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Housing - Renovation: Insulating solid floor, with minimal cost/disruption?

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  1.  
    • CommentAuthorEbeneezer
    • CommentTimeJan 10th 2021
     
    I have a bungalow which has ~70% is suspended timber floor and ~30% solid floor. The easy to reach parts of the suspended floor have been insulated with Rockwool between the joists and the hard to reach parts will be done as other improvement work goes on.

    My question is what low cost/disruption options are available for the solid floor. Digging out the concrete, insulating and covering with a new screed would be outside of the budget so is there anything worth doing that would be a significant upgrade on just using very good underlay?

    These rooms will be be carpeted so if there was product with was [x]mm of “good” insulation that could have carpet laid directly on top of it that would be ideal.

    I have seen the Sempafloor product but when I asked about the U-Values I wasn’t impressed. Is there anything you would recommend?


    We are doing quiet a bit of improvement and these rooms will probably be the last things we do but I want to keep the floor (mostly) level across the house so if that is going to be 25mm (or whatever) higher I’d like to plan for it before we start on the other rooms.
  2.  
    20mm EPS then T&G OSB under the carpet will make a big difference. About 40mm rise, door threshold might be a problem but you could cut the bottom of the door to suit
    • CommentAuthorFred56
    • CommentTimeJan 10th 2021
     
    Aerogel based products?
    • CommentAuthortony
    • CommentTimeJan 10th 2021
     
    Not good on floors unless in rigid sheet form

    I would go for external perimeter insulation and EWI too
    • CommentAuthorEbeneezer
    • CommentTimeJan 10th 2021
     
    Posted By: Peter_in_Hungary20mm EPS then T&G OSB under the carpet will make a big difference. About 40mm rise, door threshold might be a problem but you could cut the bottom of the door to suit

    Hi Peter,

    Thank you , this looks like a possible option, I assume 18mm OSB?

    To reduce the height difference, would fitting OSB over the floorboards in the connecting rooms be a silly idea?
    • CommentAuthorEbeneezer
    • CommentTimeJan 10th 2021
     
    Posted By: tonyNot good on floors unless in rigid sheet form

    I would go for external perimeter insulation and EWI too


    Hi Tony,

    In an ideal world that is what I would do. The solid floor exists where the house was extended and is on the North and East sides, which never see the sun so EWI would be great, but the extended area also has a “flat” roof and the eaves leave no overhang. So adding EWI would then involve work to the roof and costs start escalating.

    Thanks
    • CommentAuthorEbeneezer
    • CommentTimeJan 10th 2021
     
    Posted By: Fred56Aerogel

    Hi Fred,

    That sounds expensive, though it is something I have considered for window reveals.

    Is there a supplier you would recommend for Spacetherm?

    Thanks
    • CommentAuthortony
    • CommentTimeJan 10th 2021
     
    20mm of floor insulation is too little , hundreds of mm needed
  9.  
    Hi Ebenezer, this is a job you only want to do once, so don't skimp it! The building regs/stds set out the minimum acceptable insulation values, but you will have warmer feet if you do better than the bare legal minimum.

    Depending what shape your floor is, you will have a
    bigger or smaller existing heat loss, so you top up the insulation to get to the legal u value or better.

    If you use a basic insulation like EPS you will need a lot of it (70-100mm) So it is worth considering higher performance insulation materials like phenolic or even aerogel if you need to keep the height down.

    Most of the cold comes in from the perimeter of a solid floor, so turn the insulation up the wall behind the skirting as far as possible to stop cold from bridging into your floor from the edges.

    If your existing floor has a cement screed over a concrete slab, you can remove the screed to gain some depth.

    Instead of plain OSB on top, you can get boards that have channels cut in them, so you can lay underfloor heating pipes while you are at it!

    We found that insulating and draughtproofing the floors was a transformation for the 'livability' of our house, having warm feet makes everything else feel warmer!
    • CommentAuthorCWatters
    • CommentTimeJan 10th 2021 edited
     
    Posted By: Peter_in_Hungary20mm EPS then T&G OSB under the carpet will make a big difference. About 40mm rise, door threshold might be a problem but you could cut the bottom of the door to suit


    I would recommend fixing down 20mm battens to take the load as otherwise the EPS will break up over time.

    PIR instead of EPS would give a slight improvement.

    Posted By: Ebeneezer
    Posted By: Peter_in_Hungary20mm EPS then T&G OSB under the carpet will make a big difference. About 40mm rise, door threshold might be a problem but you could cut the bottom of the door to suit

    Hi Peter,

    Thank you , this looks like a possible option, I assume 18mm OSB?

    To reduce the height difference, would fitting OSB over the floorboards in the connecting rooms be a silly idea?


    18mm T&G is the minimum normally recommended for floors. Personally I like my floors solid so I would go with 21mm.

    Putting OSB over the existing floor boards would be fine.

    If you want to tile some rooms then WBP plywood screwed down is better as the floor needs to be quite rigid.
  11.  
    Posted By: EbeneezerThank you , this looks like a possible option, I assume 18mm OSB?

    To reduce the height difference, would fitting OSB over the floorboards in the connecting rooms be a silly idea?

    Yes 18mm OSB thiner if you can get T&G - I think you might be able to get 12mm but the OSB must be T&G. It is just to spread the point loads on the EPS.

    OSB on the adjacent room would reduce the difference but unless you are wheeling stuff around (or have a wheel chair) I would not expect a problem.I have a 40mm floor difference between 2 rooms with a 50mm threshold from the lower floor and don't have problems (2 year old grandson tripped a couple of times when first toddling but takes it in his stride now)

    Posted By: EbeneezerIn an ideal world that is what I would do. The solid floor exists where the house was extended and is on the North and East sides, which never see the sun so EWI would be great, but the extended area also has a “flat” roof and the eaves leave no overhang. So adding EWI would then involve work to the roof and costs start escalating.


    You can add EWI without roofing work by putting flashing (angled slightly to the outside) on the upper edge of the EWI, but for the EWI to work the cavity must be properly filled so first good CWI then EWI.

    Edit - Cross posted with CW. If the floor is flat (without dips) then IMO a thinner OSB should be OK. A 100 grade EPS is what is used under concrete so should be OK on the floor or use XPS which is denser and harder. (over here 100 grade EPS is used under engineered wood floating flooring)
  12.  
    As an example, we are thinking about our kitchen/diner with an external perimeter wall length P of 10m and a floor area A of 20m2

    So P/A = 0.5

    The existing U value is from the BRE formula

    U = 0.05 + 1.65(P/A) – 0.6(P/A)² = 0.725W/mK
    And existing R value = 1/U = 1.38 mK/W

    The max legal U value from Scottish building stds tech handbook is 0.18 W/mK. (Is subject to various getouts, but who are we trying to cheat here!)

    So required R = 1/U = 1/0.18 = 5.55 mK/W

    We need to add insulation to improve the R value, by 5.55 - 1.38 = 4.17 mK/ W

    Using EPS with a conductivity of 0.037, we would need 4.17*0.037 = 150mm

    Using phenolic with a conductivity of 0.018, we would need 4.17*0.018 = 75mm

    Using aerogel with conductivity of 0.014 we would need 4.17*0.014 = 60 mm

    Plus whatever surface layer on top - OSB+carpet, or more likely cementboard+ufh+vinyl in our case.
    • CommentAuthorEbeneezer
    • CommentTimeJan 10th 2021
     
    Thank you all for the feedback, plenty to think about.

    I agree it is job that I only want to once but aiming to achieve the higher U value’s will probably lead to a situation where perfect is the enemy of done and no improvement happens. I’ll have to weigh up the options.
    • CommentAuthorJeff B
    • CommentTimeJan 11th 2021
     
    I have used EPS 100 under 22mm T&G chipboard with no battens i.e. a floating floor in a chapel situation (lots of footfall). A tip I was given was to put DPM over the EPS to prevent the boards squeaking when walking over them - it worked, but of course I'll never know whether they would have if I hadn't used the DPM! It did make the laying of the T&G a bit easier as the boards slid easily across the polythene.

    Regarding the difference in level between rooms. On a different job to the one above, we made a ramp from a piece of varnished 6" timber at the threshold. It looked as though it was a part of the door frame and worked a treat.
  15.  
    Aerogel has been mentioned already in this thread. Here is a floor product:

    https://www.thermablok.co.uk/our-products/thermablok-aerogel-magnesium-floor-board/

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