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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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    • CommentAuthorSprocket
    • CommentTimeNov 11th 2018 edited
    Our next house is about to get a major make-over before we move in. Old heating system is 22 yr old polybutylene pipe throughout so it ALL needs to go. Downstairs is in thin screed so we just dig it up and replace (in Pex-A).

    The upstairs UFH has more to think about. Living space is upstairs, beds downstairs and whilst it will be fairly draught-free and well glazed it is by no means an modern eco-build. There are a few gas fires but I would like to spec to get all the heat from UFH if we can.

    Considering using some sort of UFH pipe-guide system with 100 or 150mm pipe spacing incorporating insulation and reflective surface although of course this would sit on top of joists so will raise all the floor levels a little. But what to put over the top?

    The numbers make we want to put ceramic tiles everywhere but I'm also concerned about rigidity of the floor and possibility of losing all the grout to cracks with movement which makes me want to put thicker backing board over the UFH... which of course stuffs up the heating. My wife is wondering about timber floors, maybe a bit of parquet; oh and carpet in the upstairs master bedroom (and boy does carpet+underlay stuff up the numbers). Anything with glue also limits my below-floor temp to 27 degrees so I can't just raise UFH temp to get more heat out.

    Is there a major solution to some of these problems (from flooring over UFH on floor joists) that I might be overlooking? Particular UFH systems I should look at? How much decent support for my flooring can I get from the UFH and how much (and what) do I need to consider putting over the top eg. for tiles?

    Any thoughts/ideas appreciated.
    • CommentTimeNov 11th 2018
    You could look at using screed boards. The various manufacturers have drawings of their recommended build-ups.

    Posted By: SprocketAnything with glue limits my below-floor temp to 27 degrees

    What makes you say this? Some of the adhesive products specify 40°C as an upper limit.

    You could consider bamboo as an alternative to timber. It tends to be very uniform.

    Personally I like carpet in the bedroom as well. It doesn't need to be the most expensive carpet, so it wouldn't be a total disaster if you put it in and later want to take it up again. As an alternative, you could put a thin matting or a laminate over the whole room and some thicker rugs at the most sensitive points.
    • CommentAuthortony
    • CommentTimeNov 11th 2018
    Wood floor on top is fine so is carpet, crucial to have insulation under the pipes, also sound insulation will be a requirement if you are in the UK
    Tiles are nice under bare feet when the heating is on, but perversely they are uncomfortable in the spring and autumn months if the heating isn't on.
    We ended up running the heating in some rooms all year just to keep the floor tiles warm...

    Next time there will be carpet or vinyl in all bedrooms and bathrooms, and if that means no ufh then so be it!
    Actually we didn't need a lot of heating upstairs anyway, so electric panel radiators worked out well instead of the cost of running wet plumbing upstairs in an extension.
    • CommentAuthorCWatters
    • CommentTimeNov 13th 2018 edited
    Old heating system is 22 yr old polybutylene pipe throughout so it ALL needs to go.

    22 years isn't that old. Presumably because it's the stuff without an oxygen barrier?
    • CommentAuthorCWatters
    • CommentTimeNov 13th 2018 edited
    One option would be something like 21mm thick Engineered Oak (or other species). This is typically 14mm plywood with a 7mm layer of oak on top. The good stuff is >200mm wide and when laid you can't really tell it's not solid wood. You can also re-sand it the same number of times as solid oak (eg until the T&G appears). The main difference is that the boards tend to be, and stay, flatter than solid wood. Less risk of cupping with UFH.

    Boards supported on joists have to be at least 18mm thick. Engineered Oak typically comes in 14 mm and 20-22mm versions so you need the thicker one. The 14mm version would need something under it like OSB or flooring grade chipboard which would increase the thickness too much in my opinion.

    We got ours from "Woods of Wales" http://www.woodsofwales.co.uk/ and it came already treated with Hardwaxoil. We have had the flow temperature up as high as 55C without any issue (but I don't know if it's rated for that). I have also wet mopped some of it with a damp mop!

    We have it in a dining room, hall and master bedroom. Hall shows very little wear after 12 years (and we have twins age 16 so it gets well used).

    Do shop around and get samples. We picked up a load of different ready finished samples from a self build show. They all looked good at the show but some were a horrible colour when we got them home in natural light, some were positively orange. As with solid oak you can generally choose how much character (knots) they have. Personally I like more rather than less.
    • CommentAuthorCWatters
    • CommentTimeNov 13th 2018
    Tiles really need a pretty rigid floor or they can crack, and I mean the tiles not just the grout. Opinions differ on how rigid it needs to be but you would first need to check the joists don't flex too much. Then some places recommend one layer of 18mm Plywood WBP or two layers of 12mm WBP with staggered joints. All glued and screwed down every 100mm (lots of screws!). Use a flexible adhesive.

    Best advice is to try and find a very experienced tiler who knows what they are doing and get them involved at the outset before you do any work on the floor.
    • CommentAuthorSprocket
    • CommentTimeNov 13th 2018 edited
    > 22 years isn't that old. Presumably because it's the stuff without an oxygen barrier?

    Indeed, no oxygen barrier. But there is worse...

    Polybutylene goes brittle with age, especially if exposed to chlorine from tap water. There was a big failure in the USA about 10 years after people began using it on a lot of big developments. That resulted in a 1.3 BILLION DOLLARS class action suit. As a result you won't find polybutylene pipe in use anywhere in the US.

    Plumbers here have also told me that it "sweats" when used in a heating system. I don't know about that but there is quite a bit of corrosion around it.

    There have already been a few failures (repaired). I won't risk it.
    • CommentAuthorSprocket
    • CommentTimeNov 15th 2018
    Thanks CWatters. We are now leaning towards 14mm engineered Parquet and other engineered timber boards for all but the bedroom (which will be carpet over...something TBD).

    Not completely ruled out ceramic tiles yet. Was going to still use them in the upstairs bathroom but now not so sure.

    Regarding really firm support for eg. ceramic tiles...
    Adding a huge thickness of effectively insulating boards between the UFH pipes and surface does not appeal. Is there by any chance some sort of UFH former system that can sit on top of the joists and carry the pipes AND also support the layer above really well so we could get away with a thinner (eg. 6mm) carrier layer over?
    • CommentAuthorgyrogear
    • CommentTimeNov 15th 2018
    Posted By: Sprocketsome sort of UFH former system that can sit on top of the joists and carry the pipes AND also support the layer above

    how about this ?


    • CommentAuthorCWatters
    • CommentTimeNov 15th 2018
    We are now leaning towards 14mm engineered Parquet

    Just note my comment about >18mm needed if unsupported. Think it might even be a building regs thing.

    For carpet keep the TOG as low as possible. Ideally nearer 2.0 rather than 2.5. There are special underlays with a TOG of 0.6 or below for use with UFH.

    When you find a carpet beware the small print on the order. Some carpets come in two versions - Rubber backed or Hessian backed. The small print sometimes allows them to supply either version. Obviously the rubber backed will have a higher TOG. The hessian will feel harder but have lower TOG. Try out a sample of the carpet and underlay together in the shop in bear feet.
    ''Try out a sample of the carpet and underlay together in the shop in bear feet.''

    Or just use your own...
    • CommentAuthorCWatters
    • CommentTimeNov 16th 2018
    • CommentAuthorTimSmall
    • CommentTimeNov 24th 2018
    Ceramic tiles will feel cold underfoot when the heating isn't on (and even when it is on at low temperatures, because they have high thermal conductivity - so they're good at removing heat from your feet), if that doesn't matter, then go for it.

    So for the 1st floor bathroom, we went for a high grade of linoleum. Very comfortable under foot (summer and winter), and the lower thermal conductivity is cancelled out by the much thinner build-up - meaning that the UFH output is about the same as tiles, but the touch comfort is a lot better.

    I used wood flooring, bonded down with ms-polymer adhesive over UFH on the ground floor (pipe in thin screed - 80% GGBS / 20% portland screed with polycarboxylate super plasticiser - the polycarboxylate increases thermal conductivity, and reduces cracking and drying time).

    UFH is not normally recommended with solid wood flooring, but since our flow temperatures are very low I've not had any problems in the 5 years that it's been down. I went with solid wood flooring since it was already on site (we took it up and reconditioned it).

    I avoided carpet - for rooms which we decided to have carpeted, we fitted rads instead, with the rads designed to work with the 35C max flow temperature of the UFH to avoid the need for any mixer valves.
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