which is in very poor state anyway. I'll dig down 225mm below finished floor level

    I'm guessing it would be best to do the floor in 75mm + 75mm EPS70 staggered?

    Sand or chippings as a sub-base or not required as weight of screed will compress the EPS anyway?

    Any requirement for expansion joints in the screed? It is 5m x1m then 5x1m in a 'Z' shape.

    Finally, as the porch sub base is in good order any point in lifting that and insulating? As no UFH going in that area....

    I'm even tempted to do away with UFH and just create a 150mm EPS floating floor and keep the radiators - good idea?'
    Digging down to what appears to be the footings of the internal wall. I'm guessing not to go lower than that so it gives me 16cm depth. I'm thinking 60mm screed, 100mm insulation?
    • CommentAuthorriboid007
    • CommentTimeJan 8th 2020
    The folks are right that 50mm is nowhere near enough. Ph is approx 175mm for real performance, so the 150mm would be good.
    I can't fit 150mm due to the footings, the total space is 160mm so 100mm insulation and 60mm screed...

    My next question is I have a load of pir boards spare, I'm assuming these will be okay instead of eps? I was going to use 50mm on top of 50mm staggered
    The U-Value of the floor with 100mm PIR is 0.1, that is fine as there is only 1m perimeter exposed, the rest is all within the thermal envelope (being a terraced house)
    What's the best way to deal with this porchway?

    The tiles will be coming up, the existing concrete is in good order. Do I need to take up the concrete, insulate the floor and then put UFH in? Seems illogical to me....

    It's an entrance way which I guess is part of the thermal envelope but isn't currently heated....

    If I don't do anything with it, do I use 25mm PIR up against the porch floor? If so, how do you put a floor finish on top of PIR?
    picture now attached
    • CommentTimeJan 8th 2020
    Posted By: VictorianecoThe U-Value of the floor with 100mm PIR is 0.1

    How do you work that out? The conductivity is 0.022 W/m.K AFAIK. PIR should be fine.

    Even aerogel wouldn't give you as low as 0.1 W/m²K for 100 mm.

    You can dig deeper by sloping the sides of the hole at 45° away from the walls, if its worth it.

    The tiles will be coming up, the existing concrete is in good order. Do I need to take up the concrete, insulate the floor and then put UFH in? Seems illogical to me....

    Well yes, if you want to put insulation in then you have to make space for it. I'm not sure why that would seem illogical? Whether to put UFH in depends on your overall plan.
    Because the perimeter to area ratio is 0.1, so using 100mm kingspan it gives a u value of 0.1

    Not sure what the issue is? It's a 10m2 floor with only 1m exposed
    VE is right. Un-insulated U value for a floor with a P/A ratio of 0.1 is 0.21, therefore R = 1/0.21 =4.762m2K/W. 100mm PIR with a lambda of 0.022 gives an R of 4.54. 4.762+4.54 = 9.302, so U = 0.107 - OK so I'd call that 0.11, but we are in the same ball-park.
    I think people tend to get hung up on depths and specs without looking at the context.

    Anyway nick, would you take up the last bit in the porch and insulate it or leave as is, disc off and then put ufh up to the second door...
    It's even better than that :-)
    The formula for U (based on P/A), assumes a normal heat flow path where heat flows from the floor, under a wall, to the outside air. But VE's hall has an extra-long heat flow path, under the porch floor, to the outside air, so more ground resistance to heat flow than the formula gives you credit for.

    It certainly would be illogical to add ufh to the unheated porch.
    If the porch is simply a 'buffer zone', and the door between house and porch is 'external quality', then no particular need to insulate or heat. There will of course be thermal bridges, but there are anywhere that 'in' meets 'out'. Just mitigate as far as possible.
    I wouldn't say the second door is external quality as it's an original Victorian single glazed timber door, the front door is no better. But they have both been draught proofed as best they can.

    I guess the difference would be negligible.

    We intend to now keep the mosaiics in that area and going for LVT in the hallway.
    Just a question regarding screed then....

    My local liquid screed supplier has said I need a minimum of 75mm, other resources say 60mm is fine on the website.

    Or do I go for traditional sand/cement screed but with fibres? Is that fine in 60mm?
    Floor is a bit uneven at the moment, what is the best sub base material (type 1?) to level off the floor prior to the insulation going down?

    Anyone? Hoping to get out down this weekend. Thanks
    • CommentAuthorGreenPaddy
    • CommentTimeJan 11th 2020
    If it's not too uneven (+/- 15mm), you could level it with sand - easy to barrow in, and doesn't need compacting. You ought really to have a layer of sand below any DPM/insulation anyway, so not an untried method.

    If it's more uneven than that, then type1 or even type2, which is finer, and much easier to get flat.
    Okay great, if it's already ash down then sand can just go straight on top yeah?
    Ordering up today...

    So sand or stone dust on top of existing to level up?
    • CommentAuthorGreenPaddy
    • CommentTimeJan 13th 2020
    Not knowing exactly what the solum/subfloor is, it's not a call that can be made. If you've a few inches of well compacted inert material, bash on.
    Got my insulation down tonight. Leaving me 50mm space for screed spot on.

    Is metal rebar essential in the screed at that depth?

    I'm not going to heat the understairs area, how do I separate the hallway from under the stairs assuming we want the same floor (LVT) in both areas and I'd rather the floor levels be the same height
    I would be tempted to forget about the screed as you don't have enough depth for it really unless you are talking about a modern pumped self levelling type as opposed to sand/cement. If you are only putting tile or vinyl then fill the void with suitable insulation boards and top with flooring boards instead. Screed far more work and more likely to fail in this case.
    Screed fail at 50mm with fibres?

    What's your reasoning? I was told 50mm is the minimum depth for traditional and 75mm for self levelling concrete?
    If not I could take off the 2nd layer of 50mm insulation and use 25mm if required to ensure correct depths?

    The goal is to get UFH in the hallway to take advantage of the ASHP
    Just a Q. Is the general rule 'x mm including UFH pipe' or 'x mm *over* UFH pipe? If the latter that would mean you need 65 - 66 mm, so your idea of taking off the 50 and using 25 would be needed.
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